A distributed optical fiber sensing device with color and mode field coordinated encoding

Abstract

The present invention discloses a distributed fiber optic sensing device with coordinated color and mode field coding, comprising a light source, an optical coupling device, an optical fiber, a color coding structure, a detector, and a computing module. The light source, the optical coupling device, and the optical fiber are arranged in sequence, and the light emitted by the light source enters the optical fiber through the optical coupling device. The color coding structure is located on a side of the optical fiber away from the optical coupling device. The color coding structure is connected to the optical fiber along the axial direction of the optical fiber. The detector is configured to collect the signal output by the optical fiber. The computing module is electrically connected to the detector, and the computing module is configured to establish a mapping relationship between the signal collected by the detector and the measured physical quantity. The distributed fiber optic sensing device of the present invention has a simple structure, a small size, and a low cost, and is suitable for promotion and application in clinical personal diagnosis, treatment, and nursing.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic information technology, and in particular to a distributed optical fiber sensing device with color and mode field collaborative coding. Background Art

[0002] Fiber optic sensing offers numerous advantages, including high sensitivity, compact probe size, biocompatibility, and electromagnetic compatibility. It is widely used in the transportation, chemical, mechanical, and environmental fields to measure physical quantities such as vibration, temperature, pressure, concentration, liquid level, and flow rate. In recent years, these advantages have led to its increasing application in biomedical engineering.

[0003] The principle of fiber optic sensing is as follows: When electromagnetic waves propagate through an optical fiber waveguide, they are disturbed, causing a change in their state. A detector detects this change and then implements sensing based on a mapping between it and the degree of disturbance. The disturbance can originate from the optical fiber waveguide itself, the specific optical structure integrated with the waveguide, or other materials incorporated into the structure. The electromagnetic wave state change can be detected using any optically measurable property, such as amplitude, phase, frequency (wavelength), and polarization.

[0004] In terms of space, fiber optic sensing can be divided into single-point and distributed types. Single-point sensing can only perform measurements at a specific location on the fiber waveguide, while distributed sensing can perform (quasi-) continuous measurements over a length of fiber.

[0005] Distributed fiber optic sensing generally involves four technical approaches: optical time-domain reflectometry (OTDR), optical frequency-domain reflectometry (OFDR), optical low-coherence reflectometry (OLCR), and quasi-distributed sensing. The first three rely on physical processes in optical fiber: Rayleigh scattering, Brillouin scattering, and Raman scattering. Their sensing mechanisms are based on the time-of-flight of light pulses in the fiber and optical coherence detection (or optical heterodyne detection), respectively. The fourth utilizes wavelength division multiplexing (WDM) using Bragg gratings inscribed at different locations on the fiber. Although this approach is also called quasi-distributed sensing, its spatial resolution far exceeds that of most OTDRs.

[0006] With the exception of OTDR, these technologies generally require the use of highly complex and costly swept-frequency light sources, optical interferometers, and spectrometers. While the cost and size of existing distributed fiber optic sensors are perfectly acceptable for industrial and urban construction applications, including biomedical laboratory research, they are still beyond the acceptable level for clinical applications in personal diagnosis, treatment, and nursing care.

[0007] Therefore, those skilled in the art are committed to providing a distributed optical fiber sensing device with coordinated color and mode field coding, so as to simplify the structure of the optical fiber sensing device and reduce its cost. Summary of the Invention

[0008] In view of the defects in the prior art, the technical problem to be solved by the present invention is how to provide a distributed optical fiber sensing device with a simple structure and reduced cost.

[0009] To achieve the above-mentioned objectives, the present invention provides a distributed optical fiber sensing device with coordinated color and mode field coding, comprising a light source, an optical coupling device, an optical fiber, a color coding structure, a detector, and a computing module. The light source, the optical coupling device, and the optical fiber are arranged in sequence, and the light emitted by the light source enters the optical fiber through the optical coupling device. The color coding structure is located on the side of the optical fiber away from the optical coupling device. The color coding structure is connected to the optical fiber along the axial direction of the optical fiber. The detector is configured to collect the signal output by the optical fiber. The computing module is electrically connected to the detector, and the computing module is configured to establish a mapping relationship between the signal collected by the detector and the measured physical quantity.

