A distributed fiber optic sensing integrated system and its implementation method

Abstract

This invention proposes a distributed optical fiber sensing integrated system and its implementation method. The system includes a transmitter, a sensing receiver, a communication receiver, and a transmission link unit. The transmitter generates an LFM-PSK sensing integrated optical signal and one LFM optical signal. The sensing receiver performs matched filtering on the LFM-PSK sensing integrated optical signal and the Rayleigh scattering signal returned from the transmission link unit to detect and analyze changes in the phase information of the transmission optical fiber. The communication receiver performs heterodyne correlation detection on the LFM-PSK sensing integrated optical signal and the other LFM optical signal to reconstruct the PSK communication signal, and then obtains the original service signal based on the PSK communication signal. Compared with existing technologies, this system has a higher signal-to-noise ratio and better sensing performance in environments with strong noise interference.

Description

Technical Field

[0001] This invention relates to the field of optical communication technology, and in particular to a distributed optical fiber sensing integrated system and its implementation method. Background Technology

[0002] With the continuous development of communication networks, communication systems and sensing systems are becoming increasingly similar in terms of hardware and information processing. Building upon the existing fiber optic network architecture, exploring and promoting the integrated development of sensing and communication equipment to achieve hybrid transmission and mutual utilization of communication and sensing signals, thus realizing integrated communication and sensing, is the optimal technical path to improve sensing measurement distance and accuracy, save network fiber core resources, and reduce operation and maintenance costs. This has become a research trend and hot topic in recent years. Distributed fiber optic sensing systems seamlessly integrate fiber optic communication and fiber optic sensing technologies, providing new possibilities for information transmission and environmental perception.

[0003] The applicant found that the current distributed fiber optic sensing system has a limited signal-to-noise ratio and unsatisfactory sensing performance in environments with strong noise interference. Summary of the Invention

[0004] In view of the above problems, it is necessary to propose a distributed optical fiber sensing integrated system to solve or partially solve the above problems. The technical solution proposed by this invention is as follows:

[0005] A distributed optical fiber sensing integrated system includes a transmitter, a sensing receiver, a communication receiver, and a transmission link unit, wherein:

[0006] The transmitting end is used to modulate the original service signal on the phase to form a PSK communication signal; it is also used to generate two LFM optical signals with a wavelength gap; it is also used to use one LFM optical signal as a carrier to embed the PSK communication signal to generate an LFM-PSK integrated sensing optical signal; it is also used to couple the LFM-PSK integrated sensing optical signal and the other LFM optical signal and send them to the transmission link unit.

[0007] The sensing receiver is used to perform matched filtering on the received LFM-PSK integrated sensing optical signal and the Rayleigh scattering signal returned by the transmission link unit, so as to detect and analyze the changes in the phase information of the transmission optical fiber, thereby distinguishing the vibration intensity and frequency of the transmission optical fiber.

[0008] The communication receiver is used to perform heterodyne correlation detection on the received LFM-PSK integrated optical signal and the other LFM optical signal to restore the PSK communication signal, and then obtain the original service signal based on the PSK communication signal.

[0009] Furthermore, the transmission link unit may include a beam splitter, a circulator, a transmission optical fiber, and a vibrator. The input end of the beam splitter is connected to the transmitting end, and the two output ends of the beam splitter are respectively connected to the input end of the circulator and the sensing receiving end. The two output ends of the circulator are respectively connected to the transmission optical fiber and the sensing receiving end. The other end of the transmission optical fiber is also connected to the communication receiving end. The vibrator vibrates the transmission optical fiber near the communication receiving end to generate a Rayleigh scattering signal, which returns to the sensing receiving end via the transmission optical fiber and the circulator.

[0010] Furthermore, the transmitting end may include a laser, a Mach-Zehnder modulator, a wavelength selection switch, a first optical amplifier, a phase modulator, a second optical amplifier, and a coupler connected in sequence. The transmitting end also includes an arbitrary waveform generator, which is used to generate an LFM electrical signal to the Mach-Zehnder modulator and a PSK electrical signal to the phase modulator. The other output terminal of the wavelength selection switch is directly connected to the coupler.

[0011] Furthermore, the Mach-Zehnder modulator outputs an LFM optical signal, and the phase modulator outputs the LFM-PSK integrated sensing optical signal. The expression for the LFM optical signal is:

[0012]

[0013] Among them, A S f is the signal amplitude. i Let k be the carrier frequency of the LFM optical signal, k be the frequency modulation slope, and T be the frequency variation period; the expression for the LFM-PSK integrated sensing optical signal is:

[0014]

[0015] in, M represents the PSK modulation order, a i Represents the PSK symbol.

[0016] Furthermore, the sensing receiver includes at least: a matched filter and a first oscilloscope, one input of the matched filter is connected to the circulator, the other input is connected to the beam splitter, and the output of the matched filter is connected to the first oscilloscope.

[0017] Furthermore, the sensing receiver also includes a third optical amplifier and a first optical bandpass filter. The input of the third optical amplifier is connected to the circulator, and the output is connected to the first optical bandpass filter. The output of the first optical bandpass filter is connected to a first oscilloscope.

