CN113624267A - Fiber grating center wavelength demodulation system and demodulation instrument based on edge filtering - Google Patents
Fiber grating center wavelength demodulation system and demodulation instrument based on edge filtering Download PDFInfo
- Publication number
- CN113624267A CN113624267A CN202110825989.XA CN202110825989A CN113624267A CN 113624267 A CN113624267 A CN 113624267A CN 202110825989 A CN202110825989 A CN 202110825989A CN 113624267 A CN113624267 A CN 113624267A
- Authority
- CN
- China
- Prior art keywords
- filter
- photoelectric conversion
- edge
- center wavelength
- demodulation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 239000000835 fiber Substances 0.000 title claims abstract description 71
- 238000001914 filtration Methods 0.000 title claims abstract description 42
- 238000006243 chemical reaction Methods 0.000 claims abstract description 63
- 238000000034 method Methods 0.000 claims abstract description 38
- 230000003287 optical effect Effects 0.000 claims abstract description 31
- 238000005070 sampling Methods 0.000 claims abstract description 30
- 230000003750 conditioning effect Effects 0.000 claims abstract description 26
- 239000013307 optical fiber Substances 0.000 claims description 36
- 230000003321 amplification Effects 0.000 claims description 22
- 238000003199 nucleic acid amplification method Methods 0.000 claims description 22
- 238000005259 measurement Methods 0.000 claims description 12
- 230000008859 change Effects 0.000 claims description 10
- 230000005540 biological transmission Effects 0.000 claims description 6
- 238000010276 construction Methods 0.000 claims 1
- 238000012545 processing Methods 0.000 abstract description 3
- 238000001514 detection method Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000002310 reflectometry Methods 0.000 description 3
- 238000001228 spectrum Methods 0.000 description 3
- 239000000919 ceramic Substances 0.000 description 2
- 230000006855 networking Effects 0.000 description 2
- 238000000411 transmission spectrum Methods 0.000 description 2
- 229910000530 Gallium indium arsenide Inorganic materials 0.000 description 1
- KXNLCSXBJCPWGL-UHFFFAOYSA-N [Ga].[As].[In] Chemical compound [Ga].[As].[In] KXNLCSXBJCPWGL-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35306—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement
- G01D5/35309—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer
- G01D5/35316—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer using a Bragg gratings
Abstract
The invention provides a fiber grating center wavelength demodulation system, a fiber grating center wavelength demodulation method and a fiber grating center wavelength demodulation instrument based on edge filtering, which relate to the technical field of fiber demodulation instruments and comprise the following steps: the device comprises an optical path unit, a photoelectric conversion unit, a signal conditioning unit, an A/D sampling unit and an upper computer; the fiber grating central wavelength demodulation system is simple in structure, the light intensity and the wavelength of reflected light of the fiber grating sensor correspond to each other through the filter slope, the flatness requirement on a light source is low, the system can be simultaneously suitable for application environments with high frequency and low frequency demodulation as long as the operation speed of a CPU (central processing unit) of an upper computer is enough, and the problems that the cost is high, the requirement on the flatness of the light source is high, the high frequency demodulation and low frequency demodulation application environments are difficult to meet simultaneously and the like in the existing demodulation system are solved.
Description
Technical Field
The invention relates to the technical field of fiber-optic demodulators, in particular to a fiber grating center wavelength demodulation system based on edge filtering.
Background
The fiber grating sensor reflects the change of an external physical parameter through the change of a central wavelength, so that the most important part in a fiber grating sensing system is a method for demodulating the wavelength of the fiber grating sensor.
(1) And (3) detection by a spectrometer: the center wavelength and its shift can be detected directly with a spectrometer or monochromator. The method has simple structure and is suitable for laboratories. However, the resolution of the conventional spectrometer based on a dispersion prism or a diffraction grating is low, and the conventional spectrometer cannot meet the requirements. Although high resolution spectrometers are adequate, these spectrometers are expensive and bulky, and the resulting systems lack the necessary compactness and robustness, and the detection of wavelengths by this method is impractical in sensor systems for practical engineering applications.
(2) And (3) matched filtering method: the matched filtering method is to utilize a reference grating or a band-pass filter device, track the wavelength change of the sensing grating by means of heterodyne carrier technology under the action of a driving element, and acquire external physical parameters such as measured stress or temperature and the like by tracking and scanning of a driving signal, so as to realize the demodulation of the reference grating to the sensing grating signal. This method can be further classified into a reflection type and a transmission type as 0. Light reflected by the sensing grating enters the reference grating through the coupler, the reference grating is driven by the driving element to scan, when the reflection center wavelength of the reference grating is matched with the reflection wavelength of the sensing grating, the output of the detector is the largest, and the size of the driving signal at the moment is recorded according to the output of the detector, so that the size of the measured object can be obtained. The method has the advantages that the precision is greatly influenced by the stability of the light source and external interference, and the requirement on the detector is high.
(3) Tunable narrowband light source demodulation method: the method demodulates the sensing grating array through the calibrated adjustable narrow linewidth laser light source, thereby determining the central wavelength of the Bragg fiber grating.