[0010] Furthermore, the wavelength range of the light output by the light source is 400-700 nm; the light source is one of an LED, a halogen lamp, and a supercontinuum light source.

[0011] Furthermore, the optical fiber satisfies the normalized frequency At any operating wavelength The following are all greater than 2.405, among which:

[0012] ,

[0013] Where, is the core radius of the optical fiber, is the numerical aperture of the optical fiber.

[0014] Preferably, the color coding structure is an intrinsic structure of the optical fiber, and specifically may be a fiber Bragg grating.

[0015] Preferably, the color coding structure is a combination of exogenous optical material and optical fiber microstructure.

[0016] Furthermore, the color coding structures are distributed along the axial direction of the optical fiber, and the number of the color coding structures is no less than 2.

[0017] Preferably, the detector is a CCD or CMOS two-dimensional photoelectric sensor.

[0018] Preferably, the algorithm of the computing module adopts a deep convolutional neural network.

[0019] Preferably, the detector and the optical coupling device are located on both sides of the optical fiber in the length direction of the optical fiber.

[0020] Preferably, the detector and the optical coupling device are located on the same side of the optical fiber in the longitudinal direction of the optical fiber, and a spectroscopic element is provided between the detector and the optical fiber. The signal output by the optical fiber is collected by the detector after passing through the spectroscopic element.

[0021] The present invention has at least the following beneficial technical effects:

[0022] 1. The distributed optical fiber sensing device with color and mode field collaborative coding provided by the present invention uses any continuous white light source, such as LED, halogen lamp, etc., which is much cheaper than pulse, swept frequency, optical frequency comb and other laser sources, and does not rely on nonlinear optical effects, so no high-power light source is required.

[0023] 2. The distributed optical fiber sensing device with color and mode field collaborative coding provided by the present invention uses ordinary color CCD or CMOS components as detectors, which are much cheaper than high-precision spectrum analyzers, high-speed (broadband) photodiodes, etc.

[0024] 3. The distributed optical fiber sensing device with color and mode field collaborative coding provided by the present invention consists only of a light source, an optical fiber and a detector, and does not require complex optical devices such as optical interference and spatial gratings. It has a simple structure and a small size.

[0025] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 1 is a schematic structural diagram of a distributed optical fiber sensing device according to embodiment 1 of the present invention;

[0027] Figure 2 2 is a schematic structural diagram of a distributed optical fiber sensing device according to embodiment 2 of the present invention;

[0028] Figure 3 2 is a schematic structural diagram of a distributed optical fiber sensing device according to embodiment 3 of the present invention;

[0029] Figure 4 It is a schematic diagram of the coding of the detector of the present invention within the wavelength range of the color space;

[0030] Figure 5 Schematic diagram of the coding of the detector of the present invention in the mode field space;

[0031] Figure 6 It is a data processing flow diagram of the present invention. DETAILED DESCRIPTION

[0032] The following describes preferred embodiments of the present invention to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0033] In the drawings, components with identical structures are denoted by the same reference numerals, and components with similar structures or functions are denoted by similar reference numerals. The size and thickness of each component shown in the drawings are arbitrary and are not limited by the present invention. For clarity, the thickness of components in some places in the drawings is appropriately exaggerated.

[0034] Example 1

[0035] like Figure 1 As shown, the distributed fiber optic sensing device of this embodiment includes a light source 11, an optical coupler 12, an optical fiber 13, a color coding structure 14, a detector 15, and a computing module 16. The optical coupler 12 and the detector 15 are located on both sides of the optical fiber 13 along the length direction. The color coding structure 14 is connected to the optical fiber 13 along the axial direction of the optical fiber 13 and is located on the side away from the optical coupler 12. The following are arranged in order along the light output direction: the light source 11, the optical coupler 12, the optical fiber 13, the color coding structure 14, and the detector 15. The computing module 16 receives the signal collected by the detector 15 and establishes a mapping relationship between the signal and the measured physical quantity.

[0036] The light source 11 outputs "white light", that is, the wavelength of the output light covers the range of 400-700nm. The light source 11 can be specifically selected from LED, halogen lamp, supercontinuum light source, etc.

[0037] The light output by the light source 11 enters the optical fiber 13 after passing through the optical coupling device 12 . The optical coupling device 12 may specifically be a lens assembly.

