WO2023061025A1 - 片上集成波分复用器及芯片 - Google Patents

片上集成波分复用器及芯片 Download PDF

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Publication number
WO2023061025A1
WO2023061025A1 PCT/CN2022/112099 CN2022112099W WO2023061025A1 WO 2023061025 A1 WO2023061025 A1 WO 2023061025A1 CN 2022112099 W CN2022112099 W CN 2022112099W WO 2023061025 A1 WO2023061025 A1 WO 2023061025A1
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Prior art keywords
wavelength division
flat
polarization
stage
multiplexing
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PCT/CN2022/112099
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English (en)
French (fr)
Inventor
郭德汾
林天华
李显尧
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苏州湃矽科技有限公司
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Publication of WO2023061025A1 publication Critical patent/WO2023061025A1/zh

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G02B6/124—Geodesic lenses or integrated gratings
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/126—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind using polarisation effects
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems

Definitions

  • the present application relates to the technical field of optical communication, in particular to an on-chip integrated wavelength division multiplexer and chip.
  • wavelength division multiplexing In high-speed and large-capacity optical communications, wavelength division multiplexing (Wavelength Division Multiplexing, WDM) is an effective means to increase the capacity of optical communications, and combined with photonic integrated chips, it can effectively reduce the size of devices and improve system
  • WDM wavelength division Multiplexing
  • MUX wavelength division multiplexing device
  • DEMUX wavelength division multiplexing device
  • the wavelength division multiplexer based on the cascaded Mach-Zehnder interferometer (MZI) structure in the existing silicon optical chip consists of three parallel and Cascade-connected Mach-Zehnder interferometers 10' constitute, wherein each Mach-Zehnder interferometer 10' includes two 2 ⁇ 2 3dB couplers 11' and two connecting arms 12', a monitoring probe device 13', one of the connecting arms is an adjustable phase shift arm (indicated by a dotted line in the figure).
  • MZI Mach-Zehnder interferometer
  • the above-mentioned existing wavelength division multiplexer needs to be combined with the monitoring detector 13' to adjust the adjustable phase-shift arms of the cascaded Mach-Zehnder interferometers 10' when in use, which causes the adjustment process to be inconvenient. consumes more.
  • the optical bandwidth of the 3dB coupler 11' is limited, therefore, multiple cascaded Mach-Zehnder interferometers 10' have multiple 3dB couplers 11' in the optical path of the wavelength division multiplexer, which significantly reduces the wavelength division Multiplexer performance.
  • the ideal wavelength division multiplexing device should be purely passive and does not need to be adjusted.
  • the optical waveguide device in the silicon-based wavelength division multiplexer will be affected by the width, inclination angle change, and silicon waveguide thickness change caused by the processing technology. and temperature changes, etc., resulting in the shift of the center wavelength of the silicon-based wavelength division multiplexing device, thus, the shift of the center wavelength of the existing silicon-based wavelength division multiplexing device will cause the difference between the optical signals of adjacent channels crosstalk occurs.
  • the purpose of this application is to provide an on-chip integrated wavelength division multiplexer and chip, which is used to improve the crosstalk problem between optical signals of adjacent channels, and has the advantages of low power consumption and large optical bandwidth.
  • an on-chip integrated wavelength division multiplexer which includes a first-stage multiplexing module and a second-stage multiplexing module, the first-stage multiplexing module has a plurality of input ports and two output ports, the second-level multiplexing module has two input ports and one output port, and the two output ports of the first-level multiplexing module are respectively corresponding to the input of the second-level multiplexing module Port optical coupling; the first-level multiplexing module includes at least two flat-top wavelength division multiplexing structures, each of which has two input ports and one output port, wherein each of the flat-top wavelength division multiplexing structures The bandwidth of the flat-top wavelength division multiplexing structure covers the frequency band range corresponding to the center wavelength of the incident light respectively received by its two input ports plus a preset offset threshold.
  • the first-stage multiplexing module multiplexes the incident lights with the same polarization state received by the multiple input ports to generate two first-stage multiplexed optical signals
  • the two first-stage combined optical signals are respectively input to the corresponding input ports of the second-stage multiplexing module, and the second-stage multiplexed module combines the two first-stage combined optical signals received by its two input ports.
  • the second-stage multiplexed optical signal includes a first group of optical wave components and a second group of optical wave components, and the first group of optical wave components and the second group of optical wave components have different polarization states; the second-stage multiplexing module performs polarization multiplexing on the first group of light wave components and the second group of light wave components.
  • n ⁇ 4, And n is an even number; for each of the flat-topped wavelength division multiplexing structures, an incident optical signal of an odd channel is input from an input port of the flat-topped wavelength division multiplexing structure, and from the flat-topped wavelength division multiplexing structure The other input port inputs the incident optical signal of the even channel.
  • the at least two flat-top wavelength division multiplexing structures are composed of any combination of the following structures: multiple cascaded Mach-Zehnder interference structures, arrayed waveguide grating structures, etched diffraction grating structures , a combined structure composed of a mode multiplexer and a multimode Bragg grating, and a reverse Bragg grating directional coupler structure.
  • the on-chip integrated wavelength division multiplexer is a silicon-based wavelength division multiplexer.
  • the difference between the central wavelengths of the incident light received by the two input ports of each of the flat top wavelength division multiplexing structures is greater than a preset wavelength difference threshold.
  • the on-chip integrated wavelength division multiplexer further includes a coupling structure connected to the output port of the second-stage multiplexing module for multiplexing the second-stage
  • the second stage multiplexed optical signal output by the output port of the module is coupled with an external optical fiber array to output the multiplexed optical signal.
  • the second-stage multiplexing module is a polarization rotation beam splitter, and the polarization rotation beam splitter combines the two received first-stage combined optical signals into The polarization states of the first set of lightwave components and the second set of lightwave components.
  • the polarization rotating beam splitter includes a through-waveguide and a cross-waveguide, a through-port and a cross-port respectively connecting the through-waveguide and the cross-waveguide, and a mode conversion structure connected to the through-waveguide;
  • the through waveguide and the cross waveguide form a mode multiplexing structure;
  • the through port and the cross port both include a wedge-shaped structure in which a strip waveguide is transformed into a ridge waveguide; and the mode conversion structure is a double-layer wedge-shaped mode conversion structure.
  • the second-stage multiplexing module is a polarization beam combiner
  • the on-chip integrated wavelength division multiplexer further includes a polarization rotator, and the input port of the polarization rotator is connected to the first
  • An output port of the multiplexing module is optically coupled to receive light output from the output port, and an output port of the polarization rotator is optically coupled to an input port of the polarization beam combiner to output to the polarization beam combiner light, wherein the polarization beam combiner is used to combine two received light beams with different polarization states into one light beam, and the polarization rotator is used to change the polarization state of the received light beams; wherein the polarization rotation
  • the detector changes the original polarization state of the received light beam to a polarization state perpendicular to the original polarization state.
  • the second-level multiplexing module is a polarization beam combiner
  • the on-chip integrated wavelength division multiplexer further includes at least one polarization rotator, and for each polarization rotator, its input The port is used to receive one path of incident light, and its output port is optically coupled to the input port of one of the at least two flat-topped wavelength division multiplexing structures, so as to output light to the flat-topped wavelength division multiplexing structure
  • the polarization beam combiner is used to combine two received light beams with different polarization states into one light beam
  • the polarization rotator is used to change the polarization state of the received light beams, and is changed by the at least one polarization rotator
  • the light of the polarization state is output by only one output port of the first-stage multiplexing module; wherein each of the polarization rotators changes the original polarization state of the received light beam to a polarization state perpendicular to the original polarization state
  • each of the flat-top wavelength division multiplexing structures includes at least two 1dB flat-tops, wherein each 1dB flat-top is a wavelength range corresponding to the optical attenuation range of 1dB, and each 1dB flat-top The wavelength range corresponding to the top is greater than 20 nanometers.
  • the distance between two adjacent 1 dB flat tops of the same flat top wavelength division multiplexing structure is less than 5 nanometers.
  • the wavelength range corresponding to the 1dB flat-top in one of the flat-top wavelength division multiplexing structures is the same as the flat-top wavelength range of the other one.
  • the wavelength ranges corresponding to the 1dB flat top in the division multiplexing structure partially overlap.
  • a chip is provided, and the chip includes the on-chip integrated wavelength division multiplexer described in any one of the foregoing embodiments.
  • the bandwidth of each flat-top wavelength division multiplexing structure in the first-level multiplexing module can cover the incident signals respectively received by its two input ports.
  • the central wavelength of the light plus the frequency band corresponding to the preset offset threshold thus making the flat-top band bandwidth of the two first-stage multiplexed optical signals generated by the first-stage multiplexing module wider, which can cover various
  • the problem of crosstalk between adjacent channels caused by the shift of the center wavelength caused by factors has realized the multiplexing of incident optical signals of different wavelengths; in addition, the first-level multiplexing module and the second-level multiplexing module do not need to Any feedback regulation improves work efficiency, reduces device loss, and helps reduce the sensitivity of the on-chip integrated wavelength division multiplexer to waveguide width, waveguide height, and waveguide inclination.
  • Fig. 1 is the structural representation of the MZI type on-chip integrated wavelength division multiplexer in the existing silicon light chip
  • Figure 2a is a schematic structural diagram of an on-chip integrated wavelength division multiplexer provided by an embodiment of the present application
  • FIG. 2b is a schematic structural diagram of an on-chip integrated wavelength division multiplexer provided by another embodiment of the present application.
  • FIG. 2c is a schematic structural diagram of an on-chip integrated wavelength division multiplexer provided by another embodiment of the present application.
  • FIG. 3 is a schematic structural diagram of a polarization rotating beam splitter (PSR) in an embodiment of the present application
  • Figures 4a-4e are schematic diagrams of multiple implementations of a flat-top wavelength division multiplexing structure formed by using multiple cascaded Mach-Zehnder interference structures in the embodiment of the present application;
  • FIG. 5 is a schematic diagram of using an arrayed waveguide grating structure as a flat-top wavelength division multiplexing structure in an embodiment of the present application
  • FIG. 6 is a schematic diagram of using an etched diffraction grating structure as a flat-top wavelength division multiplexing structure in an embodiment of the present application
  • FIG. 7 is a schematic diagram of a flat-top wavelength division multiplexing structure using a combined structure composed of a mode multiplexing device and a multimode Bragg grating in an embodiment of the present application;
  • FIG. 8 is a schematic diagram of using an inverted Bragg grating directional coupler structure as a flat-top wavelength division multiplexing structure in an embodiment of the present application;
  • Fig. 9 is a simulated spectrum diagram of a flat-top wavelength division multiplexing structure composed of any combination of multiple cascaded Mach-Zehnder interference structures, arrayed waveguide grating structures, and etched diffraction grating structures in an embodiment of the present application;
  • Fig. 10 is the spectrogram of the beam near the central wavelength of 1291nm in the spectrogram shown in Fig. 9;
  • Figure 11 is a set of light waves generated by using a flat-top wavelength division multiplexing structure composed of a combined structure composed of a mode multiplexer and a multimode Bragg grating, and an arbitrary combination of an inverted Bragg grating directional coupler structure in an embodiment of the present application
  • Figure 12 is another group of light waves generated by the flat-top wavelength division multiplexing structure composed of any combination of mode multiplexers and multimode Bragg gratings and any combination of inverse Bragg grating directional coupler structures in the embodiment of the present application
  • FIG. 13 is a schematic structural diagram of an on-chip integrated wavelength division multiplexer provided in another embodiment of the present application.
  • FIG. 14 is a schematic structural diagram of a polarization rotator (PR) in the on-chip integrated wavelength division multiplexer shown in FIG. 13;
  • PR polarization rotator
  • FIG. 15 is a schematic structural diagram of a polarization beam combiner (PBC) in the on-chip integrated wavelength division multiplexer shown in FIG. 13;
  • PBC polarization beam combiner
  • FIG. 16 is a schematic structural diagram of an on-chip integrated wavelength division multiplexer provided by another embodiment of the present application.
  • first and second herein are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, a feature defined as “first” or “second” may explicitly or implicitly include one or more of said features. In the description of the present application, “plurality” means two or more, unless otherwise specifically defined.
  • connection should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection. Connected, or integrally connected; it can be mechanically connected, or electrically connected, or can communicate with each other; it can be directly connected, or indirectly connected through an intermediary, and it can be the internal communication of two components or the interaction of two components relation. Those of ordinary skill in the art can understand the specific meanings of the above terms in this application according to specific situations.
  • FIGS. 2a-2c are schematic structural diagrams of an on-chip integrated wavelength division multiplexer provided by an embodiment of the present application
  • FIG. 3 is a schematic structural diagram of a polarization rotating beam splitter in an embodiment of the present application.
