CN-122001475-A - Fiber bragg grating wavelength demodulation device and method based on double Sagnac rings

CN122001475ACN 122001475 ACN122001475 ACN 122001475ACN-122001475-A

Abstract

The application provides a fiber grating wavelength demodulation device based on double Sagnac rings, which comprises a pulse light source, a fiber grating, a first fiber coupler, first and second Sagnac rings, a photoelectric detector, an analog-to-digital converter and a signal processing module, wherein the pulse light source is configured to emit detection pulse light, the fiber grating is configured to reflect specific light components in the light to generate reflected light corresponding to the specific light components, the first fiber coupler is configured to divide the reflected light into first and second light beams, the first and second Sagnac rings are respectively configured to filter the light beams to generate first and second filtered light signals, relative wavelength displacement exists between transmission spectrums of the first and second filtered light signals, optical path difference exists between output light paths of the first and second filtered light signals, the photoelectric detector is configured to convert the filtered light signals to generate analog electric signals, the analog-to-digital converter is configured to convert the analog electric signals into digital electric signals, and the signal processing module is configured to demodulate the Bragg wavelength drift amount of the fiber grating based on the intensity relation between two paths of sampling values processed by the first fiber coupler in the digital electric signals.

Inventors

TAN XIAO
LI CHENYING
MIAO YANLI
LIU JIANJUN
Sa ling
LI XIAOHAN

Assignees

国网江苏省电力有限公司电力科学研究院

Dates

Publication Date: 20260508
Application Date: 20260128

Claims (10)

1. The fiber bragg grating wavelength demodulation device based on the double Sagnac rings is characterized by comprising: A pulse light source configured to emit detection pulse light; a fiber grating configured to reflect a light component of the probe pulse light that matches a Bragg wavelength of the fiber grating to generate reflected light corresponding to the fiber grating; A first fiber coupler configured to split the reflected light into a first light beam and a second light beam; a first Sagnac loop configured to filter the first optical beam to produce a first filtered optical signal; A second Sagnac loop configured to filter the second light beam to produce a second filtered light signal, wherein there is a relative wavelength shift between the transmission spectra of the first and second Sagnac loops, and wherein there is an optical path difference between the output optical paths of the first and second Sagnac loops such that the first and second filtered light signals are separated in the time domain; a photodetector configured to convert the first and second filtered optical signals to produce an analog electrical signal; An analog-to-digital converter configured to convert the analog electrical signal into a digital electrical signal, and And the signal processing module is configured to demodulate the Bragg wavelength drift amount of the fiber bragg grating based on the intensity relation between two paths of sampling values processed by the first fiber coupler in the digital electric signal.
2. The fiber grating wavelength demodulation apparatus according to claim 1, wherein the fiber grating comprises a plurality of sub-fiber gratings spatially separated and having different bragg wavelengths.
3. The fiber grating wavelength demodulation apparatus according to claim 2, wherein an additional fiber section is provided between at least two adjacent fiber gratings, the additional fiber section being for increasing a time interval between reflected signals of the corresponding fiber gratings.
4. The fiber grating wavelength demodulation device according to claim 1, wherein the first and second Sagnac loops each comprise a single mode fiber, a high birefringence fiber, and a single mode fiber connected in sequence, and the first and second Sagnac loops are provided with a first polarization controller configured to adjust a transmission spectrum center wavelength of the first Sagnac loop and a second polarization controller configured to adjust a transmission spectrum center wavelength of the second Sagnac loop, respectively, in the respective loops, and wherein The first and second Sagnac rings each include a high birefringent fiber configured to introduce a wavelength dependent phase difference to light components propagating along their fast and slow axes, the first and second polarization controllers being configured to have different polarization control states to achieve the relative wavelength shift.
5. The fiber grating wavelength demodulation apparatus according to claim 4, wherein the first and second Sagnac loops comprise a second and third fiber couplers, respectively, wherein The second and third fiber couplers are configured to divide a respective one of the first and second light beams into two beams of coherent light propagating clockwise and counterclockwise and cause the two beams of coherent light to rejoin after interference within the respective one of the first and second Sagnac loops to produce a respective one of the first and second filtered light signals, respectively.
6. The fiber grating wavelength demodulation apparatus according to claim 1, wherein the first and second Sagnac loops comprise fourth and fifth fiber couplers, respectively, and the first and second Sagnac loops are provided with first and second non-reciprocal phase shifting elements, respectively, in the respective loops, and wherein The fourth and fifth fiber couplers are configured to divide a respective one of the first and second light beams into two beams of coherent light propagating clockwise and counterclockwise, and to cause the two beams of coherent light to rejoin after passing through the respective one of the first and second non-reciprocal phase-shifting elements to produce a respective one of the first and second filtered light signals, The first and second non-reciprocal phase-shifting elements are configured to have different amounts of phase shift to achieve the relative wavelength shift.
7. The fiber grating wavelength demodulation apparatus according to claim 1, wherein the signal processing module is further configured to determine a physical quantity monitor value corresponding to the fiber grating based on the Bragg wavelength shift amount.
8. The fiber grating wavelength demodulating apparatus according to claim 7, wherein the fiber grating is arranged on a surface or inside of an energy storage battery, and the physical quantity monitoring value includes a temperature or a strain of a position in the energy storage battery corresponding to the fiber grating.
9. The fiber grating wavelength demodulation apparatus of claim 8, wherein the signal processing module is further configured to: determining the temperature of the energy storage battery based on the corresponding relation between the Bragg wavelength drift amount and a preset temperature sensitivity coefficient, or And determining the strain of the energy storage battery based on the corresponding relation between the Bragg wavelength drift amount and a preset strain sensitivity coefficient.
10. The fiber bragg grating wavelength demodulation method based on the double Sagnac rings is characterized by comprising the following steps of: transmitting the detection pulse light to a fiber bragg grating by using a pulse light source, wherein the fiber bragg grating reflects a light component matched with the self Bragg wavelength to generate reflected light; Dividing the reflected light into a first light beam and a second light beam using an optical fiber coupler; filtering the first light beam with a first Sagnac loop to produce a first filtered light signal; Filtering the second light beam with a second Sagnac loop to produce a second filtered light signal, wherein there is a relative wavelength shift between the transmission spectra of the first and second Sagnac loops, and wherein there is an optical path difference between the output optical paths of the first and second Sagnac loops such that the first and second filtered light signals are separated in the time domain; photoelectric converting the first and second filtered optical signals with a photodetector to generate an analog electrical signal; converting the analog electrical signal into a digital electrical signal using an analog-to-digital converter, and And demodulating the Bragg wavelength drift amount of the fiber bragg grating based on the intensity relation between two paths of sampling values obtained by processing the fiber coupler in the digital electric signal by utilizing a signal processing module.