[0018] Furthermore, the communication receiver includes at least a fourth optical amplifier, a second optical bandpass filter, a coherent receiver, and a second oscilloscope, wherein: the input of the fourth optical amplifier is connected to the transmission optical fiber, and the output is connected to the second optical bandpass filter; the output of the second optical bandpass filter is connected to the input of the coherent receiver, and the output of the coherent receiver is connected to the second oscilloscope.

[0019] Furthermore, the communication receiver also includes a polarizer and an adjustable attenuator connected to each other. The input end of the polarizer is connected to the output end of the fourth optical amplifier, and the output end of the adjustable attenuator is connected to the input end of the second optical bandpass filter.

[0020] Furthermore, the coherent receiver is used to receive the LFM-PSK integrated sensing optical signal and the other LFM optical signal, use the other LFM optical signal as a reference light to achieve heterodyne coherent detection, and remove the LFM optical signal used as a carrier in the LFM-PSK integrated sensing optical signal to obtain the PSK communication signal.

[0021] On the other hand, the present invention also discloses a method for implementing a distributed optical fiber sensing integrated system, comprising:

[0022] The original service signal is modulated onto the phase to form a PSK communication signal;

[0023] Two LFM optical signals with a wavelength gap are generated;

[0024] Using one LFM optical signal as a carrier, embedding a PSK communication signal to generate an LFM-PSK integrated sensing optical signal;

[0025] The LFM-PSK integrated sensing optical signal and another LFM optical signal are coupled together and sent to the transmission link unit;

[0026] The sensing receiver performs matched filtering on the received LFM-PSK integrated sensing optical signal and the Rayleigh scattering signal returned by the transmission link unit to detect and analyze the changes in the phase information of the transmission optical fiber, thereby distinguishing the vibration intensity and frequency of the transmission optical fiber.

[0027] The communication receiver performs heterodyne correlation detection on the received LFM-PSK integrated optical signal and the other LFM optical signal to restore the PSK communication signal, and then obtains the original service signal based on the PSK communication signal.

[0028] Based on the above technical solution, the beneficial effects of the present invention compared with the prior art are as follows:

[0029] This invention uses Digital Signal Processing (DSP) to modulate service information onto the phase, forming a Phase Shift Keying (PSK) communication signal. Simultaneously, a Linear Frequency Modulation (LFM) waveform is generated as a sensing probe. Using the LFM waveform as a carrier, the communication signal is embedded by changing the phase of the LFM optical signal, generating an integrated LFM-PSK sensing optical signal. The communication receiver uses coherent reception to detect the LFM-PSK optical signal, then removes the LFM carrier and demodulates the PSK communication signal to complete high-speed, high-spectral-efficiency information transmission. The sensing receiver receives the Rayleigh scattering signal from the transmission link unit and uses coherent detection to separate the phase change component caused by fiber vibration, detecting the intensity and frequency of the vibration to achieve distributed sensing.

[0030] LFM-PSK integrated sensing optical signal is an integrated waveform that enables communication and sensing functions simultaneously at the same wavelength and polarization, without additional overhead, and can be directly applied to existing fiber optic systems. For fiber optic communication, the LFM optical signal is a linear frequency modulation technique with minimal interference to its underlying phase modulation signal, allowing for higher transmission rates and spectral efficiency through the use of higher-order phase modulation. For fiber optic sensing, compared to an LFM signal without a communication signal, the introduction of the PSK communication signal makes the LFM signal closer to a random signal, increasing the peak-to-sidelobe ratio of the scattered signal after autocorrelation processing. Compared to existing technologies, this system exhibits a higher signal-to-noise ratio and better sensing performance even in environments with strong noise interference. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of a distributed optical fiber sensing integrated system in an embodiment of the present invention;

[0032] Figure 2 This is a schematic diagram of the sending end in some embodiments;

[0033] Figure 3 This is a schematic diagram of the structure of the communication receiver in some embodiments;

[0034] Figure 4 In some embodiments, the autocorrelation function plot of the LFM-PSK waveform obtained experimentally;

[0035] Figure 5 In some embodiments, the autocorrelation function diagram of the LFM-PAM waveform obtained experimentally;

[0036] Figure 6This is a flowchart illustrating a method for implementing a distributed optical fiber sensing system in an embodiment of the present invention. Detailed Implementation

[0037] The research on distributed fiber optic sensing systems mainly involves two key aspects: First, by using optical fiber as the transmission medium, an integrated system design of fiber optic communication and sensing is implemented to achieve efficient information transmission and accurate environmental data perception. Fiber optic communication, as a carrier of information, has many advantages, including large broadband information capacity, long transmission distance, and strong anti-interference capability. Simultaneously, fiber optic sensing technology utilizes the interaction between light and the medium during transmission in optical fibers to achieve accurate perception of environmental parameters such as temperature, pressure, and strain. Therefore, combining these two technologies allows for seamless connection between information transmission and environmental perception within the same fiber optic channel. Second, through the joint waveform design and application of fiber optic communication and sensing technologies, simultaneous information processing and real-time feedback of environmental perception are achieved. This means that not only can information be transmitted in the fiber optic cable, but environmental parameters can also be monitored and analyzed during transmission and fed back to the system for processing in a timely manner. This real-time feedback mechanism can greatly improve the system's response speed and accuracy, thereby better meeting the needs of various application scenarios.

