Optical fiber F-P sensor high-speed phase demodulation system based on arrayed waveguide grating and space intensity parallel detection

Abstract

The invention belongs to the technical field of optical fiber sensing, testing and measuring, and discloses an optical fiber F-P sensor high-speed phase demodulation system based on array waveguide grating and space intensity parallel detection, which comprises a broadband light source, an optical circulator, an optical fiber FP sensor, an array waveguide grating, a photoelectric detection array, a signal acquisition and processing module and a data output module, mapping from a spectrum to a space is realized by using an array waveguide grating, high-speed demodulation of phase information of the optical fiber Fabry-Perot sensor is realized by combining parallel detection of a high-speed photoelectric detection array, phase demodulation precision is further improved by introducing an interpolation algorithm, and dynamic and high-precision demodulation of the optical fiber Fabry-Perot sensor is realized. The optical fiber F-P sensor high-speed phase demodulation system does not contain any passive regulation and control element or discrete detection device, so that the system can provide demodulation performance with higher integration level and better stability.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic sensing and testing technology, and relates to a high-speed phase demodulation system for a fiber optic FP sensor based on arrayed waveguide gratings and spatial intensity parallel detection. Background Technology

[0002] Fiber Fabry-Perot (FP) sensors are based on the principle of white light interference. They measure various physical quantities such as temperature, pressure, strain, and vibration by sensing changes in the cavity length of the Fabry-Perot cavity. They have advantages such as high sensitivity, resistance to electromagnetic interference, and small size, and have broad application prospects in aerospace, energy and power, biomedicine, and industrial monitoring.

[0003] The acquisition of the characteristics of a measured physical quantity using a fiber optic Fabry-Perot sensor is based on the analysis of the phase information of the sensor's interferometric spectrum. Therefore, high-speed, high-precision phase demodulation of the fiber optic Fabry-Perot sensor's interferometric spectrum is crucial for acquiring the characteristics of dynamic physical quantities. Traditional fiber optic Fabry-Perot sensor demodulation schemes, such as scanning interferometers based on tunable Fabry-Perot filters, while offering high accuracy, suffer from severely limited demodulation speeds due to their mechanical scanning mechanisms (typically on the order of hundreds of Hertz), making them unsuitable for measuring high-frequency dynamic signals. Furthermore, some schemes based on intensity demodulation or peak detection, while fast, are susceptible to light source fluctuations and link losses, resulting in insufficient accuracy and stability.

[0004] Arrayed waveguide gratings (AWRs), as a mature optical waveguide splitting device, have demonstrated advantages in high speed and multi-channel parallelism in fiber Bragg grating (FBG) wavelength demodulation systems. AWRs can spatially segment the input spectrum, achieving a mapping from the spectral domain to the spatial domain. However, FBGs are wavelength-coded sensors, and their demodulation core lies in tracking the drift of the reflected wavelength; while fiber Fabry-Perot sensors are interferometric sensors, and their demodulation core lies in recovering and analyzing the phase information of the interference spectrum. The two differ fundamentally in their demodulation principles, algorithms, and objectives. Therefore, based on the advantages of AWRs' high-precision spectral segmentation and the high-speed parallel detection of array detectors, a miniaturized, highly stable, and high-precision fiber Fabry-Perot interferometric sensor demodulation scheme can be developed, thereby solving key technical problems in the practical application of fiber Fabry-Perot interferometric sensors. Summary of the Invention

[0005] To overcome the challenge of balancing speed and accuracy in existing fiber optic Fabry-Perot interferometric sensor demodulation techniques, this invention proposes a high-speed phase demodulation system for fiber optic Fabry-Perot sensors based on an arrayed waveguide grating and parallel spatial intensity detection. This system utilizes an arrayed waveguide grating to achieve parallel spatial segmentation of the interference spectrum, synchronously acquires light intensity information through a photoelectric detection array, and combines this with a dedicated signal processing algorithm to recover the interference spectrum and calculate the phase (cavity length), thereby achieving high-speed, high-precision phase demodulation of the fiber optic Fabry-Perot interferometric sensor.

[0006] The technical solution of the present invention:

[0007] A high-speed phase demodulation system for a fiber optic FP sensor based on an arrayed waveguide grating and spatial intensity parallel detection includes a broadband light source, an optical circulator, a fiber optic Fabry-Perot sensor, an arrayed waveguide grating, a photoelectric detection array, a signal acquisition and processing module, and a data output module.

