WO2011130985A1 - 可重构编解码器及基于该设备的光码分多址无源光网络 - Google Patents

可重构编解码器及基于该设备的光码分多址无源光网络 Download PDF

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Publication number
WO2011130985A1
WO2011130985A1 PCT/CN2010/076304 CN2010076304W WO2011130985A1 WO 2011130985 A1 WO2011130985 A1 WO 2011130985A1 CN 2010076304 W CN2010076304 W CN 2010076304W WO 2011130985 A1 WO2011130985 A1 WO 2011130985A1
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Prior art keywords
optical
reconfigurable
output
awg
data
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PCT/CN2010/076304
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English (en)
French (fr)
Inventor
耿丹
朱松林
陈彪
王大伟
成亮
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中兴通讯股份有限公司
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Publication of WO2011130985A1 publication Critical patent/WO2011130985A1/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
    • G02B6/12007—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 forming wavelength selective elements, e.g. multiplexer, demultiplexer
    • G02B6/12009—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 forming wavelength selective elements, e.g. multiplexer, demultiplexer comprising arrayed waveguide grating [AWG] devices, i.e. with a phased array of waveguides
    • G02B6/12019—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 forming wavelength selective elements, e.g. multiplexer, demultiplexer comprising arrayed waveguide grating [AWG] devices, i.e. with a phased array of waveguides characterised by the optical interconnection to or from the AWG devices, e.g. integration or coupling with lasers or photodiodes
    • G02B6/12021—Comprising cascaded AWG devices; AWG multipass configuration; Plural AWG devices integrated on a single chip
    • 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
    • G02B6/12007—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 forming wavelength selective elements, e.g. multiplexer, demultiplexer
    • G02B6/12009—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 forming wavelength selective elements, e.g. multiplexer, demultiplexer comprising arrayed waveguide grating [AWG] devices, i.e. with a phased array of waveguides
    • G02B6/12033—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 forming wavelength selective elements, e.g. multiplexer, demultiplexer comprising arrayed waveguide grating [AWG] devices, i.e. with a phased array of waveguides characterised by means for configuring the device, e.g. moveable element for wavelength tuning

Definitions

  • the present invention belongs to the field of optical fiber communication technologies, and in particular, to a reconfigurable encoder/decoder, and an optical line termination (OLT, Optical Line Terminate) and an optical network unit (ONU) based on the reconfigurable encoder/decoder.
  • OLT optical line termination
  • ONU optical network unit
  • Optical Network Unit Optical Network Unit
  • OCDMA Optical Code Division Multiple Access
  • PON Passive Optical Network
  • the access network is a service node interface (SNI, Service Node).
  • SNI service node interface
  • the passive optical network has become a popular technology for optical access networks due to its wide frequency bandwidth, large capacity, convenient expansion, and suitable for high-speed data transmission.
  • time division multiple access TDMA, Time Division) Multiple Access
  • WDMA Wavelength Division Multiple Access
  • OCDMA optical code division multiple access multiplexing
  • OCDMA-PON Passive optical network based on optical code division multiple access (multiplexing) is a multiple access multiplexing technology that combines the large bandwidth of fiber medium and the flexibility of code division multiple access multiplexing (CDMA).
  • CDMA code division multiple access multiplexing
  • the optical line terminal is an optical line terminal based on optical code division multiple access technology
  • the optical network unit is an optical network unit based on optical code division multiple access technology.
  • optical optical code division multiple access multiplexing based passive optical network may further include one or more optical network terminations (ONTs), the one or more network terminals and one or more The optical network units are connected as specific users of the optical network unit.
  • OTDMA-PON optical network terminations
  • each user is assigned a unique optical encoder/decoder in the 0NU (when the encoded signal passes, it is an optical decoder, and when the original signal passes, it is an optical encoder).
  • the encoded user data is passed through the optical wiring to the OLT through the optical encoder.
  • the encoded data stream is inversely processed by the optical decoder through the optical decoder (ie, the inverse processing of the optical encoding process) to implement optical decoding.
  • the decoded data stream is then uploaded to other core networks through the transmitter in the OLT to realize mutual transmission of information between the ONUs of different PONs.
  • the data stream transmitted from the core network is modulated at the OLT end, and then encoded by the optical encoder, and then the encoded data stream is transmitted to the optical distribution network through the optical fiber channel, and the data flows through the optical distribution network to downlink data. It is transmitted to each ONU or ONT, and the data stream encoded at the ONU end is decoded by the optical decoder, and the transmission data is recovered to receive the user data.
  • the optical encoder/decoder is the core component of the OCDMA system.
  • the optical encoder converts the data bits into a spreading sequence
  • the optical decoder at the receiving end recovers the spreading sequence to data bits using the correlation decoding principle.
  • all users share the same optical segment and time segment of the same channel.
  • the signals used by different users to transmit information are distinguished by different coding sequences, that is, each user is assigned a pseudo-random sequence.
  • the pseudo-random sequence is generated by the optical encoder by each user's information.
  • the pseudo-random sequence is also unique, and each information bit of the user is encoded into a series of pulses; at the receiving end, the user Correlation operations are performed with the same pseudo-random sequence (corresponding decoder) to recover the transmitted information.
  • These pseudo-random sequences are called the user's address code, and each coded pulse is called a chip.
  • optical encoder/decoder directly affect the overall performance of the OCDMA system, which determines
  • OCDMA encoder/decoder the main types of OCDMA encoder/decoder are: time domain encoding/decoding scheme based on fiber delay line, spectral domain encoding/decoding scheme based on diffraction grating and phase mask, encoding/decoding scheme based on fiber Bragg grating, array-based waveguide The encoding/decoding scheme of the raster.
  • Fiber delay line coding system The system consists of several bundles of fibers and two ⁇ ⁇ star couplers. The difference between different codeword encoders is the delay length of the fiber delay lines.
  • the encoder divides an input light pulse into several pulses of equal power through a power divider, and the pulses are recombined by the optical coupler after different delays, thereby converting an input light pulse into a pulse.
  • This type of encoder is relatively easy to implement, but requires more devices and is cumbersome. In actual production, it is necessary to precisely control the delay length of each delay line, and the loss is relatively large.
  • the integrated grating is used to spatially separate and recombine the frequency components in the pulse, and a phase mask is used to complete the necessary pulse filtering and shaping functions.
  • This method has many disadvantages: it is too bulky, the addressing speed is slow and difficult to integrate; the dispersion is large, the transmission distance is limited; the number of users accommodated is limited (wavelength limitation).
  • the spatial light modulator ie, the optical mask
  • the spatial light modulator needs to be made very fine, and it is difficult to implement codeword reconstruction.
  • Time domain/local 2D coding based on fiber Bragg grating consists of a series of FBGs with different center wavelengths.
  • the reflection wavelength of each grating center can be adjusted by the piezoelectric ceramic device to adjust the grating period to achieve wavelength coding.
  • the position acts as a fiber delay line, which separates the different frequency components in the time domain, thereby implementing time domain/heritive hybrid coding.
  • Figure 2 shows the FBG encoder/decoder in series.
  • Each encoder/decoder consists of several FBGs with different reflection wavelengths connected in series.
  • the incident light pulse is encoded by the optical circulator 21 and the encoded FBG 22, and a pulse sequence is formed in the time domain.
  • the pulse sequences are compressed again, and a pulse is recombined.
  • the code/decoder implementation is relatively simple, but the code length of the address code is limited by the number of FBGs.
  • FBG has a broadening effect on optical pulses and is difficult to use for high-speed communication above lGbps.
  • An arrayed waveguide grating (AWG) based encoder/decoder as shown in Figure 3, Figure 3 is a two-dimensional time domain/local register based on AWG31, and Figure 4 is a one-dimensional spectral domain encoder/decoder based on AWG41.
  • the AWG-based encoder/decoder can solve the code length limitation and rate limitation of the FBG encoder and is easy to integrate.
  • the AWG-based one-dimensional encoder/decoder is similar to the one-dimensional time domain parallel encoder/decoder, and the codeword reconstruction can be performed by adding a codeword controller.
  • AWG-based 2D time domain/language encoder/decoder which is a parallel structure compared to FBG-based encoder/decoder.
  • AWG demultiplexer makes full use of the characteristics of AWG demultiplexer and adds different AWG different output wavelengths.
  • the delay length of the fiber delay is extended in the time domain, thereby achieving the purpose of two-dimensional coding.
  • AWG encoder/decoder is not compared to FBG structure Reflex is required, and the delay length of its corresponding delay line is also twice as long as the FBG structure.
  • the above two AWG-based encoder/decoders require two AWG devices, which makes the entire encoder/decoder loss more, which also makes the loss budget of the entire passive optical network system larger, which is not conducive to system cost control. Summary of the invention
  • the technical problem to be solved by the present invention is to provide a reconfigurable encoder/decoder and an optical code division multiple access multiplexed passive optical network based on the reconfigurable encoder/decoder to reduce loss and cost.
