CN113654766B - Single-mode fiber coupler phase shift measuring device, method and storage medium - Google Patents
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Abstract
The invention belongs to the technical field of optical fibers, particularly relates to a device, a method and a storage medium for measuring the phase shift of a single-mode optical fiber coupler, and aims to solve the problems of complicated measuring process and low measuring precision of the conventional coupler phase shift measuring method. The apparatus includes a spectral measurement device configured to emit a scanning light source into a hybrid Sagnac interferometer; the device is also configured to collect interference spectrum signals of a reciprocal port and a non-reciprocal port of the hybrid Sagnac interferometer and send the interference spectrum signals to a computing module; the hybrid Sagnac interferometer is configured to split an input scanning light source, generate an interference spectrum signal after passing through a polarization maintaining optical fiber and output the interference spectrum signal; and the calculation module is configured to extract valley wavelengths based on the received interference spectrum signals and calculate the phase shift value of the single-mode fiber coupler. The invention greatly reduces the complexity of the phase shift of the coupler and improves the measurement precision.
Description
Technical Field
The invention belongs to the technical field of optical fibers, and particularly relates to a device and a method for measuring phase shift of a single-mode optical fiber coupler and a storage medium.
Background
The optical fiber coupler is an optical passive device for distributing power or wavelength of optical signals, is a necessary device for realizing full optical fibers of an optical fiber communication and sensing system, can greatly reduce the loss and volume of the optical fiber system, and improves the stability of the system. For a single-mode fiber coupler, the main performance indexes of the single-mode fiber coupler include additional loss, splitting ratio, working wavelength and the like, but in some application occasions such as fiber interference systems and fiber optic gyroscopes, besides the indexes, the phase relationship among the ports of the coupler also has obvious influence on the performance of a sensing system, and the determination of the coupling phase shift characteristic of the fiber coupler has important value in improving the performance of an interference type fiber sensing detection system.
The theoretical analysis of the coupler phase shift can only determine the maximum variation range of the phase shift according to the intrinsic characteristics of the coupler, the exact value of the phase shift cannot be obtained, the coupler phase shift is susceptible to external factors such as temperature, optical wavelength and the like, and the exact phase shift value must be determined through experimental detection.
The existing phase shift detection schemes are all based on an M-Z interference structure, a modulation signal needs to be applied to a light source or a reference arm, a phase shift value is calculated through intensity demodulation of light output by each port, detection accuracy is affected by factors such as photoelectric conversion, optical path loss, performance of a light splitting coupler and the modulation signal, and large errors exist. Although some errors can be reduced through subsequent signal processing algorithms such as Bessel expansion and Fourier transform, the demodulation algorithm is complex, needs a large amount of mathematical operations, has high requirements on modulation signals, and is inconvenient to use. Based on the above, the invention provides a single-mode fiber coupler phase shift measurement device, a single-mode fiber coupler phase shift measurement method and a single-mode fiber coupler phase shift measurement storage medium.
Disclosure of Invention
In order to solve the above problems in the prior art, that is, to solve the problems of complicated measurement process and low measurement accuracy of the conventional coupler phase shift measurement method, a first aspect of the present invention provides a single-mode fiber coupler phase shift measurement apparatus, including: the system comprises a spectrum measuring device, a mixed Sagnac interferometer and a calculating module; the spectrum measuring device is respectively connected with the computing module and the hybrid Sagnac interferometer;
the spectral measurement device is configured to emit a scanning light source to the hybrid Sagnac interferometer; the device is also configured to collect interference spectrum signals of a reciprocal port and a non-reciprocal port of the hybrid Sagnac interferometer and send the interference spectrum signals to the computing module;
the hybrid Sagnac interferometer is composed of an N multiplied by N single-mode fiber coupler and a polarization-maintaining fiber, and the polarization-maintaining fiber and a tail fiber on the same side of the N multiplied by N single-mode fiber coupler are connected to form a Sagnac ring; the hybrid Sagnac interferometer is configured to split an input scanning light source, generate an interference spectrum signal after passing through a polarization maintaining optical fiber and output the interference spectrum signal;
the calculation module is configured to extract a valley wavelength based on the received interference spectrum signal and calculate a phase shift value of the NxN single-mode fiber coupler.