[0038] Fiber optic communication and sensing integration technology can not only improve the efficiency of information transmission and processing, but also reduce costs and energy consumption, thus having broad application prospects in fields such as intelligent manufacturing, smart cities, intelligent transportation, and healthcare.

[0039] 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 of the invention and are not intended to limit the invention. For ease of understanding, some technical terms involved in the embodiments of this invention are explained below:

[0040] Phase Shift Keying (PSK): A modulation technique that uses the phase of a carrier wave to represent the input signal information. PSK is divided into absolute phase shift and relative phase shift. Phase modulation using the phase of the unmodulated carrier as a reference is called absolute phase shift. Taking binary phase modulation as an example, when the symbol is "1", the modulated carrier is in phase with the unmodulated carrier; when the symbol is "0", the modulated carrier is out of phase with the unmodulated carrier; the phase difference between the modulated carriers of symbols "1" and "0" is 180°.

[0041] Linear Frequency Modulation (LFM) is a spread spectrum modulation technique that does not require pseudo-random coding sequences. Because LFM signals occupy a bandwidth much larger than the information bandwidth, they can achieve significant system processing gain. LFM signals are also known as chirp signals because their spectral bandwidth falls within the audible range, sounding like birdsong; hence, it is also called Chirp Spread Spectrum (CSS) technology. An LFM signal is a signal whose instantaneous frequency changes linearly with time.

[0042] Heterodyne coherent detection: Coherent detection uses a local oscillator beam and the input signal beam to mix in an optical mixer, obtaining an intermediate frequency (IF) signal whose frequency, phase, and amplitude vary according to the same pattern as the signal beam. In heterodyne coherent detection, the frequency difference between the local carrier and the signal carrier is greater than the baseband bandwidth. Compared to direct detection, heterodyne coherent detection is advantageous for detecting weak signals, enabling long-distance fiber optic transmission, and, with appropriate selection of the local oscillator power, can achieve a high signal-to-noise ratio. Furthermore, unlike direct modulation and detection, which can only detect signal strength, heterodyne coherent detection can obtain the phase information of the signal.

[0043] 3dB Coupler: When an optical signal enters a 3dB coupler, the two optical signals will interfere with each other. The 3dB coupler splits the input light into two equal optical power outputs through multimode interference effect.

[0044] Matched filters are optimal linear filters that maximize the signal-to-noise ratio (SNR) in a known signal containing additive random noise. They are commonly used in signal detection, associating a known signal or template with an unknown signal to detect the presence of the template in the unknown signal. This is equivalent to convolving the unknown signal with a time-reversed conjugate of the template. The derivation of the matched filter formula is complex; please refer to existing publicly available information.

[0045] Autocorrelation analysis: Autocorrelation, also known as serial correlation, is the cross-correlation of a signal with itself at different time points. Simply put, it is a function of the similarity between two observations of the same signal and the time difference between them. Autocorrelation analysis is commonly used in signal processing to analyze functions or a series of values, such as time-domain signals.

[0046] It is worth noting that the defects mentioned in the background section of the prior art are the result of the inventors' practice and careful research. Therefore, the discovery process of the above problems and the solutions proposed by the embodiments of the present invention in the following text should be considered as contributions made by the inventors to the present invention.

[0047] In some embodiments, such as Figure 1 As shown, a distributed optical fiber sensing integrated system includes a transmitter 10, a sensing receiver 20, a communication receiver 30, and a transmission link unit 40, wherein:

[0048] The transmitter 10 is used to modulate the original service signal on the phase to form a PSK communication signal; it is also used to generate two LFM optical signals with a wavelength gap; it is also used to use one LFM optical signal as a carrier to embed the PSK communication signal to generate an LFM-PSK integrated optical signal; and it is also used to couple the LFM-PSK integrated optical signal and the other LFM optical signal and send them to the transmission link unit 40.

[0049] In essence, transmitter 10 is used for signal generation. Transmitter 10 uses digital signal processing (DSP) to modulate service information onto the phase, forming a phase-shift keying (PSK) communication signal, and simultaneously generates an LFM optical signal as a sensing probe. Using the LFM optical signal as a carrier, the PSK communication signal is embedded by changing the phase of the LFM optical signal, generating a waveform for integrated sensing and communication. The symbol rate of the PSK communication signal is R. b In each time slot T s =1 / R b In this context, the symbol of a communication signal is mapped to a phase.

[0050] The sensing receiver 20 is used to perform matched filtering on the received LFM-PSK integrated sensing optical signal and the Rayleigh scattering signal returned by the transmission link unit 40, so as to detect and analyze the changes in the phase information of the transmission optical fiber 43, thereby distinguishing the vibration intensity and frequency of the transmission optical fiber 43.

[0051] The communication receiver 30 is used to perform heterodyne correlation detection on the received LFM-PSK integrated optical signal and the other LFM optical signal to restore the PSK communication signal, and then obtain the original service signal based on the PSK communication signal.

