A fiber sensing demodulation device of an arrayed tunable optical filter and a demodulation method thereof

Abstract

This invention discloses a fiber optic sensing demodulation device and method for an array-type tunable optical filter, comprising a light source, a light sensor under test, an optical beam splitter, a tunable optical filter array, a photodetector array, and a signal processing unit for determining the driving parameters of the tunable optical filter array and processing spectral information, connected in sequence. The light source passes through the optical beam splitter into a standard for wavelength calibration, and the standard is connected to the photodetector array via the tunable optical filter. This device eliminates the need to apply a high-speed periodic voltage to the tunable optical filter, significantly improving the demodulation rate; it also significantly improves demodulation accuracy; it allows for flexible selection of the number of sampling points and wavelength range according to requirements, making it simple and easy to implement; and it can simultaneously demodulate multiple light sensors under test, demodulating different types of light sensors, thus having wide applicability.

Description

Technical Field

[0001] This invention relates to a demodulation device for an optical sensor, and more particularly to an optical fiber sensing demodulation device and demodulation method for an array-type tunable optical filter. Background Technology

[0002] Fiber optic sensing is an emerging sensing technology. Its basic principle is to modulate light, causing a specific characteristic of the light to change regularly with changes in external physical quantities (such as phase, wavelength, and intensity). To obtain information from fiber optic sensors with fiber optic structures, signal demodulation is required. Key parameters of the demodulation system include demodulation rate, demodulation accuracy, and demodulation resolution, and different applications have different requirements for these parameters. Compared to traditional sensors, fiber optic sensing has higher requirements for demodulation speed and cost; therefore, a fast and accurate demodulation scheme is needed. Currently, there are various demodulation schemes. A common method is to acquire the spectral information of the fiber optic sensor. Changes in the measured quantity will cause corresponding changes in the spectrum of the fiber optic sensor, such as the center wavelength of the peak of a fiber optic grating or the valley wavelength of a fiber optic Fabry-Perot sensor. Therefore, a series of demodulation algorithms can be used to calculate the marked wavelength from the full spectrum, and then demodulate the measured physical quantity. Among methods for acquiring spectra, piezoelectric ceramics using tunable Fabry-Perot filters (tunable FP filters) can achieve high spectral resolution and high demodulation accuracy. However, limited by the scanning speed of optical filters (such as thermal tuning and piezoelectric tuning), their demodulation rate is relatively slow (typically a few kHz), restricting their application in high-speed and even ultra-high-speed signal detection above 100 kHz. Another type of demodulation scheme obtains information by measuring the optical power value corresponding to a wavelength at a certain point in the spectrum, also known as intensity demodulation. Since only a single wavelength point needs to be detected, the demodulation rate of this method is relatively fast. However, the optical power is greatly affected by external environmental interference and system noise, and the stability requirements of the light source are very high. Therefore, the demodulation accuracy is usually lower. In addition, its demodulation band is narrower, resulting in poorer flexibility. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to provide an optical fiber sensing demodulation device for an array-type tunable optical filter with fast demodulation rate and high demodulation accuracy; another purpose of this invention is to provide a demodulation method for an optical fiber sensor.

[0004] Technical solution: The fiber optic sensing demodulation device for array-type tunable optical filters of the present invention includes a light source, a light sensor to be tested, an optical beam splitter, a tunable optical filter array, a photodetector array, and a signal processing unit for determining the driving parameters of the tunable optical filter array and processing spectral information, connected in sequence.

[0005] Furthermore, the light source enters a standard for wavelength calibration via a beam splitter, and the standard is connected to a photodetector array via a tunable optical filter.

[0006] Furthermore, the etalon is a Fabry-Perot FP etalon or a gas cell etalon. The spectrum collected by the etalon is used to calibrate the spectrum collected by each tunable optical filter, so as to avoid the impact of hysteresis and other errors inside the tunable optical filter on the demodulation accuracy.

[0007] Furthermore, the optical sensor under test is connected to the optical path through an optical circulator. The optical circulator has three interfaces: port 1 is connected to the first optical beam splitter, port 2 is connected to the optical sensor under test, and port 3 is connected to the second optical beam splitter. After the light source is split by the first optical beam splitter, it enters the optical sensor under test through port 1 and port 2. The reflected spectrum enters the second optical beam splitter through port 3 for demodulating the reflected spectrum type optical sensor.

[0008] Furthermore, the tunable optical filter includes an FP filter, a fiber optic ring cavity filter, a planar ring cavity filter, or a WGM (Whispering Gallery Mode) filter.

[0009] Furthermore, the light source is a broadband light source, and an optical isolator is provided between the light source and the sensor under test to avoid interference from the light source, thereby improving demodulation accuracy.

[0010] Furthermore, the signal processing unit chip includes an FPGA (Field Programmable Gate Array) chip, a GPU (Graphics Processing Unit) chip, or a DSP (Digital Signal Processing) chip.