In some preferred embodiments, the single-mode fiber coupler phase shift measurement device further comprises a fiber isolator:
the optical fiber isolator is configured to set the nonreciprocal port as a unidirectional measurement channel, and eliminate the influence of a scanning light source of the spectrum measurement device on the interference spectrum output by the nonreciprocal port.
In some preferred embodiments, the polarization maintaining fiber is connected to the tail fiber on the same side of the N × N single-mode fiber coupler by any one of connection, butt joint, and fusion.
In some preferred embodiments, the interference spectrum signals of the reciprocal port and the non-reciprocal port of the hybrid Sagnac interferometer are expressed as:
wherein, PRP(lambda) and PNRP(lambda) respectively represents interference spectrum signals output by the reciprocal port and the non-reciprocal port,
is the phase shift value of NxN single-mode fiber coupler, 2 pi delta nL/lambda is the phase difference between polarization modes of polarization maintaining fiber in Sagnac loop, delta N is the refractive index difference of fast and slow axes of polarization maintaining fiber, L is the length of polarization maintaining fiber, lambda is the wavelength of incident light, P is the wavelength of incident light0Is the intensity factor of the output optical power.
In some preferred embodiments, the phase difference of the interference spectrum signal output by the reciprocal port is the phase difference between polarization modes of the polarization-preserving fiber in the Sagnac loop; the phase difference of the interference spectrum signal output by the nonreciprocal port is the sum of the phase difference between polarization modes of the polarization-maintaining optical fiber and twice the phase shift of the NxN single-mode optical fiber coupler.
In some preferred embodiments, "extracting a valley wavelength based on the received interference spectrum signal and calculating a phase shift value of the N × N single-mode fiber coupler" is performed by:
extracting adjacent 2 valley wavelengths in the interference spectrum signal of the reciprocal port to be used as a first valley wavelength and a third valley wavelength; extracting valley wavelengths between the first valley wavelength and the third valley wavelength in the interference spectrum signals of the nonreciprocal port to serve as second valley wavelengths;
and calculating the phase shift value of the single mode fiber coupler to be measured based on the first valley wavelength, the second valley wavelength and the third valley wavelength.
In some preferred embodiments, the method of calculating the phase shift value of the single-mode fiber coupler under test based on the first valley wavelength, the second valley wavelength and the third valley wavelength includes:
wherein λ is1、λ3Adjacent 2 valley wavelengths, i.e. the first valley wavelength, the third valley wavelength, λ, in the interference spectrum signal of the reciprocal port2The interference spectrum signal of the nonreciprocal port is a valley wavelength between the first valley wavelength and the third valley wavelength, that is, the second valley wavelength.
In a second aspect of the present invention, a single-mode fiber coupler phase shift measurement method is provided, based on the single-mode fiber coupler phase shift measurement apparatus described above, the method includes the following steps:
s100, acquiring interference spectrum signals of a reciprocal port and a non-reciprocal port of a hybrid Sagnac interferometer as input signals;
step S200, extracting adjacent 2 valley wavelengths in the interference spectrum signal of the reciprocal port as a first valley wavelength and a third valley wavelength; extracting valley wavelengths between the first valley wavelength and the third valley wavelength in the interference spectrum signals of the nonreciprocal port to serve as second valley wavelengths;
step S300, calculating a phase shift value of the single mode fiber coupler to be measured based on the first valley wavelength, the second valley wavelength and the third valley wavelength.
In a third aspect of the present invention, a computer-readable storage medium is provided, which stores computer instructions for being executed by the computer to implement the method for measuring phase shift of a single-mode fiber coupler as claimed above.
The invention has the beneficial effects that:
the invention greatly reduces the complexity of coupler phase shift, improves the measurement precision and provides an effective means for quantitative and accurate test and analysis of the single-mode fiber coupler phase shift.
