Optical communication waveband sub-pm resolution precision spectrum analysis system and method

Abstract

The invention discloses an optical communication waveband sub-pm resolution precision spectrum analysis system and method. The system comprises a to-be-detected light input module, an optical module, a detection and acquisition module, a data processing module and a main control module. The measurement method comprises the following steps: after a to-be-measured optical fiber signal is conditioned into collimated parallel space light by an optical fiber signal through the to-be-measured light input module and enters the optical module, the optical module performs interference modulation on the collimated parallel space light to complete interference light splitting, and the collimated parallel space light enters the detection and acquisition module after convergence to complete photoelectric conversion and digital sampling; and then real-time spectrum inversion is completed through the data processing module, and finally the signals enter the master control module to be subjected to series processing, so that ultrahigh-resolution real-time measurement of optical fiber signal spectrum parameters is completed. According to the invention, a double-cone angle mirror interferometer light splitting scheme with the characteristics of large stroke and rapid scanning is adopted, so that precise spectrum measurement and analysis of ultra-high spectral resolution, high wavelength precision, high measurement sensitivity and sub-pm resolution of the whole optical communication wave band are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of spectrum analysis, and in particular to a system and method for precise spectrum analysis with sub-pm resolution in an optical communication band. Background Art

[0002] Spectral analysis is a key diagnostic tool in optical applications such as communications, sensing, molecular spectrometers, and microwave generation. For example, using optical methods to measure the spectrum of ultra-high-speed signals transmitted in optical fiber communication systems to obtain an approximate value of the modulation frequency is an effective means of diagnosing and monitoring transmission signals; laser spectra contain most of the information about radiation characteristics, so laser spectrum measurement plays an important role in the design and implementation of optical networks. With the development of a new generation of optical networks, especially the application of various advanced modulation formats and the development of new optical devices, it is required to measure and analyze spectral parameters with sub-pm resolution and wavelength accuracy in a wide band of optical communication bands, and then realize the inversion and analysis of parameters of high-speed optical modulation signals.

[0003] At present, the most commonly used is the spectrum analyzer based on grating diffraction, which has the advantages of wide spectral range and high scanning speed, but its best spectral resolution and wavelength accuracy are usually limited to tens of pm. When higher resolution is required, spectral analysis techniques based on stimulated Brillouin and heterodyne coherence are usually used. Although very high spectral resolution can be achieved, it is limited by the scanning band range of the swept laser. A single instrument can only cover a single narrow band such as O, C, L, but it is difficult to achieve wide band coverage of 1260nm to 1650nm.

[0004] Therefore, the existing spectral analysis technology has obvious advantages and disadvantages, and it is difficult to simultaneously take into account the core indicators of spectral analysis such as wide wavelength coverage of the entire optical communication band, sub-pm spectral resolution and wavelength accuracy. Summary of the invention

[0005] In order to overcome the above problems existing in the prior art, the present invention proposes a sub-pm resolution precision spectrum analysis system and method in the optical communication band.

[0006] The technical solution adopted by the present invention to solve the technical problem is: a sub-pm resolution precision spectrum analysis system in the optical communication band, comprising a light input module to be measured, an optical module, a detection and acquisition module, a data processing module, and a main control module; The light input module to be tested is used to condition the optical fiber signal to be tested into collimated parallel spatial light; The optical module is connected to the light input module to be measured, and implements interference modulation and spectroscopy of collimated parallel spatial light based on a double cone-angle mirror interferometer unit to generate interference signal light; The detection and acquisition module is connected to the optical module and is used to detect the interference signal light generated by the optical module, realize photoelectric conversion and acquisition, and obtain digital interference data; The data processing module is connected to the detection and acquisition module and is used to realize real-time spectral inversion of digital interference data; The main control module is used to control the sub-pm resolution precision spectrum analysis system in the optical communication band, complete parameter setting and subsequent data processing, and display the acquired precision spectrum information of the optical fiber signal.

[0007] In the above-mentioned optical communication band sub-pm resolution precision spectrum analysis system, the light input module to be measured adopts an integrated optical fiber collimation and beam expansion unit to realize the conversion of optical fiber signal into collimated parallel spatial light.

