CN114923588B - Central wavelength demodulation method and system based on signal spectrum product analysis - Google Patents
Central wavelength demodulation method and system based on signal spectrum product analysis Download PDFInfo
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Abstract
本发明提供一种基于信号谱乘积分析的中心波长解调方法和系统，该系统包括光源、环形器、待测器件、分光模块、光电探测阵列和中心波长解调模块，光源通过环形器将光源信号提供给待测器件，待测器件将反射信号谱反向传输回该环形器，经由环形器传输给分光模块，分光模块将反射信号谱分离成多个独立的纵模，光电探测阵列对多个纵模进行一一对应的稀疏采样，并将采集到的各个纵模传输给中心波长解调模块；中心波长解调模块基于信号谱乘积，对各个纵模进行分析解调，获得待测器件的中心波长。本发明结构简单，解调所基于的数据量少，且解调方法简单，解调速度快。
The present invention provides a central wavelength demodulation method and system based on signal spectrum product analysis, the system includes a light source, a circulator, a device to be tested, a spectroscopic module, a photoelectric detection array and a central wavelength demodulation module, the light source provides a light source signal to the device to be tested through the circulator, the device to be tested transmits the reflected signal spectrum back to the circulator, and transmits it to the spectroscopic module via the circulator, the spectroscopic module separates the reflected signal spectrum into multiple independent longitudinal modes, the photoelectric detection array performs one-to-one sparse sampling on the multiple longitudinal modes, and transmits each collected longitudinal mode to the central wavelength demodulation module; the central wavelength demodulation module analyzes and demodulates each longitudinal mode based on the signal spectrum product to obtain the central wavelength of the device to be tested. The present invention has a simple structure, a small amount of data based on which demodulation is based, a simple demodulation method, and a fast demodulation speed.
Description
Technical Field
The invention belongs to the field of optical fiber sensing, and particularly relates to a center wavelength demodulation method and system based on signal spectrum product analysis.
Background
Fiber Bragg Gratings (FBGs) are refractive index modulation devices that reflect specific wavelengths associated with the measurement, and have extremely important applications in the fields of optical fiber sensing and optical fiber precision. The FBG has the unique advantages of accurate positioning, high precision and easy multiplexing, and has irreplaceable other sensing technologies in a plurality of application scenes. The fiber bragg grating can be used for sensing various parameters such as stress, strain, temperature, vibration and the like. The center wavelength of the Bragg grating, namely the Bragg wavelength, is a core performance parameter of the Bragg grating, and can directly represent the frequency stabilization characteristic of the laser and is directly and linearly related to the sensing value; therefore, it is important to accurately demodulate the center wavelength of the bragg grating, which is a core issue of the bragg grating research. The rapid development of science and society puts higher demands on the speed and accuracy of FBG demodulation.
Traditional Bragg grating demodulation methods based on spectrum measurement tend to be mature; methods that have been commercialized and industrialized can be divided into two categories, one based on broadband light sources and spectrometers and the other based on fast scanning tunable lasers and photodetectors; the basic mechanism is to calculate the Bragg wavelength from the measured reflection spectrum with limited resolution and noise, and further estimate the physical quantity to be measured or evaluate the performance of the optical function device. However, these methods face a great challenge because they all collect a large amount of useless data and require complicated calculation steps, thus resulting in a low demodulation speed. The existing commercial Bragg grating demodulators in the markets at home and abroad can not realize high-speed FBG demodulation. Such as BaySpec, FBGS, luna and other companies' Bragg grating demodulation instruments, the single channel measurement speed is only 5-10 kHz at maximum, and the typical state speed is only 100-1000 Hz.