1) Based on the relationship between the valley wavelength of an interference spectrum signal output by a reciprocal port and a non-reciprocal port of a hybrid Sagnac interferometer and the phase shift of a single-mode coupler, the phase shift value of the single-mode fiber coupler is calculated by extracting valley wavelengths between 2 adjacent valley wavelengths in a spectrum of the reciprocal port and valley wavelengths between the 2 adjacent valley wavelengths in a spectrum of the non-reciprocal port. The detection device consists of a hybrid Sagnac interferometer, a spectrum measurement device and a calculation module, no additional modulation signal is needed, the detection of the phase shift of the coupler is realized by utilizing a wavelength modulation and demodulation mode, and the relative intensity demodulation has better anti-interference performance and detection precision. The measuring method and the device have the advantages of simple structure, easy realization, strong adaptability and high measuring precision, avoid the interference caused by the fluctuation of a light source, a detector and the environment, reduce the requirement on the hardware performance of the detecting device, can be used for accurately measuring the phase shift of the 2 x 2, 3 x 3 couplers and other multiport couplers, and have high practical value.
2) The maximum error of the coupler phase shift detection obtained by the measuring device and the method provided by the invention is 0.0136 degrees, which is improved by one order of magnitude compared with the existing scheme, and the measuring result is more accurate and reliable.
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Other features, objects and advantages of the present application will become more apparent upon reading of the following detailed description of non-limiting embodiments thereof, made with reference to the accompanying drawings.
FIG. 1 is a schematic diagram of a single mode fiber coupler phase shift measurement apparatus according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an interference spectrum signal based on theoretical output of a single-mode fiber coupler phase shift measurement device according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a phase shift detection device of a 3 × 3 single-mode fiber coupler according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of an experimental apparatus applied to phase shift detection of a 2 × 2 single-mode fiber coupler according to an embodiment of the present invention;
FIG. 5 is a diagram of an interference spectrum signal output by a phase shift detection experiment applied to a 2 × 2 single-mode fiber coupler according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of an experimental apparatus applied to phase shift detection of a 3 × 3 single-mode fiber coupler according to an embodiment of the present invention;
FIG. 7 is a diagram of an interference spectrum signal output by a phase shift detection experiment applied to a 3 × 3 single-mode fiber coupler according to an embodiment of the present invention;
list of reference numerals:
the device comprises a spectrum measuring device 1, a 2 multiplied by 2 single-mode fiber coupler 2, a polarization maintaining fiber 4, a fiber connecting point 5, a computing module 8, a 3 multiplied by 3 single-mode fiber coupler 9, a fiber isolator 16, a fiber spectrum demodulator 17, a computer 18 and port labels of the single- mode fiber couplers 3, 6, 7 and 10-15.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The present application will be described in further detail with reference to the following drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention. It should be noted that, for convenience of description, only the portions related to the related invention are shown in the drawings.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.
The invention relates to a single-mode fiber coupler phase shift measuring device, which comprises: the system comprises a spectrum measuring device, a mixed Sagnac interferometer and a calculating module; the spectrum measuring device is respectively connected with the computing module and the hybrid Sagnac interferometer;
the spectral measurement device is configured to emit a scanning light source to the hybrid Sagnac interferometer; the device is also configured to collect interference spectrum signals of a reciprocal port and a non-reciprocal port of the hybrid Sagnac interferometer and send the interference spectrum signals to the computing module;
the hybrid Sagnac interferometer is composed of an N multiplied by N single-mode fiber coupler and a polarization-maintaining fiber, and the polarization-maintaining fiber and a tail fiber on the same side of the N multiplied by N single-mode fiber coupler are connected to form a Sagnac ring; the hybrid Sagnac interferometer is configured to split an input scanning light source, generate an interference spectrum signal after passing through a polarization maintaining optical fiber and output the interference spectrum signal;
the calculation module is configured to extract a valley wavelength based on the received interference spectrum signal and calculate a phase shift value of the NxN single-mode fiber coupler.
