Long-fiber wide-spectrum dispersion measuring device and measuring method
By introducing a phase locking system and an FPGA development board into an unequal arm Mach-Zendel interferometer, combined with a femtosecond laser, the problem of long fiber wide spectral dispersion measurement is solved, and high-precision and stable measurement results are achieved.
Patent Information
- Application Number
- CN202411658731.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-20
- Publication Date
- 2025-02-07
AI Technical Summary
The prior art is difficult to achieve dispersion measurements over a wide spectral range of long fibers, especially while maintaining the stability of the interference signal.
Using an unequal arm Mach-Zendel interferometer with a phase locking system, combined with a femtosecond laser and an FPGA development board, adjusts the visibility of the interference signal by matching the beam's path and polarization, and uses PID parameters and high-voltage amplifier to signal. Processing to achieve accurate measurement of long fiber wide spectral dispersion.
The precise measurement of long fiber wide spectral dispersion is achieved, and the free drift of interference signals is eliminated. The device is simple and the stability time is long.
Smart Images
Figure CN119394600A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of quantum information technology, and in particular relates to a long optical fiber wide spectrum dispersion measurement device and a measurement method. Background Art
[0002] Dispersion is an important parameter of optical fiber. Accurate measurement of optical fiber dispersion plays an important role in optical fiber communications, optical fiber nonlinear processes, etc. For example, the four-wave mixing process used to generate quantum states in optical fiber can only occur if the phase matching condition is met, and an important method to achieve phase matching is to adjust the wavelength of the pump light near the zero dispersion point of the optical fiber. Therefore, accurate measurement of the dispersion of the gain fiber is an important prerequisite for the generation of the four-wave mixing process. Examples of quantum state preparation using zero-dispersion point phase matching include: using dispersion-shifted fiber as a nonlinear medium to generate a broadband, miniaturized, all-fiber intensity difference squeezed state source with stable structure and small volume (see reference: Sun Ang, Guo Xueshi, Zhao Wen, et al. A broadband, miniaturized, all-fiber intensity difference squeezed state source [J]. Laser & Optoelectronics Progress, 2023, 60(11): 344-349.); controlling the phase difference of the counter-propagation of photon pairs by the phase difference introduced by the single-mode fiber dispersion in a Sagnac fiber ring to obtain narrowband degenerate correlated photon pairs separated by spatial modes (see reference: Yang Lei, Liu Nannan, Li Xiaoying. Experimental study on the preparation and separation of degenerate correlated photon pairs by Sagnac fiber ring [J]. Acta Physica Sinica, 2016, 65(19): 78-84.).
[0003] Using a femtosecond laser as the light source, an unequal-arm Mach-Zehnder interferometer based on FPGA phase locking is used to measure fiber dispersion, which has the advantage of being able to simultaneously measure long fiber and wide spectrum dispersion. Existing literature (see literature: WQi, XHuang, DHo, S Yoo, KT Yong and F Luan. Dispersion measurement of optical fibers by phase retrieval from spectral interferometry [J]. Journal of optics, 2017, 19 (5): 055611) uses a combination of an equal-arm Mach-Zehnder interferometer with white light as the light source and a broadband supercontinuum source to measure fiber dispersion by direct phase recovery interferometry. Although the fiber dispersion measurement with a wide spectrum of 350nm is achieved, the measurable fiber length does not exceed 50cm. Another document (see: WZhang, ZChen, XZhang, CWang, BHe, NLiu, YWu, YTao, NZhang and PXue, Dispersion Measurement withOptical Computing Optical Coherence Tomography. Photonics, 2022, 9, 48.) uses optical computational optical coherence tomography based on Mach-Zehnder interferometer to measure fiber dispersion. Although it achieves dispersion measurement of 10km long optical fiber, it maps the dispersion to the frequency domain through time domain modulation, and can only calibrate the dispersion coefficient at a specific wavelength, and cannot calibrate the correspondence between dispersion and wavelength in a wide spectral range.
[0004] Currently, there is no device that uses a femtosecond laser, an unequal-arm Mach-Zehnder interferometer, and an FPGA development board in combination to realize dispersion measurement in a long optical fiber and a wide spectral range under interference stabilization conditions. Summary of the invention
[0005] The present invention is proposed to solve the problems existing in the prior art, and its purpose is to provide a long optical fiber wide spectrum dispersion measurement device and measurement method.