  • the present invention provides a reconfigurable encoder comprising an arrayed waveguide grating AWG, N tunable fiber retarders, N being an integer and ⁇ > 1 , M reflectors, M being an integer And N > M > 1,
  • the AWG has at least N input ports and N output ports, wherein: an output port of the AWG is connected to an input end of the adjustable fiber retarder, the N tunable fibers
  • the output ends of the M tunable fiber retarders in the delay are respectively connected to the M reflectors;
  • the input signal is input from the input port of the AWG, processed through the AWG, and outputted from the corresponding output port, wherein the M path
  • the output signal is delayed by the adjustable fiber retarder and reaches the reflector. After being reflected by the reflector, it is returned to the output port of the AWG through a corresponding adjustable fiber retarder, and is output from the input port of the AWG.
  • the reconfigurable encoder further includes P adapter components, P is an integer and NM > P > 1, and output ends of P adjustable fiber retarders in the N adjustable fiber retarders are respectively connected To P adapter pieces;
  • the input signal is input from the input port of the AWG, and is output from the corresponding output port after being processed by the AWG.
  • the P output signal is delayed by the adjustable fiber delay to reach the adapter, and the signal reaching the adapter is extinguished.
  • the present invention also provides a reconfigurable decoder comprising an arrayed waveguide grating AWG, N tunable fiber retarders, N is an integer and ⁇ > 1 , M reflectors, M is An integer and N > M > 1, the AWG has at least N input ports and N output ports, where:
  • An output port of the AWG is connected to an input end of the adjustable fiber retarder, and an output of the M adjustable fiber retarders in the N adjustable fiber retarders respectively and the M reflector Connected; the input signal is input from the input port of the AWG, and is output from the corresponding output port after being processed by the AWG, wherein the M-channel output is delayed by the adjustable fiber retarder and reaches the reflector, and after being reflected by the reflector, the corresponding The adjustable fiber retarder is returned to the output port of the AWG and is output by the input port of the AWG.
  • the reconfigurable decoder further comprises P adapter components, P is an integer and N-M > P
  • the output of the P adjustable fiber retarders in the N adjustable fiber retarders is connected to the adapter; the input signal is input from the input port of the AWG, processed through the AWG, and output from the corresponding output port The P output signal is delayed by the adjustable fiber delay to reach the adapter, and the signal reaching the adapter is extinguished.
  • the present invention also provides an optical line terminal (OLT) based on the above reconfigurable encoder and a reconfigurable decoder, the OLT comprising an optical transmitter, a first optical circulator, and a second Optical circulator, third optical circulator, reconfigurable encoder, coupler, optical receiver, reconfigurable decoder, optical beam splitter, wherein:
  • the data to be transmitted is sent to the reconfigurable encoder through the optical transmitter and the first optical circulator for encoding, and the encoded data is sent to the coupler via the first optical circulator, and the coupler will receive from the plurality of optical transmitters. After the data to be transmitted is coupled, the data is output through the second optical circulator;
  • the second optical circulator receives the data and sends it to the optical beam splitter.
  • the optical beam splitter divides the data into multiple channels, each of which is sent to a third optical circulator, and the third optical circulator.
  • the data is sent to a reconfigurable decoder for decoding, and the decoded data is sent to the optical receiver via the third optical circulator.
  • the reconfigurable encoder and the reconfigurable decoder each have one, and the optical transmitter, the first optical circulator, the optical receiver, and the third optical circulator respectively have a plurality of Or the number is equal; or, the optical transmitter, the first optical circulator, the reconfigurable encoder, the optical receiver, the third optical circulator, and the reconfigurable There are multiple decoders and the number is equal.
  • the present invention also provides an optical network unit (ONU) based on the above reconfigurable encoder and a reconfigurable decoder, where the ONU includes an optical transmitter, an optical receiver, an optical circulator, a coupler, a reconfigurable encoder, a reconfigurable decoder, wherein: the reconfigurable encoder, the reconfigurable decoder, and the coupler are connected to the optical circulator, the optical transmitter, the optical receiver Connected to the coupler; After receiving the optical signal sent by the optical line terminal OLT, the optical circulator sends the optical signal to the reconfigurable decoder for decoding, and the decoded data is output from the optical circulator to the coupler. Output to the optical receiver via the coupler;
  • the optical transmitter sends the data to be transmitted to the coupler, and is sent by the coupler to the optical circulator, and sent by the optical circulator to the reconfigurable encoder for encoding, the encoded data. Output by the optical circulator.
  • the optical transmitter comprises a reflective semiconductor optical amplifier RSOA or a Fabry-Perot laser FPLD; after the optical signal reaches the coupler, the coupler is split into two paths, one output to the optical receiver, and the other output to the optical receiver.
  • the optical transmitter uses the received input light as an uplink optical carrier, and carries the to-be-transmitted data on the uplink optical carrier for transmission.
  • the present invention also provides an optical code division multiple access multiplexed passive optical network based on the above reconfigurable encoder and reconfigurable decoder, including an optical line terminal (OLT) and optical wiring.
  • OLT optical line terminal
  • ODN Optical Network Unit
  • ONU Optical Network Unit
  • the OLT includes an optical transmitter, a first optical circulator, a second optical circulator, a third optical circulator, a reconfigurable encoder, a coupler, an optical receiver, a reconfigurable decoder, and an optical beam splitter.
  • the data to be transmitted is sent to the reconfigurable encoder through the optical transmitter and the first optical circulator for encoding
  • the encoded data is sent to the coupler via the first optical circulator, and the coupler will transmit from multiple lights.
  • the data to be transmitted received by the machine is coupled and outputted by the second optical circulator;
  • the second optical circulator receives the data and sends it to the optical beam splitter, and the optical beam splitter divides the data into multiple channels, each of which is sent a third optical circulator, the third optical circulator sends the data to a reconfigurable decoder for decoding, and the decoded data is sent to an optical receiver via a third optical circulator;
  • the ONU includes an optical transmitter, an optical receiver, an optical circulator, a coupler, a reconfigurable encoder, and a reconfigurable decoder, where: when the optical circulator receives the optical signal sent by the OLT, Transmitting the optical signal to the reconfigurable decoder for decoding, the decoded data is output from the optical circulator to the coupler, and output to the optical receiver via the coupler; when the uplink data is to be transmitted, the light is emitted
  • the machine sends the data to be sent to the coupler, and is sent by the coupler to the optical circulator, and is sent by the optical circulator to the reconfigurable encoder for encoding, and the encoded data is output by the optical circulator.
  • the reconfigurable encoder and the reconfigurable decoder each have one, Each of the optical transmitter, the first optical circulator, the optical receiver, and the third optical circulator has a plurality of equal numbers; or the optical transmitter and the first optical ring Each of the row, the reconfigurable encoder, the optical receiver, the third optical circulator, and the reconfigurable decoder has an equal number; and in the ONU, the The optical transmitter comprises a reflective semiconductor optical amplifier RSOA or a Fabry-Perot laser FPLD; after the optical signal reaches the coupler, it is split into two paths through the coupler, one output to the optical receiver, and the other output to the optical transmitter; When the uplink data is to be sent, the optical transmitter uses the received input light as an uplink optical carrier, and carries the to-be-transmitted data on the uplink optical carrier for transmission.
  • RSOA reflective semiconductor optical amplifier
  • Fabry-Perot laser FPLD Fabry-Perot laser
  • the reconfigurable encoder/decoder of the present invention solves the problem of large loss of the encoder/decoder of the conventional AWG by using only one AWG device, and greatly reduces the cost.
  • the reconfigurable encoder/decoder utilizes multiple incident ports of the AWG, multiple sets of inputs can be encoded or decoded simultaneously, enabling time domain and spectral domain hybrid coding.
  • the codeword reconstruction of the encoder/decoder increases the flexibility and confidentiality of the network.
  • the invention is based on the above-mentioned reconfigurable encoder/decoder optical code division multiple access passive optical network (OCDMA PON), which can solve the problem that the code length of the passive optical network using the FBG as the encoder is limited (the number of multiplexed users can be affected) Limited) and limited communication rate.
  • OCDMA PON optical code division multiple access passive optical network
  • the OLT based on the reconfigurable codec can implement multiple reconfigurable encoder/decoders for multiple users by using multiple incident ports of the AWG, which simplifies the structure of the OLT and saves network cost; Reconstructing the ONU of the encoder/decoder, due to the full use of the RSOA feature in the structure, the laser light source, the modulator and the like which must be used in the original optical transmitter can be reduced, the ONU structure is simplified, and the network cost is saved.
  • Figure 1 is a block diagram of an OCDMA-PON passive optical network
  • FBG fiber Bragg grating
  • Figure 3 is a two-dimensional time domain/spectral domain codec/decoder diagram based on AWG;
  • 4 is a one-dimensional encoder/decoder diagram based on AWG; 5 is a structural diagram of an AWG-based reconfigurable encoder;
  • FIG. 6 is a structural diagram of an AWG-based reconfigurable decoder
  • FIG. 7 is an OLT structure diagram of an optical code division multiple access multiplexed passive optical network based on a reconfigurable encoder/decoder according to the present invention (in the case of M>1);
  • FIG. 9 is a structural diagram of an ONU of an optical code division multiple access multiplexed passive optical network based on a reconfigurable encoder/decoder according to the present invention. Preferred embodiment of the invention
  • the invention provides a reconfigurable encoder comprising an arrayed waveguide grating (AWG), N tunable fiber retarders and M reflectors, wherein N and M are integers and ⁇ > 1 , N > M > 1
  • the AWG has at least N input ports and N output ports, where:
  • An output port of the AWG is connected to an input end of the adjustable fiber retarder, an output end of the adjustable fiber retarder is connected to the reflector; an input signal is input from the AWG input port, and processed by the AWG Output from the corresponding output port, each output is delayed by the adjustable fiber retarder, reaches the reflector, is reflected by the reflector, and returned to the output port of the AWG through the corresponding adjustable fiber retarder, by the AWG Input port output.