In recent years, with rapid development of science, technology and industrial production, there is an increasing demand for detection of ultra-fast processes such as high-frequency vibration and the like. For example, in the aerospace industry, dangerous resonant frequencies are one of the main causes of damage to engine engines, cases, shafts, etc., and real-time vibration frequency detection is therefore necessary. The Bragg grating sensor can realize multi-point, distributed and deep internal measurement, and is an ideal choice. In addition, in an ultrafast laser system and a tunable laser system, the central wavelength of the Bragg grating is monitored in real time and at high speed, so that the diagnosis or performance characterization of the optical system can be effectively performed. In these processes, demodulation speeds on the order of hundreds of kHz, MHz, and even higher are often required, which is difficult to achieve with conventional methods.
Disclosure of Invention
The invention provides a center wavelength demodulation method and a system based on signal spectrum product analysis, which are used for solving the problem that the demodulation speed of the current center wavelength demodulation method is low.
According to a first aspect of an embodiment of the present invention, there is provided a center wavelength demodulation method based on signal spectrum product analysis, including:
step S110, obtaining a signal spectrum provided by a device to be tested, wherein the signal spectrum is a Gaussian signal spectrum or a Gaussian-like signal spectrum;
step S120, separating the signal spectrum into a plurality of independent longitudinal modes;
step S130, respectively sampling a plurality of longitudinal modes;
And step 140, analyzing and demodulating each acquired longitudinal mode based on the signal spectrum product to obtain the center wavelength of the device to be tested.
In an alternative implementation, the step S140 includes:
s141, multiplying the longitudinal modes to obtain a signal spectrum product;
Step S142, the logarithm of the signal spectrum product is obtained, and a parameter A and a parameter B are determined;
And step S143, based on the parameter A and the parameter B, the logarithm of the signal spectrum product is square, and the center wavelength of the device to be tested is obtained.
In another alternative implementation, after the step S140, the method further includes: and determining the central wavelength variation of the device to be tested.
In another alternative implementation, let the wavelength of each collected longitudinal mode be λ k-(N-1)/2…λk-1,λk,λk+1…λk+(N-1)/2, k be the serial number of the middle longitudinal mode, and the light intensity I (λ i) of the signal spectrum formed by each collected longitudinal mode be expressed as:
I(λi)＝αiI0·Exp{-4ln2·[(λi-λc)/Δλ]2}
i＝k-(N-1)/2～k+(N-1)/2
the signal spectrum product is expressed as:
Wherein, alpha i is a light intensity attenuation coefficient, I 0 is a constant representing photoelectric conversion efficiency, exp is an exponential function based on a natural constant e, lambda i is the wavelength of the ith longitudinal mode, lambda c is the center wavelength of a device to be tested, delta lambda is the distance between adjacent longitudinal modes, and N is the number of longitudinal modes.
In another alternative implementation, the logarithm of the signal spectrum product is expressed as:
Since the adjacent longitudinal mode interval is δ, the logarithm of the signal spectrum product can be reduced to:
the setting parameters A and B are respectively:
the logarithm of the signal spectral product can be further reduced to:
ln(prod.)＝A-B2(λk-λc)2；
Wherein, alpha i is a light intensity attenuation coefficient, I 0 is a constant representing photoelectric conversion efficiency, exp is an exponential function based on a natural constant e, lambda i is the wavelength of the ith longitudinal mode, lambda c is the center wavelength of a device to be tested, delta lambda is the distance between adjacent longitudinal modes, N is the number of longitudinal modes, and lambda k is the middle longitudinal mode.
In another alternative implementation, the center wavelength λ c of the device under test is:
where λ c is the center wavelength of the device under test, λ k is the middle longitudinal mode, ln (prod.) is the logarithm of the signal spectrum product, and a and B are the parameters determined in step S142.
In another alternative implementation, the center wavelength variation dλ of the device under test is expressed as:
where λ c is the center wavelength of the device under test, λ k is the middle longitudinal mode, ln (prod.) is the logarithm of the signal spectrum product, and a and B are the parameters determined in step S142.
In another optional implementation manner, the light source signal input to the device to be tested is a soliton optical comb with sparse discrete longitudinal modes, and the soliton optical comb has high repetition frequency and/or high signal to noise ratio; and after the device to be tested receives the soliton optical comb, reversely outputting the signal spectrum backwards, wherein the signal spectrum is a reflection spectrum.