[0006] The technical solution of the present invention is: a long optical fiber wide spectrum dispersion measuring device, comprising an optical fiber mode-locked pulse laser, wherein the output end of the optical fiber mode-locked pulse laser is connected to the input end of a No. 1 50 / 50 beam splitter, the two output ports of the No. 1 50 / 50 beam splitter are respectively connected to the two arm inputs of an unequal-arm Mach-Zehnder interferometer component, the two arm output ports of the unequal-arm Mach-Zehnder interferometer component are respectively connected to the two input ends of a No. 2 50 / 50 beam splitter, the two output ports of the No. 2 50 / 50 beam splitter are respectively connected to a spectrometer and a photodetector, and the output of the photodetector is connected to a phase-locked component through a radio frequency splitter, and the other way is connected to an oscilloscope.
[0007] Furthermore, the two arms of the unequal-arm Mach-Zehnder interferometer assembly are respectively a reference arm and a measuring arm, wherein the reference arm is provided with piezoelectric ceramics; and the measuring arm is provided with an optical fiber to be measured and an optical fiber delay line.
[0008] Furthermore, the phase-locked component includes an FPGA development board, and the communication end of the FPGA development board is connected to the computer through the signal of the WIFI router; the output end of the FPGA development board is amplified by a high-voltage amplifier and then connected to the piezoelectric ceramic.
[0009] Furthermore, the No. 1 50 / 50 beam splitter outputs a first light beam entering a reference arm and a second light beam entering a measuring arm, and the optical fiber delay line in the measuring arm controls the polarization and arrival time of the second light beam.
[0010] Furthermore, after receiving the first light beam and the second light beam, the No. II 50 / 50 beam splitter outputs a first interference light beam and a second interference light beam.
[0011] Furthermore, the detection signal of the photodetector is divided into a first detection signal and a second detection signal through a radio frequency splitter, the first detection signal is input into an FPGA development board, and the second detection signal is input into an oscilloscope.
[0012] Furthermore, the FPGA development board inputs the phase-locked signal into the piezoelectric ceramic, and the phase-locked signal is amplified by a high-voltage amplifier during transmission.
[0013] A method for measuring a long optical fiber wide spectrum dispersion measurement device comprises the following steps: A. Matching the optical paths of the first light beam and the second light beam; B. matching the polarization of the first light beam and the second light beam; C. Adjust the visibility of the interference signal; D. Adjust the PID parameters in the FPGA development board; E. Adjust the gain of the high voltage amplifier; F. Collect interference pattern data; G. Process interference pattern data and perform dispersion calculations.
[0014] Furthermore, step A matches the optical paths of the first light beam and the second light beam, and the specific process is as follows: a1. Turn on the fiber mode-locked pulse laser; a2. Disconnect the optical fiber delay line from the connection port of the No. 2 50 / 50 beam splitter, and connect the light beam output by the No. 2 50 / 50 beam splitter to the photodetector. Input the detection signal into the oscilloscope through a cable, observe the first beam detected, and calibrate it using the oscilloscope. a3. Disconnect the reference arm optical fiber from the input port of the 50 / 50 beam splitter II, and connect the light beam output by the 50 / 50 beam splitter II to the photodetector. Input the detection signal into the oscilloscope through a cable, observe the detected second light beam, and use the oscilloscope for calibration; a4. Observe the time difference of the detected electrical pulse signal of the first beam and the second beam; a5. Adjust the optical fiber delay line so that the two pulse signals on the oscilloscope coincide with each other, that is, the optical path lengths of the first and second beams reaching the 50 / 50 beam splitter II are the same; a6. The first light beam and the second light beam with the same optical path interfere in the unequal-arm Mach-Zehnder interferometer assembly to generate an interference light beam.
[0015] Furthermore, step B matches the polarization of the first light beam and the second light beam, and the specific process is as follows: b1. Connect the interference signal output by the 50 / 50 beam splitter II to the spectrometer through a long optical fiber, and observe the interference spectrum generated by the two light paths on the spectrometer; b2. Adjust the polarization controller in the optical fiber delay line to maximize the interference spectrum intensity.
[0016] The beneficial effects of the present invention are as follows: The present invention utilizes a dispersion measurement system of an unequal-arm Mach-Zehnder interferometer with a phase-locked system to achieve dispersion measurement of a long optical fiber with a wide spectrum, eliminates free drift of interference signals caused by an external environment during measurement, and is easy to operate.
