CN-121977621-A - High-speed Fabry-Perot sensor demodulation method and system based on photon time stretching and vernier effect

CN121977621ACN 121977621 ACN121977621 ACN 121977621ACN-121977621-A

Abstract

The invention relates to a demodulation method and a demodulation system of a high-speed Fabry-Perot sensor based on photon time stretching and vernier effect, wherein the method comprises the steps of emitting a pulse light signal through a pulse broadband light source and generating a primary interference signal through an MZI interferometer; the method comprises the steps of transmitting a primary interference signal to a Fabry-Perot sensor, further cascading the primary interference signal to generate a Fabry-Perot interference signal through vernier effect generated by cascading of an MZI interferometer and the Fabry-Perot sensor, transmitting the Fabry-Perot interference signal to a time stretching element, mapping the Fabry-Perot interference signal from a frequency domain to a time domain to obtain a time domain Fabry-Perot interference signal, performing photoelectric conversion and acquisition on the time domain Fabry-Perot interference signal to obtain a digital electric signal, tracking time domain feature change of the time domain Fabry-Perot interference signal, and demodulating the cavity length of the Fabry-Perot sensor. The invention can realize high-speed, high-sensitivity and high-precision demodulation of external high-frequency dynamic parameters, and has low realization cost.

Inventors

CHENG LIJUN
CHEN YURU
HU MIAO
XU MENGMENG
XU KAIREN

Assignees

杭州电子科技大学

Dates

Publication Date: 20260505
Application Date: 20260202

Claims (10)