  • an embodiment of the present application provides an on-chip integrated wavelength division multiplexer 1000 , which includes a first-stage multiplexing module 100 and a second-stage multiplexing module 200 .
  • the first stage multiplexing module 100 has a plurality of input ports and two output ports
  • the second stage multiplexing module 200 has two input ports and one output port, all of the first stage multiplexing module 100
  • the two output ports are optically coupled to the corresponding input ports of the second-level multiplexing module 200; multiplexing to generate two first-stage multiplexed optical signals, and input the two first-stage multiplexed optical signals to corresponding input ports of the second-stage multiplexing module 200 .
  • the second-stage multiplexing module 200 multiplexes the two first-stage multiplexed optical signals received by its two input ports to generate a second-stage multiplexed optical signal, wherein the second-stage multiplexed optical signal A first set of lightwave components and a second set of lightwave components are included, the first set of lightwave components and the second set of lightwave components have different polarization states.
  • the first stage multiplexing module 100 is composed of at least two flat top wavelength division multiplexing structures (110, 120), each of the flat top wavelength division multiplexing structures (110, 120) has two input ports and a output ports, wherein the bandwidth of each of the flat top wavelength division multiplexing structures (110, 120) covers the center wavelength of the incident light respectively received by its two input ports plus the preset offset threshold corresponding to frequency range.
  • the bandwidth of each flat-top wavelength division multiplexing structure in the first-stage multiplexing module can cover the center of the incident light received by its two input ports respectively.
  • the frequency band range corresponding to the wavelength plus the preset offset threshold thus making the flat-top band bandwidth of the two first-stage multiplexing optical signals generated by the first-stage multiplexing module wider, which can cover the bandwidth caused by various factors
  • the resulting center wavelength shift causes the adjacent channel crosstalk problem.
  • the first-level multiplexing module and the second-level multiplexing module do not need any feedback adjustment during the working process, which improves work efficiency and reduces device loss. And it is beneficial to reduce the sensitivity of the on-chip integrated wavelength division multiplexer to changes in waveguide width, waveguide height, waveguide inclination angle and surrounding environment temperature.
  • an on-chip integrated wavelength division multiplexer with four wavelengths of ⁇ 1, ⁇ 2, ⁇ 3, and ⁇ 4 (the wavelengths are arranged in ascending order) is taken as an example, and the on-chip integrated wavelength division multiplexer
  • the multiplexer 1000 includes a first-stage multiplexing module 100 and a second-stage multiplexing module 200.
  • the first-stage multiplexing module 100 is composed of at least two flat-top wavelength division multiplexing structures (110, 120) connected in parallel.
  • the secondary multiplexing module 200 is an integrated polarization rotating beam splitter.
  • each of the flat-top wavelength division multiplexing structures 110 has two input ports and one output port, and the polarization rotating beam splitter 200 includes two input ports and one output port, and the two The two output ports of the flat-top wavelength division multiplexing structure 110 are respectively connected to the two input ports of the polarization rotating beam splitter 200 for optical coupling; the output ports of the polarization rotating beam splitter 200 are used for output synthesis beam.
  • the two incident optical signals of ⁇ 1 and ⁇ 3 are input by two input ports of a flat-top wavelength division multiplexing structure 110, and the two incident optical signals of ⁇ 2 and ⁇ 4 are input by another flat-top wavelength division multiplexing structure 120.
  • each flat-top wavelength division multiplexing structure 110, 120
  • the frequency band range corresponding to the offset threshold that is, the bandwidth of the flat-top WDM structure 110 is greater than ⁇ 1 ⁇ and ⁇ 3 ⁇
  • the bandwidth of the flat-top WDM structure 120 is greater than ⁇ 2 ⁇ and ⁇ 4 ⁇ (where ⁇ is the passband width required by the system for the on-chip integrated wavelength division multiplexing device), so as to realize the multiplexing of incident optical signals of different wavelengths.
  • the wavelength division multiplexing structure can transmit two beams with a large difference in center wavelength, so it can tolerate the difference between adjacent channels caused by the center wavelength shift caused by the waveguide width, waveguide inclination angle, waveguide height and temperature changes. Crosstalk problem.
  • the above-mentioned on-chip integrated wavelength division multiplexer is a silicon-based wavelength division multiplexer, which includes a silicon-based substrate, and a first-level multiplexing module 100 and a second-level multiplexing module 200 are arranged on the silicon-based substrate; It may be an on-chip integrated wavelength division multiplexer structure based on other substrates, and the present invention is not limited here.
  • this dislocation multiplexing method can make the difference between the central wavelengths of the incident light received by the two input ports of each of the flat-topped wavelength division multiplexing structures (110, 120) larger, by This prevents crosstalk effects between adjacent bands within the same channel.
  • the difference between the central wavelengths of the incident light received by the two input ports of each of the flat top wavelength division multiplexing structures (110, 120) is greater than a preset wavelength difference threshold.
  • a preset wavelength difference threshold Take 4 ( ⁇ 1, ⁇ 2, ⁇ 3, ⁇ 4) wavelength-divided optical signals as an example, the wavelength difference between ⁇ 1 and ⁇ 2 is greater than or equal to 20nm, the wavelength difference between ⁇ 3 and ⁇ 4 is greater than or equal to 20nm, ⁇ 1 and ⁇ 3
  • the wavelength difference between ⁇ 2 and ⁇ 4 is greater than or equal to 40nm, and the wavelength difference between ⁇ 2 and ⁇ 4 is greater than or equal to 40nm.
  • the difference between the central wavelengths of the incident light received by the two input ports of each flat-top wavelength division multiplexing structure (110, 120) can also be set according to actual application conditions.
  • each flat-top wavelength division multiplexing structure the loss at the center wavelength ⁇ 0 of the on-chip integrated wavelength division multiplexing device constituted by it is small, and the loss in the range of ⁇ 0 ⁇ ⁇ near the center wavelength The loss compared to the center wavelength is less than 1dB.
  • ⁇ 0 ⁇ is called the 1dB flat-top range of the channel.
  • each 1dB flat-top is a wavelength range corresponding to an optical attenuation range of 1dB
  • each 1dB flat-top in the flat-top wavelength division multiplexing structure corresponds to a wavelength range larger than 20 nanometers.
  • FIG. 11 may represent a spectrum diagram of one of the top-hat wave multiplexing structures. It can be seen from the figure that it has at least two 1dB flat tops (the flat part of the horizontal axis in the figure). The center wavelength of the wavelength corresponding to one 1dB flat top is 1291 nanometers, and the center wavelength of the wavelength corresponding to the other 1dB flat top is 1331 nanometers.
  • Each 1dB plateau corresponds to a wavelength range of about 40 nanometers (the width of the flat portion in the figure).
  • Fig. 12 can represent the spectrum diagram of another top-hat wave multiplexing structure. It can be seen from the figure that it also has at least two 1dB tops. One 1dB flat top corresponds to a center wavelength of 1271 nm, and the other 1dB flat top corresponds to a center wavelength of 1311 nm. Each 1dB plateau corresponds to a wavelength range of about 40 nanometers.
  • the 1dB flat-top ranges corresponding to the center wavelength 1271 nm and the center wavelength 1291 nm partly overlap
  • the center wavelength 1291 nm and the center wavelength 1311 nm correspond to
  • the 1dB flat-top ranges of 1311nm and 1331nm center wavelengths partly overlap.
  • the wavelength ranges corresponding to the 1 dB flat-top range of these central wavelengths can be staggered, so that the function of multiplexing can be realized.
  • two adjacent 1dB flat-tops of the same flat-top multiplexing structure can be separated by a predetermined distance, so as to improve the multiplexing effect and the tolerance of the absorption process.
  • the predetermined distance of the interval may be less than 5 nanometers. It should be noted that, in this embodiment, the interval between two adjacent 1dB flat-tops refers to the distance between the edges of the two 1dB flat-tops, not the distance between the centers of the two 1dB flat-tops.
  • the above-mentioned multiplexing method uses a flat-top wavelength division multiplexing structure to first combine every two of the eight channels into four channels, and then combine the four channels of light waves into two channels to reach the polarization rotating beam splitter, and then the polarization rotating beam splitter Rotate the beam splitter to perform polarization multiplexing; in other embodiments, four of the eight optical signals ( ⁇ 1/ ⁇ 3/ ⁇ 5/ ⁇ 7) can be combined into one through a flat-top wavelength division multiplexing structure, and the other four ( ⁇ 2/ ⁇ 4/ ⁇ 6/ ⁇ 8) are combined into one path through another flat-top wavelength division multiplexing structure, and then the combined light of these two flat-top wavelength division multiplexing structures is combined into one path through a polarization rotating beam splitter.
  • the polarization rotating beam splitter (Polarization The Split Rotator (PSR) 210 includes a through waveguide 211 and a cross waveguide 212 , a through port 213 and a cross port 214 respectively connecting the through waveguide 211 and the cross waveguide 212 , and a mode conversion structure 215 connected to the through waveguide 211 .
  • the through waveguide 211 and the cross waveguide 212 form a mode multiplexing structure
  • the through port 213 and the cross port 214 both include a strip waveguide-to-ridge waveguide wedge-shaped structure, which serves as the input port of the polarization rotating beam splitter.
  • the mode conversion structure 215 is a double-layer wedge-shaped mode conversion structure, which serves as the output port of the polarization rotating beam splitter and outputs the combined optical signal.
  • ⁇ 1 and ⁇ 3 are respectively composed of one of the two flat-top WDM structures.
  • the two input ports of the top-top wavelength division multiplexing structure 110 are input, and the first-stage combined optical signal composed of ⁇ 1 ⁇ / ⁇ 3 ⁇ is output after being multiplexed by the flat-top wavelength division multiplexing structure 110; ⁇ 2 and ⁇ 4 are respectively It is input from two input ports of another flat-topped wavelength division multiplexing structure 120 in the two flat-topped wavelength division multiplexing structures, and the output is composed of ⁇ 2 ⁇ / ⁇ 4 after being combined by the flat-topped wavelength division multiplexing structure 120
  • the first stage multiplexed optical signal composed of ⁇ .
  • the above four incident optical signals ⁇ 1, ⁇ 3, ⁇ 2, and ⁇ 4 are all linearly polarized light and have the same polarization state, assuming that they are all TE0 (Transverse Electric mode (transverse electric mode) linearly polarized light is combined by the two flat-top wavelength division multiplexing structures (110, 120) respectively, and the output first-stage combined optical signal is still combined in the TE0 mode.
  • TE0 Transverse Electric mode (transverse electric mode) linearly polarized light
  • the two first-stage multiplexed optical signals (i.e., the ⁇ 1 ⁇ / ⁇ 3 ⁇ optical signal after the multiplexing and the ⁇ 2 ⁇ / ⁇ 4 ⁇ optical signal after the multiplexing) composed of the combined linearly polarized light of the TE0 mode are respectively composed of
  • the through-port 213 and the cross-port 214 of the above-mentioned integrated polarization rotating beam splitter (PSR) 210 are input, and enter the through-waveguide 211 and the cross-waveguide 212 respectively.
  • PSR integrated polarization rotating beam splitter
  • the polarization state of the ⁇ 2 ⁇ / ⁇ 4 ⁇ optical signal entering the straight-through waveguide 211 remains unchanged, and the ⁇ 2 ⁇ / ⁇ 4 ⁇ optical signal in the TE0 mode is still output after passing through the mode conversion structure 215; the ⁇ 1 ⁇ optical signal entering the cross waveguide 212
  • the / ⁇ 3 ⁇ optical signal is coupled into the straight-through waveguide 211, and is mode-multiplexed with the optical signal in the straight-through waveguide 211, and the mode of the ⁇ 1 ⁇ / ⁇ 3 ⁇ optical signal is converted from TE0 mode to TE1 (higher-order) mode.
  • the transformation structure 215 is transformed into TM0 (Transverse Magnetic mode (transverse magnetic mode) mode (that is, polarization state change) and the ⁇ 2 ⁇ / ⁇ 4 ⁇ optical signal of the TE0 mode in the original straight-through waveguide 211 are synthesized into a beam of linearly polarized light output including the TE0+TM0 mode.
  • TM0 Transverse Magnetic mode (transverse magnetic mode) mode (that is, polarization state change)
  • ⁇ 2 ⁇ / ⁇ 4 ⁇ optical signal of the TE0 mode in the original straight-through waveguide 211 are synthesized into a beam of linearly polarized light output including the TE0+TM0 mode.