According to a second aspect of the embodiment of the invention, a central wavelength demodulation system based on signal spectrum product analysis is provided, which comprises a light source, a circulator, a device to be detected, a light splitting module, a photoelectric detection array and a central wavelength demodulation module, wherein the output end of the light source is connected with the first end of the circulator, the second end of the circulator is connected with the device to be detected, and the third end of the circulator is connected with the central wavelength demodulation module sequentially through the light splitting module and the photoelectric detection array;
The light source provides a light source signal for the device to be tested through the circulator, the device to be tested reversely transmits a reflection spectrum back to the circulator, the reflection spectrum is transmitted to the light splitting module through the circulator, the light splitting module separates the reflection spectrum into a plurality of independent longitudinal modes, the photoelectric detection array performs one-to-one sparse sampling on the plurality of longitudinal modes, and each acquired longitudinal mode is transmitted to the central wavelength demodulation module; and the central wavelength demodulation module analyzes and demodulates each longitudinal mode based on the signal spectrum product to obtain the central wavelength of the device to be detected, and the reflection spectrum is a Gaussian spectrum or a Gaussian-like spectrum.
In an optional implementation manner, the central wavelength demodulation module comprises a multiplier, a logarithmic counter and an squarer, the photoelectric detection array transmits each acquired longitudinal mode to the multiplier, and the multiplier multiplies the longitudinal modes to obtain a signal spectrum product; the logarithmic device obtains the logarithm of the signal spectrum product and determines a parameter A and a parameter B; and the squarer squares the logarithm of the signal spectrum product based on the parameter A and the parameter B to obtain the center wavelength of the device to be tested.
The beneficial effects of the invention are as follows:
1. According to the invention, for the device to be tested which has the center wavelength and can provide the Gaussian signal spectrum or the Gaussian-like signal spectrum, the Gaussian signal spectrum or the Gaussian-like signal spectrum provided by the device to be tested is separated into a plurality of independent longitudinal modes, and the longitudinal modes are subjected to sparse sampling, so that less data to be processed are obtained, and the center wavelength of the device to be tested is demodulated based on the data, so that the demodulation speed can be improved; the method is based on the signal spectrum product, analyzes and demodulates each longitudinal mode to obtain the center wavelength of the device to be detected, has simple demodulation method, avoids using a high-speed analog-to-digital converter and time-consuming matrix operation in a fitting algorithm, and greatly improves demodulation speed;
2. According to the invention, when the light source signal input to the device to be tested is the soliton optical comb and has sparse discrete longitudinal modes, the longitudinal modes separated from the soliton optical comb can be subjected to sparse sampling, the acquired data quantity is less, the central wavelength of the device to be tested is demodulated based on the data, the demodulation speed can be improved, and when the soliton optical comb has high repetition frequency, the high efficiency of the longitudinal mode acquisition can be improved, so that the real-time measurement of the central wavelength of the device to be tested can be ensured; when the soliton optical comb has a high signal-to-noise ratio, the frequency of each longitudinal mode separated from the soliton optical comb is stable, so that the longitudinal modes can be subjected to one-to-one frequency resolution sampling according to different frequencies, uncertainty in reflection spectrum measurement can be eliminated, the acquisition accuracy of the longitudinal modes is improved, and the demodulation accuracy of the center wavelength of a device to be measured is further improved;
3. The soliton optical comb has the potential of integration and even on-chip integration, and is simple in structure; the soliton optical comb has hundreds of stable longitudinal modes, so that the method is suitable for the wavelength division multiplexing technology.
Drawings
FIG. 1 is a flow chart of one embodiment of a center wavelength demodulation method based on signal spectral product analysis of the present invention;
FIG. 2 is a schematic diagram of one embodiment of a center wavelength demodulation system based on signal spectral product analysis in accordance with the present invention;
FIG. 3 is a schematic diagram of a structure of an embodiment of a center wavelength demodulation module according to the present invention;
FIG. 4 is a waveform diagram of the measurement result of the temperature rise signal according to the present invention;
fig. 5 is a waveform diagram of the measurement result of the vibration signal according to the present invention.