1. The high-speed Fabry-Perot sensor demodulation method based on photon time stretching and vernier effect is characterized by comprising the following steps of: step S1, a pulse broadband light source is used for emitting a pulse light signal with a wide bandwidth; s2, dividing a pulse optical signal into two paths of optical signals through a first optical coupler, inputting the two paths of optical signals into an MZI interferometer, performing coherent beam combination on the two paths of optical signals output by the MZI interferometer through a second optical coupler, and outputting a primary interference signal; Step S3, transmitting a primary interference signal to a Fabry-Perot sensor, sensing physical quantity by the Fabry-Perot sensor, and further generating and outputting the Fabry-Perot interference signal containing cavity length information in a cascade manner on the primary interference signal through a vernier effect generated by cascading of an MZI interferometer and the Fabry-Perot sensor so as to amplify the measurement sensitivity; s4, transmitting the Fabry-Perot interference signals to a time stretching element, and mapping the Fabry-Perot interference signals from a frequency domain to a time domain by the time stretching element to obtain time domain Fabry-Perot interference signals with stretched time domains; S5, performing photoelectric conversion and acquisition on the time domain Fabry-Perot interference signals to obtain corresponding digital electric signals; And S6, processing the digital electric signal, tracking the time domain characteristic change of the time domain Fabry-Perot interference signal, and demodulating the cavity length of the Fabry-Perot sensor.
2. The demodulation method of the high-speed Fabry-Perot sensor based on photon time stretching and vernier effect as claimed in claim 1, wherein the demodulation rate of the demodulation method is the repetition frequency of the pulse broadband light source, and the higher demodulation rate can be obtained by increasing the repetition frequency of the pulse broadband light source.
3. The method for demodulating a high-speed fabry-perot sensor based on photon time stretching and vernier effect as claimed in claim 1, wherein in step S4, the time stretching element uses group velocity dispersion effect to realize mapping of fabry-perot interference signals from frequency domain to time domain.
4. A method of demodulating a high-speed fabry-perot sensor based on photon time stretching and vernier effect as claimed in claim 3, wherein said time stretching element is a dispersion compensating fiber or a chirped bragg grating.
5. The method for demodulating a high-speed fabry-perot sensor based on photon time stretching and vernier effect according to claim 1, wherein in step S6, the cavity length of the fabry-perot sensor is demodulated by tracking the temporal position change of the peak or trough of the temporal fabry-perot interference signal.
6. The demodulation method of a high-speed fabry-perot sensor based on photon time stretching and vernier effect as claimed in claim 1, wherein the MZI interferometer outputs an interference spectrum with a first free spectrum range FSR1, the fabry-perot sensor outputs an interference spectrum with a second free spectrum range FSR2, and the free spectrum range FSR of an envelope spectrum obtained by superposition of the two interference spectrums is: wherein FSR1 is close to FSR2, and the amplification factor of the measurement sensitivity is as follows: Where M represents the magnification of the measurement sensitivity.
7. The method for demodulating a high-speed Fabry-Perot sensor based on photon time stretching and vernier effect according to claim 1, wherein for a cascade system composed of an MZI interferometer and a Fabry-Perot sensor, an input pulse optical signal is set as The primary interference signal output by the pulse optical signal through the MZI interferometer is: (1) Wherein, the For the primary interference signal to be output, For the refractive index of the optical fiber, Is the difference in two arm length of the MZI interferometer, Is the wavelength of the pulsed optical signal; primary interference signal The Fabry-Perot interference signals output by the Fabry-Perot sensor are as follows: (2) Wherein, the For the output fabry-perot interference signal, For the reflectivity of the fabry-perot sensor cavity length, For the refractive index of the medium between the cavity end faces of the Fabry-Perot sensor, The cavity length of the Fabry-Perot sensor is; Fabry-Perot interference signal to be output after passing through cascade system Conversion from the wavelength domain to the frequency domain to obtain an interference signal Wherein In order to be of an angular frequency, , Is the frequency of the pulsed optical signal; Then, interfere with the signal The interference signal is transmitted to a time stretching element through a circulator, the time stretching element uses group velocity dispersion to linearly map the interference signal from an optical frequency domain to a time domain, and the frequency domain expression of the interference signal after the time domain stretching is as follows: (3) Where beta 2 is the second order group dispersion coefficient of the time stretching element, L DCF is the length of the time stretching element, Is the center angular frequency; according to formula (3), the output time domain Fabry-Perot interference signal is obtained through inverse Fourier transform, and the time domain expression is: (4) Wherein, the The output time domain Fabry-Perot interference signal; according to equation (4), the correspondence between angular frequency and time is: (5) when the Fabry-Perot cavity length changes, the time domain position change of the envelope peak value is tracked, so that the cavity length demodulation can be realized, and the method specifically comprises the following steps: If the distance vibrates in the form of a sinusoidal signal, the distance is expressed as: (6) Wherein, the In order to be a distance from each other, For the initial distance to be a certain value, For the amplitude of the vibration, Is the vibration frequency; When the repetition frequency of the pulse broadband light source, namely the measurement rate is determined, the change condition of the envelope peak value of the time domain Fabry-Perot interference signal is tracked, and the change result of the distance can be demodulated, so that the cavity length demodulation is realized.
8. A high-speed fabry-perot sensor demodulation system based on photon time stretching and vernier effect for implementing the method as claimed in any one of claims 1-7, comprising: a pulse broadband light source for generating and outputting a pulse optical signal of a wide bandwidth; the first optical coupler is connected with the pulse broadband light source and is used for dividing the pulse optical signal into two paths of optical signals and inputting the two paths of optical signals into the MZI interferometer; The MZI interferometer is connected with the first optical coupler and is used for generating optical path difference between two paths of optical signals so as to enable the optical signals to interfere in the second coupler; the second optical coupler is connected with the MZI interferometer and used for carrying out coherent beam combination and outputting a primary interference signal; The Fabry-Perot sensor is connected with an output light path of the second optical coupler and is used for generating a vernier effect with the MZI interferometer, and the Fabry-Perot sensor is further cascaded on the primary interference signal to generate a Fabry-Perot interference signal; The time stretching element is connected with an output light path of the Fabry-Perot sensor and is used for receiving the Fabry-Perot interference signal, mapping the Fabry-Perot interference signal from a frequency domain to a time domain and outputting the time domain Fabry-Perot interference signal; The photoelectric detector is connected with the output end of the time stretching element and is used for receiving the time domain Fabry-Perot interference signal and converting the time domain Fabry-Perot interference signal into an analog electric signal; The data acquisition device is connected with the photoelectric detector and is used for converting the analog electric signal into a digital electric signal; And the processing unit is connected with the data acquisition unit and is used for processing the digital electric signals to demodulate the cavity length of the Fabry-Perot sensor.
9. The high-speed fabry-perot sensor demodulation system based on photon time stretching and vernier effect according to claim 8, wherein the demodulation system further comprises a circulator, a first port of the circulator is connected with the second optical coupler, a second port of the circulator is connected with the fabry-perot sensor, and a third port of the circulator is connected with an input end of the time stretching element and is used for guiding a primary interference signal output by the second optical coupler to the fabry-perot sensor and guiding a fabry-perot interference signal generated by the fabry-perot sensor to the time stretching element.
10. The high-speed fabry-perot sensor demodulation system based on photon time stretching and vernier effect as claimed in claim 8, wherein the pulse broadband light source is a pulse laser with adjustable repetition frequency, the repetition frequency is the demodulation rate of the demodulation method, and the pulse laser obtains a higher demodulation rate by changing the repetition frequency.