In order to more clearly explain the phase shift measurement method of the single mode fiber coupler of the present invention, the following describes in detail the steps of an embodiment of the method of the present invention with reference to the attached drawings.
As shown in fig. 1, a single-mode fiber coupler phase shift measurement apparatus of the present invention includes: the device comprises a spectrum measuring device 1, a hybrid Sagnac interferometer (comprising an NxN single-mode fiber coupler 2 and a polarization-maintaining fiber 4) and a calculating module 8, wherein 3, 6 and 7 are labels corresponding to ports of the NxN single-mode fiber coupler, and 5 is a fiber connecting joint; the spectrum measuring device is respectively connected with the computing module and the hybrid Sagnac interferometer; wherein,
the spectral measurement device is configured to emit a scanning light source to the hybrid Sagnac interferometer; the device is also configured to collect interference spectrum signals of a reciprocal port and a non-reciprocal port of the hybrid Sagnac interferometer and send the interference spectrum signals to the computing module;
in this embodiment, the spectrum measuring device may be a spectrometer or a fiber spectrum demodulator; the spectral measurement device is configured to emit a scanning light source to the hybrid Sagnac interferometer; and the system is also configured to collect interference spectrum signals of a reciprocal port and a non-reciprocal port of the hybrid Sagnac interferometer and send the interference spectrum signals to the computing module.
The hybrid Sagnac interferometer is composed of an N multiplied by N single-mode fiber coupler and a polarization-maintaining fiber, and the polarization-maintaining fiber and a tail fiber on the same side of the N multiplied by N single-mode fiber coupler are connected to form a Sagnac ring; the hybrid Sagnac interferometer is configured to split an input scanning light source, generate an interference spectrum signal after passing through a polarization maintaining optical fiber and output the interference spectrum signal;
in this embodiment, the hybrid Sagnac interferometer is composed of an N × N single-mode fiber coupler and a polarization-maintaining fiber, and the polarization-maintaining fiber is connected to a pigtail on the same side as the N × N single-mode fiber coupler to form a Sagnac loop. The mode of connecting the polarization maintaining fiber and the tail fiber at the same side of the NxN single-mode fiber coupler is any one of connection, butt joint and fusion.
The hybrid Sagnac interferometer is specifically configured to: a scanning light source emitted by the spectrum measuring device is divided into two beams of light by the NxN single-mode fiber coupler and the two beams of light are respectively transmitted along the Sagnac ring in opposite directions, in the mixed Sagnac ring, phase difference is generated due to different transmission speeds of two polarization modes in the polarization-maintaining fiber, interference occurs in the NxN single-mode fiber coupler in a meeting mode, and interference spectrum signals are respectively output from the reciprocal port and the nonreciprocal port. The phase difference of the interference spectrum signal output by the reciprocal port is the phase difference between polarization modes of the polarization-preserving fiber in the Sagnac loop; the phase difference of the interference spectrum signal output by the nonreciprocal port is the sum of the phase difference between polarization modes of the polarization-maintaining fiber and twice the phase shift of the NxN single-mode fiber coupler. The output interference spectrum signals of the reciprocal port and the non-reciprocal port can be expressed as:
wherein, PRP(lambda) and PNRP(lambda) respectively represents interference spectrum signals output by the reciprocal port and the non-reciprocal port,
is the phase shift value of NxN single-mode fiber coupler, 2 pi delta nL/lambda is the phase difference between polarization modes of polarization maintaining fiber in Sagnac loop, delta N is the refractive index difference of fast and slow axes of polarization maintaining fiber, L is the length of polarization maintaining fiber, lambda is the wavelength of incident light, P is the wavelength of incident light0Is the intensity factor of the output optical power.