[0008] The above-mentioned optical communication band sub-pm resolution precision spectrum analysis system, the optical module includes a front optical path unit, a double cone angle mirror interferometer unit, a reference laser interferometer unit, and a rear optical path unit; The front optical path unit is connected to the light input module to be measured, and is used to adjust the light to be measured into uniform parallel light; The double cone angle mirror interferometer unit is connected to the front optical path unit and is used for performing interference modulation on the light to be measured to generate a target interference spectroscopic signal; The reference laser interferometer unit is connected to the double cone angle mirror interferometer unit, and is used to collect control feedback information of the double cone angle mirror interferometer unit, and to generate a reference laser interference spectroscopic signal, which is used as a sampling trigger signal of the light interference spectroscopic signal to be measured; The rear optical path unit is connected to the double cone angle mirror interferometer unit, and the interference spectroscopic signal of the light to be measured and the interference spectroscopic signal of the reference laser are respectively converged to the corresponding detection and collection modules.

[0009] The above-mentioned sub-pm resolution precision spectral analysis system in the optical communication band, the biconical mirror interferometer unit includes a beam splitter, a reflector, a biconical mirror, and a motor. After the incident light is divided into two beams by the beam splitter, the two beams enter the optical path formed by the reflector and the biconical mirror respectively and then meet at the beam splitter after reflection. The motor drives the biconical mirror to perform reciprocating linear motion through the supporting structure to generate an optical path difference, introduces the phase difference required for interference between the two beams, thereby realizing interference splitting of the incident light.

[0010] The above-mentioned sub-pm resolution precision spectral analysis system in the optical communication band, the detection and acquisition module includes a light detection and acquisition unit for measured light and a reference laser detection and acquisition unit, the light detection and acquisition unit for measured light is used to realize the detection and data acquisition of the interference light corresponding to the light to be measured, and the reference laser detection and acquisition unit is used to realize the detection and data acquisition of the interference light corresponding to the reference laser.

[0011] In the above-mentioned optical communication band sub-pm resolution precision spectrum analysis system, the data processing module includes FPGA and DSP processing units to realize real-time spectrum inversion of interference data.

[0012] In the above-mentioned optical communication band sub-pm resolution precision spectral analysis system, the FPGA and DSP processing units are used to implement the real-time spectral inversion processing flow of interference data resampling, nonlinear correction, fast Fourier transform, phase alignment, power calibration, and wavelength calibration.

[0013] A sub-pm resolution precision spectrum analysis method in an optical communication band, using the precision spectrum analysis system as described above, includes the following process: After the optical fiber signal to be tested is conditioned into collimated parallel spatial light by the optical input module to be tested, the optical module performs interference modulation on it under the action of the motor drive module to complete interference splitting. After convergence, it enters the detection and acquisition module to complete photoelectric conversion and digital sampling, and then completes real-time spectral inversion through the data processing module. Finally, it enters the main control module and performs a series of processing to complete the ultra-high resolution spectral measurement and analysis of the optical fiber signal.

[0014] The beneficial effect of the present invention is that the present invention adopts a method that combines a double-conical mirror interferometer solution, a moving mirror high-speed scanning based on a composite algorithm, and a real-time spectral inversion algorithm, fully utilizing the wide-band coverage and high-precision advantages of the interferometer to achieve the purpose of taking wide-band coverage, ultra-high spectral resolution and wavelength accuracy into consideration, while utilizing the high-speed scanning advantage of the double-conical mirror interferometer to realize real-time measurement of precise spectral parameters of optical fiber signals, eliminating the scanning speed limitation of existing spectral measurement systems when further improving indicators such as time resolution.

[0015] The spectral splitting of the present invention using a double-cone angle mirror interferometer solution can produce a 4-fold optical path difference. Compared with the 2-fold optical path difference of a conventional Michelson interferometer, it has a higher spectral resolution capability and is suitable for precise spectral analysis applications.

[0016] The spectral splitting of the present invention adopts a double-conical mirror interferometer solution. Benefiting from the high-throughput characteristics of the double-conical mirror interferometer, compared with the existing frequency-selective amplification and filtering splitting based on the principles of grating diffraction splitting, stimulated Brillouin and heterodyne coherence, it greatly improves the measurement sensitivity of precise spectral measurement, especially greatly improves the detection sensitivity of weak optical fiber signals, which is very necessary and important for advanced technology research occasions such as microwave photons, on-chip photon integration, optical neural networks, and optical quantum science.