[0052] This application uses digital signal processing (DSP) to modulate service information onto the phase, forming a phase shift keying (PSK) communication signal. Simultaneously, a linear frequency modulated (LFM) waveform is generated as a sensing probe. Using the LFM waveform as a carrier, the communication signal is embedded by changing the phase of the LFM optical signal, generating an integrated LFM-PSK sensing optical signal. The communication receiver 30 uses coherent reception to detect the LFM-PSK optical signal, then removes the LFM carrier and demodulates the PSK communication signal to complete high-speed, high-spectral-efficiency information transmission. The sensing receiver 20 receives the Rayleigh scattering signal returned by the transmission link unit 40, uses coherent detection to separate the phase change component caused by fiber vibration, and detects the intensity and frequency of the vibration, achieving distributed sensing.

[0053] The following section will describe in detail some optional structures and their specific working principles for each part, with reference to the accompanying drawings.

[0054] In some embodiments, the transmitting end 10 includes a laser 11, a Mach-Zehnder modulator 12, a wavelength selection switch 13, a first optical amplifier 14, a phase modulator 15, a second optical amplifier 16, and a coupler 17 connected in sequence. The transmitting end 10 also includes an arbitrary waveform generator 18, which generates an LFM electrical signal to the Mach-Zehnder modulator 12 and a PSK electrical signal to the phase modulator 15. Another output terminal of the wavelength selection switch 13 is directly connected to the coupler 17. In practical applications, multiple polarization controllers can generally be set to control the polarization state of the signal light; therefore, preferably, a combination of... Figure 2 As shown, the transmitting end 10 may further include a first polarization controller 191, a second polarization controller 192, and a third polarization controller 193, wherein:

[0055] The arbitrary waveform generator AWG18 can generate electrical signals of arbitrary shapes according to the input signal. In this embodiment, the output of the digital signal processing DSP is imported into the arbitrary waveform generator AWG18 to generate corresponding electrical signals. As shown in the figure, an LFM electrical signal is generated to the Mach-Zehnder modulator 12, and a PSK electrical signal is generated to the phase modulator 15.

[0056] The output of laser 11 is connected to a first polarization controller 191, and the output of the first polarization controller 191 is connected to a Mach-Zehnder modulator 12 (MZM modulator). The output of the Mach-Zehnder modulator 12 is also connected to a wavelength selection switch 13. An LFM electrical signal waveform is generated using an AWG. The laser generated by laser 11 (e.g., a continuous wavelength laser 11 generating a 1550nm laser) serves as the carrier wave. The laser and the electrical signal drive the Mach-Zehnder modulator 12, loading the electrical signal into the optical domain to generate a linear frequency modulated (LFM) optical signal as a sensing probe.

[0057] LFM signals are chirped signals whose frequency varies over time in a periodic manner. Because different frequency components of the LFM signal travel at different speeds in the optical fiber, the scattered signals generated by these different frequencies return to the transmitter 10 at different times. Therefore, different return times correspond to different positions within the optical fiber. To ensure that each position in the optical fiber corresponds to a unique frequency component in the LFM optical signal, thereby achieving precise distributed sensing, the frequency variation period of the LFM optical signal should be no less than twice the longest transmission time of light in the optical fiber. Based on the fundamental mathematical expression of LFM signals, the LFM optical signal output by the Mach-Zehnder modulator 12 of this invention is expressed as:

[0058]

[0059] Where A is S The signal amplitude of the LFM optical signal, f i Let be the carrier frequency of the LFM optical signal, k be the frequency modulation slope of the LFM optical signal, and T be the frequency variation period of the LFM optical signal.

[0060] One output of the wavelength selection switch 13 is connected to the first optical amplifier 14, and the other output is connected to the coupler 17; the output of the first optical amplifier 14 is connected to the second polarization controller 192; the output of the second polarization controller 192 is connected to the phase modulator 15; the output of the phase modulator 15 is connected to the input of the second optical amplifier 16; the output of the second optical amplifier 16 is connected to the third polarization controller 193; and the output of the third polarization controller 193 is connected to the coupler 17.

[0061] In this embodiment, a wavelength selective switch 13 is selected. This switch filters two coherent beams with a wavelength gap, which are then emitted to two separate branches, enabling heterodyne coherent detection at the receiving end. Compared to direct detection, heterodyne coherent detection is advantageous for detecting weak signals, enabling long-distance fiber optic transmission, and achieving a higher signal-to-noise ratio when the local oscillator power is appropriately selected. Furthermore, unlike direct modulation and detection, which can only detect signal strength, heterodyne coherent detection can obtain the phase information of the signal, thereby facilitating the subsequent extraction of the PSK signal.

[0062] In this embodiment, the transmitting end 10 generates a bit stream of service information. Phase-shift keying (PSK) modulation is performed on this bit stream to modulate the service information onto the phase, forming a PSK communication signal. An AWG is used to generate the PSK electrical signal waveform. Using the LFM optical signal from one branch generated by the Mach-Zehnder modulator 12 as the carrier, the PSK communication signal is embedded by changing the phase of the LFM waveform using a phase modulator 15, resulting in an LFM-PSK integrated sensing optical signal. Compared to the original LFM waveform, the LFM-PSK integrated sensing optical signal after embedding the PSK signal is closer to a random signal, and the peak-to-sidelobe ratio of the scattered signal after autocorrelation processing is increased. Therefore, this waveform design results in a higher signal-to-noise ratio and better sensing performance in environments with strong noise interference. The communication signal symbol rate is R. b In each time slot T s =1 / R b In this communication signal, a symbol is mapped to a phase. The period of the LFM signal should be much larger than the time slot T of the PSK signal. s This ensures distortion-free loading of communication signals. The LFM-PSK integrated sensing optical signal is represented as:

[0063]

[0064] in, M represents the PSK modulation order, a i Represents the PSK symbol.