[0038] The optical fiber 13 is a multimode optical fiber, that is, the optical characteristics of the optical fiber waveguide meet the multi-transverse mode transmission conditions: the normalized frequency At any operating wavelength The normalized frequency is greater than 2.405. The calculation method is:

[0039] ,

[0040] Where, is the core radius of the optical fiber, is the numerical aperture of the optical fiber.

[0041] Due to the superposition and interference of transverse mode fields of different orders during multimode fiber transmission, when the external environment causes changes in the optical properties of the fiber, this can cause changes in the distribution of the transmitted mode field within the fiber, thus serving as a coding method. The presence of color-coding structure 14 causes the frequency domain characteristics of the light transmitted within the fiber to evolve and change, thus serving as another coding method. Compared to the mode field, which is a modulation of a specific location on the fiber affected by the external environment, color-coding structure 14 is distributed axially along optical fiber 13, with no fewer than two of them. The synergy between these two structures enables (quasi-) distributed fiber optic sensing.

[0042] There are many ways to make the color coding structure 14. It can be an intrinsic structure of the optical fiber, such as a fiber Bragg grating, or it can be a combination of exogenous optical materials and optical fiber microstructures.

[0043] Detector 15 is typically a CCD or CMOS two-dimensional photoelectric sensor. Because it needs to recognize the modulation of the color-coding structure, detector 15 must be color, typically with red, green, and blue components. Other color combinations, such as a hyperspectral detector, are also possible. Optical coupling devices such as lenses may be placed between the sensor of detector 15 and multimode optical fiber 13 to ensure efficient reception.

[0044] The converted electrical signal passes through a computing module 16 to map the detector data to the measured physical quantity. The computing module typically consists of computing hardware and algorithms. The computing hardware can be a microcomputer, a mobile phone, or a server. Due to the inherent nonlinear characteristics of color and mode field co-encoding, to balance sensor accuracy and inference speed, the algorithm is typically a data-driven approach, such as a deep convolutional neural network.

[0045] Figure 4 is a schematic diagram of the coding of the detector 15 within the wavelength range of the color space, Figure 5 Schematic diagram of the encoding of the detector 15 in the mode field space. When light propagates in a multimode fiber, superposition and interference occur between the transverse mode fields, which can be expressed as:

[0046]

[0047] in, yes The distribution of the electromagnetic field of the order mode on the vibration plane, is the amplitude, is the fiber length, yes The effective refractive index of the order mode, is the wavelength. The detection intensity is the integral within the wavelength range. The reflection wavelength difference (lens) of the color-coded structure at different axial positions on the multimode fiber is as follows: Figure 4 At the same time, due to the difference in quantum efficiency of the detector color detection at different wavelengths, as shown in the dashed line. Figure 4 As shown by the red, green and blue solid lines in the figure, the signals at different axial positions on the optical fiber can be distinguished according to the detected colors. On the other hand, due to the changes in the refractive index of the optical fiber caused by the measured physical quantities such as temperature, stress, curvature, etc., the mode field distribution will be different, as shown in the figure. Figure 5 As shown, this can achieve the encoding of the detected physical quantity at a specific position.

[0048] Figure 6 The data post-processing process in this embodiment is shown. The data collected by the detector is used to establish a mapping relationship with the measured physical quantity through the algorithm in the calculation module. The method for establishing the mapping relationship can be a variety of machine learning, statistical learning and other algorithms. Considering that the detector output is an image, a deep convolutional neural network can be used to extract its features, such as ResNet-18. Since sensor measurements usually require (quasi) continuously changing data, it is necessary to connect a regression output layer after the fully connected layer of the network. Its function is to calculate the semi-mean square error loss of the regression task:

[0049]

[0050] in, is the number of responses, is the target output, Is the network response To implement this algorithm, a large amount of data, distributed as evenly as possible, must be collected within the measurement interval for network training. The trained network, with its end-to-end nature, enables rapid inference of measurement results, which is beneficial for dynamic process observation or applications requiring real-time performance.