Description

High-speed Fabry-Perot sensor demodulation method and system based on photon time stretching and vernier effect Technical Field The invention belongs to the technical field of optical fiber sensing, and particularly relates to a Fabry-Perot sensor demodulation method and system based on photon time stretching and vernier effect technology and suitable for high-speed dynamic measurement. Background The optical fiber Fabry-Perot sensor, the Fabry-Perot sensor or the optical fiber F-P for short, is the most common optical fiber sensor applied at present. Two high-reflection film layers are manufactured in the optical fiber, so that a microcavity with the cavity length of L is formed. When the coherent light is incident into the Fabry-Perot cavity, the optical signals are reflected at the two end surfaces of the Fabry-Perot cavity and then return along the original path, interference is generated after the optical signals meet, and the interference signals are related to the optical path difference of the optical interference in the cavity. When external parameters (such as vibration, strain, temperature, magnetic field and the like) act on the Fabry-Perot cavity in a certain mode, the optical path difference in the cavity is caused to change, so that the output interference signal is correspondingly changed. According to the principle, the length of the Fabry-Perot cavity and even the change of external parameters can be obtained according to the change of the interference signals so as to realize the measurement of various parameters. The Fabry-Perot sensor has the advantages of small volume, high temperature resistance, good reusability and the like, and is widely applied to various application scenes to monitor the change of various physical quantities. When the optical fiber sensor is used in a high-frequency dynamic change physical environment, the interference optical path difference in the Fabry-Perot cavity is changed rapidly, the demodulation difficulty is greatly increased, and therefore accurate demodulation of the Fabry-Perot cavity length is a key for realizing high-speed physical quantity measurement. White light interferometry is an important measurement technology in high-precision optical ranging, is limited by a measurement principle, involves a large number of scanning processes in measurement, is low in measurement speed, is not suitable for high-frequency dynamic measurement, and cannot meet the increasing requirement of high-frequency dynamic measurement. The frequency modulation continuous wave interferometry and the frequency sweep interferometry can realize very high absolute distance measurement precision, are very wide-application methods, but in the dynamic measurement process, a measured object moves at a high speed in a frequency sweep period, doppler frequency shift can be generated, so that a received interference signal has a Doppler frequency domain, a distance measurement error is caused, and the inherent working principle determines that the interference signal is not suitable for measuring high-frequency dynamic displacement and cannot meet the requirement of high-frequency dynamic measurement. The high-speed ranging method widely used in the industrial field has a multi-wavelength interferometry, and meanwhile, the precision of the method can be very high, but the signal processing is complex, phase errors are generated on a dynamic target in the dynamic measuring process, the method is difficult to apply to the influence of disturbance and the like caused by different light paths, and the measured distance change is limited by half wavelength. Although the accuracy can be very high, due to the complexity of the system, extremely severe environmental control, extremely high cost, and the realization of high accuracy is at a very high cost. Therefore, a dynamic demodulation scheme of the fabry-perot sensor, which has high-speed response, high sensitivity, high precision and easy implementation, is urgently needed. Disclosure of Invention The invention aims to overcome the defects of the prior art, provides a high-speed Fabry-Perot sensor demodulation method and a system based on photon time stretching and vernier effect, and the invention remarkably improves measurement sensitivity by introducing the vernier effect, and the photon time stretching technology is combined to linearly map the high-speed optical frequency domain interference signal to the time domain for acquisition and processing, so that the high-speed, high-sensitivity and high-precision demodulation of the external high-frequency dynamic parameters is realized, and the realization cost is low. In order to achieve the purpose, the invention adopts the following technical scheme that the high-speed Fabry-Perot sensor demodulation method based on photon time stretching and vernier effect comprises the following steps: step S1, a pulse broadband light source is used for emitting a pulse light signal with a wide