A distributed raman temperature sensing and communication cooperation method and system based on mode division multiplexing

Abstract

This invention relates to a distributed Raman temperature sensing and communication coordination method and system based on mode division multiplexing (MDM). Utilizing a two-mode optical fiber as a common transmission medium, the communication optical signal is loaded into a first spatial mode, and the sensing pump light is loaded into a second spatial mode, achieving coordinated operation of communication and distributed temperature monitoring within the same optical fiber. The pump light propagates in the two-mode fiber, generating a backscattered Raman signal. Anti-Stokes and Stokes components are extracted through mode demultiplexing and spectral separation, and the distributed temperature along the fiber is calculated based on their intensity ratio. This invention effectively reduces inter-mode crosstalk and improves the Raman detection signal-to-noise ratio and system stability by isolating the communication optical signal and the sensing pump light in spatial modes. It achieves efficient coordination of communication and distributed temperature sensing without increasing fiber resource consumption or additional wavelength resources, offering advantages such as simple structure, high resource utilization, and strong anti-interference capability.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber sensing and optical fiber communication technology, specifically relating to a distributed Raman temperature sensing and communication collaborative method and system based on mode division multiplexing. Background Technology

[0002] With the rapid development of infrastructure such as power systems, integrated utility tunnels, and oil and gas pipelines, higher demands are being placed on real-time temperature monitoring of the environment along these routes and the synchronous transmission of communication information. Currently, existing temperature sensing systems and communication systems are mostly deployed separately using independent optical fibers, or achieve coordination through wavelength division multiplexing in the same optical fiber. However, these solutions generally suffer from problems such as high optical fiber resource consumption, complex system structure, and high construction and maintenance costs, making it difficult to meet the needs of large-scale, low-cost deployment.

[0003] To improve the utilization rate of optical fiber resources, solutions that integrate communication and sensing within the same optical fiber have been proposed in recent years. Among these solutions, wavelength division multiplexing (WDM) technology achieves a certain degree of synergy by allocating different wavelengths for sensing and communication. However, such solutions require additional communication band resources, place high demands on the light source, filters, and wavelength stability of the system, and are prone to crosstalk in long-distance or complex environments, limiting their engineering applications.

[0004] The development of few-mode fiber and mode division multiplexing (MDM) technology has provided new ideas for communication and sensing synergy. By using different spatial modes to carry different signals in the same few-mode fiber, signal isolation can be achieved in the spatial dimension. However, existing technologies mostly focus on the synergy of vibration or acoustic sensing and communication, with limited research on distributed temperature sensing and communication synergy based on Raman scattering. There is still a lack of a simple, low-interference, and engineering-applicable mode division multiplexing sensing and communication synergy method and system. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings and deficiencies of existing technologies by providing a distributed Raman temperature sensing and communication coordination method and system based on mode division multiplexing. By utilizing different spatial modes in a few-mode fiber to carry communication signals and Raman temperature sensing signals respectively, communication and sensing are separated and coordinated in the spatial dimension. Distributed temperature measurement is achieved without significantly affecting communication quality, thereby improving the utilization efficiency of optical fiber resources, reducing system construction costs, and enhancing the overall operational stability of the system.

[0006] The technical problem solved by this invention is achieved through the following technical solution: A distributed Raman temperature sensing and communication collaborative system based on mode division multiplexing is characterized by comprising a narrow linewidth laser, a beam splitting module, a communication modulation module, a Raman sensing module, a coupler, a circulator, a mode multiplexer / demultiplexer, a few-mode fiber, a mode demultiplexer, a communication receiving module, a data processing unit, a Raman filtering module, and a temperature demodulation unit. The narrow-linewidth laser outputs a continuous optical signal, which is split into a communication branch and a sensing branch by a beam splitter. The optical signal of the communication branch enters the communication modulation module for data modulation to form a communication optical signal, and the optical signal of the sensing branch enters the Raman sensing module to form a sensing pump light. The communication optical signal and the sensing pump light are combined by a coupler and then injected into different spatial modes of a few-mode fiber through a circulator, a mode multiplexer, and a mode demultiplexer. The communication optical signal undergoes photoelectric conversion and data demodulation by the communication receiving module, and data recovery and system control are completed by the data processing unit; the sensing pump light propagates in the few-mode fiber to generate a backscattered Raman signal, which contains an anti-Stokes component and a Stokes component; the backscattered Raman signal is transmitted back through a circulator and undergoes mode separation by a mode demultiplexer before entering the Raman filtering module for spectral separation, and then sent to the temperature demodulation unit for temperature distribution calculation.

