CN114923507A - High-resolution spectrum demodulation system of double-array waveguide grating based on wavelength dislocation - Google Patents
High-resolution spectrum demodulation system of double-array waveguide grating based on wavelength dislocation Download PDFInfo
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 8
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- 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 discloses a high-resolution spectrum demodulation system based on a double-arrayed waveguide grating, which comprises a wide-spectrum light source, an optical isolator, a circulator, an FBG array, a Y-shaped beam splitter, an AWG, a photoelectric conversion circuit, an A/D conversion circuit and a signal processing unit. When the device is used, light output by a wide-spectrum light source enters the FBG array through the optical isolator and the circulator, incident light is reflected into narrow-band light after passing through the FBG, the narrow-band light passes through the circulator and the Y-type beam splitter again and then respectively enters the AWG with two channels with staggered central wavelengths, then the light output by the AWG channel is accessed into the photoelectric conversion circuit to output a voltage signal, and the output digital signal is accessed into the signal processing unit to be calculated through the A/D conversion circuit. When the FBG is influenced by factors such as temperature change, strain change and the like, the central wavelength of the FBG is shifted, the small offset of the central wavelength of the FBG can be demodulated by using the method, and then high-precision measurement of various physical quantities such as stress, temperature and the like of the environment where the FBG sensor is located is realized through signal processing.
Description
Technical Field
The invention relates to a high-resolution spectrum demodulation system based on a high-resolution spectrum demodulation technology of a double-arrayed waveguide grating, and belongs to the technical field of optical sensing.
Background
Fiber Bragg Grating (FBG) sensors are continuously developed due to their advantages of strong electromagnetic interference resistance, high sensitivity, simple structure, small size, and the like, and are deeply applied to various aspects such as aerospace, environmental monitoring, geological exploration, and the like. The central wavelength of the FBG reflection resonance peak can drift along with the influence of external temperature, strain, vibration, noise and the like, and the real-time monitoring of the physical quantities can be realized by demodulating the FBG resonance central wavelength.
The spectrum demodulation scheme is based on discrete free space optics and photoelectron components, and typical schemes include edge filtering demodulation method, wavelength matching method, radio frequency detection method, interference demodulation method, time domain stretching method, etc. The edge filtering method has the advantages of simple system structure, no need of expensive optical precision instruments, better linear output spectrum type, capability of effectively inhibiting the influence of optical power loss or fluctuation, higher system response speed, lower cost and convenient use, and can be used for static and dynamic measurement.
Because the signal demodulator body based on the edge filtering method generally adopts a single AWG chip at present, compared with the scheme formed by other discrete devices, the signal demodulator has a step towards integration. This solution has the advantage of small volume, but integration has not really been achieved. The accuracy of measurement near the peak is not high, which limits the accuracy of wavelength measurement of the demodulator.
Disclosure of Invention
In order to solve the problems, the invention provides a high-resolution spectrum demodulation system based on double arrayed waveguide gratings, which can realize 1540-1560nm full-wavelength coverage.
The technical scheme is as follows: the invention provides a high-resolution spectrum demodulation system based on double arrayed waveguide gratings, which comprises a wide-spectrum light source, an optical isolator, a circulator, a Fiber Bragg Grating (FBG) array, a Y-shaped beam splitter, two Arrayed Waveguide Gratings (AWG), two photoelectric conversion circuits, two A/D conversion circuits and a signal processing unit. Light output by the wide-spectrum light source enters the FBG array through the optical isolator and the circulator, incident light is reflected into narrow-band light after passing through the FBG, the narrow-band light respectively enters the AWG with the center wavelengths of the two channels staggered after passing through the circulator and the Y-type beam splitter, then the light output by the AWG channel is accessed into the photoelectric conversion circuit to output voltage signals, and finally, the output digital signals are accessed into the signal processing unit to be calculated through the A/D conversion circuit.
Furthermore, the wide-spectrum light source selects light with the wavelength of 1540nm to 1560nm as a system light source.
Further, the waveguide structure selected by the two Arrayed Waveguide Gratings (AWGs) is a rectangular waveguide.
Further, the rectangular waveguide selects silicon dioxide with the refractive index of 1.445 as a cladding material and silicon dioxide with the refractive index of 1.467 as a core material.
Furthermore, the central wavelengths of the two Arrayed Waveguide Grating (AWG) channels are staggered, and the interval is 2 nm.
Further, the photoelectric conversion circuit is composed of a PIN photodiode and an operational amplifier circuit.
Further, the A/D conversion circuit core is a 24-bit A/D conversion chip.
Furthermore, the signal processing unit is realized by an STM32 singlechip.
Has the advantages that: the invention can realize linear demodulation function in the whole wave band range of 1540 nm-1560 nm based on the Arrayed Waveguide Grating (AWG) with two staggered channel wavelengths, and makes up the defects that the linearity of a single AWG at two ends of each linear region is poor and the wavelength cannot be covered in a small range between adjacent linear demodulation regions.