Detailed Description
In order to better understand the technical solution in the embodiments of the present invention and make the above objects, features and advantages of the embodiments of the present invention more comprehensible, the technical solution in the embodiments of the present invention is described in further detail below with reference to the accompanying drawings.
In the description of the present invention, unless otherwise specified and defined, it should be noted that the term "connected" should be interpreted broadly, and for example, it may be a mechanical connection or an electrical connection, or may be a connection between two elements, or may be a direct connection or may be an indirect connection through an intermediary, and it will be understood to those skilled in the art that the specific meaning of the term may be interpreted according to the specific circumstances.
Referring to fig. 1, a flowchart of an embodiment of a method for demodulating a center wavelength based on signal spectrum product analysis according to the present invention is shown. The method may include:
step S110, obtaining a signal spectrum provided by a device to be tested, wherein the signal spectrum is a Gaussian signal spectrum or a Gaussian-like signal spectrum;
step S120, separating the signal spectrum into a plurality of independent longitudinal modes;
step S130, sampling a plurality of longitudinal modes respectively;
and step 140, analyzing and demodulating each acquired longitudinal mode based on the signal spectrum product to obtain the center wavelength of the device to be tested. It should be noted that the signal spectrum provided by the device under test may be a signal spectrum obtained by inputting a signal to the device under test and passing through the device under test.
The step S140 may include:
s141, multiplying the longitudinal modes to obtain a signal spectrum product;
Step S142, the logarithm of the signal spectrum product is obtained, and a parameter A and a parameter B are determined;
And step S143, based on the parameter A and the parameter B, the logarithm of the signal spectrum product is square, and the center wavelength of the device to be tested is obtained.
Let the wavelength of each collected longitudinal mode be λ k-(N-1)/2…λk-1,λk,λk+1…λk+(N-1)/2, k be the serial number of the middle longitudinal mode, the light intensity I (λ i) of the signal spectrum formed by each collected longitudinal mode may be expressed as:
I(λi)＝αiI0·Exp{-4ln2·[(λi-λc)/Δλ]2}
i＝k-(N-1)/2～k+(N-1)/2
The signal spectrum product may be expressed as:
Where α i is the light intensity attenuation coefficient, I 0 is a constant representing the photoelectric conversion efficiency, exp is an exponential function based on a natural constant e, λ i is the wavelength of the ith longitudinal mode, λ c is the center wavelength of the device under test, Δλ is the distance between adjacent longitudinal modes (i.e., the wavelength difference between adjacent longitudinal modes), and N is the number of longitudinal modes.
The logarithm of the signal spectrum product may be expressed as;
Since the adjacent longitudinal mode interval is δ, the logarithm of the signal spectrum product can be reduced to:
the setting parameters A and B are respectively:
the logarithm of the signal spectral product can be further reduced to:
ln(prod.)＝A-B2(λk-λc)2，
Wherein, alpha i is a light intensity attenuation coefficient, I 0 is a constant representing photoelectric conversion efficiency, exp is an exponential function based on a natural constant e, lambda i is the wavelength of the ith longitudinal mode, lambda c is the center wavelength of a device to be tested, delta lambda is the distance between adjacent longitudinal modes, N is the number of longitudinal modes, and lambda k is the middle longitudinal mode.
The center wavelength lambda c of the device under test may be:
where λ c is the center wavelength of the device under test, λ k is the middle longitudinal mode, ln (prod.) is the logarithm of the signal spectrum product, and a and B are the parameters determined in step S142.
Since the sensor is generally used to detect the amount of change in temperature, vibration, or the like, the amount of change in the center wavelength of the sensor can also be determined after the center wavelength of the sensor is obtained in step S140. The amount of change in the center wavelength of the sensor can be expressed as dλ:
where λ c is the center wavelength of the device under test, λ k is the middle longitudinal mode, ln (prod.) is the logarithm of the signal spectrum product, and a and B are the parameters determined in step S142.