[0007] The data processing unit is used to dynamically adjust the splitting ratio or pump power according to the communication error rate and the intensity of the backscattered Raman signal, so as to achieve a balance between communication performance and sensing accuracy.

[0008] A distributed Raman temperature sensing and communication collaborative method based on mode division multiplexing is characterized by: employing the aforementioned collaborative system, the method utilizes a few-mode fiber as a common transmission medium for sensing and communication, and loads the communication optical signal and the sensing pump light into different spatial modes of the few-mode fiber respectively; the sensing pump light propagates in the few-mode fiber to generate a backscattered Raman signal, which is spatially isolated from the communication optical signal; the backscattered Raman signal is extracted by a mode demultiplexer, and the intensity ratio of its anti-Stokes component and Stokes component is calculated to obtain distributed temperature information along the few-mode fiber, thereby realizing the collaborative enhancement and resource reuse of communication and sensing.

[0009] Furthermore, the communication optical signal Pcom(t) is a continuous optical modulation signal, injected into the first spatial mode of the at least-mode fiber via a mode multiplexer and transmitted along the forward propagation direction in the fiber to the far end for data transmission; the sensing pump light P pump ( t The light is a pulsed light, which is injected into the second spatial mode of a few-mode fiber via a mode multiplexer and generates Stokes and anti-Stokes Raman scattered light during propagation along the fiber. The backscattered component of the Raman scattered light propagates back along the near-end direction, is separated by the mode demultiplexer, and then enters the temperature demodulation unit. The backscattered Raman components generated at different positions along the optical fiber are arranged in the time domain according to the propagation distance, thus forming a beam of backRaman signals that corresponds one-to-one with the spatial position. P Raman ( t The temperature demodulation unit calculates the intensity ratio of the anti-Stokes Raman scattered light to the Stokes Raman scattered light to achieve distributed temperature inversion along the few-mode fiber. The sensing pump light P pump ( t During propagation, an inherent backscattering Rayleigh component P is generated. Ray ( t Furthermore, the interaction between the pump light and the vibrations of fiber molecules also generates a Stokes Raman scattering component P. S ( t ) and the anti-Stokes Raman scattering component P AS ( t ); At the receiving end, the backscattered Raman light from the second spatial mode in the few-mode fiber is superimposed with the inherent Rayleigh backscattered light to form the backscattered sensing signal. P Raman ( t ): P Raman ( t )=P AS ( t )+P S ( t )+P Ray ( t (1); The P Raman ( t The effective detection signal contains anti-Stokes component information related to the local temperature of the optical fiber. The corresponding spatial mode signal is extracted by the mode demultiplexing device, thereby effectively extracting the temperature information. Raman backscattered signal P Raman ( t During the propagation and return process from the far end to the near end, the communication optical signal branch transmits the communication optical signal. P com ( t Propagating from near to far, the communication optical signal is loaded in the first spatial mode, while the sensing pump light is loaded in the second spatial mode, achieving mode isolation between the two in the spatial dimension; when the communication signal and the sensing signal are at a certain position in the optical fiber... zWhen they coexist, their mutual influence is mainly determined by the mode coupling coefficient; During Raman scattering, a portion of the energy of the sensing pump light is transferred to the anti-Stokes scattered light, the intensity of which follows an approximately exponential relationship with the local temperature of the optical fiber: P AS ( t ) / P S ( t )∝exp(- hν / kT ( z )) (2); in: h Let be Planck's constant. ν The vibration frequency, k Boltzmann's constant, T ( z () represents the location z Temperature at that location; The backscattered Raman signal carrying temperature information continues to be output from the incident end. The returned light signal is input into the photodetector for photoelectric conversion through the mode demultiplexer and circulator to obtain the time-domain electrical signal. The Raman scattering response at each spatial location can be obtained by corresponding the signals arriving at the detector at different times with different spatial locations on the optical fiber. Subsequently, the system calculates the intensity ratio of the anti-Stokes and Stokes scattering signals to obtain the temperature distribution spectrum. Through system calibration, the correspondence between temperature and scattering intensity ratio is established, realizing distributed temperature measurement.