  • the reconfigurable encoder further comprises P adapter members, P is an integer and NM > P > 1, and an output of the M adjustable fiber retarders of the N adjustable fiber retarders is connected to The reflector, the output of the P adjustable fiber retarder is connected to the adapter; the input signal is input from the AWG input port, processed by the AWG, and outputted from the corresponding output port, and the output signal is delayed by the adjustable fiber delay
  • the signal reaching the reflector is reflected by the reflector, returned to the output port of the AWG through the corresponding adjustable fiber retarder, and outputted by the input port of the AWG; the signal reaching the adapter member is Extinction (will not reflect back).
  • the invention provides a reconfigurable decoder comprising an arrayed waveguide grating (AWG), N Adjustable fiber retarder, N is an integer and ⁇ > 1, M reflectors, M is an integer and N > M > 1, the AWG has at least N input ports and N output ports, where:
  • An output port of the AWG is connected to an input end of the adjustable fiber retarder, an output end of the adjustable fiber retarder is connected to the reflector; an input signal is input from the AWG input port, and processed by the AWG Output from the corresponding output port, each output is delayed by the adjustable fiber retarder, reaches the reflector, is reflected by the reflector, and returned to the output port of the AWG through the corresponding adjustable fiber retarder, by the AWG Input port output.
  • the reconfigurable decoder further includes P adapter components, P is an integer and NM > P > 1, and outputs of the M tunable fiber delays of the N tunable fiber delays are connected to The reflector, the output of the P adjustable fiber retarder is connected to the adapter; the input signal is input from the AWG input port, processed by the AWG, and outputted from the corresponding output port, and the output signal is delayed by the adjustable fiber delay
  • the signal reaching the reflector is reflected by the reflector, returned to the output port of the AWG through the corresponding adjustable fiber retarder, and outputted by the input port of the AWG; the signal reaching the adapter member is Extinction (will not reflect back).
  • the adapter member may be an isolator, an attenuating fiber or the like, which is arranged to attenuate the input light, thereby consciously filtering out some wavelengths of light to prevent light reflection from affecting the encoding/decoding.
  • the tunable fiber retarder is preferably a tunable fiber delay line.
  • signal reflection for different wavelengths can be realized, that is, different codewords can be generated, different register codes can be realized, and codeword reconstruction can be realized.
  • the reconfigurable encoder/decoder of the present invention is an arrayed waveguide grating (AWG) based encoder/decoder, and the reconfigurable AWG of the present invention is compared to a conventional arrayed waveguide grating (AWG) encoder/decoder.
  • the encoder/decoder uses only one AWG device.
  • the AWG uses multiple input ports to receive data, and can simultaneously encode/decode M data.
  • the use of only one AWG device solves the problem of large encoder/decoder loss of conventional arrayed waveguide gratings (AWGs).
  • the optical encoder/decoder is a core component of the OCDMA-PON system. At the transmitting end, the optical encoder converts the data bits into a code sequence, and the optical decoder at the receiving end recovers the code sequence into data bits using the correlation decoding principle. The structure and characteristics of the optical encoder/decoder directly affect the overall performance of the system.
  • the reconfigurable encoder/decoder in the present invention is an AWG-based reconfigurable encoder/decoder.
  • the optical encoder/decoder is fully profitable
  • the cycle characteristics of the AWG are used.
  • the cycle characteristic of AWG means that the wavelength of the output of different input ports at the corresponding output port is cyclic.
  • i ⁇ ⁇ i ⁇ M
  • j 1 ⁇ j ⁇ N
  • Port, N indicates the total number of wavelengths used.
  • the output port output wavelength is ⁇ 4,4, ⁇ 4 , ... ⁇
  • the output port output wavelength is ⁇ , ⁇ 4 , . . ⁇ , ⁇ , and so on.
  • the AWG-based reconfigurable encoder/decoder controls the selected reflected wavelength by controlling the connection of the reflector behind the fiber retarder or the adapter, so that each encoding/decoding does not utilize all wavelengths, but only Several wavelengths returned by the reflector are utilized.
  • N is the total number of wavelengths available for the AWG
  • the reflected wavelengths are recombined after different delays, thereby achieving two-dimensional encoding in the time domain and the spectral domain. In this way, different spectral domain coding can be realized by selecting different reflection wavelengths, that is, realizing codeword reconstruction.
  • the AWG-based reconfigurable encoder/decoder has the structure shown in Figures 5 and 6, and is mainly composed of the AWG51 of the port, the adjustable fiber retarder 52, the adapter member and the reflector.
  • the N output ports of the AWG of the MxN port are connected to N adjustable fiber retarders, but only after the K adjustable fiber retarders are connected to the reflector (ie, K reflection wavelengths are selected, ⁇ ⁇ ⁇ , , the remaining NK adjustable fiber retarders are connected to the adapter (ie, extinction of the remaining NK wavelength to prevent its reflection from affecting the encoding/decoding).
  • the AWG-based optical encoder/decoder is a parallel structure that utilizes the good spectral characteristics of the AWG.
  • Wavelength segmentation of the source pulse adding different fiber retarders at different output wavelengths, and performing time domain coding, so that both the spectral domain and the time domain are encoded, thereby implementing direct sequence (DS) code division multiple access.
  • DS direct sequence
  • FE Frequency Code
  • FE-OCDMA spectral domain code division multiple access system
  • the delay length of the fiber retarder is such that the sum of the delay lengths of the fiber delays of the respective encoders and decoders is equal; changing the fiber retarder
  • the connected reflector and adapter must simultaneously change the encoder and decoder of the same receive and transmit link in the OLT and ONU.
  • the user data source pulse enters the AWG input port through the optical circulator, and the AWG wavelength-divides it, and outputs different wavelengths of light pulses at different output ports, that is, the language is encoded/decoded, and the pulse after dividing the wavelength is different.
  • the delay length of the fiber retarder that is, the time domain encoding/decoding
  • the reflector is used to reflect the pulse back to the AWG, and the pulse is returned to the AWG after a delay of different length, and finally output through the optical circulator to obtain the final editing. / Decode data.
  • the optical transmitter is set to carrier modulation
  • the reconfigurable encoder/decoder is set to encode/decode
  • the coupler is set to data coupling
  • the optical receiver is set to carrier demodulation
  • the optical beam splitter is set to data split.
  • An optical transmitter, an optical circulator and a reconfigurable encoder are coupled to the coupler to form a data transmission link structure, and the data to be transmitted is transmitted through the optical transmitter and the first optical circulator (optical circulator A in the figure)
  • the data is sent to the reconfigurable encoder for encoding, and the encoded data is sent to the coupler through another output port of the first optical circulator.
  • An optical receiver, an optical circulator and a reconfigurable decoder are connected to the optical beam splitter to form a data receiving link structure.
  • the optical beam splitter After receiving the data, the optical beam splitter divides the data into multiple channels, each of which is sent Up to a third optical circulator (optical circulator C in the figure), the third optical circulator sends the data to a reconfigurable decoder for decoding, and the decoded data is passed through a third optical circulator An output port is sent to the optical receiver.
  • the coupler and the optical beam splitter are connected via a second optical circulator (optical circulator B in the figure), which are respectively connected to the optical circulator ports 1, 3; the second optical circulator port 2 is an output end of the OLT.
  • the coupler couples the data to be transmitted received from the plurality of optical transmitters and outputs them via the second optical circulator; the second optical circulator is further configured to be sent to the optical beam splitter after receiving the data.
  • Transmission fibers are used to connect between the above devices.
  • the OLT is connected to one or more ONUs via an ODN. The number of the above optical transmitter, first optical circulator, reconfigurable encoder, optical receiver, third optical circulator, and reconfigurable decoder is equal.
  • the optical transmitter 1 modulates the downlink data stream to the carrier light source, and then inputs it to the optical circulator A1 port 1, and the optical circulator A1 port 2 output, encoded by the reconfigurable encoder, then passed through the end of the optical circulator A1 After port 2, it is output by optical circulator A1 port 3, and finally input to the coupler.
  • the multi-coded data stream is coupled by the coupler, it enters port 1 of optical circulator B, and finally outputs from port 2 of optical circulator B, and then transmits it to the ONU or ONT through the optical fiber.
  • the data stream is decoded by the optical decoder.
  • the decoder must be in one-to-one correspondence with the encoder in the OLT, so that the data can be recovered for reception at the user end.
  • the encoded data stream transmitted by the ONU enters the port 2 of the optical circulator B, is output from the port 3 of the optical circulator B, and is split by the optical beam splitter to enter each data stream.
  • the data stream that is assigned to this link enters through port 1 of the optical circulator C1, and is output from the port 2 of the optical circulator C1 to enter the reconfigurable decoding.
  • the decoder performs decoding, and the decoded signal is output from the terminal 3 of the optical circulator C1 and finally received by the optical receiver 1.