A distributed bragg reflector laser (DBR) is fixed to a piezoelectric body (PZT), and when the PZT is driven by a sawtooth wave or sine wave voltage, the laser wavelength is scanned within a range, and when the wavelength just satisfies a certain bragg grating wavelength, light incident on the sensing grating array is reflected by the response grating. The reflected light signal is sent to a detector after passing through a 3dB circulator, and a function relation curve of the Bragg grating reflectivity and the wavelength can be obtained by connecting a digital oscilloscope. In order to improve the measurement accuracy, a small disturbance signal can be added to the scanning voltage, and a feedback closed loop is formed by locking the peak wavelength when the disturbance frequency of the detection electric signal is zero. The signal light power of the system is high, noise can be suppressed, and therefore the system has high signal-to-noise ratio and resolution. The minimum wavelength resolution obtained by the experiment is about 2.3pm, but the stability and the tunable range of the existing optical fiber laser are not ideal enough, and the number and the application range of the sensing Bragg grating are limited to a certain extent.
(4) Tunable fiber F-P filter method: the Fabry-Perot (F-P) cavity is equivalent to a narrow-band filter, if parallel light enters the Fabry-Perot (F-P) cavity in a certain wavelength range, only light with certain specific wavelength meeting the coherence condition can interfere to generate extremely high coherence, and the reflection wavelength of the optical fiber sensor array can be demodulated by utilizing the characteristic of the Fabry-Perot (F-P) cavity. When the Fabry-Perot (F-P) filter is fixed on the piezoelectric ceramic, if the transmission wavelength of the Fabry-Perot (F-P) cavity is coincident with the reflection wavelength of the fiber Bragg grating, the detector can detect the optimal light intensity, and the voltage applied to the piezoelectric ceramic corresponds to the reflection wavelength of the fiber Bragg grating, so that the measured light intensity is obtained. However, since the transmission spectrum is a convolution of the reflection spectrum and the transmission spectrum of the Fabry-Perot (F-P) filter, the bandwidth is increased and the resolution is reduced. Therefore, a small jitter voltage is added to the scanning voltage, the output is passed through a mixer and a low-pass filter, the jitter frequency is measured, and when the signal is zero, the measured signal is the central wavelength, so that the resolution of the system can be greatly improved. Due to the wide FFP tuning range, demodulation of multiple sensors can be achieved. The higher finesse FFP is too costly and the filtering loss is large.
Disclosure of Invention
Technical problem to be solved
Aiming at the defects of the prior art, the invention provides a fiber grating center wavelength demodulation system, a fiber grating center wavelength demodulation method and a fiber grating center wavelength demodulation instrument based on an edge filtering method, and aims to solve the problems that the conventional demodulation system proposed in the background art is high in cost, high in requirement on light source flatness, difficult to meet application environments of high-frequency demodulation and low-frequency demodulation and the like.
(II) technical scheme
In order to achieve the purpose, the invention is realized by the following technical scheme: a fiber grating center wavelength demodulation system based on an edge filtering method comprises:
the device comprises an optical path unit, a photoelectric conversion unit, a signal conditioning unit, an A/D sampling unit and an upper computer 1-18; the optical path unit, the photoelectric conversion unit, the signal conditioning unit, the A/D sampling unit and each device and chip in the upper computer are electrically connected with each other to form the fiber bragg grating central wavelength demodulation system;
the optical path unit includes: 1-1 of ASE light source, 1-2 of three-port circulator, 1-3 of fiber Bragg grating sensor, 1-4 of fiber coupler and 1-5 of edge filter;
the photoelectric conversion unit includes: a first photoelectric conversion circuit 1-6, a second photoelectric conversion circuit 1-7;
the signal conditioning unit comprises: a first current-voltage conversion circuit 1-8, a second current-voltage conversion circuit 1-9, a first linear amplification circuit 1-10, a second linear amplification circuit 1-11, a first low-pass filter 1-12, a second low-pass filter 1-13, a first dark current compensation circuit 1-14, a second dark current compensation circuit 1-15;
the A/D sampling unit comprises: first A/D sampling circuits 1-16, second A/D sampling circuits 1-17.
Preferably, the three-port circulator 1-2 includes: one port, two ports, three ports; near-infrared light emitted by the ASE light source 1-1 enters through one port of the three-port circulator 1-2, and after the near-infrared light exits from the two ports and enters the optical fiber Bragg grating sensor 1-3, reflected light of the near-infrared light exits to the optical fiber coupler 1-4 through the three ports of the three-port circulator 1-2.
Preferably, the optical fiber coupler 1-4 is 1: 1, and the optical fiber coupler 1-4 splits reflected light of the optical fiber Bragg grating sensor 1-3 into a measuring optical path and a reference optical path in an average manner.
Preferably, the edge filter 1-5 uses a chirped grating to linearly filter the measurement light path; the measuring optical path is filtered by an edge filter 1-5 and then transmitted to a first photoelectric conversion circuit 1-6.