The number of ports of the single mode fiber coupler is not limited in the invention, and the ports can be 2 multiplied by 2 single mode fiber couplers, 3 multiplied by 3 single mode fiber couplers or other multi-port single mode fiber couplers. As shown in fig. 1, when detecting the phase shift of a 2 × 2 single-mode fiber coupler 2, two pigtails 3 on the same side of the single-mode fiber coupler 2 are connected to two ends of a polarization maintaining fiber 4 to form a hybrid Sagnac loop. A scanning light source is input from a port 6 of a single-mode fiber coupler to be measured, the scanning light source is divided into two beams of light after passing through the single-mode fiber coupler and transmitted oppositely in a mixed Sagnac ring, interference spectrum signals are generated in the coupler in a meeting mode, and the spectrum measuring device 1 simultaneously collects the interference spectrum signals emitted by a reciprocal port 6 and a non-reciprocal port 7.
Similarly, as shown in fig. 3, when detecting the phase shift of the 3 × 3 single-mode fiber coupler 9, any two pigtails on the same side of the single-mode fiber coupler 9 are connected with the polarization maintaining fiber 4 to form a hybrid Sagnac loop, the scanning light source is input from the port 11 of the single-mode fiber coupler to be detected, and is divided into three beams after passing through the single-mode fiber coupler, the two beams of light connected with the polarization maintaining fiber are transmitted in the hybrid Sagnac loop in opposite directions, and generate interference spectrum signals when meeting each other in the single-mode fiber coupler, and the spectrum measuring device 1 simultaneously collects the interference spectrum signals emitted from the reciprocal port (i.e., the port of the reciprocal end, and the same in other figures) 11 and the non-reciprocal ports 10 and 12 (i.e., the ports of the non-reciprocal end, and the same in other figures).
The polarization maintaining fiber can be a panda type polarization maintaining fiber, a bow tie type polarization maintaining fiber, a polarization maintaining photonic crystal fiber or any other type of polarization maintaining fiber.
The calculation module is configured to extract a valley wavelength based on the received interference spectrum signal and calculate a phase shift value of the NxN single-mode fiber coupler.
In this embodiment, the calculation module may be a computer, a single chip, or other micro-processing module, and is configured to extract 2 adjacent valley wavelengths in the interference spectrum signal of the reciprocal port, as the first valley wavelength and the third valley wavelength; extracting valley wavelengths between the first valley wavelength and the third valley wavelength in the interference spectrum signals of the nonreciprocal port to serve as second valley wavelengths; only one unique valley exists between the first valley wavelength and the third valley wavelength, so that the valley wavelength (namely, the second valley wavelength) between the first valley wavelength and the third valley wavelength is unique; calculating a phase shift value of the NxN single-mode fiber coupler based on the first valley wavelength, the second valley wavelength, and the third valley wavelength.
Wherein, the process of calculating the phase shift value of the nxn single-mode fiber coupler is shown in formula (3):
wherein λ is1、λ3Adjacent 2 valley wavelengths, i.e. the first valley wavelength, the third valley wavelength, λ, in the interference spectrum signal of the reciprocal port2The interference spectrum signal of the nonreciprocal port is a valley wavelength between the first valley wavelength and the third valley wavelength, that is, the second valley wavelength.
The principle of measuring the phase shift value of the NxN single-mode fiber coupler in the invention is as follows:
taking the phase shift value measurement of a 2 × 2 single-mode fiber coupler as an example, as shown in fig. 1, a scanning light source is input from one end of a single-mode fiber coupler to be measured, and is divided into two beams of light after passing through the single-mode fiber coupler to be transmitted respectively along Sagnac loops in opposite directions.