Drawings
FIG. 1 is a schematic diagram of the overall structure of the dual-arrayed waveguide grating-based high-resolution spectral demodulation technique of the present invention;
FIG. 2 is a graph of the output spectrum of an Arrayed Waveguide Grating (AWG) channel of the present invention;
FIG. 3 is a graph showing the output spectra of three adjacent channels of two Arrayed Waveguide Gratings (AWG) with 2nm difference in center wavelength;
FIG. 4 is a schematic diagram of an Arrayed Waveguide Grating (AWG) based demodulation FBG of the present invention;
fig. 5 shows the output optical power of two adjacent channels of Arrayed Waveguide Grating (AWG) and its demodulation function.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
As shown in fig. 1, an embodiment of the present invention, a dual-arrayed waveguide grating-based high-resolution spectrum demodulation technique, includes a wide-spectrum light source, an optical isolator, a circulator, a Fiber Bragg Grating (FBG) array, a Y-splitter, two Arrayed Waveguide Gratings (AWGs), two photoelectric conversion circuits, two a/D conversion circuits, and a signal processing unit.
As shown in fig. 2, a single AWG channel outputs a spectral plot, and both AWGs are kept consistent except for 2nm difference in center wavelength. Fig. 3 is a graph of the output spectra of three adjacent channels of two Arrayed Waveguide Gratings (AWGs).
The method specifically comprises the following steps:
1. light output by the wide-spectrum light source enters the FBG array through the optical isolator and the circulator by the optical path 1.
2. After entering the FBG, the incident light generates mode coupling, narrow-band light meeting the Bragg condition is reflected, and the central wavelength of the reflected light is
λ FBG ＝2n eff Λ (1)
Wherein λ is FBG Is the Bragg wavelength of the fiber grating, Λ is the grating period of the fiber grating, n eff Is the effective index of the core of the fiber. When the external environment changes, n of the grating eff And Λ will change, resulting in reflectionCentral wavelength of light lambda FBG And (4) changing. The FBG reflection spectrum has a functional expression of
Wherein R is 0 Is a normalization factor, λ, of the FBG reflection spectrum FBG Is the central wavelength of the FBG, Δ λ FBG Is the half-peak bandwidth of the FBG reflection spectrum.
3. The reflected light enters the Y-shaped beam splitter from the light path 2 through the circulator again and is split into two same beams of light.
4. The two beams of light enter the AWG with two channels with staggered central wavelengths respectively. For any AWG, two output channels of the AWG corresponding to the central wavelength of the FBG are Ch (m), Ch (m +1) and lambda m 、λ m+1 The overlapping part of the FBG reflection spectrum and the AWG channel transmission spectrum determines the output light intensity of the arrayed waveguide grating channel for the central wavelength of m and m +1 of two adjacent channels of the AWG, as shown in FIG. 4. In order to facilitate theoretical analysis, only temperature influence factors are considered, and both the fiber Bragg grating reflection spectrum and the transmission spectrum of the arrayed waveguide grating channel are approximately expressed by Gaussian functions, so that the transmission spectrum function expression of the AWG channel m is
Wherein, T 0 Is the normalization factor of the AWG transmission spectrum, lambda and lambda m Respectively representing the wavelength of the incident light and the central wavelength of the AWG channel m, Delta lambda m Is the half-peak bandwidth of the m transmission spectrum of the AWG channel.
The output light intensity of each channel of the AWG is the integral of the product of the emission spectrum of the light source, the FBG reflection spectrum and the AWG transmission spectrum in the whole spectral range, and the output light intensities of the channel m and the channel m +1 are respectively obtained by the formulas (2) and (3)
Wherein, P m 、P m+1 Output light intensities, L, of AWG channel m and channel m +1, respectively m 、L m+1 The attenuation factors of the AWG channel m and the channel m +1, respectively, can be considered to be equal in the same AWG wavelength demodulation system, i.e. Lm ═ L m+1 ＝L，I S (lambda) is the emission spectrum of the light source, and as can be seen from the equations (2) and (3), the intensity of the light is mainly determined by the wavelength at lambda m 、λ FBG The nearby light determination, i.e. the integration of equations (4) and (5) only in a narrow band, whereas the spectral density of a broadband light source in a narrow band can be regarded as a constant value I S (λ)＝I S Then the formulas (4) and (5) can be simplified to
Under the condition that the transmission coefficients and half-peak bandwidths of the channels of the AWG are equal, the ratio of the formula (7) to the formula (6) is made to obtain the light intensity ratio of the channel m of the AWG to the channel m + 1:
wherein Δ λ ═ λ m+1 -λ m The interval between two adjacent channels of AWG can be regarded as a fixed value, and the logarithm with e as the base is taken on two sides of the formula (8):
the formula (9) is a theoretical formula of the AWG wavelength demodulation algorithm, and the logarithm of the output light intensity ratio of the AWG and the central wavelength of the FBG sensor are in a linear relationship. As shown in fig. 5, the test results of processing two AWGs with central wavelengths of the channels differing by 0.2nm by Matlab, resulted in a substantially linear demodulation function.