  • the on-chip integrated wavelength division multiplexer 1000 also includes a coupling structure 300, and the coupling structure 300 is connected to the output port of the second-stage multiplexing module 200 for connecting the The output port of the second-stage multiplexing module 100 outputs a bundle of multiplexed optical signals (the second-stage multiplexed optical signal) to be coupled with an external optical fiber array, so as to input the optical signal to be modulated and the modulated optical signal The signal is output, which has high coupling efficiency and can reduce the loss of the entire optical path.
  • the coupling structure 300 may be a low polarization-dependent loss edge coupler (low PDL edge coupler).
  • FIG. 4a-4e are schematic diagrams of various implementations of using multiple cascaded Mach-Zehnder interference structures to form a flat-top wavelength division multiplexing structure in the embodiment of the present application. As shown in FIG. 4a-FIG. 4e, 121-125 in the diagrams represent each different implementation of the flat-top wavelength division multiplexing structure.
  • each of the flat-topped wavelength division multiplexing structures 110 is Designed as a digital filter
  • the digital filter is composed of at least two cascaded Mach-Zehnder interference structures (MZI), assuming that the digital filter is represented by the symbol A, and the 2*2 coupler is represented by the symbol B , the phase shift arm is expressed as C, then B and C can be synthesized into A, and the numerical value of the splitting ratio on the coupler and the phase shift on the phase shift arm represent the coefficients in front of B and C, how much A cascaded MZI represents how many orders of approximation.
  • MZI Mach-Zehnder interference structures
  • the number 0.5 indicates that the splitting ratio of the cross port of the 2*2 3-dB coupler is 0.5, that is, the output of one port is 0.5 , the output of the other port is 0.5;
  • the number 0.29 means that the splitting ratio of the 2*2 coupler cross port is 0.29, that is, the output of one port is 0.29, and the output of the other port is 0.71;
  • the number 0.08 means the 2*2 coupler cross port
  • the splitting ratio is 0.08, that is, the output of one port is 0.08, and the output of the other port is 0.92; the rest of the numbers represent the same analogy, and we will not give examples here.
  • ⁇ L corresponds to the length of the waveguide where light is transmitted on the upper and lower phase shift arms of a single Mach-Zehnder interference structure (MZI);
  • L ⁇ corresponds to the length of light traveling on the upper and lower phase shift arms of a single Mach-Zehnder interference structure (MZI) Transmission produces a waveguide length that is phase shifted by ⁇ .
  • an approximately rectangular waveform can be synthesized, which realizes widening the flat-top band bandwidth of each flat-top wavelength division multiplexing structure 110, so that it can cover the incident light respectively received by its two input ports.
  • the frequency band range corresponding to the center wavelength plus the preset offset threshold.
  • each flat-top wavelength division multiplexing structure 110 By designing each flat-top wavelength division multiplexing structure as a form of digital filter, the flat-top bandwidth of each flat-top wavelength division multiplexing structure 110 can be widened so that it can tolerate the waveguide width , waveguide inclination angle, waveguide height and temperature changes caused by the center wavelength shift problem, and no need to set any feedback adjustment, not only improves the work efficiency, but also reduces the device loss.
  • FIG. 5 is a schematic diagram of using an arrayed waveguide grating structure as a flat-top wavelength division multiplexing structure in an embodiment of the present application.
  • each of the flat-top wavelength division multiplexing structures is composed of an arrayed waveguide grating structure
  • the arrayed waveguide grating structure (Array Waveguide Gratings, AWG) 130 includes a plurality of arrayed waveguides 131 (also referred to as waveguide channels), and the arrayed waveguides 131 adopt a linear waveguide structure.
  • the number of channels of the arrayed waveguide 131 is 6, of course, it can also be other numbers, which is not limited in this patent.
  • the arrayed waveguide grating structure 130 is fabricated on a silicon on insulator (Silicon On Insulator, SOI) material using an etching process.
  • SOI silicon on Insulator
  • the SOI material includes a top layer of silicon, a buried oxide layer of silicon dioxide, and a substrate silicon.
  • the thickness of the top layer of silicon is 220nm
  • the arrayed waveguide 131 and other structures can be formed on the top layer of silicon by etching, and the etching depth is, for example, 220nm.
  • the two incident optical signals ⁇ 1 and ⁇ 3 are synthesized into a first-stage multiplexed optical signal ( ⁇ 1/ ⁇ 3) after phase modulation by multiple arrayed waveguides 131 in the arrayed waveguide grating structure 130 .
  • the two incident optical signals ⁇ 2 and ⁇ 4 are synthesized into a bundle of first-stage multiplexed optical signals ( ⁇ 2/ ⁇ 4) after being phase-modulated by multiple arrayed waveguides 131 in the arrayed waveguide grating structure 130 .
  • the arrayed waveguide grating structure 130 can also widen the flat-top wavelength band bandwidth of the flat-top wavelength division multiplexing structure, so that it can cover the incident light respectively received by its two input ports.
  • the frequency band range corresponding to the central wavelength plus the preset offset threshold, and compared to the flat-top wavelength division multiplexing structure composed of multiple cascaded Mach-Zehnder interferometer structures, the above-mentioned array grating structure 130 has It has the advantages of compact structure, small size, low insertion loss, narrow wavelength division multiplexing interval and low process difficulty.
  • FIG. 6 is a schematic diagram of using an etched diffraction grating structure as a flat-top wavelength division multiplexing structure in an embodiment of the present application.
  • each of the flat-top wavelength division multiplexing structures is composed of an etched diffraction grating structure.
  • the etched diffraction grating structure 140 includes an input waveguide (141, 142) , an output waveguide 143, a Rowland circle 144, and a concave grating 145.
  • the inside of the Rowland circle 144 is a free propagation area, and the reflective surface of the concave grating 145 is composed of multiple sub-curved surfaces (not shown in the figure), and the multiple sub-curved surfaces can realize the decomplexing of optical signals use.
  • both the input waveguide ( 141 , 142 ) and the output waveguide 143 are arranged on the Rowland circle 144 .
  • the two incident optical signals ⁇ 1 and ⁇ 3 When working, the two incident optical signals ⁇ 1 and ⁇ 3 generate two input mode spots after passing through the interior of the Rowland circle 144, and then the two input mode spots enter the free propagation area of the Rowland circle 144 and propagate, incident on the reflection of the concave grating 145 surface, after being reflected and focused by the concave grating 145, a bundle of first-stage multiplexed optical signals ( ⁇ 1/ ⁇ 3) is output from the output waveguide 143.
  • the two incident optical signals ⁇ 2 and ⁇ 4 pass through the interior of the Rowland circle 144, two input mode spots are generated, and then the two input mode spots enter the free propagation area of the Rowland circle 144 to propagate, and are incident on the reflection of the concave grating 145 surface, after being reflected and focused by the concave grating 145, a bundle of first-stage multiplexed optical signals ( ⁇ 2/ ⁇ 4) is output from the output waveguide 143.
  • the above-mentioned flat-top wavelength division multiplexing structure composed of the etched diffraction grating structure 140 can also widen the flat-top wavelength band bandwidth of the flat-top wavelength division multiplexing structure, so that it can cover the signals received by its two input ports respectively.
  • the central wavelength of the incident light plus the frequency band corresponding to the preset offset threshold, and the above-mentioned etched diffraction grating structure 140 is relatively multiple In terms of structure, the requirements for processing accuracy are low, the overall integration is high, the size of the output waveguide is relatively small, and the overall size is more optimized.
  • FIG. 7 is a schematic diagram of a flat-top wavelength division multiplexing structure using a combined structure composed of a mode multiplexing device and a multimode Bragg grating in an embodiment of the present application.
  • each of the flat top wavelength division multiplexing structures 110 is composed of a combined structure of a mode multiplexing device 151 and a multimode Bragg grating 152, wherein the mode multiplexing device 151 For making the input light incident into the multimode Bragg grating 152, the mode multiplexing device 151 includes a first port, a second port and a third port, and the first port and the second port are respectively used for input or output For optical signals, the third port is connected to the output port of the multimode Bragg grating 152 .
  • two incident optical signals ⁇ 1 and ⁇ 3 are input to the first port of the mode multiplexer 151 and to the input port of the multimode Bragg grating 152, for example,
  • the incident optical signal of wavelength ⁇ 3 such as TE0 mode
  • the polarization state mode of the incident optical signal of wavelength ⁇ 3 TE0
  • the incident optical signal (for example, TE0 mode) of the ⁇ 1 wavelength passes through the mode multiplexer 151 and is converted into TE1 mode or higher-order mode light and is transmitted from the
  • the third port of the mode multiplexer 151 is incident into the multimode Bragg grating 152, and is converted into the TE0 mode after being reflected by the multimode Bragg grating 152, and then the optical signal of the wavelength ⁇ 1 passes through the
  • two incident optical signals ⁇ 2 and ⁇ 4 are respectively input to the first port of the mode multiplexer 151 and input to the input port of the multimode Bragg grating 152.
  • the incident optical signal of wavelength ⁇ 4 such as TE0 mode
  • the polarization state mode of the optical signal of wavelength ⁇ 4 TE0
  • the second port of the mode multiplexer 151 exits; and the incident optical signal (such as TE0 mode) of the ⁇ 2 wavelength passes through the mode multiplexer 151 and is converted into the TE1 mode or the light of a higher order mode is multiplexed from the mode
  • the third port of the device 151 is incident into the multi-mode Bragg grating 152, and after being reflected by the multi-mode Bragg grating 152, it is transformed into a TE0 mode, and then the optical signal
  • the output first-stage multiplexed signal ( ⁇ 2/ ⁇ 4 ), which is still linearly polarized in TE0 mode.
  • the above-mentioned flat-top wavelength division multiplexing structure using a combined structure composed of a mode multiplexing device and a multimode Bragg grating can also widen the flat-top wavelength band bandwidth of the flat-top wavelength division multiplexing structure, so that it can cover two The frequency band range corresponding to the center wavelength of the incident light received by the input ports plus the preset offset threshold.
  • FIG. 8 is a schematic diagram of using an inverted Bragg grating directional coupler structure as a flat-top wavelength division multiplexing structure in an embodiment of the present application.
  • each of the flat top wavelength division multiplexing structures 110 is composed of a reverse Bragg grating directional coupler structure
  • the reverse Bragg grating directional coupler 160 includes a first reverse A Bragg grating directional coupling structure 161 and a second inverse Bragg grating directional coupling structure 162 .
  • two incident light signals ⁇ 1 and ⁇ 3 are respectively input from the forward port of the second reverse Bragg grating directional coupling structure 162 and the reverse port of the first reverse Bragg grating directional coupling structure 161, Since the ⁇ 3 wavelength optical signal is input from the reverse port of the first inverse Bragg grating directional coupling structure 161, the first inverse Bragg grating directional coupling structure 161 has no effect on the ⁇ 3 wavelength optical signal (TE), The ⁇ 3 wavelength optical signal is directly emitted from the forward port of the first reversed Bragg grating directional coupling structure 161; port input, so the second reverse Bragg grating directional coupling structure 162 acts on the ⁇ 1 wavelength optical signal (TE), and the ⁇ 1 wavelength optical signal is input from the forward port of the second reverse Bragg grating directional coupling structure 162 Afterwards, it will run into the first reverse Bragg grating directional coupling structure 161 near the center position of the second reverse
  • the optical signal ⁇ 4 (TE) input at the reverse port of the first reverse Bragg grating directional coupling structure 161 and the optical signal ⁇ 4 (TE) input at the second reverse Bragg grating directional coupling structure 162 The optical signal ⁇ 2(TE) input to the forward port finally generates the second-stage combined optical signal ( ⁇ 2(TE)/ ⁇ 4(TE )).
  • the flat-top wavelength division multiplexing structure using the reverse Bragg grating directional coupler structure can also widen the flat-top wavelength band bandwidth of the flat-top wavelength division multiplexing structure, so that it can cover the signals received by its two input ports respectively.
  • the at least two flat-top wavelength division multiplexing structures are composed of any combination of the following structures: multiple cascaded Mach-Zehnder interference structures, arrayed waveguide grating structures, Etched diffraction grating structure, combined structure of mode multiplexer and multimode Bragg grating, reversed Bragg grating directional coupler structure.
  • FIG. 9 is a simulated spectrum diagram of a flat-top wavelength division multiplexing structure composed of any combination of multiple cascaded Mach-Zehnder interference structures, arrayed waveguide grating structures, and etched diffraction grating structures in an embodiment of the present application.
  • FIG. 10 is a spectrum diagram of light beams whose center wavelength is around 1291 nm in the spectrum diagram shown in FIG. 9 .