  • the resulting recovered data stream signal is finally uploaded to the core network.
  • M > 1 Another structure (M > 1) of the OLT based on the above reconfigurable encoder/decoder is shown in Fig. 8.
  • the M data transmission/reception links share an MxN port-based AWG reconfigurable encoder 81 and a reconfigurable decoder 82, which simplifies the structure of the OLT and saves the network cost.
  • the structure of the ONU is as shown in FIG. 9.
  • the ONU is mainly composed of an optical transmitter 91, an optical receiver 92, an optical circulator (optical circulator D in the figure) 93, a coupler 94, a reconfigurable encoder 95, and
  • the reconstruction decoder 96 is composed of, wherein the optical transmitter comprises a reflective semiconductor optical amplifier (RSOA).
  • RSOA reflective semiconductor optical amplifier
  • the optical circulator D, the reconfigurable decoder, the coupler and the optical receiver are connected to form a data receiving link structure; when the optical circulator D receives the data sent by the OLT, the data is sent to the reconfigurable decoder.
  • the decoded data is divided into two paths from the other output port of the optical circulator D through the coupler, one output to the optical receiver, and the other output to the optical transmitter.
  • the optical circulator D, the reconfigurable encoder, the coupler, and the optical transmitter constitute a data transmission link structure; when the data is to be uplinked, the optical transmitter receives the input data to be transmitted, and then sends the signal to the coupling.
  • the device is sent to the optical circulator D by the coupler, and is sent by the optical circulator D to the reconfigurable encoder for encoding, and the encoded data is output by the other output port of the optical circulator D.
  • Transmission fibers are used to connect between the above devices.
  • the i-th ONU is taken as an example and transmitted from the OLT.
  • the encoded data stream is input to port 1 of optical circulator D, output from port 2 of optical circulator D, decoded by a reconfigurable decoder, and output from port 3 of optical circulator D for final recovery.
  • the outgoing data stream is split into two paths by the coupler, one is received by the optical receiver, and the other is received by the RSOA (used as uplink remodulation).
  • the ONU When the ONU processes the uplink data, the final recovered data stream of the downlink is received by the optical receiver through a part of the coupler, and a part of the data stream is received by the RSOA.
  • the RSOA receives the data to be transmitted, and the RSOA uses part of the downlink signal light as the uplink optical carrier, and then uplinks.
  • the signal is modulated onto the optical carrier, returned to the coupler, and then enters the optical circulator D port 3.
  • the optical circulator D port 4 enters the reconfigurable encoder for encoding, and then is output by the optical circulator D port 1 and transmitted through the ODN. Go to the OLT.
  • the RSOA can not only amplify the optical signal, but also modulate the optical signal.
  • the modulation is uplink remodulation, that is, part of the downlink signal light is used as an uplink optical carrier, and then the uplink signal is modulated onto the optical carrier.
  • the ONU utilizes the uplink remodulation function of the RSOA to save a light source and a modulator, simplifying the structure of the ONU and reducing the network cost.
  • the ONU of the present invention is a wavelength-independent device, and the wavelength at the time of uplink transmission is determined by the wavelength of the downlink optical carrier.
  • FPLD Bulb-Perot laser
  • the optical encoder is similar in structure to the optical decoder (AWG, tunable fiber retarder and reflector), and the difference between the two is that the delay length of the fiber retarder of the corresponding wavelength is different, and Complementary, that is, the sum of the lengths of delays of the tunable fiber delays of the encoder and the decoder at the respective wavelengths is constant, and the sum of the delay lengths of the tunable fiber retarders of the different wavelengths of the encoder and the decoder is equal.
  • the sum of the delay lengths of the two tunable fiber retarders 1 in Figures 5 and 6 is equal to the sum of the delay lengths of the two tunable fiber retarders K.