5. And then, light output by each AWG channel is accessed into a photoelectric conversion circuit, wherein a PIN photodiode converts an optical signal into an electric signal, the working mode is a photovoltaic mode, the responsivity is 0.9A/W, voltage amplification is realized through an operational amplification circuit, if the output light power of the AWG channel is 1nW, the response current is 0.9nA, and the output voltage of the amplification circuit is U-IR-0.9 nA × 330k Ω -0.297 mV.
6. The output voltage is connected to an A/D conversion circuit to convert an analog signal into a digital signal, wherein a 24-bit A/D conversion chip is used to realize the conversion of the output voltage U equal to 0.297 mV.
7. And finally, the output digital signals are accessed into a signal processing unit, namely, an STM32 singlechip is used for calculating formula (9) to demodulate, and the result is calculated.
In this embodiment, the channel spacing of each AWG is 0.4nm, the insertion loss is about 4.5dB, and the 1dB bandwidth is about 0.18 nm.
In summary, the invention demodulates the FBG reflected wavelength by using two parallel AWGs, connects the Y-shaped beam splitter with the two AWGs, and allows the input signal to enter the AWGs with staggered central wavelengths of the two channels through the beam splitter, so that the slope of the linear demodulation function is significantly better than the scheme of increasing the spectral overlap of the single AWG, thereby achieving higher demodulation resolution, making up the problem that the wavelength range of the single AWG between the demodulation channels cannot be covered, and achieving 1540 and 1560nm demodulation range full coverage.
Claims (8)
1. A high-resolution spectrum demodulation system based on double arrayed waveguide gratings is characterized in that: the device comprises a wide-spectrum light source, an optical isolator, a circulator, an FBG array, a Y-type beam splitter, an AWG, a photoelectric conversion circuit, an A/D conversion circuit and a signal processing unit; when the optical fiber grating array is used, light output by the wide-spectrum light source enters the FBG array through the optical isolator and the circulator, incident light is reflected into narrow-band light after passing through the FBG, the narrow-band light respectively enters the two AWGs after passing through the circulator and the Y-type beam splitter again, then the light output by the AWG channel is connected to the photoelectric conversion circuit to output voltage signals, and finally the output digital signals are connected to the signal processing unit to be calculated through the A/D conversion circuit.
2. The dual-arrayed-waveguide-grating-based high-resolution spectral demodulation system of claim 1, wherein: the wide-spectrum light source selects light with the wavelength of 1540 nm-1560 nm as a system light source.
3. The dual-arrayed-waveguide-grating-based high-resolution spectral demodulation system of claim 1, wherein: the waveguide structure selected by the AWG is a rectangular waveguide.
4. The dual-arrayed-waveguide-grating-based high-resolution spectral demodulation system of claim 3, wherein: the rectangular waveguide selects silicon dioxide with the refractive index of 1.445 as a cladding material and silicon dioxide with the refractive index of 1.467 as a core material.
5. The dual-arrayed waveguide grating-based high-resolution spectral demodulation system of claim 3, wherein: the two AWG channels are staggered in center wavelength.
6. The dual-arrayed-waveguide-grating-based high-resolution spectral demodulation system of claim 1, wherein: the photoelectric conversion circuit is composed of a PIN photodiode and an operational amplification circuit.
7. The dual-arrayed-waveguide-grating-based high-resolution spectral demodulation system of claim 1, wherein: the A/D conversion circuit core is a 24-bit A/D conversion chip.
8. The dual-arrayed waveguide grating-based high-resolution spectral demodulation system of claim 1, wherein: the signal processing unit is realized by an STM32 singlechip.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN201476800U (en) * | 2009-05-08 | 2010-05-19 | 刘信 | High-speed multi-channel fiber grating sensor demodulating system based on AWG |
| CN103549941A (en) * | 2013-11-04 | 2014-02-05 | 天津工业大学 | AWG (arrayed waveguide grating) wavelength demodulation system with temperature compensation function, heartbeat detection device and application |
| CN106643840A (en) * | 2016-12-19 | 2017-05-10 | 北京遥测技术研究所 | Fiber grating sensor demodulation device based on dual arrayed waveguide gratings |
| CN111189556A (en) * | 2020-01-06 | 2020-05-22 | 太原理工大学 | Real-time multichannel fiber grating temperature measurement system based on AWG |
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- 2022-05-17 CN CN202210538826.8A patent/CN114923507A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN201476800U (en) * | 2009-05-08 | 2010-05-19 | 刘信 | High-speed multi-channel fiber grating sensor demodulating system based on AWG |
| CN103549941A (en) * | 2013-11-04 | 2014-02-05 | 天津工业大学 | AWG (arrayed waveguide grating) wavelength demodulation system with temperature compensation function, heartbeat detection device and application |
| CN106643840A (en) * | 2016-12-19 | 2017-05-10 | 北京遥测技术研究所 | Fiber grating sensor demodulation device based on dual arrayed waveguide gratings |
| CN111189556A (en) * | 2020-01-06 | 2020-05-22 | 太原理工大学 | Real-time multichannel fiber grating temperature measurement system based on AWG |
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