[0008] The broadband light source is connected to the input end of the optical circulator to provide broadband detection light;

[0009] The input and output terminals of the optical circulator are connected to the fiber optic Fabry-Perot sensor, transmitting broadband probe light to the fiber optic Fabry-Perot sensor and receiving the broadband interference spectrum from the fiber optic Fabry-Perot sensor; the cavity length of the fiber optic Fabry-Perot sensor changes according to the change of the external measured physical quantity, and reflects back a broadband interference spectrum with phase modulation; the output terminal of the optical circulator is connected to the input terminal of the arrayed waveguide grating, inputting the broadband interference spectrum reflected by the fiber optic Fabry-Perot sensor into the arrayed waveguide grating;

[0010] The arrayed waveguide grating serves as a beam splitting element, used to divide the input broadband interference spectrum by wavelength and distribute it to different output channels according to wavelength, thereby realizing the conversion from the spectral domain to the spatial domain.

[0011] The photoelectric detection array is used to synchronously and parallelly detect the light intensity of each output channel of the array waveguide grating, thereby converting the wavelength-intensity correspondence into a spatial position-wavelength correspondence. The signal acquisition and processing module is connected to the photoelectric detection array and is used to acquire the intensity information of each pixel of the photoelectric detection array in real time, and recover the discrete interference spectrum of the fiber optic Fabry-Perot sensor according to the preset mapping relationship between pixel position and wavelength. The signal acquisition and processing module also embeds an interpolation algorithm to further refine the discrete interference spectrum through interpolation calculation, obtain an interference spectrum with higher spectral resolution, and finally calculate the real-time cavity length data of the fiber optic Fabry-Perot sensor based on the interference spectrum with higher spectral resolution. The data output module is used to output the calculated real-time cavity length data to a host computer or display device.

[0012] Furthermore, the pixels of the photoelectric detection array correspond one-to-one with the output channel wavelength of the array waveguide grating. Based on the mapping relationship between the pixel position and the channel wavelength, as well as the pixel intensity information, the interference spectrum of the fiber optic Fabry-Perot sensor is recovered.

[0013] Furthermore, the photodetector array is a 256-pixel indium gallium arsenide linear CCD with a response range of 900nm-1700nm and a photosensitive area length of 12.8mm.

[0014] Furthermore, the demodulation algorithm executed by the signal acquisition and processing module includes interpolation calculation. Based on multiple continuous intensity information, a more refined fiber optic Fabry-Perot sensor interference spectrum is obtained through interpolation, thereby achieving higher system spectral resolution.

[0015] Furthermore, the arrayed waveguide grating is configured as a 1×48 channel with a 50GHz channel spacing, covering wavelengths from 1544.92 to 1563.86 nm.

[0016] Furthermore, the 48 output channels of the arrayed waveguide grating are densely packed to form a 10mm long fiber array, and the fiber array is polished to efficiently couple light to the photoelectric detection array.

[0017] The beneficial effects of this invention: This invention discloses a high-speed phase demodulation system for a fiber optic FP sensor based on an arrayed waveguide grating and parallel spatial intensity detection. The system includes a broadband light source, an optical circulator, a fiber optic FP sensor, an arrayed waveguide grating, a photodetector array, a signal acquisition and processing module, and a data output module. This invention utilizes the arrayed waveguide grating to achieve spectral-to-spatial mapping, combined with parallel detection by a high-speed photodetector array, to achieve high-speed demodulation of phase information from the fiber optic Fabry-Perot sensor. By introducing an interpolation algorithm, the phase demodulation accuracy can be further improved, thereby achieving dynamic and high-precision demodulation of the fiber optic Fabry-Perot sensor. The proposed high-speed phase demodulation system for a fiber optic FP sensor based on an arrayed waveguide grating and parallel spatial intensity detection does not contain any passive control elements or discrete detection devices, such as optical switches or discrete optical detection units. Therefore, this system can provide demodulation performance with higher integration and better stability. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a high-speed phase demodulation system for an optical fiber FP sensor based on an arrayed waveguide grating and spatial intensity parallel detection.

[0019] Figure 2 This is a schematic diagram of the optical signal detection and processing principle of the demodulation system.

[0020] Figure 3 This is a schematic diagram illustrating the detection principle of a photoelectric detection array.