The light source signal input to the device to be tested can be a soliton optical comb with sparse discrete longitudinal modes, and the soliton optical comb has high repetition frequency and/or high signal to noise ratio; after the soliton optical comb is received, the device to be tested can reversely output the signal spectrum backwards, wherein the signal spectrum is a reflection spectrum, and the reflection spectrum can be Bragg scattered light. According to the invention, when the light source signal input to the device to be tested is the soliton optical comb and has sparse discrete longitudinal modes, the longitudinal modes separated from the soliton optical comb can be subjected to sparse sampling (for example, 3-7 longitudinal modes in a reflection spectrum can be acquired), the acquired data quantity is less, the central wavelength of the device to be tested is demodulated based on the data, the demodulation speed can be improved, and when the soliton optical comb has high repetition frequency, the high efficiency of the longitudinal mode acquisition can be improved, so that the real-time measurement of the central wavelength of the device to be tested can be ensured. When the soliton optical comb has a high signal-to-noise ratio, the frequency of each longitudinal mode separated from the soliton optical comb is stable, so that the longitudinal modes can be subjected to one-to-one frequency resolution sampling according to different frequencies, uncertainty in reflection spectrum measurement can be eliminated, the acquisition accuracy of the longitudinal modes is improved, and the demodulation accuracy of the center wavelength of a device to be measured is further improved. The soliton optical comb has the potential of integration and even on-chip integration, and is simple in structure; the soliton optical comb has hundreds of stable longitudinal modes, so that the method is suitable for the wavelength division multiplexing technology. In addition, the invention not only can realize the measurement of the center wavelength of one device to be measured, but also can realize the measurement of the center wavelengths of a plurality of devices to be measured which are connected in series. The device to be tested can be a fiber bragg grating sensor and the like.
As can be seen from the above embodiments, for the device to be tested having a center wavelength and capable of providing a gaussian signal spectrum or a gaussian-like signal spectrum, the present invention separates the gaussian signal spectrum or the gaussian-like signal spectrum provided by the device to be tested into a plurality of independent longitudinal modes, and performs sparse sampling on the longitudinal modes, so that less data to be processed is obtained, and therefore, the center wavelength of the device to be tested is demodulated based on the data, and the demodulation speed can be increased; the invention analyzes and demodulates each longitudinal mode based on the signal spectrum product to obtain the center wavelength of the device to be detected, has simple demodulation method, avoids using a high-speed analog-digital converter and time-consuming matrix operation in a fitting algorithm, and greatly improves the demodulation speed.
Referring to fig. 2, a schematic structural diagram of an embodiment of a central wavelength demodulation system based on signal spectrum product analysis according to the present invention is shown. The system can comprise a light source 1, a circulator 2, a device to be tested 6, a light splitting module 3, a photoelectric detection array 4 and a central wavelength demodulation module 5, wherein the output end of the light source 1 is connected with the first end of the circulator 2, the second end of the circulator 2 is connected with the device to be tested 6, and the third end is connected with the central wavelength demodulation module 5 sequentially through the light splitting module 3 and the photoelectric detection array 4; the light source 1 provides a light source signal to the device to be tested 6 through the circulator 2, the device to be tested 6 reversely transmits a reflection spectrum back to the circulator 2, the reflection spectrum is transmitted to the light splitting module 3 through the circulator 2, the light splitting module 3 separates the reflection spectrum into a plurality of independent longitudinal modes, the photoelectric detection array 4 performs one-to-one sparse sampling on the plurality of longitudinal modes, and each acquired longitudinal mode is transmitted to the central wavelength demodulation module 5; the central wavelength demodulation module 5 performs analysis demodulation on each longitudinal mode based on the signal spectrum product to obtain the central wavelength of the device to be tested, and the reflection spectrum is a Gaussian spectrum or a Gaussian-like spectrum.