  • the above-mentioned reconfigurable codec-based OLT and ONU together with ODN constitute a reconfigurable encoder/decoder based OCDMA PON, and the OCDMA PON according to the present invention can provide better by using a reconfigurable AWG encoder/decoder.
  • Optical code division multiple access multiplexed passive optical network performance Enhance network flexibility and confidentiality.
  • the reconfigurable encoder/decoder provided by the present invention can solve the problem of large loss of the encoder/decoder of the conventional AWG by using only one AWG device, and greatly reduce the cost; the present invention provides based on the reconfigurable/ The optical line terminal OLT of the decoder realizes that a plurality of users share a reconfigurable encoder/decoder by using multiple incident ports of the AWG, which simplifies the structure of the OLT and saves network cost;
  • the optical network unit ONU of the structure/decoder makes full use of the characteristics of RSOA in the structure, reduces the laser light source, modulator and other devices that must be used in the original optical transmitter, simplifies the ONU structure, and is more conducive to saving network cost.
  • optical code division multiple access multiplexed passive optical network the optical code division multiple access passive optical network (OCDMA PON) based on the above reconfigurable encoder/decoder provided by the invention can solve the passive use of FBG as an encoder
  • the optical network has a limited code length and limited communication rate, which enhances network performance.

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Abstract

本发明公开了一种可重构编/解码器，以及基于该可重构编/解码器的OLT、ONU和光码分多址复用无源光网络。可重构编码器包括一个阵列波导光栅（AWG），N个可调光纤延迟器，N为整数且N≥1，M个反射器，M为整数且N≥M≥1，AWG至少有N个输入端口和N个输出端口，其中：AWG的输出端口与可调光纤延迟器的输入端相连，可调光纤延迟器的输出端与反射器相连；输入信号从AWG的输入端口输入，经由AWG处理后从对应的输出端口输出，每一路输出经可调光纤延迟器延时后到达反射器，经反射器反射后，通过对应的可调光纤延迟器返回至AWG的输出端口，由AWG的输入端口输出。本发明的技术方案可降低损耗和成本。

Description

可重构编解码器及基于该设备的光码分多址无源光网络
技术领域
本发明属于光纤通信技术领域， 特别涉及一种可重构 （ reconfigurable ) 编 /解码器， 以及基于该可重构编 /解码器的光线路终端 （OLT, Optical Line Terminate )、光网络单元（ ONU、 Optical Network Unit )和光码分多址（ Optical Code Division Multiple Access, OCDMA )无源光网络 ( PON ) 。
背景技术
在当前的数据通信中， 接入网由于是业务节点接口 （SNI, Service Node
Interface )和相关用户网络接口 （ UNI, User-to-network interface ) 的传送实 体而成为通信网的基础设施。 正由于这个特点， 接入网应该釆用一种公平、 灵活、 安全的多址技术。 而无源光网络（PON ) 因频带宽， 容量大， 扩容方 便， 适合高速数据传输等特点成为光接入网的热门技术； 在现有的多址技术 中， 时分多址（ TDMA, Time Division Multiple Access )和波分多址（ WDMA, Wavelength Division Multiple Access ) 能够有效利用光纤的巨大带宽， 但是在 传输速度和安全性方面有一定的局限性， 因此光码分多址复用 （OCDMA ) 以其在容量、带宽、安全性等方面的独特优势，成为与 PON结合的优良选择。
基于光码分多址复用的无源光网络（OCDMA-PON )是一种将光纤介质 的大带宽和码分多址复用 （CDMA ) 的灵活性相结合的多址复用技术， 对于 升级现有的 PON***或是作为下一代 PON的主要技术， OCDMA-PON都是 备受关注， 因为 OCDMA-PON可以使用相对简单的， 无需要同步的 OLT、 ONU设计， 现有的 PON也不需要为了适用 OCDMA而作太大的升级， 另外 OCDMA本身一些吸引人的技术， 比如全光处理、 真正的异步传输、 软容量、 协议透明和服务质量（ QoS )的灵活控制等， 也使得 OCDMA-PON的研究日 益受到人们的重视。
基于光码分多址复用的无源光网络（OCDMA-PON ) , 如图 1所示， 包 括 OLT ( Optical Line Terminate, 光线路终端） 11 , ODN ( Optical Distribution Network, 光配线网） 12和 ONU ( Optical Network Unit, 光网络单元） 13 , 其中： 光线路终端是基于光码分多址技术的光线路终端， 光网络单元是基于 光码分多址技术的光网络单元。
上述基于光码分多址复用技术的无源光网络（OCDMA-PON )还可以包 括一个或多个光网络终端（ONT, Optical Network Terminator ) , 所述一个或 多个网络终端与一个或多个光网络单元连接， 作为光网络单元的具体用户。
在 0CDMA-P0N中每一个用户在 0NU中分配有唯一的光编 /解码器（当 编码后的信号通过时为光解码器， 当原始信号通过时为光编码器） 。 用户数 据流被调制到光载波上后， 再通过光编码器， 编码后的用户数据通过光配线 网上行到 OLT。在 OLT中， 编码后的数据流通过光解码器做光信息的反处理 (即光编码过程的反处理）， 实现光解码。 解码后的数据流再通过 OLT中的 发射机上传到其他核心网， 实现不同 PON间各个 ONU的信息的互相传输。 从核心网下传的数据流在 OLT端经调制后， 再通过光编码器编码， 然后将编 码后的数据流通过光纤通道下传到光配线网， 数据流经光配线网将下行数据 流传到各个 ONU或 ONT, 在 ONU端编码后的数据流经光解码器实现解码， 恢复出传输数据以便用户数据的接收。
光编 /解码器是 OCDMA***的核心部件。在发送端光编码器将数据比特 转换成扩频序列， 在接收端光解码器利用相关解码原理将扩频序列恢复为数 据比特。 在 OCDMA通信***中， 所有用户共同占用同一信道的相同光语段 和时间段， 不同用户传输信息所用的信号靠不同的编码序列来区分， 即每个 用户都分配一个伪随机序列。 在发送端， 由每个用户的信息通过光编码器产 生伪随机序列， 由于编码器是唯一的， 所以伪随机序列也是唯一的， 用户的 每个信息比特编码成一串脉冲； 在接收端， 用户用相同的伪随机序列 （对应 的解码器）进行相关运算来恢复传输的信息。 这些伪随机序列就叫做用户的 地址码， 而每一个编码脉冲则称为一个码片。
光编 /解码器的结构和特性直接影响到 OCDMA***的总体性能， 决定着
OCDMA***能否投入实际应用。 目前， OCDMA编 /解码器主要类型： 基于 光纤延迟线的时域编 /解码方案、基于衍射光栅和相位掩模板的谱域编 /解码方 案、 基于光纤布拉格光栅的编 /解码方案、 基于阵列波导光栅的编 /解码方案。
最初使用的编码器大都基于光纤延迟线的时域编码。 光纤延迟线编码系 统是由并行的几束光纤和 2个 Ι χΡ星形耦合器构成的， 不同码字编码器之间 的差别在于光纤延迟线的延时长度不同。 该编码器是将一个输入光脉冲经过 功分器分成等功率的几路光脉冲， 这些脉冲经过不同的时延后再由光耦合器 重新合成一路， 从而实现将一个输入光脉冲变成一个脉冲序列 （编码） 的效 果。 这种编码器实现起来比较容易， 但需要器件较多， 比较笨重， 在实际制 作中需要精确控制各路延时线的延时长度， 而且损耗比较大。 基于衍射光栅和相位掩模板的谱域编 /解码方案， 釆用一体光栅对脉冲中 的各频率成分进行空间分离和重组， 用一相位掩模板来完成必要的脉冲滤波 和整形功能。 该方法有很大的缺点： 体积太大， 选址速度慢且难于集成； 受 色散影响大， 传输距离受限； 容纳的用户数目有限（波长的限制）等。 在实 际的工艺实现中， 空间光调制器（即光语掩模板）需要制作的很精细， 且不 易实现码字重构。