[0021] In the diagram: 1 Broadband light source, 2 Optical circulator, 3 Fiber Fabry-Perot sensor, 4 Arrayed waveguide grating, 5 Photodetector array, 6 Signal acquisition and processing module, 7 Data output module. Detailed Implementation

[0022] The specific embodiments of the present invention will be described in detail below with reference to the technical solutions and accompanying drawings.

[0023] See Figure 1 As shown, a high-speed phase demodulation system for a fiber optic Fabry-Perot sensor based on an arrayed waveguide grating and spatial intensity parallel detection includes a broadband light source 1, an optical circulator 2, a fiber optic Fabry-Perot sensor 3, an arrayed waveguide grating 4, a photodetector array 5, a signal acquisition and processing module 6, and a data output module 7. This system can be used for high-speed, high-precision phase demodulation of fiber optic Fabry-Perot sensors.

[0024] Broadband light emitted from broadband light source 1 enters through the input end of optical circulator 2 and is transmitted from its input / output end to fiber optic Fabry-Perot sensor 3. Fiber optic Fabry-Perot sensor 3 changes its cavity length according to changes in the external measured physical quantity, thereby reflecting back a phase-modulated broadband interference spectrum. This broadband interference spectrum is input to arrayed waveguide grating 4 through the output end of optical circulator 2.

[0025] The arrayed waveguide grating 4 employs a 1×48-channel configuration with a 50GHz channel spacing, covering wavelengths from 1544.92 to 1563.86 nm. The arrayed waveguide grating 4 divides the input broadband interference spectrum into 48 discrete spectral channels according to wavelength, achieving a conversion from the spectral domain to the spatial domain. These 48 discrete spectra are then closely packed to form an optical fiber array approximately 10 mm in length, and the polished fiber array efficiently couples the light to the photodetector array 5.

[0026] The photodetector array 5 employs a 256-pixel indium gallium arsenide linear CCD with a response range of 900nm-1700nm and a photosensitive area length of 12.8mm. The optical signals from the 48 discrete spectral channels of the arrayed waveguide grating 4 are received in parallel by the corresponding pixels of the CCD, and the light intensity signals are converted into electrical signals. A precise mapping relationship is pre-established between the pixel positions of the CCD and the channel wavelengths of the arrayed waveguide grating 4. To ensure the long-term stability of the system, the output end face of the arrayed waveguide grating 4 and the photosensitive surface of the photodetector array 5 are rigidly fixed and optically aligned using a precision structure, forming an integrated spectral detection module. The optical signals output from each channel of the arrayed waveguide grating 4 are received by the pixels of the photodetector array 5. The geometric width of the optical signal output from each channel of the arrayed waveguide grating is the same, and there is no overlap between channels. Therefore, each pixel of the photodetector array 5 receives the average light intensity of the optical signal across its geometric width. In summary, even if the fiber array of the arrayed waveguide grating 4 and the photoelectric detection array 5 are slightly displaced in the lateral direction, it will not affect the final detection and demodulation results, which will greatly improve the system's ability to resist disturbances.

[0027] The signal acquisition and processing module 6 acquires the light intensity data output by the photodetector array 5 in real time. First, based on the pixel-wavelength mapping relationship and the light intensity value, the signal acquisition and processing module 6 reconstructs the discrete interference spectrum of the fiber optic Fabry-Perot sensor 3. Then, the signal acquisition and processing module 6 calls the embedded interpolation algorithm to perform fine interpolation on the discrete spectral data, obtaining an interference spectrum with higher spectral resolution. Finally, based on this refined spectrum, algorithms such as peak finding, phase extraction, or white light interference fringe contrast analysis are used to calculate the real-time cavity length data of the fiber optic Fabry-Perot sensor 3.

[0028] The calculated cavity length data is transmitted to the host computer through the data output module 7 to complete the entire phase demodulation process.

[0029] In this system, the arrayed waveguide grating is configured with 1×48 channels at a 50GHz channel spacing, covering a wavelength range of 1544.92-1563.86nm. In practical applications, the parameters of the arrayed waveguide grating 4 can be adjusted appropriately according to actual needs.

[0030] The output channels of the arrayed waveguide grating 4 are arranged in close rows to form an optical fiber array. This design not only improves the optical coupling efficiency, but also makes the system structure more compact.