[0065] In this embodiment, the coupler 17 is preferably a 3dB coupler 17. The signal output by the phase modulator 15 is amplified to a suitable power by the second optical amplifier 16, coupled to another LFM carrier output by the wavelength selection switch 13 through the 3dB coupler 17, and then output through the beam splitter 41 of the transmission link unit 40.

[0066] In some embodiments, combined with Figure 1 As shown, the transmission link unit 40 includes a beam splitter 41, a circulator 42, a transmission optical fiber 43, and a vibrator. The input end of the beam splitter 41 is connected to the transmitter 10, and the two output ends of the beam splitter 41 are respectively connected to the input end of the circulator 42 and the sensing receiver 20. The two output ends of the circulator 42 are respectively connected to the transmission optical fiber 43 and the sensing receiver 20. The other end of the transmission optical fiber 43 is also connected to the communication receiver 30. The vibrator vibrates the transmission optical fiber 43 near the communication receiver 30 to generate a Rayleigh scattering signal, which returns to the sensing receiver 20 via the transmission optical fiber 43 and the circulator.

[0067] The beam splitter 41 of the transmission link unit 40 can be a 1:1 beam splitter 41. One of its output optical signals serves as a reference light for coherent reception of scattered signals at the sensing receiver 20, while the other serves as a communication signal and a detection signal for communication and sensing. The vibrator used in the transmission link unit 40 has a fixed vibration frequency and is positioned at the end of the transmission optical fiber 43 and before the communication receiver 30. When the transmission optical fiber 43 is subjected to vibration by an external force, the fiber length, core diameter, and core refractive index change, causing a change in the phase of the light wave propagating in the fiber. This phase change can be expressed as:

[0068]

[0069] Where β is the propagation constant, L is the length of the transmission fiber 43, n is the refractive index of the transmission fiber core, a is the diameter of the transmission fiber core, ΔL is the change in length of the transmission fiber 43, Δn is the change in refractive index of the transmission fiber 43 core, and Δa is the change in diameter of the transmission fiber 43 core. In some embodiments, the propagation constant β = 2*pi / lambda, where lambda is the wavelength of light.

[0070] The magnitude of external disturbances and other parameters are linearly related to the phase change on the optical fiber. Therefore, information related to external vibration signals can be sensed by detecting the phase change. This patent primarily uses Rayleigh scattering as the sensing signal. Compared to the integrated sensing optical signal of LFM-PSK, the Rayleigh scattering signal has an additional phase change component caused by external force, which is expressed as follows:

[0071]

[0072] Among them, A R Let φ(t) be the amplitude of the Rayleigh scattering signal, and let φ(t) be the phase change caused by the external force.

[0073] In some embodiments, combined with Figure 1 As shown, the sensing receiver 20 includes at least a matched filter 23 and a first oscilloscope 24. One input of the matched filter 23 is connected to the circulator 42, and the other input is connected to the beam splitter 41. The output of the matched filter 23 is connected to the first oscilloscope 24. The transmitting end 10 generates an LFM-PSK integrated sensing optical signal and a scattered light signal returned by the circulator 42, which are simultaneously input into the matched filter 23 to complete the matched filtering. The matched filtering ensures that the obtained signal achieves the maximum signal-to-noise ratio output, while also reflecting the phase characteristics of the signal as much as possible, thereby accurately extracting the phase change of the sensing signal. The sensed received signal is represented as follows:

[0074]

[0075] Δt is twice the time it takes for light to travel through the optical fiber, and can be determined by the sampling frequency of the first oscilloscope 24 and the number of samples per data frame. Specifically, because light travels at a certain speed in the optical fiber, such as from point A to point B, it takes a certain amount of time to traverse the entire fiber. For example, when a light signal reaches point B and generates a Rayleigh reflection signal at point B, the reflected signal reaches point A and is received. This time is actually the time it takes for the light to travel from A to B and back to A. Similarly, the reflected signals at all points between A and B in the optical fiber need to undergo the same process, and the closer to A, the shorter the time required. Based on this principle, by observing the received signal at point A, the different points of the received signal from morning to evening correspond to the reflected signals at different locations in the optical fiber. For example, if the transmission fiber 43 is 1000m long, the sensing resolution is 1m, and the first oscilloscope 24 receives 10000 data frames at a sampling rate of 10, after downsampling, it becomes 1000 frames. The first frame corresponds to the scattered signal at 0-1m in the optical fiber, the second frame corresponds to 1-2m, and so on. The time of receiving each frame is displayed on the first oscilloscope 24.