  • the first-stage multiplexing module 100 is composed of any combination of the plurality of cascaded Mach-Zehnder interference structures, the arrayed waveguide grating structure and the etched diffraction grating structure, the final generated total
  • the simulated spectrum diagram of is shown in Figure 9, in which, a flat-top WDM structure with TE (Transverse Electric mode (transverse electric mode) polarization mode realizes the sharing of channels (channels) whose center wavelengths are respectively 1271nm/1311nm (Wavelength), and another flat-top wavelength division multiplexing structure uses TM (Transverse The Magnetic mode (transverse magnetic mode) polarization mode realizes the sharing of channels whose center wavelengths are respectively 1291nm/1331nm wavelength (Wavelength).
  • the finally generated second-stage multiplexing signal includes a first group of light wave components and a second group of light wave components, wherein the first group of light wave components and the second group of light wave components have different polarization states.
  • the flat-top band bandwidth of the optical channel corresponding to the center wavelength of 1291nm is close to 34nm, therefore, even if the corresponding wavelength division multiplexing structure is affected by factors such as waveguide width, height, inclination angle and temperature change
  • the beam with a center wavelength of 1291nm shifts to the long wavelength band (red shift) or shifts to the short wavelength band (blue shift), it can also ensure that the center wavelength is 1291nm ⁇ 6nm in the range of flat areas.
  • the first-stage multiplexed optical signal generated in the optical channel (channel) can tolerate the influence of waveguide width, height, inclination angle and temperature changes on the central wavelength shift, reducing the influence on waveguide width, height or inclination angle. sensitivity.
  • Figure 11 is a set of light waves generated by using a flat-top wavelength division multiplexing structure composed of a combined structure composed of a mode multiplexer and a multimode Bragg grating, and an arbitrary combination of an inverted Bragg grating directional coupler structure in an embodiment of the present application
  • the simulation spectrogram of the component, Fig. 12 is the flat top wavelength division multiplexing that adopts the combination structure that is formed by mode multiplexer and multimode Bragg grating, the arbitrary combination of reverse Bragg grating directional coupler structure in one embodiment of the present application A simulated spectrum plot of another set of light wave components generated by the structure.
  • the bandwidth of the flat-top band of the beam path with a center wavelength of 1291nm is greater than 12nm, which can ensure that the center wavelength is 1291nm ⁇ 6nm in the flat area, and the bandwidth of the flat-top band of the beam path with a center wavelength of 1331nm It is also greater than 12nm, which can ensure that the center wavelength is in the range of 1331nm ⁇ 6nm to be a flat region.
  • the bandwidth of the flat-top band of the beam path with a central wavelength of 1271nm is greater than 12nm, which can ensure a flat area within the range of the central wavelength of 1271nm ⁇ 6nm, and the bandwidth of the flat-top band of the beam path with a central wavelength of 1311nm is greater than 12nm, which can ensure that the center wavelength is 1311nm ⁇ 6nm in the range of flat areas.
  • the center wavelength band shifts to the long-wave band (red shift) or shift to the short-wavelength band (blue shift)
  • the center wavelength is within the range of ⁇ 6nm are flat areas. That is to say, the first-stage multiplexed optical signal generated in the optical channel can tolerate the influence of factors such as waveguide width, height, inclination angle and temperature changes on the central wavelength shift, reducing the impact of the flat-top wavelength division multiplexing structure on the waveguide width, Altitude or inclination sensitivity.
  • FIG. 13 is a schematic structural diagram of an on-chip integrated wavelength division multiplexer provided by another embodiment of the present application
  • FIG. 14 is a structural schematic diagram of a polarization rotator (PR) in the on-chip integrated wavelength division multiplexer shown in FIG. 13
  • FIG. 15 is a schematic structural diagram of a polarization beam combiner (PBC) in the on-chip integrated wavelength division multiplexer shown in FIG. 13 .
  • PR polarization rotator
  • PBC polarization beam combiner
  • the second-stage multiplexing module in the on-chip integrated wavelength division multiplexer 2000 is a polarization beam combiner (Polarization Beam Combiner, PBC) 230
  • the on-chip integrated wavelength division multiplexer 2000 also includes a polarization rotator (polarization rotator, PR) 220
  • the input port of the polarization rotator 220 is connected with one of the first multiplexing module 100
  • the output port is optically coupled to receive light output by the output port
  • the output port of the polarization rotator 220 is optically coupled to an input port of the polarization beam combiner 230, so as to output light to the polarization beam combiner 230
  • the polarization beam combiner 230 is used to combine two received light beams with different polarization states into one light beam
  • the polarization rotator 220 is used to change the polarization state of the received light beams.
  • the first-stage multiplexing module 100 has a plurality of input ports and two output ports; the polarization beam combiner 230 includes two input ports and one output port; the first-stage multiplexing module 100 The two output ports of the polarization beam combiner are respectively connected to the two input ports of the polarization beam combiner 230; the multiple incident optical signals ( ⁇ 1, ⁇ 2, ⁇ 3, ⁇ 4 (the wavelengths are arranged in ascending order)) with the same polarization state are respectively sent to the A plurality of input ports of the first-stage multiplexing module 100 are input, and after the multiplexing of the first-stage multiplexing module 100, the two output ports of the first-stage multiplexing module 100 output two first-stage Among the multiplexed optical signals, one path is directly optically coupled to an input port of the polarization beam combiner 230, so as to input the first-stage multiplexed optical signal to an input port of the polarization beam combiner 230; The polarization rotator 220 is optically coupled to
  • the polarization rotator (PR) 220 and the polarization beam combiner (PBC) 230 may also be silicon-based polarization rotators (PR) and silicon-based polarization beam combiners (PBC).
  • the polarization rotator 220 is used to change the original polarization state of the received light beam to a polarization state perpendicular to the original polarization state.
  • the polarization rotator (PR) 220 includes a ridge waveguide 221 and a part of the planar waveguide 222 on one side of the ridge waveguide 221 .
  • the ridge waveguide 221 includes a first wedge structure 221a, a linear structure 221b and a second wedge structure 221c connected in sequence.
  • the first wedge-shaped structure 221a is used as the input end of the polarization rotator 220, and its width gradually narrows along the optical path until it is flush with and connected to the linear structure 221b; the width of the second wedge-shaped structure 221c gradually widens along the optical path until it is in line with the external light waveguide connection.
  • Part of the planar waveguide 222 has a height lower than that of the ridge waveguide 221 and includes a third wedge structure 222 a and a fourth wedge structure 222 b located on the same side of the ridge waveguide 221 and connected to each other.
  • the third wedge-shaped structure 222a is close to the side of the first wedge-shaped structure 221a
  • the fourth wedge-shaped structure 222b is close to the side of the linear structure 221b
  • the tip of the third wedge-shaped structure 222a is close to the side of the wider end of the first wedge-shaped structure 221a
  • the fourth wedge-shaped structure is adjacent to the narrower end of the second wedge-shaped structure 221c.
  • Linearly polarized light is incident from the wider end of the first wedge-shaped structure 221a of the ridge waveguide 221, and in the section of the first wedge-shaped structure 221a and the linear structure 221b, the light mode is distributed into the ridge waveguide 221 and the planar waveguide 222, so that its polarization state is rotated , the polarization state has been rotated by 90 degrees when incident on the second wedge-shaped structure 221c, and then coupled into the external optical waveguide through the second wedge-shaped structure 221c.
  • the polarization rotator-beam combiner (PSR) shown in Figure 3 can also be used as the polarization rotator.
  • the linearly polarized light is incident from the cross port, coupled to the straight-through waveguide through the cross waveguide, and finally output through the mode conversion structure The polarization state of linearly polarized light is rotated by 90 degrees.
  • the polarization beam combiner 230 is composed of three identical mode conversion couplers, and each mode conversion coupler includes a single-mode access waveguide and a multi-mode bus waveguide.
  • the first mode conversion coupler 231 and the second mode conversion coupler 232 are connected in parallel and located at the input end of the polarization beam combiner 230 .
  • the single-mode access waveguide 231a of the above-mentioned first mode conversion coupler 231 and the single-mode access waveguide 232a of the second mode conversion coupler 232 are respectively connected to the output end of the polarization rotator 220 and a flat-top wavelength division multiplexing structure 110. output.
  • the third mode conversion coupler 233 cascades the above two mode conversion couplers 231, 232, and the multimode bus waveguide 233b of the third mode conversion coupler 233 is connected to the output end of the multimode bus waveguide 231b of the first mode conversion coupler 231 , the single-mode access waveguide 233a of the third mode conversion coupler 233 is connected to the output end of the single-mode access waveguide 232a of the second mode conversion coupler 232 .
  • the polarization beam combiner 230 composed of three mode conversion couplers combined with the polarization rotator 220 is used to pair the two first channels with the same linear polarization state output by the two flat top wavelength division multiplexing structures 110. Polarized beam combining is performed on the multiplexed optical signals to reduce crosstalk.
  • the mode conversion coupler since the mode conversion coupler has the characteristics of low loss and large bandwidth, the optical loss is further reduced, and the optical bandwidth of the device is improved.
  • Fig. 16 is a schematic structural diagram of an on-chip integrated wavelength division multiplexer provided by another embodiment of the present application.
  • the second-stage multiplexing module 200 in this embodiment is Polarization beam combiner (Polarization Beam Combiner, PBC) 230
  • said on-chip integrated wavelength division multiplexer 3000 also includes at least one polarization rotator (polarization rotator, PR) 220, for each said polarization rotator 220, its input The port is used to receive one of the incident light, and its output port is optically coupled with the input port of one of the at least two flat-topped wavelength division multiplexing structures 110, so as to output light to the flat-topped wavelength division multiplexing structure 110
  • the polarization beam combiner 230 is used to combine two received light beams with different polarization states into one light beam
  • the polarization rotator 220 is used to change the polarization state of the received light beams, and the The light whose polarization
  • the first-stage multiplexing module 100 has multiple input ports and two output ports; the polarization beam combiner 230 includes two input ports and one output port; the flat The two output ports of the top broadband wavelength division multiplexing combination structure 100 are respectively connected to the two input ports of the polarization beam combiner 230; for each of the polarization rotators 220, its output port is used to receive one incident light, For changing the polarization state of the received light beam, at least two incident optical signals are respectively optically coupled to the input port of one of the flat-top wavelength division multiplexing structures 110 through the corresponding polarization rotator 220, through the The polarization rotator 220 rotates the polarization states of the at least two incident optical signals by 90° and then couples them to an input port of the on-chip integrated wavelength division multiplexer 110 of the flat top broadband, and then the flat top wavelength division
  • the output port of the multiplexing structure 110 outputs the first-stage multiplexed optical signal after multiplexing; at least two incident optical signals are
  • the present application also proposes a chip, which includes the on-chip integrated wavelength division multiplexer described in any one of the foregoing embodiments.
  • the bandwidth of each flat-top wavelength division multiplexing structure in the first-level multiplexing module can cover the bandwidth received by its two input ports respectively.