Preferably, the reference optical path is directly input into the second photoelectric conversion circuit 1 to 7.
Preferably, the method further comprises the following steps: and inputting the filtered measuring light path and the filtered reference light path into the signal conditioning unit to obtain effective voltage values corresponding to the measuring light path and the reference light path, sampling the effective voltage values by the A/D sampling unit, and converting the effective voltage values into digital signals which can be directly processed by the upper computer 1-18.
Preferably, the first photoelectric conversion circuit 1-6 and the second photoelectric conversion circuit 1-7 are PIN photodiodes.
Preferably, after the filtered measurement optical path and the filtered reference optical path are input into the signal conditioning unit, the current signal is logarithmically amplified and then converted into a voltage signal by the first current-voltage conversion circuit 1-8 and the second current-voltage conversion circuit 1-9, the converted voltage is secondarily amplified by the first linear amplification circuit 1-10 and the second linear amplification circuit 1-11, the high-frequency noise is filtered by the first low-pass filter 1-12 and the second low-pass filter 1-13, and the first dark current compensation circuit 1-14 and the second dark current compensation circuit 1-15 are used for canceling an error generated by a dark current possessed by a PIN photodiode of the photoelectric conversion unit.
The invention also provides a fiber grating center wavelength demodulation method based on edge filtering, which comprises the following steps:
calibrating the wavelength and the light intensity of an edge filter, wherein the edge filter selects a chirped grating and linearly filters the measuring light path;
the ASE light source emits near infrared light, and the emitted near infrared light enters the fiber grating sensor through the three-port circulator;
the fiber coupler splits reflected light of the fiber grating sensor into a measuring light path and a reference light path on average;
the measuring optical path is filtered by an edge filter and then transmitted to a first photoelectric conversion circuit; the reference light path is directly input into the second photoelectric conversion circuit;
converting the drift amount of the central wavelength of the grating into the change of the light intensity of the transmission end of the edge filter;
inputting current signals of a measurement light path and a reference light path which are subjected to filtering and photoelectric conversion into the signal conditioning unit, and performing current-voltage conversion, linear amplification and low-pass filtering on the input current signals by the signal conditioning unit and outputting voltage signals;
and the voltage signal output by the signal conditioning unit enters an A/D sampling circuit, an analog quantity signal is converted into a digital quantity signal which can be directly processed by an upper computer, and then the digital quantity signal is transmitted to the upper computer for inversion calculation to obtain the central wavelength drift amount of the reflected light and display a result.
The invention also provides a fiber grating center wavelength demodulator based on the edge filtering method, which adopts any fiber grating center wavelength demodulating system based on the edge filtering method to build the hardware of the demodulator.
(III) advantageous effects
The invention provides a fiber grating center wavelength demodulation system and method based on an edge filtering method and a demodulation instrument. The method has the following beneficial effects:
the fiber grating central wavelength demodulation system is simple in structure, the light intensity and the wavelength of reflected light of the fiber grating sensor are corresponding through the filter slope, the requirement on the flatness of a light source is low, and the fiber grating central wavelength demodulation system can be simultaneously suitable for application environments with high frequency and low frequency demodulation as long as the operation speed of a CPU (central processing unit) of an upper computer is enough, so that the problems that the cost is high, the requirement on the flatness of the light source is high, the high-frequency demodulation application environment and the low-frequency demodulation application environment are difficult to meet simultaneously and the like in the conventional demodulation system are solved;
the invention adopts the edge filtering method as the demodulation method, can effectively reduce the requirement of the demodulation system on the flatness of the wide-spectrum light source, improves the demodulation precision of the demodulator, enables the demodulator to be applied to a high-frequency demodulation environment, simplifies the structure of the optical fiber sensing system, can reduce the cost in the actual engineering, and can meet the application requirements of optical fiber sensor array networking and distributed measurement.
Drawings
Fig. 1 is a schematic structural diagram of a fiber grating center wavelength demodulation system based on an edge filtering method according to the present invention;
FIG. 2 is a flowchart of a fiber grating center wavelength demodulation method based on an edge filtering method according to the present invention;
FIG. 3 is a schematic structural diagram of a fiber grating center wavelength demodulator based on an edge filtering method according to the present invention;
FIG. 4 is a graph of wavelength and intensity calibration of chirped gratings;
FIG. 5 is a schematic diagram of the edge filtering demodulation principle;
in the figure: the optical fiber Bragg grating sensor comprises an ASE light source 1-1, a three-port circulator 1-2, an optical fiber Bragg grating sensor 1-3, an optical fiber coupler 1-4, an edge filter 1-5, a first photoelectric conversion circuit 1-6 and a second photoelectric conversion circuit 1-7; the optical fiber Bragg grating sensor comprises a first current-voltage conversion circuit 1-8, a second current-voltage conversion circuit 1-9, a first linear amplification circuit 1-10, a second linear amplification circuit 1-11, a first low-pass filter 1-12, a second low-pass filter 1-13, a first dark current compensation circuit 1-14, a second dark current compensation circuit 1-15, a first A/D sampling circuit 1-16, a second A/D sampling circuit 1-17, an upper computer 1-18, an ASE light source 1, a three-port circulator 2, an optical fiber Bragg grating sensor 3, an optical fiber coupler 4, an edge filter 5, a first photoelectric converter 6, a second photoelectric converter 7, a signal conditioning circuit 8, an A/D sampling circuit 9 and an upper computer 10.