Description

Fiber bragg grating wavelength demodulation device and method based on double Sagnac rings Technical Field The application relates to the field of fiber grating wavelength demodulation, in particular to a fiber grating wavelength demodulation device based on double Sagnac rings. In addition, the application also relates to a fiber grating wavelength demodulation method based on the double Sagnac rings. Background The Bragg wavelength of the fiber bragg grating (Fiber Bragg Grating, FBG) is sensitive to physical quantities such as external temperature, strain and the like, and has the advantages of stable performance, electromagnetic interference resistance, chemical corrosion resistance and the like. Compared with other types of sensors, the FBG sensor has the advantages of high stability, good linearity, strong multiplexing capability, mass production and the like, and is widely applied to industrial production. The quasi-distributed measurement of a plurality of monitoring points can be realized by etching the sensing optical fibers of a plurality of fiber gratings with different wavelengths on a single optical fiber. However, the existing fiber grating wavelength demodulation technology is difficult to achieve low cost, high speed and high stability, namely, the peak searching method needs to traverse the light intensity of all wavelengths within a certain bandwidth, so that the calculation amount is large, the requirements on photoelectric detection equipment and data acquisition equipment are high, the cost is high, measurement errors caused by light source power floating and transmission loss change cannot be resisted, the matching filtering method needs to continuously scan the wavelengths within the bandwidth of a reflected signal, so that the demodulation rate is low, and the grating wavelength demodulation method based on a tunable laser/dual-optical frequency comb has the defects of high cost, large system volume, low demodulation speed, large measurement errors caused by light source power floating and the like. Disclosure of Invention According to one aspect of the present application, there is provided a fiber grating wavelength demodulation device based on a dual Sagnac ring, including a pulse light source configured to emit probe pulse light; the optical fiber grating is configured to reflect light components of the probe pulse light, which are matched with Bragg wavelengths of the optical fiber grating, to generate reflected light corresponding to the optical fiber grating, a first optical fiber coupler configured to split the reflected light into a first light beam and a second light beam, a first Sagnac loop configured to filter the first light beam to generate a first filtered light signal, a second Sagnac loop configured to filter the second light beam to generate a second filtered light signal, wherein relative wavelength shift exists between transmission spectrums of the first Sagnac loop and the second Sagnac loop, and wherein an optical path difference exists between output optical paths of the first Sagnac loop and the second Sagnac loop, so that the first filtered light signal and the second filtered light signal are separated in a time domain, a photoelectric detector configured to convert the first filtered light signal and the second filtered light signal to generate an analog electric signal, an analog-to-digital converter configured to-digital electric signal, and a signal processing module configured to demodulate the obtained sample values of the Bragg grating based on the wavelength shift relation between the transmission spectrums of the first coupler in the digital electric signal. According to another aspect of the present application, there is provided a fiber grating wavelength demodulation method based on dual Sagnac loops, comprising transmitting probe pulse light to a fiber grating using a pulse light source, the fiber grating reflecting a light component matched with its own Bragg wavelength to generate reflected light, dividing the reflected light into a first light beam and a second light beam using a fiber coupler, filtering the first light beam using the first Sagnac loop to generate a first filtered light signal, filtering the second light beam using the second Sagnac loop to generate a second filtered light signal, wherein there is a relative wavelength shift between transmission spectra of the first Sagnac loop and the second Sagnac loop, and wherein there is an optical path difference between output optical paths of the first Sagnac loop and the second Sagnac loop such that the first filtered light signal and the second filtered light signal are separated in a time domain, photoelectrically converting the first filtered light signal and the second filtered light signal using a photodetector to generate an analog electrical signal, converting the analog electrical signal to a digital electrical signal using an analog electrical signal using a second Sagnac