基于光纤布拉格光栅（FBG ) 的时域 /语域二维编码， 由一系列中心波长 不同的 FBG组成，每个光栅中心反射波长可由压电陶瓷装置调节光栅周期进 行改变， 实现波长编码， 光栅的位置起到光纤延迟线的作用， 使不同的频语 分量在时域上分开， 从而实现时域 /语域混合编码。 图 2为串联结构 FBG编 / 解码器，每个编码 /解码器都由几个不同反射波长的 FBG串联在一起组成。入 射光脉冲经过光环行器 21、编码 FBG22进行语域编码，在时域上形成一个脉 冲序列， 然后在经过解码 FBG23、 光环行器 21后， 这些脉冲序列又被压缩， 并重新合成一个脉冲。该编 /解码器实现比较简单，但地址码的码长受 FBG数 目的限制。 另夕卜， FBG对光脉冲有展宽作用，难以用于 lGbps以上高速通信。
基于阵列波导光栅 ( AWG )的编 /解码器，如图 3所示，图 3为基于 AWG31 的二维时域 /语域编码器， 图 4为基于 AWG41 的一维谱域编 /解码器。 基于 AWG的编 /解码器可以解决 FBG编码器的码长受限和速率受限问题， 且易集 成。 基于 AWG的一维编 /解码器类似于一维时域并行编 /解码器， 可以通过加 一个码字控制器来进行码字的重构。 基于 AWG的二维时域 /语域编 /解码器， 相比于基于 FBG的编 /解码器， 该结构属于并行结构， 充分利用了 AWG分波 器的特点， 在 AWG不同输出波长处加不同延时长度的光纤延迟， 进行时域 扩展， 从而也达到二维编码的目的。 相对于 FBG结构， AWG编 /解码器因不 需要反射， 其相应延迟线的延时长度也比 FBG结构长了一倍。 不过以上两个 基于 AWG编 /解码器都需要两个 AWG器件， 使得整个编 /解码器损耗较大， 也使得整个无源光网络***的损耗预算变大， 不利于***成本控制。 发明内容
本发明要解决的技术问题是提供一种可重构编 /解码器， 以及基于该可重 构编 /解码器的光码分多址复用无源光网络， 降低损耗和成本。
为解决上述技术问题， 本发明提供了一种可重构编码器， 包括一个阵列 波导光栅 AWG, N个可调光纤延迟器， N为整数且^^ > 1 , M个反射器， M 为整数且 N > M > 1 ,所述 AWG至少有 N个输入端口和 N个输出端口，其中： 所述 AWG的输出端口与所述可调光纤延迟器的输入端相连， 所述 N个 可调光纤延迟器中的 M个可调光纤延迟器的输出端分别与所述 M个反射器 相连； 输入信号从所述 AWG的输入端口输入， 经由 AWG处理后从对应的 输出端口输出， 其中的 M路输出信号经可调光纤延迟器延时后到达反射器， 经反射器反射后， 通过对应的可调光纤延迟器返回至所述 AWG的输出端口， 由所述 AWG的输入端口输出。
优选地， 所述可重构编码器还包括 P个适配器件， P为整数且 N-M > P > 1 , 所述 N个可调光纤延迟器中的 P个可调光纤延迟器的输出端分别连接 至 P个适配器件；
输入信号从所述 AWG的输入端口输入， 经由 AWG处理后从对应的输 出端口输出， 其中的 P路输出信号经可调光纤延迟器延时后到达适配器件， 到达适配器件的信号被消光。
为解决上述技术问题， 本发明还提供了一种可重构解码器， 包括一个阵 列波导光栅 AWG, N个可调光纤延迟器， N为整数且^^ > 1 , M个反射器， M为整数且 N > M > 1 , 所述 AWG至少有 N个输入端口和 N个输出端口， 其中：
所述 AWG的输出端口与所述可调光纤延迟器的输入端相连， 所述 N个 可调光纤延迟器中的 M个可调光纤延迟器的输出端分别与所述 M个反射器 相连； 输入信号从所述 AWG的输入端口输入， 经由 AWG处理后从对应的 输出端口输出， 其中的 M路输出经可调光纤延迟器延时后到达反射器， 经反 射器反射后， 通过对应的可调光纤延迟器返回至所述 AWG的输出端口， 由 所述 AWG的输入端口输出。
优选地， 所述可重构解码器还包括 P个适配器件， P为整数且 N-M > P
> 1 , 所述 N个可调光纤延迟器中的 P个可调光纤延迟器的输出端连接至适 配器件； 输入信号从所述 AWG的输入端口输入， 经由 AWG处理后从对应 的输出端口输出， 其中的 P路输出信号经可调光纤延迟器延时后到达适配器 件， 到达适配器件的信号被消光。
为解决上述技术问题， 本发明还提供了一种基于上述可重构编码器和可 重构解码器的光线路终端（OLT ) , 所述 OLT包括光发射机、 第一光环行器、 第二光环行器、 第三光环行器、 可重构编码器、 耦合器、 光接收机、 可重构 解码器、 光分束器， 其中：
待发送数据经光发射机、 第一光环行器送至可重构编码器进行编码， 编 码后的数据经第一光环行器送至耦合器， 所述耦合器将从多个光发射机接收 到的待发送数据耦合后经第二光环行器输出；
所述第二光环行器接收到数据后送至光分束器， 所述光分束器将数据分 成多路， 每一路送至一第三光环行器， 所述第三光环行器将所述数据送至可 重构解码器进行解码， 解码后的数据经第三光环行器送至光接收机。
优选地， 所述可重构编码器、 可重构解码器各有一个， 所述光发射机、 所述第一光环行器、 所述光接收机和所述第三光环行器分别有多个， 且个数 相等； 或者， 所述光发射机、 所述第一光环行器、 所述可重构编码器、 所述 光接收机、 所述第三光环行器和所述可重构解码器分别有多个， 且个数相等。
为解决上述技术问题， 本发明还提供了一种基于上述可重构编码器和可 重构解码器的光网络单元（ONU ) , 所述 ONU 包括光发射机、 光接收机、 光环行器、 耦合器、 可重构编码器、 可重构解码器， 其中： 所述可重构编码器、 可重构解码器和耦合器与所述光环行器相连， 所述 光发射机、 光接收机与所述耦合器相连； 当所述光环行器接收到光线路终端 OLT发送的光信号后，将所述光信号 送至所述可重构解码器进行解码， 解码后的数据从所述光环行器输出至耦合 器， 经耦合器输出至光接收机；
当要发送上行数据时， 所述光发射机将待发送数据发送至耦合器， 由耦 合器送至光环行器， 由光环行器送至所述可重构编码器进行编码， 编码后的 数据由光环行器输出。
优选地， 所述光发射机包括反射式半导体光放大器 RSOA或者法布里- 珀罗激光器 FPLD; 光信号到达耦合器后， 经耦合器分成两路， 一路输出至光 接收机， 另一路输出至光发射机； 当要发送上行数据时， 所述光发射机将接 收到的输入光作为上行光载波， 将所述待发送数据承载在所述上行光载波上 发送出去。
为解决上述技术问题， 本发明还提供了一种基于上述可重构编码器和可 重构解码器的光码分多址复用无源光网络， 包括光线路终端 （OLT ) 、 光配 线网 （ODN )和光网络单元（ONU ) , 其中：
所述 OLT包括光发射机、第一光环行器、第二光环行器、第三光环行器、 可重构编码器、 耦合器、 光接收机、 可重构解码器、 光分束器， 其中： 待发 送数据经光发射机、 第一光环行器送至可重构编码器进行编码， 编码后的数 据经第一光环行器送至耦合器， 所述耦合器将从多个光发射机接收到的待发 送数据耦合后经第二光环行器输出； 所述第二光环行器接收到数据后送至光 分束器， 所述光分束器将数据分成多路， 每一路送至一第三光环行器， 所述 第三光环行器将所述数据送至可重构解码器进行解码， 解码后的数据经第三 光环行器送至光接收机；
所述 ONU包括光发射机、光接收机、光环行器、耦合器、可重构编码器、 可重构解码器， 其中： 当所述光环行器接收到 OLT发送的光信号后， 将所述 光信号送至所述可重构解码器进行解码， 解码后的数据从所述光环行器输出 至耦合器， 经耦合器输出至光接收机； 当要发送上行数据时， 所述光发射机 将待发送数据发送至耦合器， 由耦合器送至光环行器， 由光环行器送至所述 可重构编码器进行编码， 编码后的数据由光环行器输出。
优选地， 在所述 OLT中， 所述可重构编码器、 可重构解码器各有一个， 所述光发射机、 所述第一光环行器、 所述光接收机和所述第三光环行器分别 有多个， 且个数相等； 或者， 所述光发射机、 所述第一光环行器、 所述可重 构编码器、 所述光接收机、 所述第三光环行器和所述可重构解码器分别有多 个， 且个数相等； 在所述 ONU中， 所述光发射机包括反射式半导体光放大器 RSOA或者法布里 -珀罗激光器 FPLD; 光信号到达耦合器后， 经耦合器分成 两路， 一路输出至光接收机， 另一路输出至光发射机； 当要发送上行数据时， 所述光发射机将接收到的输入光作为上行光载波， 将所述待发送数据承载在 所述上行光载波上发送出去。
本发明所述的可重构编 /解码器， 由于只使用一个 AWG器件， 可解决传 统 AWG的编 /解码器损耗较大的问题， 并且大大降低成本。 另外， 由于该可 重构编 /解码器利用了 AWG的多个入射端口， 可同时对多组输入进行编码或 解码， 可以实现时域和谱域混合编码。 利用该可重构编 /解码器中可调光纤延 迟器的延迟可调性， 和控制被反射的波长选择（通过可调光纤延迟器后连接 反射器或适配器件的选择来实现） ， 可实现编 /解码器的码字重构， 增加网络 的灵活性和保密性。
本发明基于上述可重构编 /解码器的光码分多址无源光网络（ OCDMA PON ) , 能解决使用 FBG为编码器的无源光网络码长受限（可导致复用用户 数受限）及通信速率受限问题。 其中， 基于上述可重构编解码器的 OLT, 利 用 AWG的多个入射端口， 可实现多个用户共用一个可重构编 /解码器， 简化 了 OLT的结构， 节约了网络成本； 基于上述可重构编 /解码器的 ONU, 由于 结构中充分利用 RSOA特性， 可减少原来光发射机中必须使用的激光光源、 调制器等器件， 简化了 ONU结构， 更有利于节约网络成本。
附图概述
图 1为 OCDMA-PON无源光网络框图；
图 2为基于光纤布拉格光栅（FBG ) 的编 /解码器图；
图 3为基于 AWG的二维时域 /谱域编 /解码器图；
图 4为基于 AWG的一维编 /解码器图； 图 5为基于 AWG的可重构编码器的结构图；
图 6为基于 AWG的可重构解码器的结构图；
图 7为本发明基于可重构编 /解码器的光码分多址复用无源光网络的 OLT 结构图 （M>1的情况） ；
图 8为本发明基于可重构编 /解码器的光码分多址复用无源光网络的 OLT 结构图 （M=l的情况） ；
图 9 为本发明基于可重构编 /解码器的光码分多址复用无源光网络的 ONU结构图。 本发明的较佳实施方式
为使本发明的技术方案和优点更加清楚， 下面结合附图对本发明的具体 实施例进行详细的说明。
本发明提出一种可重构编码器， 包括一个阵列波导光栅（AWG ) 、 N个 可调光纤延迟器和 M个反射器， 其中 N和 M为整数且^^ > 1、 N > M > 1 , 所 述 AWG至少有 N个输入端口和 N个输出端口， 其中：