[0017] The invention can be used for accurate measurement of wide spectrum dispersion of long optical fiber, and the device is simple and has a long stabilization time. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 It is a connection schematic diagram of the present invention; Figure 2 is the dispersion curve when not phase-locked in the present invention; Figure 3 is the dispersion curve during phase locking in the present invention; in: 1 Fiber mode-locked pulse laser 2 No. Ⅰ 50 / 50 beam splitter 3 High Voltage Amplifier 4 Piezoelectric Ceramics 5 Fiber under test 6 Fiber delay line 7 No. Ⅱ 50 / 50 beam splitter 8 Photodetector 9 Spectrometer 10 RF splitter 11 FPGA development board 12 Oscilloscope 13 WIFI router 14 Computer. DETAILED DESCRIPTION
[0019] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings and embodiments: like Figures 1 to 3 As shown, a long optical fiber wide spectrum dispersion measuring device comprises an optical fiber mode-locked pulse laser 1, wherein the output end of the optical fiber mode-locked pulse laser 1 is connected to the input end of a No. 1 50 / 50 beam splitter 2, the two output ports of the No. 1 50 / 50 beam splitter 2 are respectively connected to the two arm inputs of an unequal-arm Mach-Zehnder interferometer component, the two arm output ports of the unequal-arm Mach-Zehnder interferometer component are respectively connected to the two input ends of a No. 2 50 / 50 beam splitter 7, the two output ports of the No. 2 50 / 50 beam splitter 7 are respectively connected to a spectrometer 9 and a photodetector 8, the output of the photodetector 8 is connected to a phase-locked component through a radio frequency splitter 10, and the other way is connected to an oscilloscope 12.
[0020] The two arms of the unequal-arm Mach-Zehnder interferometer assembly are respectively a reference arm and a measuring arm. The reference arm is provided with a piezoelectric ceramic 4 ; the measuring arm is provided with an optical fiber to be measured 5 and an optical fiber delay line 6 .
[0021] The phase-locked component includes an FPGA development board 11 , and a communication end of the FPGA development board 11 is connected to a computer 14 via a signal from a WIFI router 13 ; an output end of the FPGA development board 11 is amplified by a high-voltage amplifier 3 and then connected to a piezoelectric ceramic 4 .
[0022] The No. Ⅰ 50 / 50 beam splitter 2 outputs a first light beam entering the reference arm and a second light beam entering the measuring arm. The optical fiber delay line 6 in the measuring arm controls the polarization and arrival time of the second light beam.
[0023] After receiving the first light beam and the second light beam, the No. II 50 / 50 beam splitter 7 outputs a first interference light beam and a second interference light beam.
[0024] The detection signal of the photodetector 8 is divided into a first detection signal and a second detection signal through a radio frequency splitter. The first detection signal is input into an FPGA development board 11 , and the second detection signal is input into an oscilloscope 12 .
[0025] The FPGA development board 11 inputs the phase-locked signal into the piezoelectric ceramic 4 , and the phase-locked signal is amplified by the high-voltage amplifier 3 during the transmission process.
[0026] Specifically, the FPGA development board 11 is controlled by a computer 14 connected to the same WIFI network, and performs proportional, integral, and differential (PID) calculations on the input signal to form a phase-locked signal. The phase-locked signal output by the FPGA development board 11 is input into the piezoelectric ceramic 4, and a high-voltage amplifier 3 for amplifying the phase-locked signal is arranged between the FPGA development board 11 and the piezoelectric ceramic 4.
[0027] Specifically, the fiber mode-locked pulse laser 1 outputs a wide-spectrum laser beam, and the wide-spectrum laser beam outputs a first beam and a second beam through a No. 1 50 / 50 beam splitter 2. The first beam is input into a No. 2 50 / 50 beam splitter 7 through an optical fiber wound around a piezoelectric ceramic 4. At the same time, the second beam is input into the optical fiber to be tested 5 and an optical fiber delay line 6 with polarization control, and enters the No. 2 50 / 50 beam splitter 7.
[0028] Specifically, the No. II 50 / 50 beam splitter 7 outputs a first interference beam to a photodetector 8, and the No. II 50 / 50 beam splitter 7 also outputs a second interference beam to a spectrometer 9 for dispersion analysis.