[0011] The present invention also provides a demodulation method for an optical fiber sensing demodulation device utilizing the array-type tunable optical filter, comprising the following steps:

[0012] (S1) Determine the wavelength range of the tunable optical filter array based on the actual demodulation requirements;

[0013] (S2) Determine the driving parameters for each wavelength by using the relationship between the wavelength and driving parameters of the tunable optical filter;

[0014] (S3) Drive the tunable optical filter array to perform spectral decomposition under different driving parameters;

[0015] (S4) The photodetector collects the optical signal in the tunable optical filter array and demodulates the spectral information in real time through the signal processing unit.

[0016] Furthermore, the driving parameters in step (S2) are transmitted to the tunable optical filter array via a programmable device.

[0017] Furthermore, the signal processing unit in step (S4) further includes calibrating the spectrum acquired by the optical sensor under test by applying scanning parameters to a tunable optical filter connected to a standard datum.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: 1. The device does not require the application of a high-speed periodic voltage to the tunable optical filter, and the demodulation rate can reach the GHz level or above when combined with a high-speed signal processing unit, greatly improving the demodulation rate; 2. The demodulation accuracy is significantly improved; 3. The acquisition wavelength can be selected through driving parameters, which is simple and easy to implement; 4. The number of sampling points can be flexibly set as needed to effectively acquire spectral information; 5. It can demodulate multiple optical sensors under test simultaneously, demodulate different types of optical sensors, calculate and output the demodulation results in real time, and has a high response rate and wide applicability. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the device of the present invention;

[0020] Figure 2 This is a schematic diagram of the device of the present invention equipped with a standard.

[0021] Figure 3 This is a schematic diagram of the device for processing multiple optical sensors according to the present invention;

[0022] Figure 4 This is a schematic diagram of the device for demodulating a reflectance spectral optical sensor according to the present invention;

[0023] Figure 5 This is a schematic diagram of the device of the present invention for demodulating multiple reflectance spectral optical sensors; Detailed Implementation

[0024] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0025] Example 1

[0026] like Figure 1 The illustrated array-type fiber optic sensing demodulation device for demodulating transmission spectral optical sensors includes, in sequence, a light source, an optical isolator, an optical sensor under test, an optical beam splitter, a tunable FP filter array, a photodetector array, and a signal processing unit for determining the driving parameters of the tunable FP filter array and processing spectral information. The photodetector is an InGaAs photodiode; the signal processing unit is an FPGA chip.

[0027] Example 2

[0028] like Figure 2 The illustrated array-type fiber optic sensing demodulation device for demodulating transmission spectral optical sensors includes a broadband light source, an optical isolator, a first optical beamsplitter, an optical path transmission unit, a photodetector array, and a signal processing unit connected in sequence. The optical path transmission unit comprises two paths: one path sequentially connects to the optical sensor under test, a second optical beamsplitter, and an array of multiple tunable FP filters; the other path sequentially connects to an etalon and a tunable FP filter. One end of the photodetector is connected to the tunable FP filter, and the other end is connected to the signal processing unit. The etalon is a gas-cell etalon; the photodetector is an InGaAs photodiode; and the signal processing unit uses an FPGA chip.

[0029] Example 3

[0030] like Figure 3 The illustrated array-type fiber optic sensing demodulation device for demodulating multiple transmission-spectrum optical sensors includes a broadband light source, an optical isolator, a first optical beamsplitter, an optical path transmission unit, a photodetector array, and a signal processing unit connected in sequence. The optical path transmission unit comprises two paths: one path sequentially connects to the optical sensor array under test, an optical switch, a second optical beamsplitter, and multiple tunable fiber optic ring cavity filter arrays; the other path sequentially connects to an etalon and the tunable fiber optic ring cavity filters. One end of the photodetector is connected to the tunable fiber optic ring cavity filter, and the other end is connected to the signal processing unit. The etalon is a Fabry-Perot FP etalon; the photodetector is an InGaAs photodiode; and the signal processing unit uses a GPU chip. The optical sensor under test is selected for detection by the optical switch.

[0031] Example 4

[0032] like Figure 4 The illustrated array-type fiber optic sensing demodulation device for demodulating a reflectance spectral optical sensor includes a broadband light source, an optical isolator, a first optical beamsplitter, an optical path transmission unit, a photodetector array, and a signal processing unit connected in sequence. The optical path transmission unit comprises two paths: one path sequentially connects to the optical sensor under test, a second optical beamsplitter, and an array of multiple tunable planar ring cavity filters; the other path sequentially connects to an etalon and a tunable planar ring cavity filter. One end of the photodetector is connected to the tunable planar ring cavity filter, and the other end is connected to the signal processing unit. The optical sensor under test is connected to the optical path through an optical circulator with three interfaces: port 1 connects to the first optical beamsplitter, port 2 connects to the optical sensor under test, and port 3 connects to the second optical beamsplitter. The etalon is a Fabry-Perot FP etalon. The photodetector is an InGaAs photodiode. The signal processing unit uses a DSP chip.