所述 AWG的输出端口与所述可调光纤延迟器的输入端相连， 所述可调 光纤延迟器的输出端与所述反射器相连； 输入信号从所述 AWG输入端口输 入， 经由 AWG处理后从对应的输出端口输出， 每一路输出经可调光纤延迟 器延时后到达反射器， 经反射器反射后， 通过对应的可调光纤延迟器返回至 所述 AWG的输出端口， 由所述 AWG的输入端口输出。
优选地， 所述可重构编码器还包括 P个适配器件， P为整数且 N-M > P > 1 , 所述 N个可调光纤延迟器中的 M个可调光纤延迟器的输出端连接至反 射器， P个可调光纤延迟器的输出端连接至适配器件； 输入信号从所述 AWG 输入端口输入， 经由 AWG处理后从对应的输出端口输出， 输出信号经可调 光纤延迟器延时后到达反射器或适配器件， 到达反射器的信号经反射器反射 后， 通过对应的可调光纤延迟器返回至所述 AWG的输出端口， 由所述 AWG 的输入端口输出； 到达适配器件的信号被消光（不会反射回来） 。
本发明提出一种可重构解码器， 包括一个阵列波导光栅（AWG ) , N个 可调光纤延迟器， N为整数且^^ > 1、 M个反射器， M为整数且 N > M > 1 , 所述 AWG至少有 N个输入端口和 N个输出端口， 其中：
所述 AWG的输出端口与所述可调光纤延迟器的输入端相连， 所述可调 光纤延迟器的输出端与所述反射器相连； 输入信号从所述 AWG输入端口输 入， 经由 AWG处理后从对应的输出端口输出， 每一路输出经可调光纤延迟 器延时后到达反射器， 经反射器反射后， 通过对应的可调光纤延迟器返回至 所述 AWG的输出端口， 由所述 AWG的输入端口输出。
优选地， 所述可重构解码器还包括 P个适配器件， P为整数且 N-M > P > 1 , 所述 N个可调光纤延迟器中的 M个可调光纤延迟器的输出端连接至反 射器， P个可调光纤延迟器的输出端连接至适配器件； 输入信号从所述 AWG 输入端口输入， 经由 AWG处理后从对应的输出端口输出， 输出信号经可调 光纤延迟器延时后到达反射器或适配器件， 到达反射器的信号经反射器反射 后， 通过对应的可调光纤延迟器返回至所述 AWG的输出端口， 由所述 AWG 的输入端口输出； 到达适配器件的信号被消光（不会反射回来） 。
上述适配器件可以是隔离器、 衰减光纤等器件， 其设置为对输入光进行 衰减消光， 这样可以有意识地过滤掉一些波长的光， 防止光反射对编 /解码造 成影响。
所述可调光纤延迟器优选为可调光纤延迟线。 通过调节可调光纤延迟器 延迟的时间长度， 可实现对不同波长的信号反射， 即可以产生不同的码字， 实现不同的语域编码， 实现码字重构。
本发明所述可重构编 /解码器是基于阵列波导光栅（AWG )的编 /解码器， 相对于传统的阵列波导光栅（AWG )的编 /解码器，本发明中的可重构的 AWG 编 /解码器只使用一个 AWG器件， 该 AWG釆用多个输入口接收数据， 可以 同时对 M组数据进行编 /解码。 另外， 仅使用一个 AWG器件可解决传统阵列 波导光栅（AWG ) 的编 /解码器损耗较大的问题。
光编 /解码器是 OCDMA-PON ***的核心部件。 在发送端， 光编码器将 数据比特转换成码序列， 在接收端光解码器利用相关解码原理将码序列恢复 为数据比特。 光编 /解码器的结构和特性直接影响着***的总体性能。 本发明 中的可重构编 /解码器是基于 AWG的可重构编 /解码器。该光编 /解码器充分利 用了 AWG的循环特性。 AWG的循环特性是指不同的输入口在相应的输出口 输出的波长是循环的， 如果用 i ( \≤i<M )来指代输入口， j ( 1≤ j≤N )来指 代输出口， N表示所用的波长总数。 当 i=l时，输出口输出的波长分别是 { 4,4, Λ4, ...... },当 i=2的时候，输出口输出的波长分别是 λ,, λ4, ...... ^, }, 以此类推。 基于 AWG的可重构编 /解码器， 通过控制光纤延迟器后 面连接反射器还是适配器件， 来控制选择被反射的波长， 这样一来每个编 /解 码并没有利用全部的波长， 而是只利用了反射器返回的几个波长。 如果用 i ( \≤i≤M )来指代输入口， j ( 1≤ j≤N )来指代输出口， N表示 AWG可用 总波长数，选择 K个波长作为反射波长，假设 K=5, 5个反射波长分别为
4, ^， ， 则当 i=l时， 输出口输出的波长分别是 { 4, Α,, Α,, ,, A,}, 当 i=2的时候， 输出口输出的波长分别是 Α,, λ,, Α,, }, 以此 类推。 被反射的 Κ个波长在经过不同的时延后重新合成信号， 从而实现了在 时域和谱域的二维编码。 这样通过对 Κ个不同反射波长的选择， 可实现不同 的谱域编码， 即实现码字的重构。
基于 AWG的可重构编 /解码器， 结构分别如图 5、 6所示， 主要由 Μχ Ν 端口的 AWG51、 可调光纤延迟器 52、 适配器件和反射器组成。 MxN端口的 AWG的 N个输出口对应连接 N个可调光纤延迟器， 但只在其中的 K个可调 光纤延迟器后连接反射器（即选择 K个反射波长， Ν≥Κ、 , 剩余的 N-K个 可调光纤延迟器后连接适配器件（即对剩余 N-K波长进行消光， 防止其反射 对编 /解码的影响） 。 基于 AWG的光编 /解码器属于并行结构， 利用了 AWG 良好的分光特性， 对光源脉冲进行波长分割， 在其不同输出波长处加上不同 的光纤延迟器， 进行时域编码， 这样在谱域和时域均进行了编码， 从而实现 直接序列 （ DS )码分多址 /语域编码（ FE )码分多址混合 OCDMA***的编 / 解码； 若各光纤延迟器延迟的时间长度相等， 则可完成谱域编码码分多址系 统（FE-OCDMA)谱域编 /解码。 通过不同反射波长的选择（控制光纤延迟器 连接是反射器还是适配器件）和改变可调光纤延迟器延迟的时间长度， 或者 仅通过改变可调光纤延迟器延迟的时间长度， 就可以实现码字的重构， 需要 注意的是， 改变相应光纤延迟器延迟的时间长度时须同时改变 OLT和 ONU 中同一接收、 发射链路的编码器和解码器的光纤延迟器的延时长度， 使得各 个对应的编码器和解码器的光纤延迟器延时长度之和相等； 改变光纤延迟器 连接的反射器和适配器件时须同时改变 OLT和 ONU中同一接收、 发射链路 的编码器和解码器。
信道中， 用户数据光源脉冲通过光环行器进入 AWG输入端口， AWG对 其进行波长分割， 在不同的输出口输出不同波长的光脉冲， 即进行语域编 /解 码，分割波长后的脉冲经过不同延时长度的光纤延迟器，即进行时域编 /解码， 反射器用于将脉冲反射回 AWG, 脉冲再经过一次不同长度的时延后， 返回 AWG, 最后经光环行器输出， 得到最后的编 /解码数据。
基于上述可重构编 /解码器的 OLT的一种结构（ AWG输入端口 M=l )如 图 7所示， 包括光发射机 71、 光环行器 72、 可重构编码器 73、 耦合器 74、 光接收机 75、 可重构解码器 76、 光分束器 77。 其中： 光发射机设置为载波 调制， 可重构编 /解码器设置为编 /解码、耦合器设置为数据耦合、 光接收机设 置为载波解调、 光分束器设置为数据分流。 一个光发射机、 一个光环行器和 一个可重构编码器与耦合器相连构成一路数据发送链路结构， 待发送数据经 光发射机、 第一光环行器（图中的光环行器 A )送至可重构编码器进行编码， 编码后的数据经第一光环行器的另一输出口送至耦合器。 一个光接收机、 一 个光环行器和一个可重构解码器与光分束器相连构成一路数据接收链路结 构， 所述光分束器接收到数据后， 将数据分成多路， 每一路送至一第三光环 行器 （图中的光环行器 C ) , 所述第三光环行器将所述数据送至可重构解码 器进行解码， 解码后的数据经第三光环行器的另一输出口送至光接收机。 耦 合器与光分束器经第二光环行器（图中的光环行器 B )连接， 二者分别与光 环行器端口 1、 3相连； 第二光环行器端口 2为 OLT的输出端， 耦合器将从 多个光发射机接收到的待发送数据耦合后经第二光环行器输出； 第二光环行 器还设置为在接收到数据后送至光分束器。 以上各个器件之间均使用传输光 纤进行连接。 该 OLT通过 ODN与一个或多个 ONU相连。 上述光发射机、 第一光环行器、 可重构编码器、 光接收机、 第三光环行器和可重构解码器的 个数相等。
信道中， 当 OLT处理下行信号时， 以光发射机 1这一链路为例， 光发射 机 1将下行的数据流调制到载波光源后， 输入到光环行器 A1端口 1 , 从光环 行器 A1端口 2输出， 经可重构编码器进行编码后， 再经过光环行器 A1的端 口 2后， 由光环行器 A1端口 3输出， 最后输入到耦合器中。 多路编码后的数 据流经耦合器耦合后， 进入光环行器 B的端口 1 , 最后从光环行器 B的端口 2输出，再通过光纤传输到 ONU或 ONT。在 ONU端数据流经光解码器解码， 这个解码器必须是与 OLT中的编码器一一对应的，这样才能恢复出数据以便 在用户端接收。
当 OLT处理上行数据时， 由 ONU传输来的编码后的数据流由光环行器 B的端口 2进入， 从光环行器 B的端口 3输出后， 经光分束器分束后进入各 个数据流接收链路， 以光接收机 1这一链路为例， 分到这一链路的数据流由 光环行器 C1的端口 1进入， 从光环行器 C1的端口 2输出后进入可重构解码 器进行解码， 解码后的信号从光环行器 C1 的端 3输出， 最终被光接收机 1 接收。 得到的最后恢复出的数据流信号， 最后上传到核心网中。
基于上述可重构编 /解码器的 OLT的另一种结构 （M > 1 )如图 8所示， 此处各个器件的作用功能、信号处理过程均与 M=l情况下相同， 只是每一个 接收、 发射链路均分配有一个唯一的基于 l x N端口 AWG的编 /解码器。 上 述结构的 OLT中 M个数据发送 /接收链路共享一个基于 MxN端口的 AWG的 可重构编码器 81和可重构解码器 82, 简化了 OLT的结构， 更大大的节约了 网络成本。
所述 ONU的结构如图 9所示， ONU主要由光发射机 91、 光接收机 92、 光环行器（图中的光环行器 D ) 93、 耦合器 94、 可重构编码器 95、 可重构解 码器 96组成， 其中， 光发射机包括反射式半导体光放大器（RSOA ) 。 光环 行器 D、 可重构解码器、耦合器和光接收机相连构成一路数据接收链路结构； 当所述光环行器 D接收到 OLT发送的数据后，将数据送至可重构解码器进行 解码， 解码后的数据从光环行器 D的另一输出口， 经耦合器分成两路， 一路 输出至光接收机， 另一路输出至光发射机。 上述光环行器 D、 可重构编码器、 耦合器、 光发射机构成一路数据发送链路结构； 当要上行发送数据时， 所述 光发射机接收输入的待发送数据， 处理后送至耦合器， 由耦合器送至光环行 器 D, 由光环行器 D送至可重构编码器进行编码， 编码后的数据由光环行器 D的另一输出口输出。 以上各个器件之间均使用传输光纤进行连接。