[0010] The advantages and beneficial effects of this invention are as follows: 1. This invention utilizes different spatial modes in a few-mode optical fiber to carry communication signals and Raman temperature sensing signals respectively, thereby achieving spatial separation and coordinated transmission of communication and sensing. This enables distributed temperature measurement without significantly affecting communication quality, thereby improving the utilization efficiency of optical fiber resources, reducing system construction costs, and enhancing the overall operational stability of the system.

[0011] 2. This invention utilizes the characteristics of low inter-mode coupling and relatively independent mode transmission in few-mode optical fibers to ensure that the Raman backscattered signal is mainly retained in its excitation mode, thereby reducing interference to the communication mode. At the same time, through reasonable power control and mode allocation, the signal stability of temperature measurement and system coordination efficiency are improved.

[0012] 3. This invention introduces dual-mode optical fiber and mode-division multiplexing technology into the Raman distributed temperature sensing system, carrying communication signals through different spatial modes. P com ( t ) and sensing signals P Raman ( tThis enables the coordinated operation of communication and temperature monitoring.

[0013] 4. This invention reduces pattern crosstalk by isolating communication signals and sensing signals in the spatial dimension; simultaneously, it selectively extracts signals from the second spatial pattern. P Raman ( t This improves the signal-to-noise ratio of temperature detection and enables efficient utilization of two-mode fiber resources. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the collaborative system of the present invention; Figure 2 This is a schematic diagram of the spatial modes and signal propagation direction distribution of the dual-mode fiber of the present invention; Figure 3 This is a schematic diagram of the temperature demodulation process of the present invention.

[0015] Explanation of reference numerals in the attached figures 1. Narrow linewidth laser; 2. Beam splitting module; 3. Communication modulation module; 4. Raman sensing module; 5. Coupler; 6. Circulator; 7. Mode multiplexer / demultiplexer; 8. Dual-mode fiber; 9. Mode demultiplexer; 10. Communication receiving module; 11. Data processing unit; 12. Raman filter module; 13. Temperature demodulation unit. Detailed Implementation

[0016] The present invention will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0017] This invention employs dual-mode optical fiber as the transmission and sensing medium. Mode division multiplexing is used within the same optical fiber to achieve coordinated transmission of communication signals and Raman temperature sensing signals. The system structure is as follows: Figure 1 As shown.

[0018] This invention leverages the spatial mode isolation characteristics of dual-mode optical fiber to load communication optical signals into a first spatial mode (LP). 01 ), loading the sensing pump light into the second spatial mode (LP) 11 This enables signal separation in the spatial dimension, thereby achieving distributed temperature measurement without affecting communication performance.

[0019] like Figure 1As shown, the mode division multiplexing sensing and communication cooperative system based on dual-mode fiber of the present invention includes: a narrow linewidth laser (1), a beam splitting module (2), a communication modulation module (3), a Raman sensing module (4), a coupler (5), a circulator (6), a mode multiplexer / demultiplexer (7), a dual-mode fiber (8), a mode demultiplexer (9), a communication receiving module (10), a data processing unit (11), a Raman filtering module (12), and a temperature demodulation unit (13).

[0020] The output center frequency of the narrow linewidth laser (1) is f The continuous optical signal of 0 is split into two paths by the beam splitter (2). One path enters the communication modulation module (3) for data modulation to form the communication optical signal P. com (t); another path enters the Raman sensing module (4) for pulse modulation to form the sensing pump light P. pump (t).