In this embodiment, the light source signal may be a broadband light source, for example, a soliton optical comb with sparse discrete longitudinal modes. The soliton optical comb may have a high repetition frequency and/or a high signal to noise ratio. According to the invention, when the light source signal is the soliton optical comb and the light source signal has sparse discrete longitudinal modes, the photoelectric detection array can perform sparse sampling on the longitudinal modes separated from the soliton optical comb (for example, 3-7 longitudinal modes in the fiber bragg grating reflection signal spectrum can be collected), the collected data quantity is less, the central wavelength of the device to be detected is demodulated based on the data, the demodulation speed can be improved, and when the soliton optical comb has high repetition frequency, the high efficiency of the longitudinal mode collection can be improved, so that the real-time measurement of the central wavelength of the device to be detected can be ensured. When the soliton optical comb has a high signal-to-noise ratio, the frequency of each longitudinal mode separated from the soliton optical comb is stable, so that each pixel in the photoelectric detection array can carry out one-to-one frequency resolution sampling on the longitudinal modes according to different frequencies, uncertainty in reflection spectrum measurement can be eliminated, the acquisition accuracy of the longitudinal modes is improved, and the center wavelength demodulation accuracy of a device to be detected is further improved. The soliton optical comb has the potential of integration and even on-chip integration, and is simple in structure; the soliton optical comb has hundreds of stable longitudinal modes, so that the method is suitable for the wavelength division multiplexing technology. In addition, the invention not only can realize the measurement of the center wavelength of one device to be measured, but also can realize the measurement of the center wavelengths of a plurality of devices to be measured which are connected in series. The device to be tested can be a fiber bragg grating sensor and the like.
In order to ensure that the photoelectric detection array performs one-to-one sparse sampling on a plurality of longitudinal modes, parameters of the light splitting module 3 can be set so that each longitudinal mode corresponds to a pixel in the photoelectric detection array 4 one by one, and therefore each pixel in the photoelectric detection array 4 can perform one-to-one frequency resolution sampling on the longitudinal modes according to different frequencies. The soliton optical comb 1 can be a micro resonant cavity optical frequency comb or a high-repetition-frequency ultrafast laser frequency comb and is characterized by high-repetition-frequency and stable multiple longitudinal modes; the light splitting module 3 may be a grating, a wavelength division multiplexing device, an arrayed waveguide grating, etc.; the photo-detection array 4 is a photodiode array or a linear array image sensor, etc.; the bragg wavelength demodulation module 5 may be implemented in a hardware circuit or may be implemented digitally in a programmed manner.
In addition, as shown in fig. 3, the central wavelength demodulation module may include a multiplier 7, a logarithmic counter 8 and an squarer 9, where the photoelectric detection array 4 transmits each collected longitudinal mode to the multiplier 7, and the multiplier 7 multiplies the longitudinal modes to obtain a signal spectrum product; the logarithmic unit 8 obtains the logarithm of the signal spectrum product and determines a parameter A and a parameter B; the squarer 9 squares the logarithm of the signal spectrum product based on the parameter a and the parameter B to obtain the center wavelength of the device under test. Let the wavelength of each collected longitudinal mode be λ k-(N-1)/2…λk-1,λk,λk+1…λk+(N-1)/2, k be the serial number of the middle longitudinal mode, the light intensity I (λ i) of the signal spectrum (i.e. the reflection spectrum) formed by each collected longitudinal mode by the photoelectric detection array may be expressed as:
I(λi)＝αiI0·Exp{-4ln2·[(λi-λc)/Δλ]2}
i＝k-(N-1)/2～k+(N-1)/2
Where α i is the light intensity attenuation coefficient, I 0 is a constant representing the photoelectric conversion efficiency, exp is an exponential function based on a natural constant e, λ i is the wavelength of the ith longitudinal mode, λ c is the center wavelength of the device under test, Δλ is the distance between adjacent longitudinal modes (i.e., the wavelength difference between adjacent longitudinal modes), and N is the number of longitudinal modes.