信道中， 当 ONU处理下行光信号时， 以第 i个 ONU为例， 从 OLT中传 来的编码后的数据流输入到光环行器 D的端口 1 , 从光环行器 D的端口 2输 出， 经可重构解码器进行解码后， 从光环行器 D的端口 3输出， 得到最终恢 复出来的数据流，经耦合器分成两路，一路被被光接收机接收，一路被 RSOA 接收（用作上行再调制） 。
当 ONU处理上行数据时，下行的最终恢复出来的数据流经耦合器一部分 被光接收机接收， 一部分进入 RSOA, RSOA接收待发送的数据， RSOA将部 分下行信号光作为上行光载波， 然后将上行信号调制到此光载波上， 返回耦 合器， 再进入光环行器 D端口 3 , 由光环行器 D端口 4进入可重构编码器进 行编码， 然后由光环行器 D端口 1输出， 通过 ODN传输到 OLT中。
RSOA不仅可以对光信号进行放大， 还可以对光信号进行调制， 此处的 调制为上行再调制， 即将部分下行信号光作为上行光载波， 然后将上行信号 调制到此光载波上。 本发明中 ONU利用 RSOA的上行再调制功能， 可节省 一个光源和一个调制器， 简化了 ONU的结构的同时， 也降低了网络成本。 另 夕卜， 由于釆用了 RSOA, 本发明的 ONU是与波长无关的设备， 其上行发送时 的波长由下行光载波的波长决定。
也可以用法布里 -珀罗激光器（FPLD )代替 RSOA, 或者用现有普通光发 射机作为上述光发射机。
OLT和 ONU中， 光编码器与光解码器（AWG、 可调光纤延迟器和反射 器组合） 结构相似， 两者之间的不同之处在于相应波长的光纤延迟器延迟的 时间长度不同， 且成互补， 即相应波长处编码器和解码器的可调光纤延迟器 延迟的时间长度之和为常数， 不同波长的编码器和解码器的可调光纤延迟器 延时长度之和相等。 例如： 图 5、 6中两个可调光纤延迟器 1的延时长度之和 与两个可调光纤延迟器 K的延时长度之和相等。
上述基于可重构编解码器的 OLT和 ONU与 ODN共同组成了基于可重 构编 /解码器的 OCDMA PON, 本发明所述的 OCDMA PON利用可重构的 AWG编 /解码器可以提供更好的光码分多址复用无源光网络性能： 增强网络 的灵活性、 保密性。
本领域普通技术人员可以理解上述方法中的全部或部分步骤可通过程序 来指令相关硬件完成， 所述程序可以存储于计算机可读存储介质中， 如只读 存储器、 磁盘或光盘等。 可选地， 上述实施例的全部或部分步骤也可以使用 一个或多个集成电路来实现。 相应地， 上述实施例中的各模块 /单元可以釆用 硬件的形式实现， 也可以釆用软件功能模块的形式实现。 本发明不限制于任 何特定形式的硬件和软件的结合。
工业实用性
本发明提供的可重构编 /解码器， 由于只使用一个 AWG器件， 可解决传 统 AWG的编 /解码器损耗较大的问题， 并且大大降低成本； 本发明提供的基 于该可重构编 /解码器的光线路终端 OLT, 利用 AWG的多个入射端口， 实现 了多个用户共用一个可重构编 /解码器，简化了 OLT的结构，节约了网络成本； 本发明提供的基于该可重构编 /解码器的光网络单元 ONU,由于结构中充分利 用了 RSOA的特性， 减少了原来光发射机中必须使用的激光光源、 调制器等 器件， 简化了 ONU结构， 更有利于节约网络成本和光码分多址复用无源光网 络； 本发明提供的基于上述可重构编 /解码器的光码分多址无源光网络 ( OCDMA PON ) , 能解决使用 FBG为编码器的无源光网络码长受限及通信 速率受限问题， 增强了网络性能。

Claims

权 利 要 求 书
1、 一种可重构编码器， 包括一个阵列波导光栅 AWG, N个可调光纤延 迟器， N为整数且^^>1, M个反射器， M为整数且 N>M>1, 所述 AWG 至少有 N个输入端口和 N个输出端口， 其中：
所述 AWG的输出端口与所述可调光纤延迟器的输入端相连， 所述 N个 可调光纤延迟器中的 M个可调光纤延迟器的输出端分别与所述 M个反射器 相连；
输入信号从所述 AWG的输入端口输入， 经由 AWG处理后从对应的输 出端口输出， 其中的 M路输出信号经可调光纤延迟器延时后到达反射器， 经 反射器反射后， 通过对应的可调光纤延迟器返回至所述 AWG的输出端口， 由所述 AWG的输入端口输出。
2、如权利要求 1所述的可重构编码器， 所述可重构编码器还包括 P个适 配器件， P为整数且 N-M>P>1, 所述 N个可调光纤延迟器中的 P个可调光 纤延迟器的输出端分别连接至 P个适配器件；
输入信号从所述 AWG的输入端口输入， 经由 AWG处理后从对应的输 出端口输出， 其中的 P路输出信号经可调光纤延迟器延时后到达适配器件， 到达适配器件的信号被消光。
3、 一种可重构解码器， 包括一个阵列波导光栅 AWG, N个可调光纤延 迟器， N为整数且^^>1, M个反射器， M为整数且 N>M>1, 所述 AWG 至少有 N个输入端口和 N个输出端口， 其中：
所述 AWG的输出端口与所述可调光纤延迟器的输入端相连， 所述 N个 可调光纤延迟器中的 M个可调光纤延迟器的输出端分别与所述 M个反射器 相连；
输入信号从所述 AWG的输入端口输入， 经由 AWG处理后从对应的输 出端口输出， 其中的 M路输出经可调光纤延迟器延时后到达反射器， 经反射 器反射后， 通过对应的可调光纤延迟器返回至所述 AWG的输出端口， 由所 述 AWG的输入端口输出。
4、如权利要求 3所述的可重构解码器， 所述可重构解码器还包括 P个适 配器件， P为整数且 N-M > P > 1 , 所述 N个可调光纤延迟器中的 P个可调光 纤延迟器的输出端连接至适配器件；
输入信号从所述 AWG的输入端口输入， 经由 AWG处理后从对应的输 出端口输出， 其中的 P路输出信号经可调光纤延迟器延时后到达适配器件， 到达适配器件的信号被消光。
5、一种基于权利要求 1所述的可重构编码器和权利要求 3所述的可重构 解码器的光线路终端 OLT, 所述 OLT包括光发射机、 第一光环行器、 第二光 环行器、 第三光环行器、 可重构编码器、 耦合器、 光接收机、 可重构解码器、 光分束器， 其中：
待发送数据经光发射机、 第一光环行器送至可重构编码器进行编码， 编 码后的数据经第一光环行器送至耦合器， 所述耦合器将从多个光发射机接收 到的待发送数据耦合后经第二光环行器输出；
所述第二光环行器接收到数据后送至光分束器， 所述光分束器将数据分 成多路， 每一路送至一第三光环行器， 所述第三光环行器将所述数据送至可 重构解码器进行解码， 解码后的数据经第三光环行器送至光接收机。
6、 如权利要求 5所述的光线路终端， 其中，
所述可重构编码器、 可重构解码器各有一个， 所述光发射机、 所述第一 光环行器、 所述光接收机和所述第三光环行器分别有多个， 且个数相等； 或者， 所述光发射机、 所述第一光环行器、 所述可重构编码器、 所述光 接收机、 所述第三光环行器和所述可重构解码器分别有多个， 且个数相等。
7、一种基于权利要求 1所述的可重构编码器和权利要求 3所述的可重构 解码器的光网络单元 ONU, 所述 ONU包括光发射机、 光接收机、 光环行器、 耦合器、 可重构编码器、 可重构解码器， 其中：
所述可重构编码器、 可重构解码器和耦合器与所述光环行器相连， 所述 光发射机、 光接收机与所述耦合器相连；
当所述光环行器接收到光线路终端 OLT发送的光信号后，将所述光信号 送至所述可重构解码器进行解码， 解码后的数据从所述光环行器输出至耦合 器， 经耦合器输出至光接收机； 当要发送上行数据时， 所述光发射机将待发送数据发送至耦合器， 由耦 合器送至光环行器， 由光环行器送至所述可重构编码器进行编码， 编码后的 数据由光环行器输出。
8、 如权利要求 7所述的光网络单元， 其中，
所述光发射机包括反射式半导体光放大器 RSOA或者法布里-珀罗激光 器 FPLD; 光信号到达耦合器后， 经耦合器分成两路， 一路输出至光接收机， 另一路输出至光发射机； 当要发送上行数据时， 所述光发射机将接收到的输 入光作为上行光载波，将所述待发送数据承载在所述上行光载波上发送出去。
9、一种基于权利要求 1所述的可重构编码器和权利要求 3所述的可重构 解码器的光码分多址复用无源光网络， 包括光线路终端 OLT、光配线网 ODN 和光网络单元 ONU,
所述 OLT包括光发射机、第一光环行器、第二光环行器、第三光环行器、 可重构编码器、 耦合器、 光接收机、 可重构解码器、 光分束器， 其中： 待发 送数据经光发射机、 第一光环行器送至可重构编码器进行编码， 编码后的数 据经第一光环行器送至耦合器， 所述耦合器将从多个光发射机接收到的待发 送数据耦合后经第二光环行器输出； 所述第二光环行器接收到数据后送至光 分束器， 所述光分束器将数据分成多路， 每一路送至一第三光环行器， 所述 第三光环行器将所述数据送至可重构解码器进行解码， 解码后的数据经第三 光环行器送至光接收机；
所述 ONU包括光发射机、光接收机、光环行器、耦合器、可重构编码器、 可重构解码器， 其中： 当所述光环行器接收到 OLT发送的光信号后， 将所述 光信号送至所述可重构解码器进行解码， 解码后的数据从所述光环行器输出 至耦合器， 经耦合器输出至光接收机； 当要发送上行数据时， 所述光发射机 将待发送数据发送至耦合器， 由耦合器送至光环行器， 由光环行器送至所述 可重构编码器进行编码， 编码后的数据由光环行器输出。
10、 如权利要求 9所述的光码分多址复用无源光网络， 其中，
在所述 OLT中， 所述可重构编码器、 可重构解码器各有一个， 所述光发 射机、 所述第一光环行器、 所述光接收机和所述第三光环行器分别有多个， 且个数相等； 或者， 所述光发射机、 所述第一光环行器、 所述可重构编码器、 所述光接收机、 所述第三光环行器和所述可重构解码器分别有多个， 且个数 相等；
在所述 ONU中， 所述光发射机包括反射式半导体光放大器 RSOA或者 法布里 -珀罗激光器 FPLD; 光信号到达耦合器后， 经耦合器分成两路， 一路 输出至光接收机， 另一路输出至光发射机； 当要发送上行数据时， 所述光发 射机将接收到的输入光作为上行光载波， 将所述待发送数据承载在所述上行 光载波上发送出去。
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