The spectrum measuring device is used for simultaneously collecting the output interference spectrums of the reciprocal port and the non-reciprocal port of the hybrid Sagnac interferometer, a typical 2 x 2 single-mode fiber coupler is used for measuring the output spectrums as shown in figure 2, the spectrum in figure 2 is an interference spectrum signal, under an ideal condition, the coupling phase shift of the 2 x 2 single-mode fiber coupler is 90 degrees, the relative phase difference between the reciprocal end and the non-reciprocal end is equal to the non-reciprocal phase shift
Therefore, the two output interference spectrums are complementary, the phase difference corresponding to the wavelengths of the adjacent peak values (or valley values) on the same spectrum curve is 2 pi, the phase difference corresponding to the wavelengths of the adjacent peak values (valley values) on different spectrum curves is the nonreciprocal coupler phase shift, the derivation can be obtained by combining the formulas (1) and (2), and the calculation formula of the coupler phase shift is as follows:
the detection precision of the coupling phase shift is determined by the measurement precision of the valley wavelength, and the wavelength positioning precision of the spectrometer is set as eλ1pm, substituting into a typical value λ of the theoretical spectrum1＝1546.041nm，λ2＝1553.696nm，λ3When the detection method is used, the limit error of the coupler phase shift detection obtained by the detection method is 1562.240nm according to the error analysis theory:
in addition, the single-mode fiber coupler phase shift measuring device also comprises a fiber isolator; the optical fiber isolator is configured to set the non-reciprocal port as a unidirectional measurement channel, and eliminate the influence of a scanning light source of the spectrum measurement device on an interference spectrum (i.e., an interference spectrum signal) output by the non-reciprocal port. Namely, the influence of the scanning light source of the spectrum measuring device on the interference spectrum of the CH4 channel in FIG. 4 and the CH1 and CH4 channels in FIG. 6 is eliminated.
Besides, the invention provides a specific embodiment applied to the phase shift detection of a 2 × 2 single-mode fiber coupler and a specific embodiment applied to the phase shift detection of a 3 × 3 single-mode fiber coupler. The method comprises the following specific steps:
fig. 4 shows a schematic structural diagram of a 2 × 2 single-mode fiber coupler phase shift detection device built by using a fiber spectrum demodulator 17, which includes the fiber spectrum demodulator 17, an isolator 16, a 2 × 2 single-mode fiber coupler 2 to be detected, a polarization maintaining fiber 4, and a computer 18 for signal processing. A1510-1590 nm scanning light source is integrated in an optical fiber spectrum demodulator, the light enters a port 6 of a 2 multiplied by 2 single-mode optical fiber coupler from a channel 1, passes through a single-mode optical fiber coupler 2 and then enters a hybrid Sagnac interference ring for transmission, interference spectrum signals are generated in the single-mode optical fiber coupler and then are respectively output to a detection channel 1 and a channel 4 of an optical fiber spectrum demodulator 17 from a reciprocal port 6 and a non-reciprocal port 7, the acquired interference spectrum signals are shown in figure 5, interference spectrum information is input into a computer 18, and adjacent 2 valley wavelengths lambda of the reciprocal port spectrum near 1550nm of the single-mode optical fiber coupler are extracted1＝1542.244nm、λ31559.281nm, and a valley wavelength λ between the above-mentioned adjacent 2 valley wavelengths in the non-reciprocal port spectrum2The phase shift of the 2 × 2 single-mode fiber coupler is calculated according to equation (3) as 1550.648nm
The average value of multiple detections under the same condition is taken as the actual phase shift value of the single-mode fiber coupler, and the deviation of the actual phase shift value of the 2 multiplied by 2 single-mode fiber coupler from the theoretical phase shift value of 90 degrees can be obtained.
Fig. 6 shows a schematic structural diagram of a phase shift detection device of a 3 × 3 single-mode fiber coupler built by using a fiber spectrum demodulator 17, which includes the fiber spectrum demodulator 17, an isolator 16, a 3 × 3 single-mode fiber coupler 9 to be detected, a polarization maintaining fiber 4, and a computer 18 for signal processing. In ports 13-15 of 3 x 3 single mode fibre coupler 9And optional two ports are connected with the polarization-maintaining optical fiber 4 to form a mixed Sagnac interference ring. A scanning light source (1510-1590nm) integrated in the fiber spectrum demodulator is incident to a port 11 of a 3 multiplied by 3 single-mode fiber coupler from a channel 2, passes through a single-mode fiber coupler 9 and then enters a hybrid Sagnac interference ring for transmission, interference spectrum signals are generated in the single-mode fiber coupler and then are respectively output to a detection channel 1, a channel 2 and a channel 4 of a fiber spectrum demodulator 17 from a reciprocal port 11 and non-reciprocal ports 10 and 12, the three groups of acquired interference spectrum signals are shown in figure 7, the interference spectrum signals are input into a computer 18, and adjacent 2 valley wavelengths lambda in the spectrum of the reciprocal port near 1550nm of the single-mode fiber coupler are extracted1＝1542.941nm、λ31559.358nm, and a valley wavelength λ between the above-mentioned adjacent 2 valley wavelengths in the two nonreciprocal port spectra211548.517nm and λ221553.946nm, the phase shift of the two non-reciprocal ports of the 3 × 3 single-mode fiber coupler relative to the reciprocal port is calculated according to the formula (3)
The actual phase shift value of the 3 × 3 single-mode fiber coupler is deviated from the theoretical phase shift value of 120 °.