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Abstract

一种片上集成波分复用器（1000）及芯片，片上集成波分复用器（1000）包括第一级复用模块（100）和第二级复用模块（200），第一级复用模块（100）具有多个输入端口和两个输出端口，第二级复用模块（200）具有两个输入端口和一个输出端口，第一级复用模块（100）的两个输出端口分别与第二级复用模块（200）对应的输入端口光耦合；其中，第一级复用模块（100）包括两个平顶波分复用结构（110、120），每个平顶波分复用结构（110、120）的带宽覆盖由其两个输入端口分别接收到的入射光的中心波长加上预设的偏移量阈值对应的频带范围。第一级复用模块（100）生成的两路第一级合波光信号的平顶波段带宽较宽，从而避免了各种因素导致的中心波长偏移所引起的相邻通道串扰问题，且无需任何反馈调节，提高了工作效率，降低了器件损耗。

Description

片上集成波分复用器及芯片 技术领域
本申请涉及光通信技术领域，具体涉及一种片上集成波分复用器及芯片。
 背景技术
在高速和大容量的光通信中，波分复用（wavelength Division Multiplexing，WDM）是一项用于提高光通信容量的有效手段，同时结合光子集成芯片，可有效减小器件的尺寸，提高***的集成度，其关键器件是波分复用器件（MUX）和波分解复用器件（DEMUX）。
如图1所示，以四通道的波分复用为例，现有的硅光芯片中的基于级联马赫-曾德尔干涉仪（MZI）结构的波分复用器由3个通过并联及级联方式连接的马赫-曾德尔干涉仪10’构成，其中，每个马赫-曾德尔干涉仪10’包括两个2×2的3dB耦合器11’和两个连接臂12’、一个监视探测器13’，其中一个连接臂为可调相移臂(图中以虚线表示)。上述现有的波分复用器在使用时需要结合监视探测器13’对级联的各个马赫-曾德尔干涉仪10’的可调相移臂进行调节，由此导致调节过程不方便，功耗较大。此外，3dB耦合器11’的光学带宽有限，因此，多个级联的马赫-曾德尔干涉仪10’的波分复用器的光路中具有多个3dB耦合器11’，显著降低了波分复用器的性能。
理想的波分复用器件应该是纯被动而不需要进行调节的，然而，由于硅基波分复用器中的光波导器件会受到加工工艺引起的宽度、倾角变化、硅片波导厚度的变化以及温度的变化等影响，造成硅基波分复用器件的中心波长的偏移，由此，现有的硅基波分复用器件的中心波长的偏移会引起相邻通道的光信号之间发生串扰。
 技术问题
本申请的目的在于提供一种片上集成波分复用器及芯片，用以改善相邻通道的光信号之间的串扰问题，并且具有低功耗和光学带宽较大的优点。
 技术解决方案
根据本申请的一个方面，提供了一种片上集成波分复用器，其包括第一级复用模块和第二级复用模块，所述第一级复用模块具有多个输入端口和两个输出端口，所述第二级复用模块具有两个输入端口和一个输出端口，所述第一级复用模块的所述两个输出端口分别与所述第二级复用模块对应的输入端口光耦合；所述第一级复用模块包括至少两个平顶波分复用结构，每个所述平顶波分复用结构具有两个输入端口和一个输出端口，其中，每个所述平顶波分复用结构的带宽覆盖由其两个输入端口分别接收到的入射光的中心波长加上预设的偏移量阈值对应的频带范围。
根据本申请的一个实施例，所述第一级复用模块将由所述多个输入端口接收到的具有同一偏振态的入射光进行合波以生成两路第一级合波光信号，并将所述两路第一级合波光信号分别输入至所述第二级复用模块对应的输入端口，所述第二级复用模块将其两个输入端口接收到的所述两路第一级合波光信号进行合波以生成第二级合波光信号，其中，所述第二级合波光信号包含第一组光波分量和第二组光波分量，所述第一组光波分量和第二组光波分量具有不同的偏振态；所述第二级复用模块对第一组光波分量和第二组光波分量进行偏振合波。。
根据本申请的一个实施例，当把具有预定波长间隔的λ1、λ2、λ3……λn波长分割光信号输入所述第一级复用模块的所述多个输入端口时，其中n≥4，且n为偶数；针对每个所述平顶波分复用结构，从所述平顶波分复用结构的一个输入端口输入奇数信道的入射光信号，从所述平顶波分复用结构的另一个输入端口输入偶数信道的入射光信号。
根据本申请的一个实施例，所述至少两个平顶波分复用结构由下列结构的任意组合构成：多个级联的马赫-曾德尔干涉结构、阵列波导光栅结构、刻蚀衍射光栅结构、模式复用器和多模布拉格光栅构成的组合结构、反向布拉格光栅定向耦合器结构。
根据本申请的一个实施例，所述片上集成波分复用器是硅基波分复用器。
根据本申请的一个实施例，每个所述平顶波分复用结构的两个输入端口接收到的入射光的中心波长之间的差值大于预设的波长差阈值。
根据本申请的一个实施例，所述片上集成波分复用器还包括耦合结构，所述耦合结构与所述第二级复用模块的输出端口相连，用于将所述第二级复用模块的输出端口输出的所述第二级合波光信号与外部光纤阵列进行耦合，以将合波完成的光信号进行输出。
根据本申请的一个实施例，所述第二级复用模块是偏振旋转分束器，所述偏振旋转分束器将接收到的所述两路第一级合波光信号合波成具有相互垂直的偏振态的所述第一组光波分量和所述第二组光波分量。
根据本申请的一个实施例，所述偏振旋转分束器包括直通波导和交叉波导、分别连接所述直通波导和交叉波导的直通端口和交叉端口，以及连接所述直通波导的模式变换结构；所述直通波导与所述交叉波导组成模式复用结构；所述直通端口和交叉端口均包括条波导转脊波导的楔形结构；所述模式变换结构为双层楔形的模式变换结构。
根据本申请的一个实施例，所述第二级复用模块是偏振合束器，所述片上集成波分复用器还包括偏振旋转器，所述偏振旋转器的输入端口与所述第一复用模块的一个输出端口光耦合，以接收该输出端口输出的光，所述偏振旋转器的输出端口与所述偏振合束器的一个输入端口光耦合，以向所述偏振合束器输出光，其中，所述偏振合束器用于将接收到的两路具有不同偏振态的光束合波成一路光束，所述偏振旋转器用于改变接收到的光束的偏振态；其中，所述偏振旋转器将接收到的光束的原始偏振态改变成与所述原始偏振态垂直的偏振态。
根据本申请的一个实施例，所述第二级复用模块是偏振合束器，所述片上集成波分复用器还包括至少一个偏振旋转器，针对每个所述偏振旋转器，其输入端口用于接收一路所述入射光，其输出端口与所述至少两个平顶波分复用结构中的一个的输入端口光耦合，以向该平顶波分复用结构输出光，其中，所述偏振合束器用于将接收到的两路具有不同偏振态的光束合波成一路光束，所述偏振旋转器用于改变接收到的光束的偏振态，并且由所述至少一个偏振旋转器改变偏振态的光仅由所述第一级复用模块的一个输出端口输出；其中，每个所述偏振旋转器将接收到的光束的原始偏振态改变成与所述原始偏振态垂直的偏振态。
根据本申请的一个实施例，每个所述平顶波分复用结构包括至少两个1dB平顶，其中，每个1dB平顶是光衰减1dB范围内所对应的波长范围，每个1dB平顶所对应的波长范围大于20纳米。
根据本申请的一个实施例，同一个平顶波分复用结构的相邻的两个1dB平顶的间隔小于5纳米。
根据本申请的一个实施例，所述至少两个平顶波分复用结构中，其中一个的平顶波分复用结构中的1dB平顶所对应的波长范围与其中另一个的平顶波分复用结构中的1dB平顶所对应的波长范围部分重叠。
根据本申请的又一方面，提供了一种芯片，所述芯片包括前述任一实施例所述的片上集成波分复用器。
 有益效果
在本申请实施例提供的片上集成波分复用器及芯片中，第一级复用模块中的每个平顶波分复用结构的带宽能够覆盖由其两个输入端口分别接收到的入射光的中心波长加上预设的偏移量阈值对应的频带范围，由此使得第一级复用模块生成的两路第一级合波光信号的平顶波段带宽较宽，能够覆盖由各种因素导致的中心波长偏移所引起的相邻通道串扰问题，实现了对不同波长的入射光信号的复用；此外，第一级复用模块以及第二级复用模块在工作过程中，无需任何反馈调节，提高了工作效率，降低了器件损耗，并有利于降低片上集成波分复用器对波导宽度、波导高度以及波导倾角的敏感性。
 附图说明
下面结合附图，通过对本申请的具体实施方式详细描述，将使本申请的技术方案及其它有益效果显而易见。
图1为现有的硅光芯片中的MZI型片上集成波分复用器的结构示意图；
图2a为本申请一实施例提供的片上集成波分复用器的结构示意图；
图2b为本申请另一实施例提供的片上集成波分复用器的结构示意图；
图2c为本申请又一实施例提供的片上集成波分复用器的结构示意图；
图3为本申请实施例中的偏振旋转分束器(PSR)的结构示意图;
图4a-图4e是本申请实施例中采用多个级联的马赫-曾德尔干涉结构构成平顶波分复用结构的多种实施方式的示意图；
图5为本申请一实施例中采用阵列波导光栅结构作为平顶波分复用结构的示意图；
图6为本申请一实施例中采用刻蚀衍射光栅结构作为平顶波分复用结构的示意图；
图7为本申请一实施例中采用模式复用器件和多模布拉格光栅构成的组合结构作为平顶波分复用结构的示意图；
图8为本申请一实施例中采用反向布拉格光栅定向耦合器结构作为平顶波分复用结构的示意图；
图9为本申请一实施例中采用由多个级联的马赫-曾德尔干涉结构、阵列波导光栅结构、刻蚀衍射光栅结构的任意组合构成的平顶波分复用结构的仿真光谱图；
图10为图9示出的光谱图中的中心波长为1291nm附近的光束的光谱图；
图11为本申请一实施例中采用由模式复用器和多模布拉格光栅构成的组合结构、反向布拉格光栅定向耦合器结构的任意组合构成的平顶波分复用结构生成的一组光波分量的仿真光谱图；
图12为本申请实施例中采用由模式复用器和多模布拉格光栅构成的组合结构、反向布拉格光栅定向耦合器结构的任意组合构成的平顶波分复用结构生成的另一组光波分量的仿真光谱图；
图13为本申请又一实施例提供的片上集成波分复用器的结构示意图；
图14为图13示出的片上集成波分复用器中的偏振旋转器(PR)的结构示意图；
图15为图13示出的片上集成波分复用器中的偏振合束器(PBC)的结构示意图；
图16为本申请又一实施例提供的片上集成波分复用器的结构示意图。
 本发明的实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述。显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
文中的术语“第一”、“第二”仅用于描述目的，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量。由此，限定有“第一”、“第二”的特征可以明示或者隐含地包括一个或者更多个所述特征。在本申请的描述中，“多个”的含义是两个或两个以上，除非另有明确具体的限定。
在本申请的描述中，需要说明的是，除非另有明确的规定和限定，术语“安装”、“相连”、“连接”应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或一体地连接；可以是机械连接，也可以是电连接或可以相互通讯；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通或两个元件的相互作用关系。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本申请中的具体含义。
下文的公开提供了许多不同的实施方式或例子用来实现本申请的不同结构。为了简化本申请的公开，下文中对特定例子的部件和设置进行描述。当然，它们仅仅为示例，并且目的不在于限制本申请。此外，本申请可以在不同例子中重复参考数字和/或参考字母，这种重复是为了简化和清楚的目的，其本身不指示所讨论各种实施方式和/或设置之间的关系。
图2a-图2c为本申请一实施例提供的片上集成波分复用器的结构示意图，图3为本申请实施例中的偏振旋转分束器的结构示意图。
参阅图2a-图2c以及图3所示，本申请一实施例提供了一种片上集成波分复用器1000，其包括第一级复用模块100和第二级复用模块200。所述第一级复用模块100具有多个输入端口和两个输出端口，所述第二级复用模块200具有两个输入端口和一个输出端口，所述第一级复用模块100的所述两个输出端口分别与所述第二级复用模块200对应的输入端口光耦合；所述第一级复用模块100将由所述多个输入端口接收到的具有同一偏振态的入射光进行合波以生成两路第一级合波光信号，并将所述两路第一级合波光信号分别输入至所述第二级复用模块200对应的输入端口。所述第二级复用模块200将其两个输入端口接收到的所述两路第一级合波光信号进行合波以生成第二级合波光信号，其中，所述第二级合波光信号包含第一组光波分量和第二组光波分量，所述第一组光波分量和第二组光波分量具有不同的偏振态。所述第一级复用模块100由至少两个平顶波分复用结构（110、120）组成，每个所述平顶波分复用结构（110、120）具有两个输入端口和一个输出端口，其中，每个所述平顶波分复用结构（110、120）的带宽覆盖由其两个输入端口分别接收到的入射光的中心波长加上预设的偏移量阈值对应的频带范围。
 
