Distributed long-distance receiving system based on heterodyne interference
By using a distributed long-distance receiving system based on heterodyne interferometry, and combining extended optical fibers and optical circulators with optical power amplification, the problems of short sensing distance and insufficient accuracy in existing technologies are solved, and high-sensitivity and high-precision long-distance acoustic signal monitoring is achieved.
Patent Information
- Application Number
- CN202511698145.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-19
- Publication Date
- 2026-02-13
AI Technical Summary
Existing distributed fiber optic sensing systems are limited by laser power, detector sensitivity, and fiber loss in long-distance acoustic signal detection, resulting in short sensing distances and insufficient measurement accuracy.
A distributed long-distance receiving system based on heterodyne interferometry is adopted. By introducing extended optical fibers, optical circulators and optical power amplification modules, combined with optical signal generation, detection, acquisition, filtering and phase demodulation units, real-time monitoring and high-precision detection of long-distance acoustic signals can be achieved.
It achieves dynamic acoustic signal monitoring at the 100-kilometer level, with a frequency band of 20Hz-20kHz, high sensitivity and accuracy, adaptability to harsh environments, and the ability to maintain high-frequency bandwidth and high sensitivity of the signal.
Smart Images
Figure CN121521246A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of distributed optical fiber sensing system technology, and in particular to a distributed long-distance receiving system based on heterodyne interferometry. Background Technology
[0002] In recent years, fiber optic distributed sensors have developed rapidly and are now being used in various fields such as energy transportation, transportation networks, homeland security and perimeter security, and underwater detection, with a very broad application prospect.
[0003] Fiber optic distributed sensors are of great significance in long-distance acoustic signal detection research. By providing a distributed, high-capacity, high-precision, and electromagnetically interference-resistant monitoring method, they help improve the scientific rigor and operability of various fields such as marine science, civil engineering monitoring, and long-distance communication. Currently, distributed fiber optic sensing systems are limited by laser power, detector sensitivity, and fiber loss, resulting in relatively short sensing distances. Real-world applications often require monitoring capabilities of tens or even hundreds of kilometers. Therefore, extending the sensing distance while maintaining sufficient measurement accuracy and spatial resolution at this distance has become the core driving force and main challenge of research in this field. Summary of the Invention
[0004] The purpose of this invention is to provide a distributed long-distance receiving system based on heterodyne interference, which can monitor effective acoustic signals from hundreds of kilometers away in real time by adding extended optical fibers without reducing the detection frequency and sensitivity. By changing the heterodyne frequency of the optical pulse, the detectable signal range can be 20Hz-20kHz.
[0005] To achieve the above objectives, the present invention provides a heterodyne interferometric distributed long-distance receiving system, including an optical generation and processing module. The optical generation and processing module is connected to a first optical circulator via a guide fiber. The first optical circulator is connected to a second optical circulator via an extension transmission fiber. A sensing fiber is connected to the second optical circulator. An extension reflection fiber is also connected between the first optical circulator and the second optical circulator.
[0006] Preferably, the guide fiber and the sensing fiber are connected together by an optical power amplification module.
[0007] Preferably, the optical power amplification module is bidirectional Raman pumped.
[0008] Preferably, the optical signal generation and processing module has a built-in optical signal generation unit, a detector unit, a data acquisition card unit, a filtering and amplification unit, and a phase demodulation unit.
[0009] Preferably, the acoustic signal detection process includes the following steps: S1. Determine the distance between the signal being measured and the optical generation and processing module, determine the length of the extended transmission fiber and the extended reflection fiber, the gain of the optical power amplification module, and connect it to the sensing fiber through the first optical circulator and the second optical circulator. S2. The optical signal generation unit of the optical generation and processing module generates a pair of probe optical pulses, which are then injected into the extension transmission fiber and the sensing fiber through the optical power amplification module. S3. The detection light pulse passes through the sensing fiber and generates a Rayleigh scattering signal. When an external acoustic signal acts on the sensing fiber, the phase of the Rayleigh scattering signal changes. S4. The generated reverse Rayleigh scattering signal is amplified by the optical power amplification module and then transmitted to the detector unit in the optical generation and processing module through the second optical circulator, the extended reflection fiber, the first optical circulator and the guide fiber. S5. The detector unit amplifies the optical signal a second time and converts it into a digital signal, which is then received by the acquisition card unit. S6. The filtering and amplification unit uses a denoising algorithm to amplify and denoise the received digital signal. S7. The denoised signal is demodulated by the I / Q demodulation algorithm of the phase demodulation unit to restore the phase change of the probe light pulse pair and demodulate and restore the external acoustic signal.