Detailed Description
The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.
The embodiment of the invention provides a fiber grating center wavelength demodulation system based on an edge filtering method, as shown in fig. 1, comprising:
the device comprises an optical path unit, a photoelectric conversion unit, a signal conditioning unit, an A/D sampling unit and an upper computer 1-18; the optical path unit, the photoelectric conversion unit, the signal conditioning unit, the A/D sampling unit and each device and chip in the upper computer are electrically connected with each other to form the fiber bragg grating central wavelength demodulation system;
the optical path unit includes: 1-1 of ASE light source, 1-2 of three-port circulator, 1-3 of fiber Bragg grating sensor, 1-4 of fiber coupler and 1-5 of edge filter;
in the embodiment, the CS-ASE light source 1 provided by shenzhenjiki science and technology limited is selected, and the ASE light source has the advantages of good flatness, 10mw of output power, high stability, low noise and low polarization.
The photoelectric conversion unit includes: a first photoelectric conversion circuit 1-6, a second photoelectric conversion circuit 1-7;
in this embodiment, the photoelectric conversion circuit is an LSIPD-UL0.3-PIN indium gallium arsenide photodiode provided by beijing optical technology ltd, and the diode is packaged by optical fiber single-mode transmission and has an interface of an FC-APC interface.
The signal conditioning unit comprises: a first current-voltage conversion circuit 1-8, a second current-voltage conversion circuit 1-9, a first linear amplification circuit 1-10, a second linear amplification circuit 1-11, a first low-pass filter 1-12, a second low-pass filter 1-13, a first dark current compensation circuit 1-14, a second dark current compensation circuit 1-15;
in this embodiment, an AD825 chip is used as a current-voltage conversion circuit to convert a current signal into a voltage signal that can be sampled;
because the voltage converted by the current-voltage conversion circuit is only about a few millivolts to a few tens of millivolts generally, and the voltage value is too small, the bit number of A/D sampling is limited, therefore, the NE5532 is adopted to design a linear amplification circuit, and the amplification factor can be adjusted by 100 times under the condition of small signals. For the voltage signal after amplification, high-frequency noise may be amplified at the same time, the occurrence of the high-frequency noise only affects the experimental result, and is a potential threat for the sampling interface, so a second-order butterworth low-pass filter circuit is designed by adopting MAX275ACWP to process the amplified signal, and the interference of the high-frequency noise is eliminated. Finally, a dark current compensation circuit is designed by using NE5532, and errors generated by dark current of the photodiode are offset by adding bias voltage. And finally, voltage values respectively corresponding to the reference light and the measured light are obtained.
The A/D sampling unit comprises: first A/D sampling circuits 1-16, second A/D sampling circuits 1-17.
Preferably, the three-port circulator 1-2 includes: one port, two ports, three ports; near-infrared light emitted by the ASE light source 1-1 enters through one port of the three-port circulator 1-2, and after the near-infrared light exits from the two ports and enters the optical fiber Bragg grating sensor 1-3, reflected light of the near-infrared light exits to the optical fiber coupler 1-4 through the three ports of the three-port circulator 1-2.
Preferably, the optical fiber coupler 1-4 is 1: 1, and the optical fiber coupler 1-4 splits reflected light of the optical fiber Bragg grating sensor 1-3 into a measuring optical path and a reference optical path in an average manner.
Preferably, the edge filter 1-5 uses a chirped grating to linearly filter the measurement light path; the measuring optical path is filtered by an edge filter 1-5 and then transmitted to a first photoelectric conversion circuit 1-6;
the optical fiber devices which can be used as linear filter devices in the market at present mainly comprise three filter devices, namely a wavelength division multiplexer, a chirped grating and a Fabry-Perot (F-P) filter. However, the fabry-perot filter is difficult to satisfy the condition of linear filtering and to realize demodulation in an application environment with high precision, and the existing coarse wavelength division multiplexer and the existing dense wavelength division multiplexer cannot satisfy the filtering range of a single channel of 3 nm.
The chirp grating filter is mainly suitable for application environments with higher frequency and low frequency demodulation, and the chirp grating filter range can reach 11nm to the maximum extent, so that the chirp grating filter has the basis of large-range linear filtering. Therefore, the chirped grating is selected as the edge filter in this embodiment.
Preferably, the reference optical path is directly input into the second photoelectric conversion circuit 1 to 7.
Preferably, the method further comprises the following steps: and inputting the filtered measuring light path and the filtered reference light path into the signal conditioning unit to obtain effective voltage values corresponding to the measuring light path and the reference light path, sampling the effective voltage values by the A/D sampling unit, and converting the effective voltage values into digital signals which can be directly processed by the upper computer 1-18.