[0029] Specifically, the photodetector 8 converts the optical signal of the first interference light beam into an electrical signal, and the photodetector 8 inputs a first detection signal to the FPGA development board 11 through the output port of the RF splitter 10 , and inputs a second detection signal to the oscilloscope 12 .
[0030] Specifically, the FPGA development board 11 inputs the adjusted phase-locked signal to the high-voltage amplifier 3, and the high-voltage amplifier 3 inputs the amplified phase-locked signal to the piezoelectric ceramic 4, thereby forming a complete long optical fiber wide spectrum dispersion measurement device.
[0031] Specifically, the preparation work of the FPGA development board 11 is as follows: Hardware Preparation First, the FPGA development board 11 and the computer 14 are connected to the same network environment through the WIFI router 13, and then the program of each functional module is burned into the memory card SD card inserted into the FPGA development board 11; The SD card burning process includes the following four steps: Download the latest installation system from the official website of FPGA development board 11, decompress the system files into ".ing" files; Download "Win32DiskImager" Use "Win32DiskImager" to select the ".ing" file, select the SD card as the device, and start writing the installation system; Insert the burned SD card into the FPGA development board 11.
[0032] Network connection Enter the URL on the back of the FPGA development board 11 in the web browser. If the web page jumps to the function page of the FPGA development board 11, it means that the network connection is successful.
[0033] Software Preparation The software preparation process consists of the following two steps: Anaconda. Download the old version of the software from the official website, and the latest version of the software may not work; Environment preparation. Open "Anaconda Prompt" in the computer start menu and enter the command "conda envcreat _f environment.yml". After completion, enter the command "cd pyrpl_qpit" again. At this point, the Python environment is set up.
[0034] Launch the software Open "Anaconda Prompt" in the computer start menu and enter the command "python file name.py".
[0035] At this point, the function operation interface of the FPGA development board 11 can be opened, and the PID phase lock module can be selected on the function operation page to complete the phase lock of the interference signal by adjusting the PID parameters.
[0036] A method for measuring a long optical fiber wide spectrum dispersion measurement device comprises the following steps: A. Matching the optical paths of the first light beam and the second light beam; B. matching the polarization of the first light beam and the second light beam; C. Adjust the visibility of the interference signal; D. Adjust the PID parameters in the FPGA development board 11; E. Adjust the amplification factor of the high voltage amplifier 3; F. Collect interference pattern data; G. Process interference pattern data and perform dispersion calculations.
[0037] Step A matches the optical paths of the first light beam and the second light beam. The specific process is as follows: a1. Turn on the fiber mode-locked pulse laser 1; a2. Disconnect the optical fiber delay line 6 from the connection port of the 50 / 50 beam splitter 7, and connect the output beam of the 50 / 50 beam splitter 7 to the photodetector 8. The detection signal is input into the oscilloscope 12 by a cable, and the first beam detected is observed and calibrated using the oscilloscope 12; a3. Disconnect the reference arm optical fiber from the input port of the 50 / 50 beam splitter 7, and connect the light beam output by the 50 / 50 beam splitter 7 to the photodetector 8. The detection signal is input to the oscilloscope 12 via a cable, and the detected second light beam is observed and calibrated using the oscilloscope 12; a4. Observe the time difference of the detected electrical pulse signal of the first beam and the second beam; a5. Adjust the optical fiber delay line 6 so that the two pulse signals on the oscilloscope 12 coincide with each other, that is, the first beam and the second beam have the same optical path when they reach the 50 / 50 beam splitter 7 of No. Ⅱ; a6. The first light beam and the second light beam with the same optical path interfere in the unequal-arm Mach-Zehnder interferometer assembly to generate an interference light beam.
[0038] Step B matches the polarization of the first light beam and the second light beam. The specific process is as follows: b1. The interference signal outputted from the 50 / 50 beam splitter 7 is connected to the spectrometer 9 through a long optical fiber, and the interference spectrum generated by the two beams is observed on the spectrometer 9; b2. Adjust the polarization controller in the optical fiber delay line 6 to maximize the interference spectrum intensity.
[0039] Specifically, step C adjusts the visibility of the interference signal, and the specific process is as follows: c1. Output a stable triangle wave signal to the unequal-arm Mach-Zehnder interferometer through the FPGA development board 11; c2. After the triangular wave signal is amplified by the high-voltage amplifier 3, the piezoelectric ceramic 4 is driven, and the pulse waveform of the interference signal is observed on the oscilloscope 12; c3. By adjusting the optical fiber delay line 6 and the light intensities of the first light beam and the second light beam, the intensity of the interference signal on the oscilloscope 12 is maximized.