After the multiplier 7 multiplies the longitudinal modes, the obtained signal spectrum product can be expressed as:
After the signal spectrum product passes through the logarithmic unit 8, the logarithm of the signal spectrum product obtained can be expressed as;
Since the adjacent longitudinal mode interval is δ, the logarithm of the signal spectrum product can be reduced to:
the setting parameters A and B are respectively:
the logarithm of the signal spectral product can be further reduced to:
ln(prod.)＝A-B2(λk-λc)2，
Wherein, alpha i is a light intensity attenuation coefficient, I 0 is a constant representing photoelectric conversion efficiency, exp is an exponential function based on a natural constant e, lambda i is the wavelength of the ith longitudinal mode, lambda c is the center wavelength of a device to be tested, delta lambda is the distance between adjacent longitudinal modes, N is the number of longitudinal modes, and lambda k is the middle longitudinal mode.
After the parameters a and B are input to the squarer, the squarer squares the logarithm of the signal spectrum product based on the parameters a and B, and the obtained center wavelength λ c of the device to be tested may be:
Where λ c is the center wavelength of the device under test, λ k is the middle longitudinal mode, ln (prod.) is the logarithm of the signal spectrum product, and a and B are the parameters determined in the logarithmic device.
Since the sensor is generally used to detect the amount of change in temperature, vibration, etc., the amount of change in the center wavelength of the device under test can also be determined after the center wavelength of the device under test is obtained. The amount of change in the center wavelength of the device under test can be expressed as dλ:
Where λ c is the center wavelength of the device under test, λ k is the middle longitudinal mode, ln (prod.) is the logarithm of the signal spectrum product, and a and B are the parameters determined in the logarithmic device.
As can be seen from the above embodiments, for the device to be tested having a center wavelength and capable of providing a gaussian signal spectrum or a gaussian-like signal spectrum, the present invention separates the gaussian signal spectrum or the gaussian-like signal spectrum provided by the device to be tested into a plurality of independent longitudinal modes, and performs sparse sampling on the longitudinal modes, so that less data to be processed is obtained, and therefore, the center wavelength of the device to be tested is demodulated based on the data, and the demodulation speed can be increased; the invention analyzes and demodulates each longitudinal mode based on the signal spectrum product to obtain the center wavelength of the device to be detected, has simple demodulation method, avoids using a high-speed analog-digital converter and time-consuming matrix operation in a fitting algorithm, and greatly improves the demodulation speed. In addition, the invention has simple structure.
In one example, the measurement of temperature signals and dither signals is achieved by using a 50 GHz-repetition frequency micro-resonator optical frequency comb as a light source, a non-parallel grating pair for light splitting, and a high-speed InGaAs array as a detection array, as shown in FIGS. 4 and 5, respectively. Fig. 4 (a) shows the continuous measurement result of the temperature at 10s, fig. 4 (b) shows the error with respect to the reference value, fig. 5 (a) shows the measurement result of the vibration signal at 20ms, fig. 5 (b) shows the partial amplification result at 10-10.5ms, fig. 5 (c) shows the measurement error, and fig. 5 (d) shows the spectrum of the measurement result.
Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of the application following, in general, the principles of the application and including such departures from the present disclosure as come within known or customary practice within the art to which the application pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the application being indicated by the following claims.
It is to be understood that the invention is not limited to the precise arrangements and instrumentalities shown in the drawings, which have been described above, and that various modifications and changes may be effected without departing from the scope thereof. The scope of the invention is to be governed only by the following claims.