[0017] The present invention adopts a method that combines a double-conical mirror interferometer solution, a moving mirror high-speed scanning based on a composite algorithm, and a real-time spectral inversion algorithm. Benefiting from the 4-fold optical path design and high-speed scanning design of the double-conical mirror interferometer solution, the precise spectral analysis method proposed in the present invention can achieve sub-pm spectral resolution and wavelength accuracy in the entire optical communication band of 600nm~1700nm, better than -80dBm / 50MHz sensitivity, ±0.5dB optical power measurement accuracy and other indicators of precise spectral measurement and analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the precise spectrum analysis system of the present invention; Figure 2 It is a structural diagram of a double cone angle mirror interferometer unit of the present invention; Among them, 1. beam splitter; 2. reflector; 3. biconical mirror; 4. motor. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0020] This embodiment discloses a sub-pm resolution precision spectrum analysis system in the optical communication band, such as Figure 1 As shown, it includes a light input module to be measured, an optical module, a detection and acquisition module, a motor drive module, a data processing module, and a main control module.

[0021] 1. Optical input module to be measured The optical input module to be tested conditions the optical fiber signal to be tested into collimated parallel spatial light. In this embodiment, the optical fiber collimation and beam expansion unit in the optical input module to be tested adopts an integrated design to achieve the best coupling efficiency from the optical fiber signal to the spatial light, and at the same time achieve the best parallel collimation of the coupled output spatial light.

[0022] 2. Optical module The optical module is connected to the light input module to be measured, and is used to perform high-resolution, high-speed, and high-sensitivity interference modulation and spectroscopy on the incident light to be measured to generate interference signal light. The optical module includes a front optical path unit, a double cone angle mirror interferometer unit, a reference laser interferometer unit, and a rear optical path unit.

[0023] (1) The front optical path unit is connected to the light input module to be measured and is used to adjust the collimated parallel spatial light into uniform parallel light suitable for the entrance pupil angle of the double-cone mirror interferometer unit. The front optical path unit adopts a folded optical path and coating design to achieve efficient transmission of the light to be measured in the optical communication band and reduce losses, and can generate parallel and collimated incident light that meets the requirements of the double-cone mirror interferometer unit.

[0024] (2) A double-conical mirror interferometer unit, connected to the front optical path unit, for interferometrically modulating the light to be measured to generate an interference spectroscopic signal of the light to be measured; the double-conical mirror interferometer unit is as follows: Figure 2 As shown, it is mainly composed of a beam splitter 1, a reflector 2, a biconical mirror 3, and a motor 4. The working principle is: after the incident light is split into two beams by the beam splitter, they enter the two optical paths formed by the two reflectors 2 and the biconical mirror 3 respectively, and then meet at the beam splitter 1 after reflection. The motor 4 drives the biconical mirror 3 to make reciprocating linear motion through the supporting structure to generate an optical path difference, thereby introducing the phase difference required for interference between the two beams, thereby realizing the interference splitting of the incident light.

[0025] The biconical mirror interferometer of the present invention can generate a 4-fold optical path difference. The motor 4 moves 1 cm, which correspondingly generates a 4-cm optical path difference. Combined with the automatic calibration of the biconical mirror 3, the beam splitter and compensator in the beam splitter 1 adopt 30 0 The angle placement can achieve the best modulation efficiency, which can well realize high-speed, high-resolution, high-precision and high-sensitivity interference modulation spectrometry, and ensure the realization of precise spectral measurement and analysis with sub-pm resolution.

[0026] (3) A reference laser interferometer unit connected to a double-conical mirror interferometer unit is used to generate control feedback information for the motor drive module and to generate a reference laser interference spectrometer signal, which is used as a sampling trigger signal for the interference spectrometer signal to be measured. The reference laser interferometer unit uses a high-frequency-stable He-Ne laser or a semiconductor DFB laser based on a Lamb dip frequency stabilization method as a reference light, and is integrated with the double-conical mirror interferometer unit. Combined with a polarization phase shifting design, it can provide a high-precision sampling reference benchmark for the detection and acquisition module, as well as provide the motor drive module with high-precision motion feedback information that meets the requirements, including parameters such as motion speed, motion direction, speed uniformity, and motion direction consistency.

[0027] (4) The rear optical path unit is connected to the double-conical mirror interferometer unit, which converges the interference spectroscopic signal of the light to be measured and the interference spectroscopic signal of the reference laser to the corresponding detection and acquisition modules respectively, thereby completing the detection of the interference light and data acquisition.