[0040] Specifically, step D adjusts the PID parameters in the FPGA development board 11, and the specific process is as follows: d1. Under the premise of turning off the waveform generator function, open the PID parameter adjustment module of the FPGA development board 11 and turn on all the module inputs and outputs; d2. Set the "setpoint" value, that is, the phase lock position of the interference signal, and then adjust the proportional, integral, and differential parameters respectively to observe whether the interference signal on the oscilloscope is stable at the phase lock position.
[0041] Specifically, step E adjusts the gain of the high voltage amplifier 3, and the specific process is as follows: First, the phase-locked signal input to the high-voltage amplifier 3 by the FPGA development board 11 must not exceed the threshold voltage of the piezoelectric ceramic 4 and must not be a negative voltage; Then, under the drive of the high voltage amplifier 3, the expansion and contraction amount of the piezoelectric ceramic 4 is required to make the interference fringes reach four to five cycles within half a triangle wave cycle.
[0042] Specifically, step F collects interference pattern data, and the specific process is as follows: Adjust the scanning band range and step length of the spectrometer 9 to observe whether the spectrum of each scan is stable and does not change. If the spectrum is stable, store the data.
[0043] Specifically, step G processes the interference pattern data and performs dispersion calculation. The specific process is as follows: g1. Use Excel to normalize the interference spectrum data. After processing, the wavelength of the extreme point needs to be found. The extreme value can be a maximum value or a minimum value. g2. Calculate the frequency corresponding to the wavelength of each extreme point based on the relationship between wavelength and frequency, and use Matlab software to perform fourth-order fitting on the frequency and corresponding phase data to obtain the coefficients required for the dispersion function; g3. Substitute all coefficients into the dispersion fitting formula to obtain the complete dispersion function. Use the drawing software Origin to draw the dispersion curve of the measured optical fiber.
[0044] As an implementation method The dispersion curve of 200-meter dispersion-shifted optical fiber was measured using this dispersion measurement device and method. The measurement results are shown in Figure 2 , Figure 3 And as shown in Table 1.
[0045] Figure 2 , Figure 3 The dispersion curves are respectively when not phase-locked and phase-locked. By comparison, it can be seen that the dispersion measurement system of the unequal-arm Mach-Zehnder interferometer with a phase-locked system can achieve high-precision long fiber wide spectrum dispersion measurement in a stable state, with good effect and simple operation.
[0046]
[0047] The zero dispersion points obtained by three measurements are extracted from the dispersion curve, as shown in Table 1. It can be seen that when the system is not phase-locked, the measured value of the zero dispersion point of the 200m dispersion-shifted fiber varies greatly, indicating that the interference signal is not stable. When the system is phase-locked, the zero dispersion of the 200m dispersion-shifted fiber is fixed at 1535.4nm, indicating that the interference signal is very stable.
[0048] The merchant gave the zero dispersion point as 1520-1540nm. The zero dispersion point obtained by multiple measurements using this measuring device was 1535.4±0.2nm, with high measurement accuracy.
[0049] The present invention utilizes a dispersion measurement system of an unequal-arm Mach-Zehnder interferometer with a phase-locked system to achieve dispersion measurement of a long optical fiber with a wide spectrum, eliminates free drift of interference signals caused by an external environment during measurement, and is easy to operate.
[0050] The invention can be used for accurate measurement of wide spectrum dispersion of long optical fiber, and the device is simple and has a long stabilization time.
Claims
1. A long optical fiber wide spectrum dispersion measurement device, comprising an optical fiber mode-locked pulse laser (1), characterized in that: The output end of the fiber mode-locked pulse laser (1) is connected to the input end of a No. 1 50 / 50 beam splitter (2); the two output ports of the No. 1 50 / 50 beam splitter (2) are respectively connected to the two arm inputs of an unequal-arm Mach-Zehnder interferometer component; the two arm output ports of the unequal-arm Mach-Zehnder interferometer component are respectively connected to the two input ends of a No. 2 50 / 50 beam splitter (7); the two output ports of the No. 2 50 / 50 beam splitter (7) are respectively connected to a spectrometer (9) and a photodetector (8); the output of the photodetector (8) passes through a radio frequency splitter (10) and is connected to a phase-locking component on one side, and is connected to an oscilloscope (12) on the other side.