[0033] Example 5

[0034] like Figure 5 The illustrated array-type fiber optic sensing demodulation device for demodulating multiple reflectance spectral optical sensors includes a broadband light source, an optical isolator, a first optical beamsplitter, an optical path transmission unit, a photodetector array, and a signal processing unit connected in sequence. The optical path transmission unit comprises two paths: one path sequentially connects to the optical sensor array under test, an optical switch, a second optical beamsplitter, and an array of multiple tunable WGM filters; the other path sequentially connects to an etalon and a tunable WGM filter. One end of the photodetector is connected to the tunable WGM filter, and the other end is connected to the signal processing unit. The optical sensor under test is connected to the optical path via an optical circulator with three interfaces: port 1 connects to the first optical beamsplitter, port 2 connects to the optical sensor under test, and port 3 connects to the optical switch. The etalon is a Fabry-Perot FP etalon. The photodetector is an InGaAs photodiode. The signal processing unit uses an FPGA chip. The optical switch selects the optical sensor under test for connection to the detection device for testing.

[0035] The method for demodulating an optical sensor using the apparatus of Examples 1-5 described above includes the following steps:

[0036] (S1) Determine the wavelength range of the tunable optical filter array according to the demodulation requirements;

[0037] (S2) Determine the driving parameters for each wavelength by using the relationship between the wavelength and driving parameters of the tunable optical filter;

[0038] (S3) Different driving parameters are transmitted to the tunable optical filter array through a digital-to-analog converter to drive the tunable optical filter array to perform spectral decomposition.

[0039] (S4) The photodetector collects the optical signal in the tunable optical filter array. The spectral information collected by applying scanning parameters to the tunable optical filter connected to the standard datum is used to calibrate the spectrum collected by the optical sensor under test. Then, the spectral information is demodulated according to different algorithms according to actual needs.

Claims

1. A demodulation method of a fiber sensing demodulation apparatus of an arrayed tunable optical filter, characterized by, Includes the following steps: (S1) Determine the wavelength range of the tunable optical filter array based on actual demodulation requirements; (S2) Determine the driving parameters for each wavelength by using the relationship between the wavelength and driving parameters of the tunable optical filter; (S3) Drive the tunable optical filter array to perform spectral decomposition under different driving parameters; (S4) The photodetector collects the optical signal in the tunable optical filter array and demodulates the spectral information through the signal processing unit; The fiber optic sensing demodulation device for the array-type tunable optical filter includes a light source, a light sensor under test, an optical beam splitter, a tunable optical filter array, a photodetector array, and a signal processing unit for determining the driving parameters of the tunable optical filter array and processing spectral information, connected in sequence. The light source enters a standard for wavelength calibration through the optical beam splitter, and the standard is connected to the photodetector array through the tunable optical filter.

2. The demodulation method of the fiber sensor demodulation apparatus of the arrayed tunable optical filter according to claim 1, characterized by, The etalon mentioned is a Fabry-Perot FP etalon or a gas cell etalon.

3. The demodulation method of the fiber optic sensing demodulation device for an array-type tunable optical filter according to claim 1, characterized in that, The optical sensor under test is connected to the optical path through an optical circulator; the optical circulator has three interfaces: port 1 is connected to the first optical beam splitter, port 2 is connected to the optical sensor under test, and port 3 is connected to the second optical beam splitter.

4. The demodulation method of the fiber sensor demodulation apparatus of the arrayed tunable optical filter according to claim 1, characterized by, The tunable optical filter includes an FP filter, an optical fiber ring cavity filter, a planar ring cavity filter, or a WGM filter.

5. The demodulation method of the fiber sensor demodulation apparatus of the arrayed tunable optical filter according to claim 1, characterized by, The light source is a broadband light source, and an optical isolator is provided between the light source and the sensor under test to avoid interference from the light source.

6. The demodulation method of the fiber sensor demodulation apparatus of the arrayed tunable optical filter according to claim 1, characterized by, The signal processing unit chip includes an FPGA chip, a GPU chip, or a DSP chip.

7. The demodulation method of the fiber sensor demodulation apparatus of the arrayed tunable optical filter according to claim 1, characterized by, The driving parameters in step (S2) are transmitted to the tunable optical filter array via a programmable device.

8. The demodulation method of the fiber optic sensing demodulation device for an array-type tunable optical filter according to claim 1, characterized in that, The processing of the optical signal by the signal processing unit in step (S4) also includes calibrating the spectrum acquired by the optical sensor under test by applying scanning drive parameters to a tunable optical filter connected to a standard.

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