[0021] The communication optical signal is a continuous optical modulation signal, which is injected into the LP of the two-mode fiber via a mode multiplexer. 01 The mode is transmitted in the forward propagation direction in the optical fiber to the remote end to realize the data transmission function.

[0022] The sensing pump light is pulsed light, injected into the LP of the two-mode fiber via a mode multiplexer. 11 In this mode, as the pump light propagates along the optical fiber, Stokes and anti-Stokes Raman scattered light are generated in the fiber, and the intensity of the anti-Stokes Raman scattered light is related to the local temperature of the optical fiber.

[0023] The Raman scattered light belongs to LP 11 The backscattered components of the mode propagate back along the near-end direction, are separated by the mode demultiplexer, and then enter the temperature demodulation unit. The backscattered Raman components generated at different positions along the fiber are arranged in the time domain according to the propagation distance, thus forming a backscattered Raman signal that corresponds one-to-one with the spatial position. P Raman ( t The temperature demodulation unit calculates the intensity ratio of the anti-Stokes Raman scattered light to the Stokes Raman scattered light to achieve distributed temperature inversion along the two-mode fiber.

[0024] Meanwhile, since the communication signal is mainly loaded onto the LP 01 The mode, while Raman pump light is loaded onto LP 02 Under reasonable power configuration, the impact of Raman backscattering on the communication mode is limited, thereby achieving stable distributed temperature monitoring while ensuring that the communication bit error rate meets the requirements.

[0025] The communication optical signal adopts on-off keying modulation or orthogonal frequency division multiplexing modulation; the pulse width of the sensing pump light is set according to the required spatial resolution; the communication optical power and the pump light power are coordinated and adjusted by the control module to achieve a balance and optimization between communication performance and temperature measurement signal-to-noise ratio.

[0026] The communication optical signal P com After being combined with the pump light Ppump(t) via coupler (5), the mode multiplexer / demultiplexer (7) is injected from the same port through circulator (6) and loaded into different spatial modes of the dual-mode fiber (8), where the communication optical signal is loaded in the first spatial mode and the sensing pump light is loaded in the second spatial mode, thereby realizing mode division multiplexing transmission in the dual-mode fiber (8).

[0027] During propagation in a two-mode fiber (8), the pump light P pump (t) The backscattered signal P is generated by the interaction of fiber molecular vibrations. Raman (t), the signal contains the anti-Stokes Raman scattering component P AS (t), Stokes Raman scattering component P S (t) and the inherent Rayleigh scattering component P Ray (t), the backscattered signal returns along the optical fiber to the near end, and after spatial mode separation by the mode multiplexer / demultiplexer (7) and the mode demultiplexer (9), it enters different processing paths respectively.

[0028] In the communication path, the communication signal undergoes photoelectric conversion and data demodulation by the communication receiving module (10), and data recovery and system control are completed by the data processing unit (11); in the sensing path, the Raman backscattered signal undergoes spectral separation by the Raman filtering module (12) to extract P. AS (t) and P S (t) component, and suppress P Ray (t) Rayleigh component, then enters the temperature demodulation unit (13), and calculates P AS (t) / P S (t) The intensity ratio is used to obtain the distributed temperature T(z) along the two-mode fiber (8). Due to the communication signal P com (t) and sensing pump light P pump (t) are loaded into different spatial modes of the dual-mode fiber (8), and the coupling coefficient between modes is small, thereby realizing spatial isolation and collaborative operation of communication and Raman temperature sensing, and realizing distributed temperature monitoring while ensuring communication performance.

[0029] In the distributed Raman measurement system using ordinary single-mode fiber, the acquisition of temperature information essentially relies on the anti-Stokes Raman scattering component P generated by the pump light at a local location in the fiber. AS (z). Since Raman scattering is a spontaneous scattering process with a small scattering cross section and weak backscattered light power, the fundamental factor affecting the signal-to-noise ratio of temperature measurement in single-mode fiber is the intensity of backscattered light.

[0030] In traditional single-mode optical fibers, the backscattered signal is mainly the inherent Rayleigh scattering component P. Ray (z) and Raman scattering component P AS (z), P S (z). Due to P Ray (z) and P AS (z) Compared to the large differences in intensity, the system usually needs to improve the detection accuracy by averaging over a long period of time or by increasing the pump power, but this will increase the risk of system noise or nonlinearity.

[0031] This invention introduces dual-mode fiber and employs a mode-division multiplexing structure to enable the sensing pump light P... pump (t) is loaded into the second spatial mode, in which a relatively independent scattering channel is formed, thereby realizing spatial enhancement and mode-selective extraction of the backscattered signal.

[0032] like Figure 2 As shown, the dual-mode fiber is configured with a near end (z=0) and a far end (z=L) along its length. The system uses mode-division multiplexing to simultaneously carry communication and sensing signals in the same dual-mode fiber: Communication signal P com (t) is loaded into the fundamental mode LP 01 The information is transmitted from the near end to the far end in a forward direction; Raman sensing pump light P pump (t) is loaded into the higher-order mode LP 11 Similarly, propagating from near to far, it excites backscattered signals at any location in the optical fiber, where the backscattered Raman signal P... Raman (t) is mainly retained in LP 11 The sensor transmits the data back from the far end to the near end in the reverse direction, realizing the back-transmission detection of the sensing link; the communication channel and the Raman sensing channel are isolated in the spatial dimension, thereby reducing crosstalk and ensuring the stability of cooperative operation.

[0033] like Figure 3 As shown, the temperature demodulation process first processes the returned backscattered signal P Raman (t) is used for data acquisition, and then LP is extracted through mode demultiplexing / mode selection steps. 11 The sensing component in the mode avoids interference from the communication mode; subsequently, the signal is spectrally separated in the Raman filtering module to obtain the anti-Stokes component P.AS (t) and Stokes component P S Based on this, the intensity ratio is calculated, and the temperature inversion is completed by combining the calibration curve or model fitting. Finally, the distributed temperature results along the optical fiber are output, realizing distributed real-time monitoring of the temperature along the dual-mode optical fiber.

[0034] The dual-mode fiber described in this invention is not limited to a fixed-mode structure; the mode multiplexer and demultiplexer can employ photonic lanterns or other equivalent mode coupling structures. In addition to direct detection, this invention can also employ heterodyne or self-heterodyne detection structures to achieve Raman signal acquisition and demodulation.

[0035] Although embodiments and drawings of the present invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A distributed Raman temperature sensing and communication cooperative system based on module division multiplexing, characterized in that: It includes a narrow linewidth laser (1), a beam splitting module (2), a communication modulation module (3), a Raman sensing module (4), a coupler (5), a circulator (6), a mode multiplexer / demultiplexer (7), a few-mode fiber (8), a mode demultiplexer (9), a communication receiving module (10), a data processing unit (11), a Raman filtering module (12), and a temperature demodulation unit (13). The narrow linewidth laser (1) outputs a continuous optical signal, which is split into a communication branch and a sensing branch by a beam splitter (2). The optical signal of the communication branch enters the communication modulation module (3) for data modulation to form a communication optical signal. The optical signal of the sensing branch enters the Raman sensing module (4) to form a sensing pump light. The communication optical signal and the sensing pump light are combined by a coupler (5) and then injected into different spatial modes of a few-mode fiber through a circulator (6), a mode multiplexer (7), and a mode demultiplexer (9). The communication optical signal is converted into photoelectric signals and demodulated by a communication receiving module (10), and the data recovery and system control are completed by a data processing unit (11). The sensing pump light propagates in the few-mode fiber and generates a backscattered Raman signal, which contains an anti-Stokes component and a Stokes component. The backscattered Raman signal is transmitted back through a circulator (6) and separated by a mode demultiplexer (7) before entering a Raman filter module (12) for spectral separation. After separation, it is sent to a temperature demodulation unit (13) for temperature distribution calculation. The data processing unit (11) is used to dynamically adjust the splitting ratio or pump light power according to the communication bit error rate and the intensity of the backscattered Raman signal to achieve a balance between communication performance and sensing accuracy.