[0031] The interpolation algorithm embedded in the signal acquisition and processing module 6 can obtain a more refined interference spectrum of the fiber optic Fabry-Perot sensor 3 by interpolating multiple consecutive light intensity information. This technology enables the system to achieve higher equivalent spectral resolution with a limited number of hardware channels, thereby improving the cavity length calculation accuracy.

[0032] The high-speed phase demodulation system for fiber optic FP sensors based on arrayed waveguide gratings and parallel spatial intensity detection described in this invention utilizes arrayed waveguide gratings 4 to achieve parallel mapping from the spectrum to space. Combined with high-speed photoelectric detection and interpolation algorithms, it realizes high-speed and high-precision demodulation of the phase of the fiber optic Fabry-Perot sensor 3. The system adopts an all-fiber design with no moving mechanical parts, and has the advantages of compact structure and high stability. It is suitable for measuring physical quantities with rapid changes such as dynamic pressure and vibration.

Claims

1. A high-speed phase demodulation system for an optical fiber FP sensor based on an arrayed waveguide grating and spatial intensity parallel detection, characterized in that, The high-speed phase demodulation system for the fiber optic Fabry-Perot sensor includes a broadband light source, an optical circulator, a fiber optic Fabry-Perot sensor, an arrayed waveguide grating, a photodetector array, a signal acquisition and processing module, and a data output module. The broadband light source is connected to the input of the optical circulator to provide broadband detection light; The input and output terminals of the optical circulator are connected to the fiber optic Fabry-Perot sensor, transmitting broadband probe light to the fiber optic Fabry-Perot sensor and receiving the broadband interference spectrum reflected by the fiber optic Fabry-Perot sensor. The fiber optic Fabry-Perot sensor changes its cavity length according to the change of the external measured physical quantity and reflects back a broadband interference spectrum with phase modulation; the output end of the optical circulator is connected to the input end of the arrayed waveguide grating, and the broadband interference spectrum reflected by the fiber optic Fabry-Perot sensor is input into the arrayed waveguide grating. The arrayed waveguide grating serves as a beam splitting element, used to divide the input broadband interference spectrum by wavelength and distribute it to different output channels according to wavelength, thereby realizing the conversion from the spectral domain to the spatial domain. The photoelectric detection array is used to synchronously and parallelly detect the light intensity of each output channel of the array waveguide grating, converting the wavelength-intensity correspondence into a spatial position-wavelength correspondence. The signal acquisition and processing module is connected to the photoelectric detection array and is used to acquire the intensity information of each pixel of the photoelectric detection array in real time, and recover the discrete interference spectrum of the fiber optic Fabry-Perot sensor according to the preset mapping relationship between pixel position and wavelength. The signal acquisition and processing module also embeds an interpolation algorithm to further refine the discrete interference spectrum through interpolation calculation, obtain an interference spectrum with higher spectral resolution, and finally calculate the real-time cavity length data of the fiber optic Fabry-Perot sensor based on the interference spectrum with higher spectral resolution. The data output module is used to output the calculated real-time cavity length data to a host computer or display device.

2. The high-speed phase demodulation system for fiber optic FP sensors according to claim 1, characterized in that, Each pixel of the photoelectric detection array corresponds one-to-one with the output channel wavelength of the array waveguide grating. Based on the mapping relationship between the pixel position and the channel wavelength, as well as the pixel intensity information, the discrete interference spectrum of the fiber optic Fabry-Perot sensor is recovered.

3. The high-speed phase demodulation system for fiber optic FP sensors according to claim 1, characterized in that, The photodetector array is a 256-pixel indium gallium arsenide linear CCD with a response range of 900nm-1700nm and a photosensitive area length of 12.8mm.

4. The high-speed phase demodulation system for fiber optic FP sensors according to claim 1, characterized in that, The interpolation algorithm executed by the signal acquisition and processing module obtains a more refined discrete interference spectrum of the fiber optic Fabry-Perot sensor by interpolation based on multiple continuous intensity information, thereby achieving higher system spectral resolution.

5. The high-speed phase demodulation system for fiber optic FP sensors according to claim 1, characterized in that, The arrayed waveguide grating is a 1×48-channel configuration with a 50GHz channel spacing, covering wavelengths from 1544.92 to 1563.86 nm.

6. The high-speed phase demodulation system for fiber optic FP sensors according to claim 1, characterized in that, The 48 output channels of the arrayed waveguide grating are densely packed to form a 10mm long fiber array.

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