Preferably, the first photoelectric conversion circuit 1-6 and the second photoelectric conversion circuit 1-7 are PIN photodiodes.
Preferably, after the filtered measurement optical path and the filtered reference optical path are input into the signal conditioning unit, the current signal is logarithmically amplified and then converted into a voltage signal by the first current-voltage conversion circuit 1-8 and the second current-voltage conversion circuit 1-9, the converted voltage is secondarily amplified by the first linear amplification circuit 1-10 and the second linear amplification circuit 1-11, the high-frequency noise is filtered by the first low-pass filter 1-12 and the second low-pass filter 1-13, and the first dark current compensation circuit 1-14 and the second dark current compensation circuit 1-15 are used for canceling an error generated by a dark current possessed by a PIN photodiode of the photoelectric conversion unit.
As shown in fig. 2, 4, and 5, an embodiment of the present specification further provides a fiber grating center wavelength demodulation method based on edge filtering, where the method includes:
s21, calibrating the wavelength and light intensity of an edge filter, wherein the edge filter selects a chirped grating and linearly filters the measuring light path;
s22, the ASE light source emits near infrared light, and the emitted near infrared light enters the fiber bragg grating sensor through the three-port circulator;
s23, the fiber coupler splits the reflected light of the fiber grating sensor into a measuring light path and a reference light path on average; the measuring optical path is filtered by an edge filter and then transmitted to a first photoelectric conversion circuit; the reference light path is directly input into the second photoelectric conversion circuit; converting the drift amount of the central wavelength of the grating into the change of the light intensity of the transmission end of the edge filter;
s24, current signals of the measurement light path and the reference light path after filtering and photoelectric conversion are input into the signal conditioning unit, and the signal conditioning unit performs current-voltage conversion, linear amplification and low-pass filtering on the input current signals and outputs voltage signals;
and S25, the voltage signal output by the signal conditioning unit enters an A/D sampling circuit, the analog quantity signal is converted into a digital quantity signal which can be directly processed by an upper computer, and then the digital quantity signal is transmitted to the upper computer for inversion calculation to obtain the shift quantity of the center wavelength of the reflected light and display the result.
As shown in fig. 5, the edge filtering demodulation principle is as follows:
when the measured value of the environment to be measured is increased, the material of the optical fiber Bragg grating coating layer is correspondingly changed, the corresponding optical fiber Bragg grating area is subjected to axial tensile stress, the central wavelength is red-shifted from the position of lambda to the position of lambda + delta lambda, and the light intensity of the position of lambda + delta lambda is changed, meanwhile, an edge filter is introduced, the edge filter is a linear filter device, and the transmissivity curve of the linear filter is equivalent to a slope in the working range, the slope is linear, and the variation of the light intensity after filtering and the variation of the central wavelength are in a linear relation with the slope of the filtering edge, so when the central wavelength of the fiber Bragg grating is changed by delta lambda, the light intensity transmitted through the filter can also be changed, so that the drift amount of the central wavelength can be obtained by detecting the variation amount of the light intensity, and the demodulation function of the central wavelength of the optical fiber Bragg grating is further realized.
The relationship between the filtered light intensity and the wavelength is linear and can be expressed by the formula (2-1), wherein k is the slope of the linear filter device, and lambda is0Is an initial value of the center wavelength, i.e. I (λ)0) Is the reference light intensity, lambda is the central wavelength to be measured, and I (lambda) is the light intensity to be measured.
I(λ0)-I(λ)＝k(λ0-λ) (2-1)
And the reflectivity of the center wavelength of the fiber Bragg grating sensor can be approximately expressed by a Gaussian curve as shown in the formula (2-2):
R(λ,λ0)＝y0+R0exp[-a(λ-λ0)2] (2-2)
wherein, y0As background reflection component；R0Is the peak reflectivity, λ0The center wavelength of the sensing array, which is a fiber Bragg grating, where a is a constant. The reflected light passing through the sensor on the edge filter can be expressed as:
p here0The formula (2-4) can be obtained by substituting the formula (2-1) and the formula (2-2) into the formula (2-3) for the output power of the light source, and the change of the wavelength of the sensor when the sensor senses the change of the external parameter is lambda + delta lambda, wherein the change quantity of the central wavelength delta lambda and the change of the reflected light intensity are linear.
Therefore, the central wavelength drift amount of the sensor can be obtained through the transmitted light intensity of the edge filter, so that the central wavelength of the sensor can be demodulated, and the formula (2-5):
preferably, the calibration of the wavelength and the light intensity of the edge filter is performed, and the edge filter selects a chirped grating to perform linear filtering on the measurement light path;
before the chirped grating is selected as the filter, the wavelength calibration is carried out on the filtering range of the chirped grating, and then the wavelength range of 1548-1551nm with better spectral curve linearity is selected and subjected to linear fitting. Fig. 4 is a calibration and fitting graph of wavelength and light intensity of the chirped grating.