[0010] Therefore, the beneficial effects of the above-mentioned heterodyne interferometric distributed long-distance receiving system of the present invention are as follows: (1) The system of the present invention is capable of receiving dynamic sound signals at a distance of hundreds of kilometers.
[0011] (2) The system of the present invention can receive signals with a frequency band range of up to 20Hz-20kHz.
[0012] (3) The system of the present invention has good sensitivity, high precision and can adapt to various harsh environments.
[0013] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description
[0014] Figure 1 This is a schematic diagram of an embodiment of a heterodyne interferometric distributed long-distance receiving system according to the present invention.
[0015] Figure Labels 1. Optical signal generation unit; 2. Detector unit; 3. Acquisition card unit; 4. Filtering and amplification unit; 5. Phase demodulation unit; 6-1. First optical circulator; 6-2. Second optical circulator; 7-1. Guide fiber; 7-2. Extension transmission fiber; 7-3. Extension reflection fiber; 8. Optical power amplification module; 9. Sensing fiber. Detailed Implementation
[0016] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.
[0017] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.
[0018] Example 1: like Figure 1 As shown, the present invention provides a distributed long-distance receiving system based on heterodyne interferometry, including an optical signal generation and processing module. In this embodiment, the optical signal generation and processing module has a built-in optical signal generation unit 1, a detector unit 2, a data acquisition card unit 3, a filtering and amplification unit 4, and a phase demodulation unit 5.
[0019] The optical signal generation unit 1 in the optical generation and processing module is used to generate a pair of probe light pulses with a fixed heterodyne frequency. The pair of probe light pulses generated by the optical signal generation unit 1 is connected to a first optical circulator 6-1 through a guide fiber 7-1. The first optical circulator 6-1 is connected to a second optical circulator 6-2 through an extension transmission fiber 7-2.
[0020] By cooperating with the first optical circulator 6-1, the second optical circulator 6-2, and the extended transmission fiber 7-2, the extended transmission fiber 7-2 located between the first optical circulator 6-1 and the second optical circulator 6-2 only performs a guiding function and does not perform a sensing function, which can effectively improve the effective transmission distance of the probe optical pulse pair within the extended transmission fiber 7-2.
[0021] A sensing fiber 9 is connected to the second optical circulator 6-2 to sense changes in the acoustic signal and generate Rayleigh scattering. An extended reflective fiber 7-3 is also connected between the first optical circulator 6-1 and the second optical circulator 6-2 to transmit the generated Rayleigh scattering signal back to the detector unit 2 in the optical generation and processing module for reception via the extended reflective fiber 7-3, the first optical circulator 6-1, and the guide fiber 7-1.
[0022] In this embodiment, an optical power amplification module 8 is connected between the guiding optical fiber 7-1 and the sensing optical fiber 9. The optical power amplification module 8 is a bidirectional Raman pump, which is used to enhance the detection light pulse pair and the reflected Rayleigh scattering signal, thereby further improving the transmission distance of the entire system.
[0023] The working principle is as follows: When the sensing fiber 9 is horizontally laid in a medium (air / water) and subjected to external sound waves, according to elasticity, the length of the sensing fiber 9 increases or decreases radially, thereby causing the phase of the detected optical pulse pair to change in the same regular pattern. The phase change caused by the vibration of the external acoustic signal is obtained through a demodulation algorithm, thus enabling the measurement of the vibration signal in underwater acoustic communication. In this embodiment, the system uses two circulators to isolate the Rayleigh scattering signal from the extended transmission fiber 7-2, and the signal reflected by the sensing fiber 9 is further amplified by the optical power amplification module 8, enabling the transmission of acoustic signals over longer distances.
[0024] The acoustic signal detection process includes the following steps: S1. Determine the distance between the signal being measured and the optical generation and processing module, determine the length of the extended transmission fiber 7-2 and the extended reflection fiber 7-3, the gain of the optical power amplification module 8, and connect them to the sensing fiber 9 through the first optical circulator 6-1 and the second optical circulator 6-2.