2. A distributed Raman temperature sensing and communication coordination method based on module division multiplexing, characterized in that: The collaborative system described in claim 1 utilizes a few-mode fiber as a common transmission medium for sensing and communication, loading the communication optical signal and the sensing pump light into different spatial modes of the few-mode fiber, respectively. The sensing pump light propagates in the few-mode fiber, generating a backscattered Raman signal, which is spatially isolated from the communication optical signal. The backscattered Raman signal is extracted by a mode demultiplexer, and the intensity ratio of its anti-Stokes component to its Stokes component is calculated to obtain distributed temperature information along the few-mode fiber, thereby achieving collaborative enhancement and resource reuse of communication and sensing.

3. The distributed Raman temperature sensing and communication coordination method based on module division multiplexing according to claim 1, characterized in that: The communication optical signal Pcom(t) is a continuous optical modulation signal, which is injected into the first spatial mode of the at least-mode fiber via a mode multiplexer and transmitted to the far end along the forward propagation direction in the fiber to realize the data transmission function; the sensing pump light P pump ( t The light is a pulsed light, which is injected into the second spatial mode of a few-mode fiber via a mode multiplexer and generates Stokes and anti-Stokes Raman scattered light during propagation along the fiber. The backscattered component of the Raman scattered light propagates back along the near-end direction, and after being separated by the mode demultiplexer, it enters the temperature demodulation unit. The backscattered Raman components generated at different locations along the optical fiber are arranged in the time domain according to the propagation distance, thus forming a backscattered Raman signal that corresponds one-to-one with the spatial location. P Raman ( t The temperature demodulation unit calculates the intensity ratio of the anti-Stokes Raman scattered light to the Stokes Raman scattered light to achieve distributed temperature inversion along the few-mode fiber. The sensing pump light P pump ( t During propagation, an inherent backscattering Rayleigh component P is generated. Ray ( t Furthermore, the interaction between the pump light and the vibrations of fiber molecules also generates a Stokes Raman scattering component P. S ( t ) and the anti-Stokes Raman scattering component P AS ( t ); At the receiving end, the backscattered Raman light from the second spatial mode in the few-mode fiber is superimposed with the inherent Rayleigh backscattered light to form the backscattered sensing signal. P Raman ( t ): P Raman ( t )=P AS ( t )+P S ( t )+P Ray ( t ) (1); The P Raman ( t The effective detection signal contains anti-Stokes component information related to the local temperature of the optical fiber. The corresponding spatial mode signal is extracted by the mode demultiplexing device, thereby effectively extracting the temperature information. Raman backscattered signal P Raman ( t During the propagation and return process from the far end to the near end, the communication optical signal branch transmits the communication optical signal. P com ( t Propagating from near to far, the communication optical signal is loaded in the first spatial mode, while the sensing pump light is loaded in the second spatial mode, achieving mode isolation between the two in the spatial dimension; when the communication signal and the sensing signal are at a certain position in the optical fiber... z When they coexist, their mutual influence is mainly determined by the mode coupling coefficient; During Raman scattering, a portion of the energy of the sensing pump light is transferred to the anti-Stokes scattered light, the intensity of which follows an approximately exponential relationship with the local temperature of the optical fiber: P AS ( t ) / P S ( t )∝exp(- hν / kT ( z )) (2); in: h Let be Planck's constant. ν The vibration frequency, k Boltzmann's constant, T ( z () represents the location z Temperature at that location; The backscattered Raman signal carrying temperature information continues to be output from the incident end. The returned light signal is input into the photodetector for photoelectric conversion through the mode demultiplexer and circulator to obtain the time-domain electrical signal. The Raman scattering response at each spatial location can be obtained by corresponding the signals arriving at the detector at different times with different spatial locations on the optical fiber. Subsequently, the system calculates the intensity ratio of the anti-Stokes and Stokes scattering signals to obtain the temperature distribution spectrum. Through system calibration, the correspondence between temperature and scattering intensity ratio is established, realizing distributed temperature measurement.

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