在本实施例提供的片上集成波分复用器中，第一级复用模块中的每个平顶波分复用结构的带宽能够覆盖由其两个输入端口分别接收到的入射光的中心波长加上预设的偏移量阈值对应的频带范围，由此使得所述第一级复用模块生成的两路第一级合波光信号的平顶波段带宽较宽，能够覆盖由各种因素导致的中心波长偏移所引起的相邻通道串扰问题，此外，第一级复用模块以及第二级复用模块在工作过程中，无需任何反馈调节，提高了工作效率，降低了器件损耗，并有利于降低片上集成波分复用器对波导宽度、波导高度、波导倾角以及周围环境温度变化的敏感性。
以下将结合图2a至图3，进一步详细描述片上集成波分复用器1000的结构及工作机制。
参阅图2a所示，示例性地，在本实施例中，以λ1，λ2，λ3，λ4（波长从小到大排列）四波长的片上集成波分复用器为例，所述片上集成波分复用器1000包括第一级复用模块100和第二级复用模块200，该第一级复用模块100由至少两个平顶波分复用结构（110、120）并联组成，该第二级复用模块200是集成的偏振旋转分束器。在本实施例中，每个所述平顶波分复用结构110具有两个输入端口和一个输出端口，所述偏振旋转分束器200包括两个输入端口和一个输出端口，两个所述平顶波分复用结构110的两个输出端口分别连接所述偏振旋转分束器200的两个输入端口，用于进行光耦合；所述偏振旋转分束器200的输出端口用于输出合成光束。
具体地，λ1和λ3的两路入射光信号由一个平顶波分复用结构110的两个输入端口输入，λ2和λ4的两路入射光信号由另一个平顶波分复用结构120的两个输入端口输入，每个所述平顶波分复用结构（110、120）的平顶波段带宽均能够覆盖由其两个输入端口分别接收到的入射光的中心波长加上预设的偏移量阈值对应的频带范围，即平顶波分复用结构110的带宽大于λ1±Δλ和λ3±Δλ，平顶波分复用结构120的带宽大于λ2±Δλ和λ4±Δλ（其中Δλ是***对片上集成波分复用器件需求的通带宽度），以实现对不同波长的入射光信号的复用，由于由该平顶波分复用结构110的带宽较宽，每个平顶波分复用结构能够传输两路中心波长相差较大的光束，故其能够容忍由于波导宽度、波导倾角、波导高度以及温度变化影响所引起的中心波长偏移带来的相邻通道之间的串扰问题。
上述片上集成波分复用器是硅基波分复用器，其包括硅基衬底，在硅基衬底上设置有第一级复用模块100和第二级复用模块200；当然也可以是基于其它衬底的片上集成波分复用器结构，本发明在此不做限制。
当把具有预定波长间隔的λ1、λ2、λ3……λn波长分割光信号输入所述第一级复用模块的所述多个输入端口时，其中n≥4，且n为偶数；针对每个所述平顶波分复用结构，从所述平顶波分复用结构的一个输入端口输入奇数信道的入射光信号，从所述平顶波分复用结构的另一个输入端口输入偶数信道的入射光信号。即将λ1和λ3分别输入一个所述平顶波分复用结构的两个输入端口进行合波、将λ2和λ4分别输入另一个所述平顶波分复用结构的两个输入端口进行合波，采用这种错位的合波方式，能够使得每个所述平顶波分复用结构（110、120）的两个输入端口接收到的入射光的中心波长之间的差值较大，由此防止在同一通道内相邻波段之间的串扰影响。
每个所述平顶波分复用结构（110、120）的两个输入端口接收到的入射光的中心波长之间的差值大于预设的波长差阈值。以4个（λ1、λ2、λ3、λ4）波长分割光信号为例，λ1和λ2之间的波长差值大于或等于20nm，λ3和λ4之间的波长差值大于或等于20nm，λ1和λ3之间的波长差值大于或等于40nm，λ2和λ4之间的波长差值大于或等于40nm。当然每个所述平顶波分复用结构（110、120）的两个输入端口接收到的入射光的中心波长之间的差值也可以根据实际应用情况进行设定。
需要说明的是，在该实施例中，针对每个平顶波分复用结构，由其构成片上集成波分复用器件的中心波长λ0损耗较小，且中心波长附近λ0±Δλ范围的损耗相比中心波长的损耗小于1dB以内。其中，λ0±Δλ称为该通道的1dB平顶范围。其中，每个1dB平顶是光衰减1dB范围内所对应的波长范围，该平顶波分复用结构中的每个1dB平顶所对应的波长范围大于20纳米。同一个平顶波分复用结构中相邻两个1dB平顶所对应的波长范围的间隔一定距离。两个平顶复用结构中的部分1dB平顶所对应的波长范围会有重合。具体，如图11和图12所示，图11可以代表其中一个平顶波复用结构的光谱图。从图中可以看到其具有至少两个1dB平顶（图中横轴平坦部分）。一个1dB平顶所对应的波长的中心波长在1291纳米，另一个1dB平顶所对应的波长的中心波长在1331纳米。每个1dB平顶所对应的波长范围约为40纳米（图中平坦部分的宽度）。图12可以代表其中另外一个平顶波复用结构的光谱图。从图中可以看到其也具有至少两个1dB平顶。一个1dB平顶所对应的中心波长在1271纳米，另一个1dB平顶所对应的中心波长在1311纳米。每个1dB平顶所对应的波长范围约为40纳米。两个平顶波分复用结构的1dB平顶所对应的波长范围中，中心波长1271纳米和中心波长1291纳米所对应的1dB平顶范围部分重合，中心波长1291纳米和中心波长1311纳米所对应的1dB平顶范围部分重合，中心波长1311纳米和中心波长1331纳米所对应的1dB平顶范围部分重合。但由于这些中心波长交叉分布于不同的平顶复用结构中，从而使这些中心波长的1dB平顶范围所对应的波长范围能够错开，以使能够实现合波的功能。另外，同一个平顶复用结构的相邻的两个1dB平顶可以间隔预定距离，以提高合波效果和吸收工艺公差。优选地，该间隔的预定距离可以小于5纳米。需要说明的是，本实施例中，相邻的两个1dB平顶的间隔是指两个1dB平顶边缘之间的距离，而非指两个1dB平顶的中心之间的距离。
应理解，如图2c所示，当把预定波长间隔且按照波长从小到大排列的λ1、λ2、λ3、λ4……λ7、λ8波长分割光信号输入所述第一级复用模块的所述多个输入端口时，同样地，采用错位的合波方式，从所述平顶波分复用结构的一个输入端口输入奇数信道的入射光信号，从所述平顶波分复用结构的另一个输入端口输入偶数信道的入射光信号。例如，将λ1、λ5输入一个所述平顶波分复用结构的两个输入端口进行合波，将λ3、λ7输入另一个所述平顶波分复用结构的两个输入端口进行合波，随后，将合波后的λ1/λ5与合波后的λ3/λ7再分别输入至同一个所述平顶波分复用结构的两个输入端口中进行合波，从而得到λ1/λ3/λ5/λ7的合波。将λ2、λ6输入一个所述平顶波分复用结构的两个输入端口进行合波，将λ4、λ8输入另一个所述平顶波分复用结构的两个输入端口进行合波，随后，将合波后的λ2/λ6与合波后的λ4/λ8再分别输入至同一个所述平顶波分复用结构的两个输入端口中进行合波，从而得到λ2/λ4/λ6/λ8的合波。可以理解的是，上述合波方式是采用平顶波分复用结构先把八路中的每两路合波形成四路后再把四路光波合成两路到达偏振旋转分束器，再由偏振旋转分束器进行偏振合波；在其它实施例中也可以把八路光信号中的其中四路（λ1/λ3/λ5/λ7）通过一个平顶波分复用结构合成一路，另外四路（λ2/λ4/λ6/λ8）通过另外一个平顶波分复用结构合成一路，然后再将这两个平顶波分复用结构合成后的光通过偏振旋转分束器合成一路。另外，当把更多预定波长间隔的λ1、λ2、λ3、λ4……λn波长分割光信号输入所述第一级复用模块的所述多个输入端口时，其中，n>8，且n为偶数，可基于同样的错位的合波方式来实现，在此不再赘述。
如图3所示，本实施例中的偏振旋转分束器（Polarization Split Rotator，PSR）210包括直通波导211和交叉波导212、分别连接直通波导211和交叉波导212的直通端口213和交叉端口214，以及连接直通波导211的模式变换结构215。这里，直通波导211与交叉波导212组成模式复用结构，直通端口213和交叉端口214均包括条波导转脊波导的楔形结构，作为偏振旋转分束器的输入端口。模式变换结构215为双层楔形的模式变换结构，作为偏振旋转分束器的输出端口，输出合波光信号。
如图2a-图3所示，在λ1、λ2、λ3、λ4（波长从小到大排列）四个波长的光信号中，λ1和λ3分别由两个平顶波分复用结构中的一个平顶波分复用结构110的两个输入端口输入，经所述平顶波分复用结构110合波后输出由λ1±Δλ/λ3±Δλ构成的第一级合波光信号；λ2和λ4分别由两个平顶波分复用结构中的另一个平顶波分复用结构120的两个输入端口输入，经所述平顶波分复用结构120合波后输出由λ2±Δλ/λ4±Δλ构成的第一级合波光信号。需要说明的是，上述四路入射的光信号λ1、λ3、λ2以及λ4均为线偏振光并且具有相同的偏振态，假设都为TE0（Transverse Electric mode，横电模）模式的线偏振光，经两个所述平顶波分复用结构（110、120）分别进行合波后，输出的第一级合波光信号依然为TE0模式的合束线偏振光。由TE0模式的合束线偏振光构成的两路第一级合波光信号（即合波后的λ1±Δλ/λ3±Δλ光信号和合波后的λ2±Δλ/λ4±Δλ光信号）分别由上述集成的偏振旋转分束器（PSR）210的直通端口213和交叉端口214输入，并分别进入直通波导211和交叉波导212。进入直通波导211内的λ2±Δλ/λ4±Δλ光信号偏振态不变，经由模式变换结构215后依然输出TE0模式的λ2±Δλ/λ4±Δλ光信号；进入交叉波导212内的λ1±Δλ/λ3±Δλ光信号耦合到直通波导211内，与直通波导211内的光信号进行模式复用，λ1±Δλ/λ3±Δλ光信号模式由TE0模式转成TE1（高阶）模式，经模式变换结构215变换为TM0（Transverse Magnetic mode，横磁模）模式（即偏振态改变）与原直通波导211内的TE0模式的λ2±Δλ/λ4±Δλ光信号合成一束包括TE0+TM0模式的线偏振光输出。
进一步地，如图2b所示，所述片上集成波分复用器1000还包括一个耦合结构300，所述耦合结构300与所述第二级复用模块200的输出端口相连，用于将所述第二级复用模块100的输出端口输出的合成一束的合波光信号（第二级合波光信号）与外部光纤阵列进行耦合，以将待调制的光信号进行输入以及将调制完成的光信号进行输出，其具有较高的耦合效率，能够降低整个光路损失。具体地，该耦合结构300可以为低偏振相关损耗的边缘耦合器（low PDL edge coupler）。
图4a-图4e是本申请实施例中采用多个级联的马赫-曾德尔干涉结构构成平顶波分复用结构的多种实施方式的示意图。如图4a-图4e所示，图示中121-125代表每一种不同实施方式平顶波分复用结构。本实施例中，为了能够使得每个所述平顶波分复用结构110输出后的第一级合波光信号为一个近似矩形的波形，将每个所述平顶波分复用结构110均设计为一种数字滤波器，该数字滤波器由至少两个级联的马赫-曾德尔干涉结构（MZI）构成，假设该数字滤波器用符号表示为A，2*2的耦合器用符号表示为B，相移臂用符号表示为C，则由B和C可以合成为A，而耦合器上的分光比的数值大小以及相移臂上的相移大小就代表了B和C前面的系数，多少个级联的MZI就代表多少阶的近似。示例性地，图4a-图4e中的单个马赫-曾德尔干涉结构（MZI）中，数字0.5表示2*2的3-dB的耦合器交叉端口的分光比为0.5，即一个端口输出为0.5，另一个端口输出为0.5；数字0.29表示2*2的耦合器交叉端口的分光比为0.29，即一个端口输出为0.29，另一个端口输出为0.71；数字0.08表示2*2的耦合器交叉端口的分光比为0.08，即一个端口输出为0.08，另一个端口输出为0.92；其余的数字表示以此类推，在此不做一一举例。另外，ΔL对应光在单个马赫-曾德尔干涉结构（MZI）的上下相移臂上传输产生相移的波导长度；Lπ对应光在单个马赫-曾德尔干涉结构（MZI）的上下相移臂上传输产生π相移的波导长度。最终可以合成得到一个近似矩形的波形，实现了将每个所述平顶波分复用结构110的平顶波段带宽变宽，使其能够覆盖由其两个输入端口分别接收到的入射光的中心波长加上预设的偏移量阈值对应的频带范围。