[0025] S2. The optical signal generation unit 1 of the optical generation and processing module generates a pair of probe light pulses with a fixed heterodyne frequency, and injects them into the extension transmission fiber 7-1 and the sensing fiber 9 through the optical power amplification module 8. The optical power amplification module 8 is bidirectional Raman pumped, enabling simultaneous amplification of the probe light pulse pair and the Rayleigh scattering signal.
[0026] S3. The probe light pulse pair passes through the second optical circulator 6-2 and the sensing fiber 9 to generate a Rayleigh scattering signal. When an external acoustic signal acts on the sensing fiber 9, the sensing fiber 9 undergoes axial deformation and refractive index change, thereby changing the phase of the Rayleigh scattering signal.
[0027] S4. The generated reverse Rayleigh scattering signal is amplified by the optical power amplification module 8 and then transmitted to the detector unit 2 in the optical generation and processing module via the second optical circulator 6-2, the extended reflection fiber 7-3, the first optical circulator 6-1 and the guide fiber 7-1.
[0028] S5. The detector unit amplifies the optical signal a second time and converts it into a digital signal, which is then received by the acquisition card unit and acquired at high speed.
[0029] S6. The filtering and amplification unit uses a denoising algorithm to amplify and denoise the received digital signal.
[0030] S7. The denoised signal is demodulated using the I / Q demodulation algorithm of the phase demodulation unit to restore the phase change of the probe optical pulse pair (this phase change is caused by the vibration of the external acoustic signal). The system can perform bandpass filtering on the obtained optical phase time domain signal according to different acoustic signal frequencies and bandwidths to filter out noise, and then extract and analyze the time and frequency domain characteristics of the signal.
[0031] Therefore, the present invention employs the above-mentioned heterodyne interference-based distributed long-distance receiving system, which has good sensitivity, high accuracy and can adapt to various harsh environments. It can receive dynamic sound signals at a distance of hundreds of kilometers and has a signal range with a frequency band of up to 20Hz-20kHz.
[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.
Claims
1. A distributed long-distance receiving system based on heterodyne interferometry, characterized in that: It includes an optical generation and processing module, which is connected to a first optical circulator via a guide fiber. The first optical circulator is connected to a second optical circulator via an extension transmission fiber. A sensing fiber is connected to the second optical circulator. An extension reflection fiber is also connected between the first optical circulator and the second optical circulator.
2. The heterodyne interferometric distributed long-distance receiving system according to claim 1, characterized in that: An optical power amplification module is connected between the guide fiber and the sensing fiber.
3. The heterodyne interferometric distributed long-distance receiving system according to claim 2, characterized in that: The optical power amplifier module is bidirectional Raman pumped.
4. The heterodyne interferometric distributed long-distance receiving system according to claim 3, characterized in that: The optical signal generation and processing module has a built-in optical signal generation unit, detector unit, acquisition card unit, filtering and amplification unit, and phase demodulation unit.
5. A heterodyne interferometric distributed long-distance receiving system according to claim 4, characterized in that, The acoustic signal detection process includes the following steps: S1. Determine the distance between the signal being measured and the optical generation and processing module, determine the length of the extended transmission fiber and the extended reflection fiber, the gain of the optical power amplification module, and connect it to the sensing fiber through the first optical circulator and the second optical circulator. S2. The optical signal generation unit of the optical generation and processing module generates a pair of probe optical pulses, which are then injected into the extension transmission fiber and the sensing fiber through the optical power amplification module. S3. The detection light pulse passes through the sensing fiber and generates a Rayleigh scattering signal. When an external acoustic signal acts on the sensing fiber, the phase of the Rayleigh scattering signal changes. S4. The generated reverse Rayleigh scattering signal is amplified by the optical power amplification module and then transmitted to the detector unit in the optical generation and processing module through the second optical circulator, the extended reflection fiber, the first optical circulator and the guide fiber. S5. The detector unit amplifies the optical signal a second time and converts it into a digital signal, which is then received by the acquisition card unit. S6. The filtering and amplification unit uses a denoising algorithm to amplify and denoise the received digital signal. S7. The denoised signal is demodulated by the I / Q demodulation algorithm of the phase demodulation unit to restore the phase change of the probe light pulse pair and demodulate and restore the external acoustic signal.