It should be noted that, the single-mode fiber coupler phase shift measurement apparatus provided in the foregoing embodiment is only illustrated by dividing the functional modules, and in practical applications, the above function distribution may be completed by different functional modules according to needs, that is, the modules or steps in the embodiment of the present invention are further decomposed or combined, for example, the modules in the foregoing embodiment may be combined into one module, or may be further decomposed into a plurality of sub-modules, so as to complete all or part of the functions described above. The names of the modules and steps involved in the embodiments of the present invention are only for distinguishing the modules or steps, and are not to be construed as unduly limiting the present invention.
A single-mode fiber coupler phase shift measurement method according to a second embodiment of the present invention is based on the single-mode fiber coupler phase shift measurement apparatus, and the method includes the following steps:
s100, acquiring interference spectrum signals of a reciprocal port and a non-reciprocal port of a hybrid Sagnac interferometer as input signals;
step S200, extracting adjacent 2 valley wavelengths in the interference spectrum signal of the reciprocal port as a first valley wavelength and a third valley wavelength; extracting valley wavelengths between the first valley wavelength and the third valley wavelength in the interference spectrum signals of the nonreciprocal port to serve as second valley wavelengths;
step S300, calculating a phase shift value of the single mode fiber coupler to be measured based on the first valley wavelength, the second valley wavelength and the third valley wavelength.
It can be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working process and related description of the system described above may refer to the corresponding process in the foregoing method embodiment, and details are not described herein again.
A computer-readable storage medium of a third embodiment of the present invention stores computer instructions for execution by the computer to implement the single-mode fiber coupler phase shift measurement method of the claims above.
It is clear to those skilled in the art that, for convenience and brevity of description, the specific working process and related descriptions of the computer-readable storage medium described above may refer to the corresponding process in the foregoing method examples, and are not described herein again.
Those of skill in the art would appreciate that the various illustrative modules, method steps, and modules described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that programs corresponding to the software modules, method steps may be located in Random Access Memory (RAM), memory, Read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. To clearly illustrate this interchangeability of electronic hardware and software, various illustrative components and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as electronic hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The terms "first," "second," and the like are used for distinguishing between similar elements and not necessarily for describing or implying a particular order or sequence.
The terms "comprises," "comprising," or any other similar term are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
So far, the technical solutions of the present invention have been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of the present invention is obviously not limited to these specific embodiments. Equivalent changes or substitutions of related technical features can be made by those skilled in the art without departing from the principle of the invention, and the technical scheme after the changes or substitutions can fall into the protection scope of the invention.