2. A long optical fiber wide spectrum dispersion measurement device according to claim 1, characterized in that: The two arms of the unequal-arm Mach-Zehnder interferometer assembly are respectively a reference arm and a measuring arm, wherein a piezoelectric ceramic (4) is arranged in the reference arm; and an optical fiber to be measured (5) and an optical fiber delay line (6) are arranged in the measuring arm.
3. The long optical fiber wide spectrum dispersion measurement device according to claim 1, characterized in that: The phase-locked component comprises an FPGA development board (11), wherein a communication end of the FPGA development board (11) is connected to a computer (14) via a signal of a WIFI router (13); and an output end of the FPGA development board (11) is amplified by a high-voltage amplifier (3) and then connected to a piezoelectric ceramic (4).
4. The long optical fiber wide spectrum dispersion measurement device according to claim 2, characterized in that: The No. 1 50 / 50 beam splitter (2) outputs a first light beam entering a reference arm and a second light beam entering a measurement arm. The optical fiber delay line (6) in the measurement arm controls the polarization and arrival time of the second light beam.
5. The long optical fiber wide spectrum dispersion measurement device according to claim 4, characterized in that: After receiving the first light beam and the second light beam, the No. II 50 / 50 beam splitter (7) outputs a first interference light beam and a second interference light beam.
6. The long optical fiber wide spectrum dispersion measurement device according to claim 1, characterized in that: The detection signal of the photoelectric detector (8) is divided into a first detection signal and a second detection signal by a radio frequency splitter, the first detection signal is input into an FPGA development board (11), and the second detection signal is input into an oscilloscope (12).
7. The long optical fiber wide spectrum dispersion measurement device according to claim 3, characterized in that: The FPGA development board (11) inputs the phase-locked signal into the piezoelectric ceramic (4), and the phase-locked signal is amplified by the high-voltage amplifier (3) during the transmission process.
8. A method for measuring a long optical fiber wide spectrum dispersion measurement device, characterized in that: The following steps are involved: A. Matching the optical paths of the first light beam and the second light beam; B. matching the polarization of the first light beam and the second light beam; C. Adjust the visibility of the interference signal; D. Adjust the PID parameters in the FPGA development board (11); E. Adjust the gain of the high voltage amplifier (3); F. Collect interference pattern data; G. Process interference pattern data and perform dispersion calculations.
9. The method for measuring the long optical fiber wide spectrum dispersion measurement device according to claim 8, characterized in that: Step A matches the optical paths of the first light beam and the second light beam. The specific process is as follows: a1. Turn on the fiber mode-locked pulse laser (1); a2. Disconnect the optical fiber delay line (6) from the connection port of the 50 / 50 beam splitter (7) and connect the output beam of the 50 / 50 beam splitter (7) to the photodetector (8). The detection signal is input into the oscilloscope (12) by a cable, and the first beam detected is observed and calibrated using the oscilloscope (12); a3. Disconnect the reference arm optical fiber from the input port of the 50 / 50 beam splitter (7) No. Ⅱ, and connect the output beam of the 50 / 50 beam splitter (7) No. Ⅱ to the photodetector (8). The detection signal is input into the oscilloscope (12) using a cable, and the detected second beam is observed and calibrated using the oscilloscope (12); a4. Observe the time difference of the detected electrical pulse signal of the first beam and the second beam; a5. Adjust the optical fiber delay line (6) so that the two pulse signals on the oscilloscope (12) coincide with each other, that is, the first beam and the second beam reach the same optical path as the 50 / 50 beam splitter (7) of II; a6. The first light beam and the second light beam with the same optical path interfere in the unequal-arm Mach-Zehnder interferometer assembly to generate an interference light beam.
10. The method for measuring the long optical fiber wide spectrum dispersion measurement device according to claim 8, characterized in that: Step B matches the polarization of the first light beam and the second light beam. The specific process is as follows: b1. The interference signal outputted from the 50 / 50 beam splitter II (7) is connected to the spectrometer (9) through a long optical fiber, and the interference spectrum generated by the two beams is observed on the spectrometer (9); b2. Adjust the polarization controller in the optical fiber delay line (6) to maximize the interference spectrum intensity.