According to the fitting result, the linear relation between the wavelength and the light intensity of the selected chirped grating linear filtering part can be expressed as:
I＝8.81427λ-13718.85 (3-1)
the fitting results showed a standard deviation of the slope of 0.054The resulting Pearson's R distribution index was 0.997, R2The division index was 0.994. Therefore, the chirped grating serving as the filtering part has good linearity, and the requirement of linear filtering can be met. Here it can be seen that the slope of the linear filter is 8.81427. Obtaining a demodulation formula of the central wavelength of the reflected light of the fiber Bragg grating:
ΔI(Δλ)＝1×8.81427×0.95×0.107Δλ≈0.8876Δλ (3-2)
where Δ λ is the drift of the center wavelength of the fiber Bragg grating and Δ I is the corresponding variation of the filtered light intensity.
As shown in fig. 3, the invention further provides a fiber grating center wavelength demodulator based on an edge filtering method, wherein the fiber grating center wavelength demodulator is built by adopting any fiber grating center wavelength demodulating system as described above to implement the hardware of the demodulator.
In conclusion, the fiber grating central wavelength demodulation system is simple in structure, the light intensity and the wavelength of the reflected light of the fiber grating sensor are corresponding through the filter slope, the flatness requirement on a light source is low, and the fiber grating central wavelength demodulation system can be simultaneously suitable for application environments with high frequency and low frequency demodulation as long as the operation speed of a CPU (central processing unit) of an upper computer is enough, so that the problems that the cost is high, the requirement on the flatness of the light source is high, the application environments with high frequency demodulation and low frequency demodulation are difficult to meet simultaneously and the like in the conventional demodulation system are solved;
the invention adopts the edge filtering method as the demodulation method, can effectively reduce the requirement of the demodulation system on the flatness of the wide-spectrum light source, improves the demodulation precision of the demodulator, enables the demodulator to be applied to a high-frequency demodulation environment, simplifies the structure of the optical fiber sensing system, can reduce the cost in the actual engineering, and can meet the application requirements of optical fiber sensor array networking and distributed measurement.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (10)
1. A fiber grating center wavelength demodulation system based on edge filtering is characterized in that: the method comprises the following steps:
the device comprises a light path unit, a photoelectric conversion unit, a signal conditioning unit, an A/D sampling unit and an upper computer (1-18); the optical path unit, the photoelectric conversion unit, the signal conditioning unit, the A/D sampling unit and each device and chip in the upper computer are electrically connected with each other to form the fiber bragg grating central wavelength demodulation system;
the optical path unit includes: the optical fiber sensor comprises an ASE light source (1-1), a three-port circulator (1-2), an optical fiber Bragg grating sensor (1-3), an optical fiber coupler (1-4) and an edge filter (1-5);
the photoelectric conversion unit includes: a first photoelectric conversion circuit (1-6) and a second photoelectric conversion circuit (1-7);
the signal conditioning unit comprises: a first current-voltage conversion circuit (1-8), a second current-voltage conversion circuit (1-9), a first linear amplification circuit (1-10), a second linear amplification circuit (1-11), a first low-pass filter (1-12), a second low-pass filter (1-13), a first dark current compensation circuit (1-14), a second dark current compensation circuit (1-15);
the A/D sampling unit comprises: a first A/D sampling circuit (1-16) and a second A/D sampling circuit (1-17).
2. The edge-filter-based fiber grating center wavelength demodulation system of claim 1, wherein: the three-port circulator (1-2) includes: one port, two ports, three ports; near-infrared light emitted by the ASE light source (1-1) enters through one port of the three-port circulator (1-2), and after the near-infrared light enters the fiber Bragg grating sensor (1-3) through the two ports, reflected light of the near-infrared light is emitted to the fiber coupler (1-4) through the three ports of the three-port circulator (1-2).
3. The edge-filter-based fiber grating center wavelength demodulation system of claim 1, wherein: the optical fiber coupler (1-4) is 1: the optical fiber Bragg grating sensor comprises an optical fiber coupler (1), wherein the optical fiber coupler (1-4) splits reflected light of the optical fiber Bragg grating sensor (1-3) into a measuring optical path and a reference optical path in an average way.
4. The edge-filter-based fiber grating center wavelength demodulation system of claim 3, wherein: the edge filter (1-5) selects a chirped grating and linearly filters the measuring light path; the measuring optical path is filtered by an edge filter (1-5) and then transmitted to a first photoelectric conversion circuit (1-6).
5. The edge-filter-based fiber grating center wavelength demodulation system of claim 4, wherein: the reference optical path is directly input into the second photoelectric conversion circuit (1-7).
6. The edge-filter-based fiber grating center wavelength demodulation system of claim 5, wherein: further comprising: and inputting the filtered measuring light path and the filtered reference light path into the signal conditioning unit to obtain effective voltage values corresponding to the measuring light path and the reference light path, sampling the effective voltage values by the A/D sampling unit, and converting the effective voltage values into digital signals which can be directly processed by an upper computer (1-18).