[0076] In this embodiment, the output of matched filter 23 is:

[0077]

[0078] x * (·) denotes the conjugate of the signal. After matching filtering with the original LFM-PSK signal to remove repetitive waveform components, the final sensing signal can be expressed as:

[0079]

[0080] Phase information can be further extracted by sensing signals. The time Δt for the Rayleigh scattering signal from the vibration location to return to the transmitting end 10 is obtained. After calculating the light propagation time, the distance to the location where the vibration occurred in the optical fiber can be determined. Therefore, by detecting and analyzing phase changes, vibration intensity and frequency can be distinguished, thus realizing distributed vibration detection in optical fibers.

[0081] In sensing signal processing, a higher peak-to-side-lobe ratio (the ratio of the height of the first sidelobe to the main lobe, in dB) of the autocorrelation function of the received signal indicates a higher signal-to-noise ratio and better sensing performance in environments with strong noise interference. Let r 感知接收 (τ s The derivative of τ is equal to 0, thus yielding the zero point τ. s And substitute the formula for calculating the peak-to-side-lobe ratio of the matched filter 23:

[0082]

[0083] The inventors discovered through extensive research that when the LFM optical signal period is much larger than the PSK symbol slot T... S At that time, the communication signal symbol rate R b The larger the peak-to-side-lobe ratio, the better the peak-to-side-lobe ratio, and the closer the proposed waveform is to a random signal. Therefore, LFM-PSK waveforms with a high peak-to-side-lobe ratio will have a stronger signal-to-noise ratio for the sensing signal. Figure 4 , Figure 5 The diagram shows a comparison of the autocorrelation functions of the experimentally obtained LFM-PSK and LFM-PAM waveforms. These two diagrams demonstrate that the LFM-PSK waveform exhibits better autocorrelation characteristics and a higher peak-to-side-lobe ratio compared to the LFM-PAM waveform, and the proposed waveform is closer to a random signal. Therefore, the LFM-PSK waveform with a high peak-to-side-lobe ratio will have a stronger signal-to-noise ratio for the sensed signal. Furthermore, the inventors found that the LFM-PSK waveform demonstrates superior performance in terms of peak-to-side-lobe ratio.

[0084] Preferably, in some embodiments, combined with Figure 1As shown, the sensing receiver 20 also includes a third optical amplifier 21 and a first optical bandpass filter 22. The input of the third optical amplifier 21 is connected to the circulator 42, and the output is connected to the first optical bandpass filter 22. The output of the first optical bandpass filter 22 is connected to the first oscilloscope 24. The third optical amplifier 21 can amplify the Rayleigh scattering signal power, and the first optical bandpass filter 22 can filter out-of-band noise.

[0085] In some embodiments, combined with Figure 1 As shown, the communication receiver 30 may include at least a fourth optical amplifier 31, a second optical bandpass filter 32, a coherent receiver 33, and a second oscilloscope 34. The input of the fourth optical amplifier 31 is connected to the transmission optical fiber 43, and its output is connected to the second optical bandpass filter 32. The output of the second optical bandpass filter 32 is connected to the input of the coherent receiver 33, and the output of the coherent receiver 33 is connected to the second oscilloscope 34. The fourth optical amplifier 31 is used to compensate for power loss in the optical fiber link. The second optical bandpass filter 32 filters out out-of-band noise. Then, another coupled LFM carrier is used as the local oscillator for heterodyne coherent detection. The second oscilloscope 34 stores the detected electrical signal. Since the transmitter 10 uses a wavelength selection switch 13 to split two coherent beams with a gap, in addition to the original LFM-PSK signal, the receiver can directly select another wavelength LFM carrier as the reference light to achieve heterodyne coherent detection. By removing the LFM carrier from the LFM-PSK signal, the PSK signal can be obtained. In this embodiment, the coherent receiver 33 receives the LFM-PSK integrated sensing optical signal and another LFM optical signal. The other LFM optical signal is used as a reference light to achieve heterodyne coherent detection. The LFM optical signal used as the carrier in the LFM-PSK integrated sensing optical signal is removed to obtain the PSK communication signal. The second oscilloscope 34 uses a DSP to obtain the transmitted service bit information stream after DC blocking, IQ compensation algorithm, low-pass filtering, and phase compensation. In this embodiment, the expression of the LFM-PSK communication signal obtained by the communication receiver 30 is:

[0086]

[0087] Where h(t) is the channel response function and n(t) is the noise, the transmitted data can be obtained by processing the received signal using the receiver algorithm. Besides the receiver algorithm mentioned in this invention, better receiver algorithms can be used to achieve better reception performance, and this invention does not impose any limitations on this.

[0088] Preferred, combined Figure 3As shown, the communication receiver 30 also includes a polarizer 35 and an adjustable attenuator 36 connected to each other. The input of the polarizer 35 is connected to the output of the fourth optical amplifier 31, and the output of the adjustable attenuator 36 is connected to the input of the second optical bandpass filter 32. The introduction of the polarizer 35 and the adjustable attenuator 36 optimizes the polarization state of the signal, making the signal more stable.

[0089] This embodiment utilizes multiple modulators, using an LFM optical signal as the carrier, and embeds a PSK communication signal by changing the phase of the LFM optical signal. This generates an integrated waveform design that enables communication and sensing functions simultaneously at the same wavelength and polarization. Then, a heterodyne coherent detection method is used to remove the LFM carrier from the LFM-PSK signal and perform compensation demodulation algorithms to obtain the complete communication signal. Furthermore, an optical circulator 42 extracts the backscattered Rayleigh signal, and a matched filtering method is used to extract the phase from the Rayleigh scattering signal to distinguish the fiber's changing position and frequency intensity. This demonstrates the mechanism and system architecture for this approach.