[0051] Example 2

[0052] like Figure 2 As shown, the distributed fiber optic sensing device of this embodiment differs from that of Example 1 in that the optical coupler 22 and detector 26 are located on the same side of the optical fiber 24 along its length, and a spectrometer 23 is provided between the optical coupler 22 and the optical fiber 24. Along the light output direction, the following are arranged in sequence: light source 21, optical coupler 22, spectrometer 23, optical fiber 24, and color coding structure 25. Light reflected or backscattered by the color coding structure 25 passes through the optical fiber 24 again, through the spectrometer 23, and reaches the detector 26 and computing module 27.

[0053] The purpose of the light splitting element 23 is to separate the incident light from the light source and the light reflected or backscattered by the color coding structure, and specifically can be a beam splitter, a fiber coupler, etc.

[0054] Since the detection light needs to be transmitted back and forth in the multimode optical fiber, which is different from the unidirectional transmission in Example 1, the mapping relationship between the detector data and the measured physical quantity is also different. Therefore, the data driving algorithm in the calculation module 27 and the calculation module 16 in Example 1 is not exactly the same.

[0055] Example 3

[0056] like Figure 3 The figure shows the all-fiber implementation of Example 2, which has significant advantages in practical applications. It can make the optical device more compact, miniaturized, dust-proof, moisture-proof, and shock-proof, so it can operate in more scenarios and be more stable.

[0057] The distributed optical fiber sensing device of this embodiment includes an optical fiber coupled output light source 31, an optical fiber splitter 32, a multimode optical fiber 33, a color coding structure 34, an optical fiber coupled detector 35 and a computing module 36. The optical fiber splitter 32 is generally Fiber coupler or fiber combiner, where , .

[0058] The preferred embodiments of the present invention have been described in detail above. It should be understood that numerous modifications and variations based on the concepts of the present invention can be made by one of ordinary skill in the art without inventive effort. Therefore, any person skilled in the art can arrive at a solution based on the concepts of the present invention through logical analysis, reasoning, or limited experimentation based on the prior art.

Claims

1. A distributed optical fiber sensing device with color and mode field coordinated coding, characterized in that: The device comprises a light source, an optical coupling device, an optical fiber, a color coding structure, a detector, and a computing module, wherein the light source, the optical coupling device, and the optical fiber are arranged in sequence, and light emitted by the light source enters the optical fiber through the optical coupling device. The color coding structure is located on a side of the optical fiber away from the optical coupling device, and the color coding structure is connected to the optical fiber along the axial direction of the optical fiber. The detector is configured to collect a signal output by the optical fiber, and the computing module is electrically connected to the detector, and the computing module is configured to establish a mapping relationship between the signal collected by the detector and a measured physical quantity. The optical fiber satisfies the normalized frequency At any operating wavelength The following are all greater than 2.405, among which: ， Where, is the core radius of the optical fiber, is the numerical aperture of the optical fiber; The color coding structures are distributed along the axial direction of the optical fiber, and the number of the color coding structures is no less than 2; The detector encodes the collected signal in the following way: Where, I is the light field intensity, i is a plural unit, yes The distribution of the electromagnetic field of the order mode on the vibration plane, is the amplitude, is the fiber length, yes The effective refractive index of the order mode, is the wavelength; The computing module uses a deep convolutional neural network algorithm to perform feature extraction.

2. The distributed optical fiber sensing device with color and mode field coordinated coding according to claim 1, wherein: The wavelength range of the light output by the light source is 400-700nm; the light source is one of LED, halogen lamp and supercontinuum light source.

3. The distributed optical fiber sensing device with color and mode field coordinated coding according to claim 1, wherein: The color coding structure is a fiber Bragg grating.

4. The distributed optical fiber sensing device with color and mode field coordinated coding according to claim 1, wherein: The color coding structure is a combination of exogenous optical materials and optical fiber microstructures.

5. The distributed optical fiber sensing device with color and mode field coordinated coding according to claim 1, wherein: The detector is a CCD or CMOS two-dimensional photoelectric sensor.

6. The distributed optical fiber sensing device with color and mode field coordinated coding according to claim 1, wherein: The detector and the optical coupling device are located on both sides of the optical fiber in the length direction of the optical fiber.

7. The distributed optical fiber sensing device with color and mode field coordinated coding according to claim 1, wherein: The detector and the optical coupling device are located on the same side of the optical fiber in the longitudinal direction of the optical fiber. A spectroscopic element is further provided between the detector and the optical fiber. The signal output by the optical fiber is collected by the detector after passing through the spectroscopic element.

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