7. The edge-filter-based fiber grating center wavelength demodulation system of claim 6, wherein: the first photoelectric conversion circuit (1-6) and the second photoelectric conversion circuit (1-7) are selected from PIN photodiodes.
8. The edge-filter-based fiber grating center wavelength demodulation system of claim 7, wherein: after current signals of the measurement optical path and the reference optical path which are subjected to filtering and photoelectric conversion are input into the signal conditioning unit, the current signals are subjected to logarithmic amplification through the first current-voltage conversion circuit (1-8) and the second current-voltage conversion circuit (1-9) and then converted into voltage signals, the converted voltage is subjected to secondary amplification through the first linear amplification circuit (1-10) and the second linear amplification circuit (1-11), high-frequency noise is filtered through the first low-pass filter (1-12) and the second low-pass filter (1-13), and the dark current compensation circuit is used for offsetting errors generated by dark current of a PIN photodiode of the photoelectric conversion unit.
9. A fiber grating center wavelength demodulation method based on edge filtering is characterized in that: the method comprises the following steps:
calibrating the wavelength and the light intensity of an edge filter, wherein the edge filter selects a chirped grating and linearly filters the measuring light path;
the ASE light source emits near infrared light, and the emitted near infrared light enters the optical fiber Bragg grating sensor through the three-port circulator;
the fiber coupler splits reflected light of the fiber grating sensor into a measuring light path and a reference light path on average; the measuring optical path is filtered by an edge filter and then transmitted to a first photoelectric conversion circuit; the reference light path is directly input into the second photoelectric conversion circuit; converting the drift amount of the central wavelength of the grating into the change of the light intensity of the transmission end of the edge filter;
inputting current signals of a measurement light path and a reference light path which are subjected to filtering and photoelectric conversion into the signal conditioning unit, and performing current-voltage conversion, linear amplification and low-pass filtering on the input current signals by the signal conditioning unit and outputting voltage signals;
and the voltage signal output by the signal conditioning unit enters an A/D sampling circuit, an analog quantity signal is converted into a digital quantity signal which can be directly processed by an upper computer, and then the digital quantity signal is transmitted to the upper computer for inversion calculation to obtain the central wavelength drift amount of the reflected light and display a result.
10. A fiber grating center wavelength demodulator is characterized in that: the fiber bragg grating central wavelength demodulation system of any one of claims 1 to 8 is adopted for the hardware construction of the demodulator.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110825989.XA CN113624267B (en) | 2021-07-21 | 2021-07-21 | Fiber bragg grating center wavelength demodulation system and demodulator based on edge filtering |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110825989.XA CN113624267B (en) | 2021-07-21 | 2021-07-21 | Fiber bragg grating center wavelength demodulation system and demodulator based on edge filtering |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN113624267A true CN113624267A (en) | 2021-11-09 |
| CN113624267B CN113624267B (en) | 2024-05-03 |
Family
ID=78380645
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202110825989.XA Active CN113624267B (en) | 2021-07-21 | 2021-07-21 | Fiber bragg grating center wavelength demodulation system and demodulator based on edge filtering |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN113624267B (en) |
Citations (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1737676A (en) * | 2005-08-26 | 2006-02-22 | 天津大学 | Optical fibre Bragg grating sensing demodulating equipment and demodulating method thereof |
| CN1945240A (en) * | 2005-10-03 | 2007-04-11 | 美国凹凸微系有限公司 | Light detecting device |
| CN101216327A (en) * | 2008-01-08 | 2008-07-09 | 西安石油大学 | High precision optical fiber grating sensing signal demodulation instrument |
| CN101458100A (en) * | 2009-01-13 | 2009-06-17 | 冉曾令 | Demodulation system of FBG sensor and demodulation method thereof |
| CN201476800U (en) * | 2009-05-08 | 2010-05-19 | 刘信 | High-speed multi-channel fiber grating sensor demodulating system based on AWG |
| CN102169272A (en) * | 2011-04-08 | 2011-08-31 | 山东大学 | Method for demodulating wavelength of fiber grating by utilizing linear tilt filter |
| WO2014167175A1 (en) * | 2013-04-12 | 2014-10-16 | Vaisala Oyj | Laser doppler velocimeter with edge filter demodulation |
| CN104848980A (en) * | 2015-06-08 | 2015-08-19 | 武汉理工大学 | Bridge stay cable force online detection method and system based on fiber sensing |