[0090] Compared with existing technologies, this invention uses digital signal processing (DSP) to modulate service information onto the phase, forming a phase shift keying (PSK) communication signal. Simultaneously, a linear frequency modulated (LFM) waveform is generated as a sensing probe. Using the LFM waveform as a carrier, the communication signal is embedded by changing the phase of the LFM optical signal, generating an integrated LFM-PSK sensing optical signal. The communication receiver 30 uses coherent reception to detect the LFM-PSK optical signal, then removes the LFM carrier and demodulates the PSK communication signal to complete high-speed, high-spectral-efficiency information transmission. The sensing receiver 20 receives the Rayleigh scattering signal from the optical circulator 42, uses coherent detection to separate the phase change component caused by fiber vibration, and detects the intensity and frequency of the vibration to achieve distributed sensing. The integrated LFM-PSK sensing optical signal is an integrated waveform that can achieve communication and sensing functions simultaneously at the same wavelength and polarization, without additional overhead, and can be directly applied to existing fiber optic systems. For fiber optic communication, the LFM optical signal is a linear frequency modulation technology with minimal interference to its carried phase modulation signal; therefore, higher-order phase modulation can be used to achieve higher transmission rates and spectral efficiency. For fiber optic sensing, compared to LFM signals without communication signals, the introduction of PSK communication signals makes the LFM signals closer to random signals, increasing the peak-to-sidelobe ratio of the scattered signal after autocorrelation processing. Compared to LFM-PAM signals, the sensing signal has a higher signal-to-noise ratio and better sensing performance in environments with strong noise interference.

[0091] Based on the above advantages, the distributed optical fiber sensing integrated system of the present invention can effectively improve the quality of information transmission and processing, and is one of the important directions for the future development of information technology. Optical fiber communication and sensing integration can be applied to many fields, such as intelligent manufacturing, smart cities, intelligent transportation, and healthcare, and has broad application prospects.

[0092] Furthermore, based on a similar inventive concept, this invention also discloses a method for implementing a distributed optical fiber sensing integrated system, which can be directly applied to existing optical fiber systems. The type of link sensing can also be changed according to actual needs, forming a modular system architecture. Specifically, such as... Figure 6 As shown, the implementation method of the distributed optical fiber sensing integrated system includes the following steps:

[0093] S110 modulates the original service signal onto the phase to form a PSK communication signal.

[0094] S120 generates two LFM optical signals with a wavelength gap.

[0095] S130 uses one LFM optical signal as a carrier and embeds a PSK communication signal to generate an integrated LFM-PSK sensing optical signal.

[0096] S140, the LFM-PSK integrated sensing optical signal and another LFM optical signal are coupled and sent to the transmission link unit.

[0097] S150, the sensing receiver performs matched filtering on the received LFM-PSK integrated sensing optical signal and the Rayleigh scattering signal returned by the transmission link unit to detect and analyze the changes in the phase information of the transmission optical fiber, thereby distinguishing the vibration intensity and frequency of the transmission optical fiber.

[0098] S160, the communication receiving end performs heterodyne correlation detection on the received LFM-PSK integrated sensing optical signal and the other LFM optical signal to restore the PSK communication signal, and then obtains the original service signal based on the PSK communication signal.

[0099] In some embodiments, the order of steps S110 and S120 can be changed or they can be performed simultaneously; the order of steps S150 and S160 can be changed or they can be performed simultaneously.

[0100] In the detailed description above, various features are combined together in a single embodiment to simplify the invention. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, the invention is presented with fewer features than all of the features in the single disclosed embodiment. Therefore, the appended claims are hereby explicitly incorporated into the detailed description, with each claim representing a separate preferred embodiment of the invention.

[0101] The foregoing description includes examples of one or more embodiments. It is certainly impossible to describe all possible combinations of components or methods in order to describe the above embodiments, but those skilled in the art will recognize that further combinations and arrangements of the various embodiments are possible. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations that fall within the scope of the appended claims. Furthermore, the term “comprising” as used in the specification or claims is interpreted in a manner similar to the term “including,” just as “including,” is interpreted as a conjunction in the claims. Additionally, the use of any term “or” in the specification of the claims is intended to mean “non-exclusive or.”

Claims

1. A distributed optical fiber sensing integrated system, characterized in that, It includes a transmitter (10), a sensing receiver (20), a communication receiver (30), and a transmission link unit (40), wherein: The transmitting end (10) is used to modulate the original service signal on the phase to form a phase shift keying (PSK) communication signal; it is also used to generate two linear frequency modulated (LFM) optical signals with a wavelength gap; it is also used to use one LFM optical signal as a carrier to embed the PSK communication signal to generate an LFM-PSK integrated sensing optical signal; and it is also used to couple the LFM-PSK integrated sensing optical signal and the other LFM optical signal and send them to the transmission link unit (40). The sensing receiver (20) is used to perform matched filtering on the received LFM-PSK integrated sensing optical signal and the Rayleigh scattering signal returned by the transmission link unit (40) to detect and analyze the changes in the phase information of the transmission optical fiber, thereby distinguishing the vibration intensity and frequency of the transmission optical fiber. The communication receiver (30) is used to perform heterodyne correlation detection on the received LFM-PSK integrated optical signal and the other LFM optical signal to restore the PSK communication signal, and then obtain the original service signal based on the PSK communication signal.

2. The distributed optical fiber sensing integrated system as described in claim 1, characterized in that, The transmission link unit (40) includes a beam splitter (41), a circulator (42), a transmission fiber (43), and a vibrator. The input end of the beam splitter (41) is connected to the transmitter (10), and the two output ends of the beam splitter (41) are respectively connected to the input end of the circulator (42) and the sensing receiver (20). The two output ends of the circulator (42) are respectively connected to the transmission fiber (43) and the sensing receiver (20). The other end of the transmission fiber (43) is also connected to the communication receiver (30). The vibrator vibrates the transmission fiber (43) near the communication receiver (30) to generate a Rayleigh scattering signal that returns to the sensing receiver (20) via the transmission fiber (43) and the circulator (42).

3. The distributed optical fiber sensing integrated system as described in claim 1, characterized in that, The transmitting end (10) includes a laser (11), a Mach-Zehnder modulator (12), a wavelength selection switch (13), a first optical amplifier (14), a phase modulator (15), a second optical amplifier (16), and a coupler (17) connected in sequence. The transmitting end (10) also includes an arbitrary waveform generator, which is used to generate an LFM electrical signal to the Mach-Zehnder modulator (12) and to generate a PSK electrical signal to the phase modulator (15). The other output terminal of the wavelength selection switch (13) is directly connected to the coupler (17).

4. The distributed optical fiber sensing integrated system as described in claim 3, characterized in that, The Mach-Zehnder modulator (12) outputs an LFM optical signal, and the phase modulator (15) outputs an LFM-PSK integrated sensing optical signal. The expression for the LFM optical signal is: ； in, For signal amplitude, For carrier frequency, For frequency modulation slope, The frequency variation period; the expression for the LFM-PSK integrated sensing optical signal is: ； in, , Indicates the PSK modulation order. Represents the PSK symbol.

5. The distributed optical fiber sensing integrated system as described in claim 1, characterized in that, The sensing receiver (20) includes a matched filter (23) and a first oscilloscope (24). One input of the matched filter (23) is connected to a circulator (42), and the other input is connected to a beam splitter (41). The output of the matched filter (23) is connected to the first oscilloscope (24).

6. The distributed optical fiber sensing integrated system as described in claim 5, characterized in that, The sensing receiver (20) further includes a third optical amplifier (21) and a first optical bandpass filter (22). The input end of the third optical amplifier (21) is connected to the circulator (42), and the output end is connected to the first optical bandpass filter (22). The output end of the first optical bandpass filter (22) is connected to the first oscilloscope (24).

7. The distributed optical fiber sensing integrated system as described in claim 1, characterized in that, The communication receiver (30) includes a fourth optical amplifier (31), a second optical bandpass filter (32), a coherent receiver (33), and a second oscilloscope (34), wherein: the input end of the fourth optical amplifier (31) is connected to the transmission optical fiber (43), and the output end is connected to the second optical bandpass filter (32); the output end of the second optical bandpass filter (32) is connected to the input end of the coherent receiver (33), and the output end of the coherent receiver (33) is connected to the second oscilloscope (34).

8. The distributed optical fiber sensing integrated system as described in claim 7, characterized in that, The communication receiver (30) also includes a polarizer (35) and an adjustable attenuator (36) connected to each other. The input end of the polarizer (35) is connected to the output end of the fourth optical amplifier (31), and the output end of the adjustable attenuator (36) is connected to the input end of the second optical bandpass filter (32).

9. The distributed optical fiber sensing integrated system as described in claim 7, characterized in that, The coherent receiver (33) is used to receive the LFM-PSK integrated sensing optical signal and the other LFM optical signal, use the other LFM optical signal as a reference light to realize heterodyne coherent detection, and remove the LFM optical signal used as a carrier in the LFM-PSK integrated sensing optical signal to obtain the PSK communication signal.

10. A method for implementing a distributed optical fiber sensing integrated system, characterized in that, include: The original service signal is modulated onto the phase to form a PSK communication signal; Two LFM optical signals with a wavelength gap are generated; Using one LFM optical signal as a carrier, embedding a PSK communication signal to generate an LFM-PSK integrated sensing optical signal; The LFM-PSK integrated optical signal and another LFM optical signal are coupled and sent to the transmission link unit (40). The sensing receiver (20) performs matched filtering on the received LFM-PSK integrated optical signal and the Rayleigh scattering signal returned by the transmission link unit (40) to detect and analyze the changes in the phase information of the transmission optical fiber (43), thereby distinguishing the vibration intensity and frequency of the transmission optical fiber (43). The communication receiver (30) performs heterodyne correlation detection on the received LFM-PSK integrated optical signal and the other LFM optical signal to restore the PSK communication signal, and then obtains the original service signal based on the PSK communication signal.

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