上述通过将每个所述平顶波分复用结构设计为一种数字滤波器的形式能够使得每个所述平顶波分复用结构110的平顶带宽变宽，使其能够容忍波导宽度、波导倾角、波导高度以及温度变化等因素所引起的中心波长偏移问题，而且无需设置任何反馈调节，不仅提高了工作效率，而且降低了器件损耗。
图5为本申请一实施例中采用阵列波导光栅结构作为平顶波分复用结构的示意图。如图5所示，在本实施例中，每个所述平顶波分复用结构由阵列波导光栅结构构成，该阵列波导光栅结构（Array Waveguide Gratings，AWG）130中包括多个阵列波导131（也称之为波导通道），阵列波导131采用直线型的波导结构。示例性地，该阵列波导131的通道数量为6个，当然也可以是其它数量，本专利在此不做限制。具体地，该阵列波导光栅结构130采用刻蚀工艺，在绝缘体硅（Silicon On Insulator，SOI）材料上制作，该SOI材料包括顶层硅、埋氧层二氧化硅以及衬底硅，顶层硅厚度为220nm，即可在顶层硅上刻蚀形成阵列波导131等结构，刻蚀深度例如为220nm。工作时，两路入射光信号λ1和λ3在经过阵列波导光栅结构130中的多个阵列波导131的相位调制后合成一束第一级合波光信号（λ1/λ3）。同样地，两路入射光信号λ2和λ4在经过阵列波导光栅结构130中的多个阵列波导131的相位调制后合成一束第一级合波光信号（λ2/λ4）。采用上述阵列波导光栅结构130形成平顶波分复用结构也能够使得平顶波分复用结构的平顶波段带宽变宽，使其能够覆盖由其两个输入端口分别接收到的入射光的中心波长加上预设的偏移量阈值对应的频带范围，并且相对于由多个级联的马赫-曾德尔干涉仪结构构成的平顶波分复用结构而言，上述阵列光栅结构130具有结构紧凑、尺寸小、***损耗低、波分复用间隔窄且工艺难度较低等优点。
图6为本申请一实施例中采用刻蚀衍射光栅结构作为平顶波分复用结构的示意图。如图6所示，在本实施例中，每个所述平顶波分复用结构由刻蚀衍射光栅结构构成，示例性地，该刻蚀衍射光栅结构140包括输入波导（141、142）、输出波导143、罗兰圆144以及凹面光栅145，罗兰圆144内部为自由传播区域，凹面光栅145的反射面由多个子曲面（图未示出）组成，多个子曲面能够实现光信号的解复用。其中，输入波导（141、142）和输出波导143均设置在罗兰圆144上。工作时，两路入射光信号λ1和λ3在经过罗兰圆144的内部后，生成两个输入模斑，随后两个输入模斑进入罗兰圆144的自由传播区域传播，入射到凹面光栅145的反射面，经凹面光栅145反射、聚焦后，从输出波导143输出一束第一级合波光信号（λ1/λ3）。同样地，两路入射光信号λ2和λ4在经过罗兰圆144的内部后，生成两个输入模斑，随后两个输入模斑进入罗兰圆144的自由传播区域传播，入射到凹面光栅145的反射面，经凹面光栅145反射、聚焦后，从输出波导143输出一束第一级合波光信号（λ2/λ4）。上述由刻蚀衍射光栅结构140构成的平顶波分复用结构也能够使得该平顶波分复用结构的平顶波段带宽变宽，使其能够覆盖由其两个输入端口分别接收到的入射光的中心波长加上预设的偏移量阈值对应的频带范围，并且上述刻蚀衍射光栅结构140相对于由多个级联的马赫-曾德尔干涉仪结构构成的平顶波分复用结构而言，对加工精度要求较低、整体集成度高、输出波导尺寸相对较小以及整体尺寸更加优化。
图7为本申请一实施例中采用模式复用器件和多模布拉格光栅构成的组合结构作为平顶波分复用结构的示意图。如图7所示，在本实施例中，每个所述平顶波分复用结构110由一个模式复用器件151以及一个多模布拉格光栅152的组合结构构成，其中，模式复用器151用于使输入光入射到所述多模布拉格光栅152内，该模式复用器件151包括第一端口、第二端口和第三端口，所述第一端口和第二端口分别用于输入或输出光信号，所述第三端口连接所述多模布拉格光栅152的输出端口。工作时，两路入射光信号λ1和λ3（例如均为TE0模式）分别向所述模式复用器151的第一端口输入以及向所述多模布拉格光栅152的输入端口输入，示例性地，该λ3波长的入射光信号（例如TE0模式）经所述多模布拉格光栅152以及所述模式复用器151后，该λ3（TE0）波长的入射光信号的偏振态模式不发生任何变化，直接从所述模式复用器151的第二端口出射；而该λ1波长的入射光信号（例如TE0模式）经过所述模式复用器151后转变为TE1模式或者更高阶模式的光并从所述模式复用器151的所述第三端口入射到所述多模布拉格光栅152内，经所述多模布拉格光栅152反射后转变为TE0模式，然后该λ1波长的光信号以TE0模式经所述模式复用器151后从所述模式复用器151的第二端口输出，TE0模式的λ1波长的光信号与TE0模式的λ3波长的光信号合波后，输出的第一级合波信号（λ1/λ3），其依然为TE0模式的线偏振光。同样地，两路入射光信号λ2和λ4（例如均为TE0模式）分别向所述模式复用器151的第一端口输入以及向所述多模布拉格光栅152的输入端口输入，同样地，该λ4波长的入射光信号（例如TE0模式）经所述多模布拉格光栅152以及所述模式复用器151后，该λ4（TE0）波长的光信号的偏振态模式不发生任何变化，直接从所述模式复用器151的第二端口出射；而该λ2波长的入射光信号（例如TE0模式）经过所述模式复用器151后转变为TE1模式或者更高阶模式的光从所述模式复用器151的所述第三端口入射到所述多模布拉格光栅152内，经所述多模布拉格光栅152反射后转变为TE0模式，然后λ2波长的光信号以TE0模式经所述模式复用器151后从所述模式复用器151的第二端口输出，TE0模式的λ2波长的光信号与TE0模式的λ4波长的光信号合波后，输出的第一级合波信号（λ2/λ4），其依然为TE0模式的线偏振光。上述采用模式复用器件和多模布拉格光栅构成的组合结构的平顶波分复用结构也能够使得该平顶波分复用结构的平顶波段带宽变宽，使其能够覆盖由其两个输入端口分别接收到的入射光的中心波长加上预设的偏移量阈值对应的频带范围。
图8为本申请一实施例中采用反向布拉格光栅定向耦合器结构作为平顶波分复用结构的示意图。如图8所示，在本实施例中，每个所述平顶波分复用结构110由一个反向布拉格光栅定向耦合器结构构成，该反向布拉格光栅定向耦合器160包括第一反向布拉格光栅定向耦合结构161和第二反向布拉格光栅定向耦合结构162。工作时，两路入射光信号λ1和λ3（例如均为TE模式）分别由第二反向布拉格光栅定向耦合结构162正向端口以及第一反向布拉格光栅定向耦合结构161的反向端口输入，由于λ3波长光信号是由所述第一反向布拉格光栅定向耦合结构161的反向端口输入，故所述第一反向布拉格光栅定向耦合结构161对λ3波长光信号（TE）不起作用，λ3波长光信号直接从所述第一反向布拉格光栅定向耦合结构161的正向端口出射；而由于λ1波长光信号（TE）是由所述第二反向布拉格光栅定向耦合结构162的正向端口输入，故所述第二反向布拉格光栅定向耦合结构162对λ1波长光信号（TE）起作用，该λ1波长光信号从所述第二反向布拉格光栅定向耦合结构162的正向端口输入后会经过所述第二反向布拉格光栅定向耦合结构162的中心位置附近运行到所述第一反向布拉格光栅定向耦合结构161中，并从所述第一反向布拉格光栅定向耦合结构161的正向端口输出，使得两路入射光信号λ1（TE）和λ3（TE）具有一定的光程差，最终在所述第一反向布拉格光栅定向耦合结构161的正向端口输出的光信号λ3（TE）和光信号λ1（TE）发生汇聚耦合后生成第一级合波光信号（λ1（TE）/λ3（TE））。同样地，基于上述同样的设置方式，在所述第一反向布拉格光栅定向耦合结构161的反向端口输入的光信号λ4（TE）和在所述第二反向布拉格光栅定向耦合结构162的正向端口输入的光信号λ2（TE），最终在所述第一反向布拉格光栅定向耦合结构161的正向端口发生汇聚耦合后生成第二级合波光信号（λ2（TE）/λ4（TE））。上述采用反向布拉格光栅定向耦合器结构的平顶波分复用结构也能够使得该平顶波分复用结构的平顶波段带宽变宽，使其能够覆盖由其两个输入端口分别接收到的入射光的中心波长加上预设的偏移量阈值对应的频带范围。
可选地，在本申请的其他实施例中，所述至少两个平顶波分复用结构由下列结构的任意组合构成：多个级联的马赫-曾德尔干涉结构、阵列波导光栅结构、刻蚀衍射光栅结构、模式复用器和多模布拉格光栅构成的组合结构、反向布拉格光栅定向耦合器结构。
图9为本申请一实施例中采用由多个级联的马赫-曾德尔干涉结构、阵列波导光栅结构、刻蚀衍射光栅结构的任意组合构成的平顶波分复用结构的仿真光谱图。图10为图9中示出的光谱图中的中心波长为1291nm附近的光束的光谱图。
当所述第一级复用模块100由所述多个级联的马赫-曾德尔干涉结构、所述阵列波导光栅结构和所述刻蚀衍射光栅结构的任意组合构成时，最终所生成的总的仿真光谱图如图9所示，其中，一个平顶波分复用结构以TE（Transverse Electric mode，横电模）偏振模式实现了中心波长分别为1271nm/1311nm波长（Wavelength）的通道（channel）的共用，另一个平顶波分复用结构以TM（Transverse Magnetic mode，横磁模）偏振模式实现了中心波长分别为1291nm/1331nm波长（Wavelength）的通道（channel）的共用。最终生成的第二级合波信号中，包含第一组光波分量和第二组光波分量，其中，所述第一组光波分量和所述第二组光波分量具有不同的偏振态。
示例性地，在图10中，对应中心波长为1291nm的光路通道的平顶波段带宽接近为34nm，因此，其对应的波分复用结构即使受到波导宽度、高度、倾角以及温度变化等因素引起该中心波长为1291nm的光束向长波段偏移（red shift）或者向短波段偏移（blue shift），也能够保证在中心波长1291nm±6nm的范围内均为平坦区。亦即，在该光路通道（channel）内生成的第一级合波光信号能够容忍波导宽度、高度、倾角以及温度变化等因素对中心波长偏移的影响，降低了对波导宽度、高度或倾角的敏感性。
图11为本申请一实施例中采用由模式复用器和多模布拉格光栅构成的组合结构、反向布拉格光栅定向耦合器结构的任意组合构成的平顶波分复用结构生成的一组光波分量的仿真光谱图，图12为本申请一实施例中采用由模式复用器和多模布拉格光栅构成的组合结构、反向布拉格光栅定向耦合器结构的任意组合构成的平顶波分复用结构生成的另一组光波分量的仿真光谱图。
在图11中，中心波长为1291nm的光束通路的平顶波段的带宽大于12nm，能够保证在中心波长1291nm±6nm的范围内均为平坦区，中心波长为1331nm的光束通路的平顶波段的带宽也大于12nm，能够保证在中心波长1331nm±6nm的范围内均为平坦区。图12中，中心波长为1271nm的光束通路的平顶波段的带宽大于12nm，能够保证在中心波长1271nm±6nm的范围内均为平坦区，中心波长为1311nm的光束通路的平顶波段的带宽大于12nm，能够保证在中心波长1311nm±6nm的范围内均为平坦区。因此，其对应的平顶波分复用结构即使受到波导宽度、高度、倾角以及温度变化影响等因素引起该中心波长的波段向长波段偏移（red shift）或者向短波段偏移（blue shift），也能够保证在中心波长±6nm的范围内均为平坦区。亦即，在该光路通道内生成的第一级合波光信号能够容忍波导宽度、高度、倾角以及温度变化等因素对中心波长偏移的影响，降低了平顶波分复用结构对波导宽度、高度或倾角的敏感性。
图13为本申请又一实施例所提供的片上集成波分复用器的结构示意图，图14为图13示出的片上集成波分复用器中的偏振旋转器(PR)的结构示意图；图15为图13示出的片上集成波分复用器中的偏振合束器(PBC)的结构示意图。
如图13所示，与前述实施例不同的是，在本实施例中，片上集成波分复用器2000中的第二级复用模块是偏振合束器(Polarization Beam Combiner，PBC)230，所述片上集成波分复用器2000还包括偏振旋转器(polarization rotator，PR)220，所述偏振旋转器220的输入端口与所述第一复用模块100的一个输出端口光耦合，以接收该输出端口输出的光，所述偏振旋转器220的输出端口与所述偏振合束器230的一个输入端口光耦合，以向所述偏振合束器230输出光，其中，所述偏振合束器230用于将接收到的两路具有不同偏振态的光束合波成一路光束，所述偏振旋转器220用于改变接收到的光束的偏振态。