| CN105044033A (en) * | 2014-12-10 | 2015-11-11 | 中国计量学院 | Intensity-demodulation optical fiber gas sensing device |
| CN111521206A (en) * | 2020-07-03 | 2020-08-11 | 武汉智慧地铁科技有限公司 | Wavelength demodulation method for fiber grating edge superposition filtering |
| CN111982839A (en) * | 2020-09-23 | 2020-11-24 | 浙江理工大学 | Method and device for detecting humidity of dryer |
-
2021
- 2021-07-21 CN CN202110825989.XA patent/CN113624267B/en active Active
Patent Citations (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1737676A (en) * | 2005-08-26 | 2006-02-22 | 天津大学 | Optical fibre Bragg grating sensing demodulating equipment and demodulating method thereof |
| CN1945240A (en) * | 2005-10-03 | 2007-04-11 | 美国凹凸微系有限公司 | Light detecting device |
| CN101216327A (en) * | 2008-01-08 | 2008-07-09 | 西安石油大学 | High precision optical fiber grating sensing signal demodulation instrument |
| CN101458100A (en) * | 2009-01-13 | 2009-06-17 | 冉曾令 | Demodulation system of FBG sensor and demodulation method thereof |
| CN201476800U (en) * | 2009-05-08 | 2010-05-19 | 刘信 | High-speed multi-channel fiber grating sensor demodulating system based on AWG |
| CN102169272A (en) * | 2011-04-08 | 2011-08-31 | 山东大学 | Method for demodulating wavelength of fiber grating by utilizing linear tilt filter |
| WO2014167175A1 (en) * | 2013-04-12 | 2014-10-16 | Vaisala Oyj | Laser doppler velocimeter with edge filter demodulation |
| CN105044033A (en) * | 2014-12-10 | 2015-11-11 | 中国计量学院 | Intensity-demodulation optical fiber gas sensing device |
| CN104848980A (en) * | 2015-06-08 | 2015-08-19 | 武汉理工大学 | Bridge stay cable force online detection method and system based on fiber sensing |
| CN111521206A (en) * | 2020-07-03 | 2020-08-11 | 武汉智慧地铁科技有限公司 | Wavelength demodulation method for fiber grating edge superposition filtering |
| CN111982839A (en) * | 2020-09-23 | 2020-11-24 | 浙江理工大学 | Method and device for detecting humidity of dryer |
Non-Patent Citations (6)
| Title |
|---|
| 周锐;乔学光;王若晖;高宏;杨扬;张敬花;: "基于长周期光纤光栅线性边缘滤波的地震波解调系统", 光电子.激光, no. 07 * |
| 康彦深: "基于WPM的高精度光纤Bragg温度传感系统研究与设计", 《仪表技术与传感器》, pages 1 - 3 * |
| 胡勇勤, 王俊杰, 罗裴: "光纤光栅水听器波长解调技术的研究", 传感器世界, no. 08 * |
| 范典;姜德生;梅加纯;: "高速双边缘光纤光栅波长解调技术", 光子学报, no. 01 * |
| 贾振安;营旭东;乔学光;丁锋;: "光纤光栅高速动态振动信号解调技术的研究", 光电子.激光, no. 05 * |
| 闫利琴;陈希明;吴小国;付长凤;夏秀兰;: "基于边缘滤波的温度传感实验研究", 天津理工大学学报, no. 05 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN113624267B (en) | 2024-05-03 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US8477296B2 (en) | Opto-electronic signal processing methods, systems, and apparatus for optical sensor interrogation | |
| US10895477B2 (en) | Sine-cosine optical frequency encoder devices based on optical polarization properties | |
| US6738140B2 (en) | Wavelength detector and method of detecting wavelength of an optical signal | |
| CN107024236B (en) | F-P/FBG optical fiber sensor demodulation system | |
| US7016047B2 (en) | Active Q-point stabilization for linear interferometric sensors | |
| CN108120378B (en) | Sine phase modulation interference absolute distance measuring device and method based on femtosecond optical frequency comb | |
| US8351473B1 (en) | System and method for laser wavelength control | |
| JP2009523248A (en) | Optical signal measurement system | |
| CN109186643B (en) | Accurate sensing system and sensing method based on reflection function resonant filter | |
| CN113218518A (en) | Sine-cosine optical frequency detection device based on integrated optical path and application of sine-cosine optical frequency detection device in optical sensing | |
| CN106017533A (en) | Rapid tuning real-time calibration fiber grating demodulation device and work method | |
| CN113624267B (en) | Fiber bragg grating center wavelength demodulation system and demodulator based on edge filtering | |
| CN111521283A (en) | Laser wavelength and power monitoring device and method | |
| RU2608394C1 (en) | Device for measuring parameters of physical fields | |
| CN216132474U (en) | Fiber grating center wavelength demodulation system and demodulation instrument | |
| CN111157127A (en) | System for measuring laser wavelength in real time | |
| US5822049A (en) | Optical fiber coupler type wavelength measuring apparatus | |
| CN113390441A (en) | Refractive index change sensing device and measuring method | |
| Zhang et al. | A Cost Effective FBG Sensor System Based on Narrow Band DBR Laser and FPGA Demodulation Technology | |
| CN113932838B (en) | High-precision fiber bragg grating demodulator and demodulation method thereof | |
| CN116865854B (en) | Wavelength detection device capable of being integrated on photon integrated chip | |
| CN111637906B (en) | Fiber grating demodulation device and method based on self-differencing coherence | |
| JP2001021415A (en) | Optical wavelength detecting method and optical wavelength detecting device | |
| JP3632825B2 (en) | Wavelength measuring device | |
| CN117928613A (en) | Fiber bragg grating demodulation device and detection method based on dichroic mirror |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant |