Low-crosstalk long-distance sensing integrated device and very low frequency sensing method

Abstract

The invention discloses a low-crosstalk long-distance sensing integrated device and a very-low-frequency sensing method, and relates to the technical field of fusion of optical fiber sensing and optical fiber communication. The device comprises a laser, a coupler, a communication modulation device, a sensing modulation device, an optical fiber transmission and relay link, a communication receiving device, a sensing receiving device and a signal processing device. The communication modulation device adopts digital subcarrier multiplexing and reserves a guard interval in a frequency spectrum center, and residual carrier filtering is combined to reduce the inductance crosstalk; the sensing modulation device realizes high-extinction-ratio pulses through a cascade light modulator, and the signal-to-noise ratio is improved. The optical fiber link adopts a bidirectional amplification relay module to synchronously amplify forward and backward signals so as to realize ultra-long distance transmission. The signal processing device carries out high-density sampling and space-time dimension fusion on the sensing beat frequency signals, and very low frequency vibration information is effectively extracted. According to the invention, common-light-source, low-crosstalk, long-distance, very-low-frequency and high-sensitivity integrated transmission and detection of communication and sensing signals are realized.

Description

A low-crosstalk, long-distance integrated sensing device and a very low-frequency sensing method Technical Field

[0001] This invention relates to the field of optical fiber sensing and optical fiber communication integration technology, and more specifically, to a low crosstalk long-distance integrated sensing device and a very low frequency sensing method. Background Technology

[0002] Fiber Optic Communication and Sensing Integration (ISAC) technology integrates distributed fiber optic sensing and high-speed fiber optic communication into a single transmission medium, enabling simultaneous and efficient data transmission and real-time environmental status perception within existing fiber optic networks. This provides a new technological approach for applications such as marine earthquake monitoring, geological exploration, and seabed observation. Especially for widely deployed submarine fiber optic networks, utilizing existing fiber optic cable resources to achieve dual communication and sensing functions can significantly reduce the deployment cost of dedicated sensor networks and enhance the system's intelligence and multifunctionality.

[0003] However, existing ISAC systems still face several key technical challenges in achieving high-capacity transmission and high-sensitivity distributed sensing collaboration. First, most systems use wavelength division multiplexing, space division multiplexing, or time division multiplexing to separate communication and sensing signals, leading to reduced spectral efficiency and increased system complexity. Second, the frequencies of sound waves generated by marine geological activities and underwater acoustic events are mostly concentrated in the very low frequency band of 0.01 Hz to 10 Hz. Existing ISAC systems, affected by laser frequency drift and phase noise, lack the ability to detect vibration signals below 10 Hz, making it difficult to meet the needs of long-term deep-sea monitoring. Furthermore, the effective transmission and sensing distance of existing integrated sensing and communication systems is often limited to the tens of kilometers range, making long-distance detection difficult.

[0004] To address the aforementioned issues, several studies have attempted to optimize the system architecture, modulation methods, and signal processing. For example, patent CN118018114B proposes an access and mode matching mechanism based on multi-core optical fibers. It achieves fiber core adaptive adaptation through polarization state identification, improving the system's compatibility in multi-core environments. However, it still relies on spatial multiplexing and does not fully realize efficient multiplexing of channels with the same wavelength. Patent CN120223192A combines RF-OFDM and LFM signals, improving spectral efficiency through Hermitian symmetry and utilizing DC and low-frequency components to carry sensing information. However, the system's signal-to-noise ratio is limited in noisy environments, and its stability for very low-frequency vibration detection is insufficient. Patent CN117856915B designs a multi-functional frame header signal with flexibly configurable bandwidth for subcarrier number identification and synchronization, enhancing the system's spectral flexibility. However, the insertion of the frame header signal still occupies some time slots and spectrum resources, impacting communication efficiency.

[0005] In summary, existing technologies struggle to systematically and simultaneously address the challenges of coordinating low crosstalk, long-distance, and very low-frequency high-sensitivity sensing within the same wavelength channel. Therefore, there is an urgent need to propose a highly integrated, coordinating sensing solution that enables innovation across the entire sensing chain, from signal generation and transmission to information processing. This would facilitate the application of ISAC technology in long-distance, large-scale monitoring scenarios such as seabed observation and geological exploration. Summary of the Invention

[0006] To address the above-mentioned deficiencies or improvement needs of existing technologies, this invention provides a low-crosstalk long-distance integrated sensing device and a very low-frequency sensing method, aiming to solve the technical problems of severe crosstalk between communication and sensing signals, short effective sensing distance, and insufficient detection capability of very low-frequency vibration signals in existing integrated fiber optic sensing systems.

[0007] To achieve the above objectives, according to one aspect of the present invention, the present invention provides a low crosstalk long-distance integrated sensing device, the device comprising a laser, a first coupler, a second coupler, a third coupler, a communication modulation device, a sensing modulation device, an optical fiber transmission and relay link, a communication receiving device, a sensing receiving device, and a signal processing device.

[0008] The continuous light output from the laser is split into a communication branch and a sensing branch by the first coupler, and then enters the communication modulation device and the sensing modulation device respectively, thereby realizing the separate modulation of the communication signal and the sensing signal and the sharing of the light source.

[0009] The communication modulation device is responsible for modulating communication information onto the communication branch light to form a communication optical signal. The second coupler splits the sensing branch light again, with one path entering the sensing modulation device and the other path being output as a local oscillator to the sensing receiver. The sensing modulation device is responsible for modulating the sensing branch light into a sensing pulse optical signal. The third coupler then combines the modulated communication optical signal with the sensing pulse optical signal to generate a unified communication and sensing optical signal, which is then injected into the optical fiber transmission and relay link.

[0010] This fiber optic transmission and relay link is not only responsible for long-distance transmission of integrated sensing optical signals and backscattered Rayleigh light, but its built-in bidirectional amplification relay function is also the key to ensuring ultra-long-distance transmission and sensing.

[0011] The communication receiving device receives and demodulates the integrated sensing optical signal after long-distance transmission. The sensing receiving device receives the backscattered Rayleigh light generated by the integrated sensing optical signal and performs interference detection with the local oscillator light to output a beat frequency signal. Finally, the signal processing device processes the beat frequency signal to extract the vibration information contained along the optical fiber.

[0012] Furthermore, the present invention provides a communication modulation device for an integrated optical fiber sensing system.

[0013] This device is one of the core modules of the integrated sensing and communication device, designed to suppress crosstalk between communication signals and sensing signals at the source. It includes a modulation unit and a residual carrier filtering unit.

[0014] The modulation unit uses digital subcarrier multiplexing technology to generate a communication electrical signal and modulates it into a communication optical signal. Its key design feature is the reservation of a specific guard interval at the center of the digital subcarrier signal's spectrum. The communication electrical signal can employ various high-order modulation formats, including but not limited to quadrature amplitude modulation (QAM) and pulse amplitude modulation (PAM), to adapt to different transmission rate and capacity requirements.

[0015] The residual carrier filtering unit filters the modulated communication optical signal. Its core function is to suppress the residual optical carrier located within the guard interval caused by the drift of the modulator bias point.

[0016] Preferably, the filtering channel bandwidth of the residual carrier filtering unit is matched with the guard interval bandwidth, thereby maximizing the filtering of residual carrier components in the center of the spectrum while allowing communication signals to pass through without loss, fundamentally reducing inductive crosstalk.

[0017] Furthermore, the present invention provides a sensing modulation device for an integrated fiber optic sensing system.

[0018] This device is a key module for improving the system's sensing distance and signal-to-noise ratio. It consists of a cascaded first optical modulator and a second optical modulator.

[0019] The two are configured to operate synchronously. The first optical modulator performs initial pulse modulation on the sensing branch light, while the second optical modulator chops its output light. This cascaded chopping structure design can increase the overall extinction ratio of the pulsed light to a level that a single modulator cannot achieve, thereby effectively suppressing leakage light noise during pulse off-peak periods and ensuring that the sensing pulse maintains a high signal-to-noise ratio even after long-distance transmission.

[0020] Preferably, the sensing modulation device is driven by a single-frequency pulse or a swept-frequency pulse signal to adapt to different detection requirements. Furthermore, the pulse width and swept-frequency bandwidth of the first optical modulator are set to be greater than those of the second optical modulator to ensure the effectiveness of chopping and the quality of the pulse waveform.

[0021] Furthermore, the present invention provides an optical fiber transmission and relay link device for an integrated optical fiber sensing system.

[0022] This device forms the physical basis for achieving ultra-long-distance integrated sensing. It includes a circulator, multi-span transmission optical fibers, and bidirectional amplification repeater modules located between adjacent optical fibers.

[0023] The circulator is responsible for inputting the integrated sensing optical signal into the multi-span transmission fiber and directionally guiding the backscattered Rayleigh light to the sensing receiver. The bidirectional amplification repeater module is the core of this device. It can simultaneously amplify the forward-transmitted integrated sensing optical signal and the weak backscattered Rayleigh light, compensating for the link loss of both, thereby extending the effective working distance of the system to over 100 kilometers.

[0024] Optionally, the bidirectional amplification relay function can be implemented using various optical amplification techniques, such as bidirectional erbium-doped fiber amplifier (EDFA), distributed Raman amplification, remote pumping amplification, or a combination thereof.

[0025] Preferably, in one specific embodiment, the number of spans M of the multi-span transmission optical fiber and the number of bidirectional amplification repeater modules N satisfy the relationship M=N+1, thereby forming an ultra-long-distance stable transmission link composed of multiple cascaded amplification repeater segments.

[0026] According to another aspect of the present invention, the present invention provides a sensing signal processing method for an integrated optical fiber sensing system for realizing very low frequency sensing.

[0027] This method is a core algorithm for efficiently processing weak signals from the sensing end and achieving high-sensitivity detection of very low frequency vibrations. It includes the following steps: First, the sensor beat frequency signal is acquired at a sampling frequency higher than the bandwidth of the target event.

[0028] Next, in the spatial dimension, the differential phase information formed by adjacent sampling points is fused to suppress the coherent fading noise inherent in Rayleigh scattering.

[0029] In the time dimension, the acquired sequence is filtered and compressed to suppress the undersampling effect introduced by out-of-band noise.

[0030] Then, differential or adaptive filtering operations are performed on the processed signal to further suppress low-frequency phase noise, thereby significantly enhancing the signal-to-noise ratio of the very low frequency signal.

[0031] Finally, based on the above-mentioned fused signal, the vibration waveform, frequency, and intensity information at each location along the optical fiber are demodulated and extracted.

[0032] The present invention also provides a computer-readable storage medium storing computer instructions for causing a processor to perform the above-described method.

[0033] The present invention also provides a computer program product, including a computer program or instructions that, when executed by a processor, implement the above-described method.

[0034] In summary, compared with existing technologies, the above-described technical solutions conceived in this invention can achieve the following beneficial effects: 1. The digital subcarrier multiplexing technology adopted in this invention has flexible spectrum management capabilities. By supporting high-order modulation formats such as 16QAM and 64QAM, it can carry higher data rates within the same spectrum bandwidth, thereby laying the physical layer foundation for realizing large-capacity data transmission at the level of hundreds of Tb / s, and significantly improving the system's communication capacity and spectrum utilization.

[0035] 2. In terms of sensing modulation, the extinction ratio of the sensing pulse is increased to over 80dB through the design of a cascaded modulator, greatly suppressing pulse leakage noise and enabling the sensing probe to maintain a high signal-to-noise ratio even after long-distance transmission. Regarding the transmission link, the introduced bidirectional amplification relay modules (such as bidirectional EDFA, distributed amplification, etc.) can simultaneously compensate for the loss of both the forward communication signal and the backward Rayleigh scattering light. The synergistic effect of these two components extends the effective sensing distance from tens of kilometers in traditional solutions to hundreds of kilometers, fundamentally solving the core problem of limited distance in single-span sections and greatly improving the system's deployment adaptability and feasibility in practical scenarios such as submarine optical cables and wide-area infrastructure monitoring.

[0036] 3. To address the challenge of detecting very low frequency (0.01 Hz ~ 10 Hz) vibration signals generated by marine earthquakes, geological activities, etc., this invention utilizes a sensor signal processing algorithm to fuse differential phase information in the spatial dimension to suppress coherent fading noise, and performs filtering and data compression in the temporal dimension to suppress out-of-band noise. Furthermore, it employs differential or adaptive filtering via a reference fiber channel to suppress low-frequency phase noise. This significantly improves the system's effective signal-to-noise ratio in the very low frequency band, achieving highly sensitive and stable detection of extremely low-frequency, weak-intensity vibration events that are difficult for traditional systems to capture, thus expanding the system's application range.

[0037] 4. This invention optimizes spectrum utilization while ensuring performance through innovative signal design and processing. Specifically, by reserving a configurable guard interval at the center of the digital subcarrier spectrum and proposing a residual carrier filtering unit to accurately filter out residual optical carriers caused by IQ modulator bias point drift, the crosstalk between communication signals and sensing signals is effectively reduced from the source, achieving low crosstalk coexistence.

[0038] 5. Finally, by employing frequency division multiplexing within the same wavelength channel to deeply fuse the optimized communication signal with the high extinction ratio sensing pulse, true "integrated communication and sensing" signal generation and transmission are achieved. This scheme avoids the additional hardware costs, spectrum waste, and system complexity associated with using multi-fiber, multi-wavelength, or complex time division multiplexing schemes, resulting in a simpler, more efficient, and easier-to-integrate and maintain system architecture. Attached Figure Description

[0039] Figure 1 is a schematic diagram of the overall architecture of the long-distance, high-capacity distributed optical fiber sensing integrated system provided by the present invention; Figure 2 is a schematic diagram of the communication modulation module in the long-distance, high-capacity distributed optical fiber sensing integrated system provided by the present invention; Figure 3 is a schematic diagram of the sensing modulation module in the long-distance, high-capacity distributed optical fiber sensing integrated system provided by the present invention; Figure 4 is a schematic diagram of the wavelength distribution after the communication signal and sensing signal are modulated and multiplexed in the long-distance, high-capacity distributed optical fiber sensing integrated system provided by the present invention; Figure 5 is a schematic diagram of the bidirectional EDFA relay module in the long-distance, high-capacity distributed optical fiber sensing integrated system provided by the present invention; Figure 6 is a schematic diagram of the communication receiving module in the long-distance, high-capacity distributed optical fiber sensing integrated system provided by the present invention; Figure 7 is a schematic diagram of the sensing receiving module in the long-distance, high-capacity distributed optical fiber sensing integrated system provided by the present invention. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0041] This invention designs a low-crosstalk long-distance integrated sensing device and a very low-frequency sensing method. As shown in Figure 1, the low-crosstalk long-distance integrated sensing device of this invention mainly includes: a laser 10, a first coupler 11, a second coupler 12, a third coupler 13, a communication modulation device 20, a sensing modulation device 30, an optical fiber transmission and relay link 40, a communication receiving device 50, a sensing receiving device 60, and a signal processing device 70.

[0042] The connection relationships and workflows of each module are as follows: Laser 10 uses a narrow-linewidth laser with a wavelength of 1550nm and a linewidth of <1kHz to generate a narrow-linewidth, highly stable continuous beam of light. This continuous beam is split into two paths by a first coupler 11 with a splitting ratio of 1:1. One path enters the communication branch, and the other path enters the sensing branch.

[0043] 1. Implementation of the Communication Modulation Device 20: The communication branch light enters the communication modulation device 20 and is modulated into a digital subcarrier communication optical signal carrying a large amount of data. It then undergoes crucial post-processing to suppress interference. Its specific structure is shown in Figure 2. The device includes an arbitrary waveform generator 21, a modulator 22, an optical amplifier 23, and a residual carrier filtering unit 24. It can be expanded to include a wavelength division multiplexing channel 25 and a wavelength division multiplexer 26. The specific implementation steps are as follows: Signal generation and modulation: The arbitrary waveform generator 21 generates a digital subcarrier multiplexed communication electrical signal offline or in real time. In this embodiment, the signal uses a four-subcarrier dual-polarization 16QAM (DP-16QAM) format with a single-wavelength net rate of 200Gb / s, illustrating that the invention supports high-order modulation and high-capacity transmission. In practice, other modulation formats such as 64QAM and PAM4 can also be used, and the number of subcarriers can be flexibly configured (e.g., 4 or 8). During the digital signal processing stage, a guard interval needs to be reserved between the two innermost subcarriers at the center of the spectrum, with a bandwidth ranging from several hundred MHz to several GHz. The specific value is determined based on the system bandwidth and interference level. In this embodiment, an 8 GHz guard interval is used. The baseband electrical signal generated by the arbitrary waveform generator 21 drives a dual-biased IQ modulator 22 to modulate the communication branch optical signal into a coherent optical signal.

[0044] Residual Carrier Filtering: Due to bias point drift in actual operation of the IQ modulator 22, in addition to the information-carrying sidebands, the modulated optical signal will have residual, incompletely suppressed optical carriers in the center of the spectrum (i.e., within the guard interval). This residual carrier is the main noise source interfering with the sensing signal. This embodiment uses a high-resolution (6.25 GHz channel spacing) wavelength selective switch as the residual carrier filtering unit 24 to solve this problem. By precisely configuring its filtering function, the passband is aligned with the effective spectrum of the communication signal (including subcarriers and their guard intervals), while the center of the passband is in a "deeply blocked" state, thereby significantly filtering out the residual carrier components located within the guard interval (suppression ratio can reach more than 20 dB). This process realizes the function of "reserving a guard interval in the center of the spectrum and performing filtering suppression" as described in claims 2 and 3, effectively reducing inductive crosstalk.

[0045] Wavelength division multiplexing (WDM): WDM channel 25 consists of a 400G transmitter board and an ASE light source, simulating the remaining communication channels. In this embodiment, 51 multiplexed channels are used. The optical signal after filtering out the residual carrier can be multiplexed with pure communication channel signals of other wavelengths through WDM multiplexer 26, further expanding the total system capacity.

[0046] 2. Implementation of the Sensing Modulation Device 30: The sensing branch light is first split again by a second coupler 12 with a splitting ratio of 10:90: 10% of the power is directly used as the local oscillator light and is led to the sensing receiver 60; 90% of the power enters the sensing modulation device 30. Its structure is shown in Figure 3, including an arbitrary waveform generator 31, a first optical modulator 32, a second optical modulator 33, and an optical amplifier 34. The core objective of the sensing modulation device 30 is to generate a detection pulse with a high extinction ratio, reduce pulse turn-off noise, improve the signal-to-noise ratio of the far-end signal, and thus extend the sensing distance.

[0047] Cascaded Pulse Modulation: An arbitrary waveform generator 31 generates a pulsed electrical signal (which can be a single-frequency pulse, a linear or nonlinear swept-frequency pulse). In this embodiment, a single-frequency pulse with a carrier frequency of 200MHz, a pulse width of 200ns, and a pulse frequency of 100Hz is used. This electrical signal synchronously drives the first acousto-optic modulator 32, initially modulating the input continuous sensing light into an optical pulse. Subsequently, the optical pulse enters the second acousto-optic modulator 33. By precisely controlling the driving timing and RF switching of the two AOMs, the modulation of the two AOMs is synchronized. When the pulse is in the "on" state, both AOMs are in the light-transmitting state; when the pulse is in the "off" state, both AOMs are in the off state. This cascaded structure makes the overall extinction ratio of the system no longer the extinction ratio of a single device, but approximately the sum of the two. In this embodiment, a commercially available AOM with an extinction ratio greater than 40 dB is selected, and after cascading, a high-quality pulse with a total extinction ratio greater than 80 dB can be achieved. This cascaded chopper structure corresponds to claims 4 and 5, significantly improving the pulse extinction ratio and suppressing turn-off noise.

[0048] Pulse amplification: The generated pulsed light is amplified by optical amplifier 34 (such as erbium-doped fiber amplifier, semiconductor optical amplifier, etc.) to a power suitable for fiber insertion, so as to improve the detection light energy. In this embodiment, an erbium-doped fiber amplifier is used.

[0049] 3. Signal Combining and Link Transmission: The communication optical signal and the sensing pulse optical signal, after independent modulation and processing, are combined at the third coupler 13 with a splitting ratio of 1:1 to form a composite optical signal integrating communication and sensing. A schematic diagram of the spectrum of this composite signal is shown in Figure 4. Figure 4 clearly shows the spectral distribution of the narrow-linewidth laser after communication and sensing modulation. The narrow-linewidth laser outputs a single-frequency carrier, which, after communication modulation, generates four subcarrier signals with an 8GHz guard interval reserved in the center. It can be seen that after coherent modulation, a residual carrier exists in the center of the spectrum. This residual carrier is further filtered out by a wavelength selective switch, and the residual carrier within the guard interval is effectively removed. Sensing modulation uses two cascaded acousto-optic modulators with a frequency shift of 200MHz for pulse modulation; therefore, a sensing pulse spectrum appears 400MHz to the right of the carrier. Finally, the communication signal and the high extinction ratio sensing pulse signal are combined, and it can be seen that they coexist without overlap.

[0050] The aforementioned integrated optical signal is injected into the optical fiber and transmitted over a long distance via the repeater link 40. During transmission, external vibrations acting on the optical fiber generate backscattered Rayleigh light. The forward-transmitted composite optical signal eventually reaches the communication receiving module 50, where it is demodulated to recover the original communication data. The backscattered Rayleigh light returns along the original path, is extracted through the circulator 41 in the optical fiber transmission link 40, and coherently detects the local oscillator light in the sensing receiving module 60, ultimately demodulating the vibration information distributed along the optical fiber.

[0051] The fiber optic transmission link 40 consists of a transmission fiber 42 and a bidirectional amplification repeater module 43 inserted therebetween. In this embodiment, a bidirectional EDFA repeater as shown in Figure 5 is used. Each bidirectional EDFA repeater module 43 includes two circulators and two EDFAs. The forward-transmitted "integrated sensing" signal is input from port 1 of circulator 41, output from port 2, enters the transmission fiber, and after passing through one span of fiber, enters the bidirectional EDFA repeater module. The signal is input from port 2 of the first circulator, output from port 3 to the forward EDFA, input from port 1 of the second circulator, output from port 2, and enters the next fiber segment. The backward Rayleigh scattered light is input from port 2 of the second circulator, output from port 3, amplified by the backward EDFA, input to port 1 of the first circulator, and finally returns to the sensing receiver from port 2. By cascading N such repeater modules, the system can support the transmission of (N+1) fiber segments. In this embodiment, three repeater modules are used, with a single span fiber length of 50km, to achieve a 200km long-distance integrated fiber optic sensing system.

[0052] 4. Signal Reception and Processing Communication Receiving Module 50, as shown in Figure 6, receives the optical signal after long-distance transmission. First, the target communication channel is filtered out by wavelength selection switch 51, and then filtered by filter 52. It then enters the coherent receiving unit composed of local oscillator laser 54 and coherent receiver 55, where it is converted into an electrical signal. Finally, the receiving board 53 and oscilloscope 56 complete the digital signal acquisition and processing. During data processing, based on a digital filtering and discrete subcarrier demodulation scheme, the DAS signal and communication signal can be separated without adding additional equipment. Simultaneously, the discrete subcarrier modulation and reception scheme can minimize channel transmission impairments (dispersion, phase, nonlinearity), effectively improve the signal-to-noise ratio of the communication signal, and increase the transmission distance.

[0053] Sensor receiving module 60: As shown in Figure 7, the weak backscattered Rayleigh light returning from the circulator is first pre-amplified by optical amplifier 61. Simultaneously, the local oscillator light branched from the sensing branch undergoes a fixed frequency shift via a third acousto-optic modulator 63 driven by signal generator 62 to reduce the beat frequency, thereby lowering the system sampling rate and reducing the load and data volume at the acquisition end. In this embodiment, a 200MHz frequency shift is used. The amplified scattered light and the frequency-shifted local oscillator light interfere in a 1:1 coupler 64 and are converted into an electrical signal by a balanced photodetector 65. This electrical signal is acquired by data acquisition card 66.

[0054] Very Low Frequency (VLF) Signal Extraction: The acquired beat frequency signal is sent to the signal processing device 70 for processing. To demonstrate the VLF detection capability, in this embodiment, the applied external vibration signal frequency is 0.01Hz, and the processing algorithm performs the following steps: oversampling the target vibration by adjusting the transmission pulse frequency to 200Hz.

[0055] Spatial dimension: The differential phase vector formed by adjacent dense sampling points is fused to suppress Rayleigh scattering coherent fading noise; Temporal dimension: The demodulated phase signal is filtered and downsampled to suppress the undersampling effect introduced by out-of-band noise; Differential operation between adjacent sensing channels is performed to further suppress low-frequency phase noise and enhance the signal-to-noise ratio of the very low frequency signal. Finally, the vibration waveform, frequency, and intensity information at various locations along the optical fiber are demodulated and extracted. Through this algorithm, the system can effectively extract very low frequency vibration information of 0.01 Hz, verifying the high-sensitivity low-frequency detection capability of the present invention.

[0056] This embodiment provides a software implementation flow of the sensing signal processing method in the device described in the above embodiment. The steps are completely consistent with those described in Part 4 "Very Low Frequency Signal Extraction" of the above embodiment, and will not be repeated here.

[0057] In summary, this specific embodiment fully demonstrates a practically constructable and operable low-crosstalk long-distance integrated sensing device and very low-frequency sensing method. Through the synergy of core technologies such as residual carrier filtering at the communication modulation end, cascaded chopping at the sensing modulation end, bidirectional relay amplification in the transmission link, and very low-frequency information fusion processing at the receiving end, this device successfully integrates shared light source, high-capacity communication, and 100-kilometer-scale, very low-frequency, high-sensitivity distributed vibration sensing within a single optical fiber.

[0058] The technical features of the embodiments described above can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. It should be noted that the terms "in one embodiment," "for example," and "again" in this invention are intended to illustrate the invention and are not intended to limit the invention.

[0059] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A low-crosstalk, long-distance sensing integrated device, characterized in that, include: The system comprises a laser, a first coupler, a second coupler, a third coupler, a communication modulation device, a sensing modulation device, an optical fiber transmission and relay link, a communication receiving device, a sensing receiving device, and a signal processing device, wherein: the continuous light output from the laser is split into a communication branch light and a sensing branch light by the first coupler, and input to the communication modulation device and the sensing modulation device respectively; the communication modulation device is connected to the communication branch light and is used to modulate communication information onto the communication branch light to generate a communication optical signal; the second coupler is used to split the sensing branch light into two paths, one of which is input to the sensing modulation device, and the other is used as a local oscillator light input to the sensing receiving device; The sensing modulation device is used to modulate the sensing branch light into a sensing pulse light signal; the communication optical signal and the sensing pulse light signal are modulated separately and share a light source; the third coupler is used to combine the communication optical signal and the sensing pulse light signal to generate a syn-sensing integrated optical signal, and input it into the optical fiber transmission and relay link; the optical fiber transmission and relay link is used to transmit the syn-sensing integrated optical signal and backscattered Rayleigh light, and sense external vibrations; the communication receiving device is used to receive the syn-sensing integrated optical signal transmitted by the optical fiber transmission and relay link; the sensing receiving device is used to receive the beat frequency signal of the syn-sensing integrated optical signal generated by backscattering Rayleigh light and interference with the local oscillator light through the optical fiber transmission and relay link; the signal processing device is used to process the beat frequency signal to extract the vibration signal.

2. The low crosstalk long-distance sensing integrated device as described in claim 1, characterized in that, The communication modulation device includes a modulation unit and a residual carrier filtering unit; the modulation unit is used to modulate the communication electrical signal generated by digital subcarrier multiplexing technology into a communication optical signal, and reserves a guard interval at the center of the spectrum of the digital subcarrier signal; the residual carrier filtering unit is used to perform residual carrier filtering on the modulated communication optical signal.

3. The low crosstalk long-distance sensing integrated device as described in claim 2, characterized in that, The filtering channel bandwidth of the residual carrier filtering unit is matched with the guard interval bandwidth of the digital subcarrier signal, so as to maximize the filtering out of residual carrier components located at the center of the spectrum while allowing communication signals to pass.

4. The low crosstalk long-distance sensing integrated device as described in claim 1, characterized in that, The sensing modulation device includes a first optical modulator and a second optical modulator; the first optical modulator and the second optical modulator are cascaded to modulate the sensing branch light into pulsed light; the first optical modulator and the second optical modulator are configured to operate synchronously, and the second optical modulator is configured to chop the light output by the first optical modulator to improve the extinction ratio of the output pulsed light.

5. The low crosstalk long-distance sensing integrated device as described in claim 4, characterized in that, The first optical modulator and the second optical modulator are configured to be driven by a single-frequency pulse signal or a swept-frequency pulse signal; and the pulse width and swept-frequency bandwidth of the first optical modulator are greater than those of the second optical modulator.

6. The low crosstalk long-distance sensing integrated device as described in claim 1, characterized in that, The optical fiber transmission and relay link includes a circulator, a multi-span transmission optical fiber, and a bidirectional amplification relay module located between adjacent optical fibers. The circulator is used to input the integrated sensing optical signal into the multi-span transmission optical fiber and to directionally guide the backscattered Rayleigh light to the sensing receiving device. The bidirectional amplification relay module is used to amplify the forward-transmitted integrated sensing optical signal and the weak backscattered Rayleigh light to compensate for the link loss of both.

7. The low crosstalk long-distance sensing integrated device as described in claim 6, characterized in that, The number of spans M of the multi-span transmission optical fiber and the number N of the bidirectional amplification repeater modules satisfy the relationship M=N+1.

8. A sensing signal processing method for an integrated fiber optic sensing system, characterized in that, Includes the following steps: Acquire sensor beat frequency signals at a sampling frequency higher than the target event bandwidth; In the spatial dimension, the differential phase vectors formed by adjacent dense sampling points are fused to suppress coherent fading noise; in the temporal dimension, the acquired sequence is filtered and compressed to suppress the undersampling effect introduced by out-of-band noise; the processed signal is subjected to differential or adaptive filtering operations on adjacent sensor channels to further suppress low-frequency phase noise and enhance the signal-to-noise ratio of very low frequency signals; based on the fused signal, the vibration waveform, frequency and intensity information at each location along the optical fiber are demodulated and extracted.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the method as described in claim 8.

10. A computer program product, comprising a computer program or instructions, characterized in that, When the computer program or instructions are executed by the processor, they implement the steps of the method as described in claim 8.

Images