示例性地，所述第一级复用模块100具有多个输入端口和两个输出端口；所述偏振合束器230包括两个输入端口和一个输出端口；所述第一级复用模块100的两个输出端口分别连接所述偏振合束器230的两个输入端口；具有相同偏振态的多路入射光信号（λ1，λ2，λ3，λ4（波长从小到大排列））分别向所述第一级复用模块100的多个输入端口输入，经所述第一级复用模块100合波之后，由所述第一级复用模块100的两个输出端口输出的两路第一级合波光信号中，一路与所述偏振合束器230一个输入端口直接光耦合，以将所述第一级合波光信号输入至所述偏振合束器230的一个输入端口上；另一路通过所述偏振旋转器220与所述偏振合束器230的另一个输入端口光耦合，以将所述第一级合波光信号经所述偏振旋转器220将其偏振态旋转90°之后的光束光耦合到偏振合束器230的另一输入端口上，最后经偏振合束器230合束输出一路具有相互垂直的两个偏振态的第二级合波光信号，其中，所述第二级合波光信号包含第一组光波分量和第二组光波分量，所述第一组光波分量和第二组光波分量具有不同的偏振态。
可选地，上述偏振旋转器(PR)220和上述偏振合束器(PBC)230也可以是硅基的偏振旋转器(PR)和硅基的偏振合束器(PBC)。
如图14所示，在本实施例中，所述偏振旋转器220用于将接收到的光束的原始偏振态改变成与所述原始偏振态垂直的偏振态。该偏振旋转器(PR)220包括一脊波导221和位于脊波导221一侧的部分平面波导222。其中，脊波导221包括依次连接的第一楔形结构221a、线性结构221b和第二楔形结构221c。第一楔形结构221a作为偏振旋转器220的输入端，其宽度沿光路方向逐渐变窄直至与线性结构221b平齐并连接，第二楔形结构221c的宽度沿光路方向逐渐变宽，直至与外部光波导连接。部分平面波导222的高度低于脊波导221的高度，包括位于脊波导221同一侧且相互连接的第三楔形结构222a和第四楔形结构222b。第三楔形结构222a紧邻第一楔形结构221a的侧面，第四楔形结构222b紧邻线性结构221b的侧面，第三楔形结构222a的尖端紧贴第一楔形结构221a较宽一端的侧面，第四楔形结构222b的尖端临近第二楔形结构221c较窄一端。线偏振光从脊波导221的第一楔形结构221a较宽的一端入射，在第一楔形结构221a和线性结构221b段，光模式分布到脊波导221和平面波导222内，使其偏振态发生旋转，在入射到第二楔形结构221c时偏振态已经旋转90度，再通过第二楔形结构221c耦合到外部光波导内。在其它实施例中，也可以采用图3所示的偏振旋转-合束器(PSR)作为偏振旋转器，线偏振光从交叉端口入射，经交叉波导耦合到直通波导，最后经模式变换结构输出的线偏振光的偏振态旋转了90度。
如图15所示，在本实施例中，该偏振合束器230由三个相同的模式转换耦合器组成，每个模式转换耦合器包括一个单模接入波导和一个多模总线波导。其中，第一模式转换耦合器231和第二模式转换耦合器232并联，并位于偏振合束器230的输入端。上述第一模式转换耦合器231的单模接入波导231a和第二模式转换耦合器232的单模接入波导232a分别连接偏振旋转器220的输出端和一个平顶波分复用结构110的输出端。第三模式转换耦合器233级联上述两个模式转换耦合器231、232，第三模式转换耦合器233的多模总线波导233b连接第一模式转换耦合器231的多模总线波导231b的输出端，第三模式转换耦合器233的单模接入波导233a连接第二模式转换耦合器232的单模接入波导232a的输出端。在本实施例中，采用三个模式转换耦合器组成的偏振合束器230结合偏振旋转器220对由前面两个平顶波分复用结构110输出的两路具有相同线偏振态的第一级合波光信号进行偏振合束，减小了串扰。而且由于模式转换耦合器具有低损耗大带宽的特性，进一步降低了光学损耗，提高了器件的光学带宽。
图16为本申请另一实施例所提供的片上集成波分复用器的结构示意图，如图16所示，与前述实施例不同的是，本实施例中的第二级复用模块200是偏振合束器(Polarization Beam Combiner，PBC)230，所述片上集成波分复用器3000还包括至少一个偏振旋转器（polarization rotator，PR）220，针对每个所述偏振旋转器220，其输入端口用于接收一路所述入射光，其输出端口与所述至少两个平顶波分复用结构110中的一个的输入端口光耦合，以向该平顶波分复用结构110输出光，其中，所述偏振合束器230用于将接收到的两路具有不同偏振态的光束合波成一路光束，所述偏振旋转器220用于改变接收到的光束的偏振态，并且由所述至少一个偏振旋转器220改变偏振态的光仅由所述第一级复用模块100的一个输出端口输出。
示例性地，在本实施例中，所述第一级复用模块100具有多个输入端口和两个输出端口；所述偏振合束器230包括两个输入端口和一个输出端口；所述平顶宽带的波分复用组合结构100的两个输出端口分别连接所述偏振合束器230的两个输入端口；针对每个所述偏振旋转器220，其输出端口用于接收一路入射光，用于改变接收到的光束的偏振态，至少两路入射光信号分别通过与之对应的所述偏振旋转器220与一个所述平顶波分复用结构110的输入端口光耦合，经所述偏振旋转器220将所述至少两路入射光信号的偏振态旋转90°之后耦合到所述平顶宽带的片上集成波分复用器110的一个输入端口上，然后由所述平顶波分复用结构110的输出端口输出合波后的第一级合波光信号；至少两路入射光信号直接入射至所述平顶波分复用结构110一个输入端口上，然后由所述平顶波分复用结构110的输出端口输出合波后的第一级合波光信号，由于所述第一级复用模块100的两个输出端口输出的两束第一级合波光信号的偏振态模式不同，故经所述偏振合束器230合波后输出具有相互垂直的两个偏振态的合波光信号（第二级合波光信号）。
本申请还提出了一种芯片，所述芯片包括前述任一实施例所述的片上集成波分复用器。
在本申请实施例所提供的片上集成波分复用器及芯片中，第一级复用模块中的每个平顶波分复用结构的带宽能够覆盖由其两个输入端口分别接收到的入射光的中心波长加上预设的偏移量阈值对应的频带范围，由此每个平顶波分复用结构能够传输两路中心波长相差较大的光束，从而能够克服由各种因素导致的中心波长偏移所引起的相邻通道串扰问题；而且第一级复用模块以及第二级复用模块在工作过程中，无需任何反馈调节，提高了工作效率，降低了器件损耗，并有利于降低片上集成波分复用器对波导宽度、波导高度、波导倾角以及周围环境温度变化的敏感性。
在上述实施例中，对各个实施例的描述都各有侧重，某个实施例中没有详述的部分，可以参见其他实施例的相关描述。
以上结合实施例对本申请所提供的片上集成波分复用器及芯片进行了详细介绍，本文中应用了具体个例对本申请的原理及实施方式进行了阐述，以上实施例的说明只是用于帮助理解本申请的技术方案及其核心思想；本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例的技术方案的范围。

Claims (15)

  1. 一种片上集成波分复用器，其特征在于，所述波分复用器包括第一级复用模块和第二级复用模块，所述第一级复用模块具有多个输入端口和两个输出端口，所述第二级复用模块具有两个输入端口和一个输出端口，所述第一级复用模块的所述两个输出端口分别与所述第二级复用模块对应的输入端口光耦合；
    所述第一级复用模块包括至少两个平顶波分复用结构，每个所述平顶波分复用结构具有两个输入端口和一个输出端口，其中，每个所述平顶波分复用结构的带宽覆盖由其两个输入端口分别接收到的入射光的中心波长加上预设的偏移量阈值对应的频带范围。
  2. 根据权利要求1所述的片上集成波分复用器，其特征在于，所述第一级复用模块将由所述多个输入端口接收到的具有同一偏振态的入射光进行合波以生成两路第一级合波光信号，并将所述两路第一级合波光信号分别输入至所述第二级复用模块对应的输入端口，所述第二级复用模块将其两个输入端口接收到的所述两路第一级合波光信号进行合波以生成第二级合波光信号，其中，所述第二级合波光信号包含第一组光波分量和第二组光波分量，所述第一组光波分量和第二组光波分量具有不同的偏振态；所述第二级复用模块对第一组光波分量和第二组光波分量进行偏振合波。
  3. 根据权利要求2所述的片上集成波分复用器，其特征在于，
    当把具有预定波长间隔的λ1、λ2、λ3……λn波长分割光信号输入所述第一级复用模块的所述多个输入端口时，其中n≥4，且n为偶数，所述λ1、λ2、λ3……λn按照波长大小顺序依次排列；
    从所述至少两个平顶波分复用结构中其中一个的输入端口输入奇数信道的入射光信号，从所述至少两个平顶波分复用结构中的另一个的输入端口输入偶数信道的入射光信号。
  4. 根据权利要求3所述的片上集成波分复用器，其特征在于，每个所述平顶波分复用结构的两个输入端口接收到的入射光的中心波长之间的差值大于预设的波长差阈值。
  5. 根据权利要求1所述的片上集成波分复用器，其特征在于，所述至少两个平顶波分复用结构由下列结构的任意组合构成：多个级联的马赫-曾德尔干涉结构、阵列波导光栅结构、刻蚀衍射光栅结构、模式复用器和多模布拉格光栅构成的组合结构、反向布拉格光栅定向耦合器结构。
  6. 根据权利要求1所述的片上集成波分复用器，其特征在于，所述片上集成波分复用器是硅基波分复用器。
  7. 根据权利要求1所述的片上集成波分复用器，其特征在于，所述波分复用器还包括耦合结构，所述耦合结构与所述第二级复用模块的输出端口相连，用于将所述第二级复用模块的输出端口输出的所述第二级合波光信号与外部光纤阵列进行耦合，以将合波完成的光信号进行输出。
  8. 根据权利要求1所述的片上集成波分复用器，其特征在于，所述第二级复用模块是偏振旋转分束器，所述偏振旋转分束器将接收到的所述两路第一级合波光信号合波成具有相互垂直的偏振态的所述第一组光波分量和所述第二组光波分量。
  9. 根据权利要求8所述的片上集成波分复用器，其特征在于，所述偏振旋转分束器包括直通波导和交叉波导、分别连接所述直通波导和交叉波导的直通端口和交叉端口，以及连接所述直通波导的模式变换结构；所述直通波导与所述交叉波导组成模式复用结构；所述直通端口和交叉端口均包括条波导转脊波导的楔形结构；所述模式变换结构为双层楔形的模式变换结构。
  10. 根据权利要求1所述的片上集成波分复用器，其特征在于，所述第二级复用模块是偏振合束器，所述波分复用器还包括偏振旋转器，所述偏振旋转器的输入端口与所述第一复用模块的一个输出端口光耦合，以接收该输出端口输出的光，所述偏振旋转器的输出端口与所述偏振合束器的一个输入端口光耦合，以向所述偏振合束器输出光，其中，所述偏振合束器用于将接收到的两路具有不同偏振态的光束合波成一路光束，所述偏振旋转器用于改变接收到的光束的偏振态；其中，所述偏振旋转器将接收到的光束的原始偏振态改变成与所述原始偏振态垂直的偏振态。
  11. 根据权利要求1所述的片上集成波分复用器，其特征在于，所述第二级复用模块是偏振合束器，所述波分复用器还包括至少一个偏振旋转器，针对每个所述偏振旋转器，其输入端口用于接收一路所述入射光，其输出端口与所述至少两个平顶波分复用结构中的一个的输入端口光耦合，以向该平顶波分复用结构输出光，其中，所述偏振合束器用于将接收到的两路具有不同偏振态的光束合波成一路光束，所述偏振旋转器用于改变接收到的光束的偏振态，并且由所述至少一个偏振旋转器改变偏振态的光仅由所述第一级复用模块的一个输出端口输出；其中，每个所述偏振旋转器将接收到的光束的原始偏振态改变成与所述原始偏振态垂直的偏振态。
  12. 根据权利要求1所述的片上集成波分复用器，其特征在于，每个所述平顶波分复用结构包括至少两个1dB平顶，其中，每个1dB平顶是光衰减1dB范围内所对应的波长范围，每个1dB平顶所对应的波长范围大于20纳米。
  13. 根据权利要求12所述的片上集成波分复用器，其特征在于，同一个平顶波分复用结构的相邻的两个1dB平顶的间隔小于5纳米。
  14. 根据权利要求12所述的片上集成波分复用器，其特征在于，所述至少两个平顶波分复用结构中，其中一个的平顶波分复用结构中的1dB平顶所对应的波长范围与其中另一个的平顶波分复用结构中的1dB平顶所对应的波长范围部分重叠。
  15. 一种芯片，其特征在于，包括权利要求1所述的片上集成波分复用器。
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