[0028] 3. Motor drive module The motor driving module is connected to the double-cone mirror interferometer unit of the optical module, and drives the control motor 4 to make the double-cone mirror 3 of the double-cone mirror interferometer unit perform reciprocating linear motion. It adopts an integral separation PID algorithm as the basis, as well as fuzzy control, and combines a composite control algorithm based on convolutional neural network feedforward to achieve high-speed, collimated, and uniform motion of the double-cone mirror interferometer, thereby introducing the optical path difference required for interference modulation spectroscopy.

[0029] 4. Detection and acquisition module The detection and acquisition module is connected to the optical module and is used to detect the interference signal light generated by the optical module, realize photoelectric conversion and acquisition, and obtain digital interference data; the detection and acquisition module includes a light detection and acquisition unit to be measured and a reference laser detection and acquisition unit.

[0030] (1) The light detection and acquisition unit is configured to detect and acquire data of the interference light corresponding to the light to be measured. An InGaAs detector scheme is used to achieve wide band coverage of 600 nm to 1700 nm. An equal time interval sampling scheme is used to improve the quality of the interference data and meet the high sampling rate required for real-time precision spectral measurement.

[0031] (2) A reference laser detection and acquisition unit, which is configured to detect and acquire reference laser interference light and adopts an equal time interval sampling scheme to improve the quality of interference data and meet the high sampling rate required for real-time precision spectral measurement.

[0032] 5. Data processing module The data processing module is connected to the detection and acquisition module to realize the real-time spectral inversion of digital interference data; the data processing module obtains the precise spectral parameters of the light to be measured, including real-time spectral inversion processing procedures such as interference data resampling, nonlinear correction, fast Fourier transform, phase alignment, power calibration, wavelength calibration, etc. The following factors need to be considered: (1) The FPGA+DSP hardware solution, combined with a specially optimized algorithm, can ensure that a spectral inversion process is completed within milliseconds; (2) In the interferometric data resampling phase, based on the laser reference interferometric data, the Brault sampling method is used to resample the interferometric data of equal time intervals corresponding to the light to be measured into sampling data of equal optical path difference intervals, and the uniformity of the interferometric data sampling is ensured so that the Fourier transform can be completed using the fast Fourier algorithm; (3) Nonlinear correction: using a lookup table to achieve rapid correction of nonlinearities introduced by detectors, ADCs, etc. (4) Fast Fourier transform, using FFTW fast Fourier transform algorithm to complete the spectral restoration of interference data; (5) Phase alignment: Phase alignment of the restored spectrum data of the measured light with the restored spectrum data of the reference laser. The phase alignment process can be implemented by the least squares fitting method, which has high accuracy and is easy to implement in hardware. (6) Power calibration: a complex power calibration scheme is used. While completing the power calibration, the phase correction of the restored spectrum can be realized, and the real part of the calibration result is used as the spectral power intensity value of the light to be measured. (7) Wavelength calibration: using a reference calibration scheme, the deviation between the measured reference laser wavelength and the nominal reference laser wavelength is calculated as the wavelength calibration parameter to complete the wavelength calibration.

[0033] 6. Main control module The main control module is connected to all the above modules and includes an embedded system for controlling the sub-pm resolution precision spectrum analysis device in the optical communication band, completing parameter setting and subsequent data processing, and displaying the acquired precision spectrum information of the light to be measured.

[0034] A sub-pm resolution precision spectral analysis system in an optical communication band of the present embodiment adopts a measurement method that combines a double-conical-angle mirror interferometer solution, a moving mirror high-speed scanning based on a composite algorithm, and a real-time spectral inversion algorithm. It can achieve sub-pm spectral resolution and wavelength accuracy, better than -80dBm / 50MHz sensitivity, ±0.5dB optical power measurement accuracy and other indicators in the entire optical communication band of 600nm to 1700nm. Precision spectral measurement and analysis.

[0035] The present embodiment proposes a method for precise spectrum analysis with sub-pm resolution in an optical communication band as follows: Under the control of the main control module, the optical fiber signal to be measured is conditioned into collimated parallel spatial light by the optical input module to be measured, and then, under the action of the motor drive module, the double-conical mirror interferometer unit in the optical path module performs interference modulation on it to complete spectral splitting, and after being converged by the rear optical path unit of the optical path module, it enters the detection and acquisition module to complete photoelectric conversion and digital sampling, and then completes real-time spectral inversion through the data processing module, and then enters the main control module, and performs a series of processing to complete the precise spectral parameter measurement of the light to be measured.