Claims (8)
1. A single mode fiber coupler phase shift measurement device, comprising: the system comprises a spectrum measuring device, a mixed Sagnac interferometer and a calculating module; the spectrum measuring device is respectively connected with the computing module and the hybrid Sagnac interferometer;
the spectral measurement device is configured to emit a scanning light source to the hybrid Sagnac interferometer; the device is also configured to collect interference spectrum signals of a reciprocal port and a non-reciprocal port of the hybrid Sagnac interferometer and send the interference spectrum signals to the computing module;
the hybrid Sagnac interferometer is composed of an N multiplied by N single-mode fiber coupler and a polarization-maintaining fiber, and the polarization-maintaining fiber and a tail fiber on the same side of the N multiplied by N single-mode fiber coupler are connected to form a Sagnac ring; the hybrid Sagnac interferometer is configured to split an input scanning light source, generate an interference spectrum signal after passing through a polarization maintaining optical fiber and output the interference spectrum signal;
the calculation module is configured to extract a valley wavelength based on the received interference spectrum signal and calculate a phase shift value of the NxN single-mode fiber coupler;
wherein, based on the received interference spectrum signal, valley wavelength is extracted, and phase shift value of NxN single mode fiber coupler is calculated, the method is as follows:
extracting adjacent 2 valley wavelengths in the interference spectrum signal of the reciprocal port to be used as a first valley wavelength and a third valley wavelength; extracting valley wavelengths between the first valley wavelength and the third valley wavelength in the interference spectrum signals of the nonreciprocal port to serve as second valley wavelengths;
and calculating the phase shift value of the single mode fiber coupler to be measured based on the first valley wavelength, the second valley wavelength and the third valley wavelength.
2. The single-mode fiber coupler phase shift measurement device of claim 1, further comprising a fiber isolator;
the optical fiber isolator is configured to set the nonreciprocal port as a unidirectional measurement channel, and eliminate the influence of a scanning light source of the spectrum measurement device on the interference spectrum output by the nonreciprocal port.
3. The single-mode fiber coupler phase shift measuring device according to claim 1, wherein the polarization maintaining fiber is connected to the tail fiber on the same side of the N × N single-mode fiber coupler in any one of connection, butt joint and fusion.
4. The apparatus of claim 1, wherein the interference spectrum signals of the reciprocal port and the non-reciprocal port of the hybrid Sagnac interferometer are expressed as:
wherein, PRP(lambda) and PNRP(lambda) respectively represents interference spectrum signals output by the reciprocal port and the non-reciprocal port,
is the phase shift value of NxN single-mode fiber coupler, 2 pi delta nL/lambda is the phase difference between polarization modes of polarization maintaining fiber in Sagnac loop, delta N is the refractive index difference of fast and slow axes of polarization maintaining fiber, L is the length of polarization maintaining fiber, lambda is the wavelength of incident light, P is the wavelength of incident light0Is the intensity factor of the output optical power.
5. The single-mode fiber coupler phase shift measurement device according to claim 4, wherein the phase difference of the interference spectrum signal output by the reciprocal port is the phase difference between polarization modes of the polarization-maintaining fiber in the Sagnac loop; the phase difference of the interference spectrum signal output by the nonreciprocal port is the sum of the phase difference between polarization modes of the polarization-maintaining optical fiber and twice the phase shift of the NxN single-mode optical fiber coupler.
6. The apparatus according to claim 4, wherein the phase shift value of the single-mode fiber coupler under test is calculated based on the first valley wavelength, the second valley wavelength and the third valley wavelength by:
wherein,
is the phase shift value, lambda, of an NxN single-mode fiber coupler1、λ3Adjacent 2 valley wavelengths, i.e. the first valley wavelength, the third valley wavelength, λ, in the interference spectrum signal of the reciprocal port2The interference spectrum signal of the nonreciprocal port is a valley wavelength between the first valley wavelength and the third valley wavelength, that is, the second valley wavelength.
7. A single mode fiber coupler phase shift measurement method based on the single mode fiber coupler phase shift measurement device of any one of claims 1 to 6, the method comprising the steps of:
s100, acquiring interference spectrum signals of a reciprocal port and a non-reciprocal port of a hybrid Sagnac interferometer as input signals;
step S200, extracting adjacent 2 valley wavelengths in the interference spectrum signal of the reciprocal port as a first valley wavelength and a third valley wavelength; extracting valley wavelengths between the first valley wavelength and the third valley wavelength in the interference spectrum signals of the nonreciprocal port to serve as second valley wavelengths;
step S300, calculating a phase shift value of the single mode fiber coupler to be measured based on the first valley wavelength, the second valley wavelength and the third valley wavelength.
8. A computer readable storage medium having stored thereon computer instructions for execution by the computer to implement the single mode fiber coupler phase shift measurement method of claim 7.
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