Claims (4)
1. A center wavelength demodulation method based on signal spectrum product analysis, comprising:
step S110, obtaining a signal spectrum provided by a device to be tested, wherein the signal spectrum is a Gaussian signal spectrum or a Gaussian-like signal spectrum;
step S120, separating the signal spectrum into a plurality of independent longitudinal modes;
step S130, respectively sampling a plurality of longitudinal modes;
step S140, analyzing and demodulating each acquired longitudinal mode based on the signal spectrum product to obtain the center wavelength of the device to be tested;
The step S140 includes:
s141, multiplying the longitudinal modes to obtain a signal spectrum product;
Step S142, the logarithm of the signal spectrum product is obtained, and a parameter A and a parameter B are determined;
Step S143, based on the parameter A and the parameter B, the logarithm of the signal spectrum product is square, and the center wavelength of the device to be tested is obtained;
after the step S140, the method further includes: determining the central wavelength variation of the device to be tested;
Let the wavelength of each collected longitudinal mode be λ k-(N-1)/2…λk-1,λk,λk+1…λk+(N-1)/2, k be the serial number of the middle longitudinal mode, and the light intensity I (λ i) of the signal spectrum formed by each collected longitudinal mode be:
I(λi)＝αiI0·Exp{-4ln2·[(λi-λc)/Δλ]2}
i＝k-(N-1)/2～k+(N-1)/2
the signal spectrum product is expressed as:
Wherein, alpha i is a light intensity attenuation coefficient, I 0 is a constant for representing photoelectric conversion efficiency, exp is an exponential function based on a natural constant e, lambda i is the wavelength of the ith longitudinal mode, lambda c is the center wavelength of a device to be tested, delta lambda is the distance between adjacent longitudinal modes, and N is the number of longitudinal modes;
the logarithm of the signal spectrum product is expressed as:
Since the adjacent longitudinal mode interval is δ, the logarithm of the signal spectrum product can be reduced to:
the setting parameters A and B are respectively:
the logarithm of the signal spectral product can be further reduced to:
ln(prod.)＝A-B2(λk-λc)2；
Wherein λ k is the intermediate longitudinal mode;
The center wavelength lambda c of the device to be tested is as follows:
wherein a and B are the parameters determined in step S142;
the central wavelength variation dλ of the device under test is expressed as:
2. the method for demodulating a center wavelength based on signal spectrum product analysis according to claim 1, wherein the light source signal input to the device under test is a soliton optical comb with sparse discrete longitudinal modes, and the soliton optical comb has high repetition frequency and/or high signal-to-noise ratio; and after the device to be tested receives the soliton optical comb, reversely outputting the signal spectrum backwards, wherein the signal spectrum is a reflection spectrum.
3. The central wavelength demodulation system based on signal spectrum product analysis is characterized by comprising a light source, a circulator, a device to be detected, a light splitting module, a photoelectric detection array and a central wavelength demodulation module, wherein the output end of the light source is connected with the first end of the circulator, the second end of the circulator is connected with the device to be detected, and the third end of the circulator is connected with the central wavelength demodulation module sequentially through the light splitting module and the photoelectric detection array;
the light source provides a light source signal for the device to be tested through the circulator, the device to be tested reversely transmits a reflection spectrum back to the circulator, the reflection spectrum is transmitted to the light splitting module through the circulator, the light splitting module separates the reflection spectrum into a plurality of independent longitudinal modes, the photoelectric detection array performs one-to-one sparse sampling on the plurality of longitudinal modes, and each acquired longitudinal mode is transmitted to the central wavelength demodulation module; the central wavelength demodulation module adopts the central wavelength demodulation method as claimed in claim 1 or 2, analyzes and demodulates each longitudinal mode based on the signal spectrum product to obtain the central wavelength of the device to be detected, and the reflection spectrum is a Gaussian spectrum or a Gaussian-like spectrum.
4. The system of claim 3, wherein the central wavelength demodulation module comprises a multiplier, a logarithmic counter and a squarer, the photoelectric detection array transmits each collected longitudinal mode to the multiplier, and the multiplier multiplies the longitudinal modes to obtain a signal spectrum product; the logarithmic device obtains the logarithm of the signal spectrum product and determines a parameter A and a parameter B; and the squarer squares the logarithm of the signal spectrum product based on the parameter A and the parameter B to obtain the center wavelength of the device to be tested.
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