[0036] The above embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the essence and protection scope of the present invention, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present invention.

Claims

1. A sub-pm resolution precision spectrum analysis system in the optical communication band, characterized in that: It includes a light input module to be measured, an optical module, a detection and acquisition module, a data processing module, and a main control module; The light input module to be tested is used to condition the optical fiber signal to be tested into collimated parallel spatial light; The optical module is connected to the light input module to be measured, and implements interference modulation and spectroscopy of the collimated parallel spatial light based on the double cone angle mirror interferometer unit to generate interference signal light; The detection and acquisition module is connected to the optical module and is used to detect the interference signal light generated by the optical module, realize photoelectric conversion and acquisition, and obtain digital interference data; The data processing module is connected to the detection and acquisition module and is used to realize real-time spectral inversion of digital interference data; The main control module is used to control the sub-pm resolution precision spectrum analysis system in the optical communication band, complete parameter setting and subsequent data processing, and display the acquired precision spectrum information of the optical fiber signal.

2. The optical communication band sub-pm resolution precision spectrum analysis system according to claim 1, characterized in that: The measured light input module adopts an integrated optical fiber collimating and beam expanding unit to realize the conversion of optical fiber signals into collimated parallel spatial light.

3. The optical communication band sub-pm resolution precision spectrum analysis system according to claim 1, characterized in that: The optical module includes a front optical path unit, a double cone mirror interferometer unit, a reference laser interferometer unit, and a rear optical path unit; The front optical path unit is connected to the light input module to be measured, and is used to adjust the light to be measured into uniform parallel light; The double cone angle mirror interferometer unit is connected to the front optical path unit and is used for performing interference modulation on the light to be measured to generate a target interference spectroscopic signal; The reference laser interferometer unit is connected to the double cone angle mirror interferometer unit, and is used to collect control feedback information of the double cone angle mirror interferometer unit, and to generate a reference laser interference spectroscopic signal, which is used as a sampling trigger signal of the light interference spectroscopic signal to be measured; The rear optical path unit is connected to the double cone angle mirror interferometer unit, and the interference spectroscopic signal of the light to be measured and the interference spectroscopic signal of the reference laser are respectively converged to the corresponding detection and collection modules.

4. The optical communication band sub-pm resolution precision spectrum analysis system according to claim 1, characterized in that: The biconical mirror interferometer unit includes a beam splitter, a reflector, a biconical mirror, and a motor. After the incident light is split into two beams by the beam splitter, the two beams enter the optical path formed by the reflector and the biconical mirror respectively and then meet at the beam splitter after reflection. The motor drives the biconical mirror to perform reciprocating linear motion through the supporting structure to generate an optical path difference, and introduces the phase difference required for interference between the two beams, thereby realizing interference splitting of the incident light.

5. The optical communication band sub-pm resolution precision spectrum analysis system according to claim 1, characterized in that: The detection and acquisition module includes a light detection and acquisition unit for measured light and a reference laser detection and acquisition unit. The light detection and acquisition unit for measured light is used to detect and acquire data of interference light corresponding to the light to be measured, and the reference laser detection and acquisition unit is used to detect and acquire data of interference light corresponding to the reference laser.

6. The optical communication band sub-pm resolution precision spectrum analysis system according to claim 1, characterized in that: The data processing module includes FPGA and DSP processing units to realize real-time spectral inversion of interference data.

7. The optical communication band sub-pm resolution precision spectrum analysis system according to claim 6, characterized in that: The FPGA and DSP processing units are used to implement the real-time spectrum inversion processing flow of interference data resampling, nonlinear correction, fast Fourier transform, phase alignment, power calibration, and wavelength calibration.

8. A method for sub-pm resolution precision spectrum analysis in the optical communication band, using the precision spectrum analysis system according to any one of claims 1 to 7, characterized in that: The process includes the following: After the optical fiber signal to be tested is conditioned into collimated parallel spatial light by the optical input module to be tested, the optical module performs interference modulation on it under the action of the motor drive module to complete interference splitting. After convergence, it enters the detection and acquisition module to complete photoelectric conversion and digital sampling, and then completes real-time spectral inversion through the data processing module. Finally, it enters the main control module and performs a series of processing to complete the ultra-high resolution spectral measurement and analysis of the optical fiber signal.

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