Scattering enhanced optical fiber based on rare earth doping and cable, system and method with scattering enhanced optical fiber

Abstract

The invention discloses a scattering enhanced optical fiber based on rare earth doping and a cable, system and method with the scattering enhanced optical fiber, and the optical fiber comprises a fiber core made of high-refractive-index quartz glass doped with rare earth elements; the cladding is made of a fluorine-doped quartz material, and the refractive index of the cladding is lower than that of the fiber core; a coating layer; and an outer protective layer. The scattering enhancement optical fiber is integrated in the cable, the laser source module, the detection module and the signal processing module are installed at the end of the cable, and the signal processing module is connected with the cloud platform or the remote monitoring terminal through the communication module, so that the cable has the functions of power transmission and optical fiber sensing monitoring. The temperature, strain distribution and alarm information of the cable can be displayed in real time, the system is suitable for high-temperature, high-humidity and corrosive environments, and a high-reliability, high-precision, long-life, long-distance, real-time and online full-life-cycle monitoring scheme is provided for the high-voltage cable.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic sensing technology, specifically relating to a rare-earth-doped scattering-enhancing optical fiber and cables, systems, and methods incorporating it. Background Technology

[0002] With the expansion of power systems and the development of smart grids, real-time monitoring of the operating status of power cables, as the core carrier of power transmission, is crucial for ensuring grid safety and preventing faults (such as localized overheating, mechanical damage, or insulation aging). Existing fiber optic distributed sensing technologies (such as Brillouin scattering and Raman scattering) have been widely applied in structural health monitoring and power cable temperature monitoring. However, traditional optical fibers are limited by the intensity of the light scattering signal, typically requiring high-power laser sources or long-term averaging to obtain data with a sufficient signal-to-noise ratio. Furthermore, the performance of traditional optical fibers may be unstable in harsh environments such as high temperature and high humidity, affecting practical application results.

[0003] In recent years, distributed optical fiber sensing (DOFS) technology has become an important direction for cable condition monitoring due to its advantages of high sensitivity, resistance to electromagnetic interference, and fully distributed measurement. However, its performance is still limited by the intensity and signal-to-noise ratio of the inherent scattered signal in the optical fiber. Current mainstream DOFS technologies (such as temperature sensing based on Raman scattering and temperature / strain dual-parameter sensing based on Brillouin scattering) rely on the weak scattering effect spontaneously generated in the optical fiber. However, the scattering coefficient of conventional silica optical fiber is low, resulting in significant signal attenuation during long-distance (>50km) monitoring, requiring complex signal amplification or high-power lasers, which increases system cost and instability. In addition, the cross-sensitivity of temperature and strain, noise interference in complex electromagnetic environments, and the material stability of optical fibers under extreme conditions remain bottlenecks restricting its engineering application. Summary of the Invention

[0004] To address the problems in the prior art, the present invention aims to provide a rare-earth-doped scattering-enhancing optical fiber, as well as cables, systems, and methods having the same.

[0005] To achieve the above objectives and technical effects, the technical solution adopted by this invention is as follows: A rare-earth-doped scattering-enhancing optical fiber includes, from the inside out, the following: The fiber core is made of high-refractive-index quartz glass doped with rare earth elements; The cladding is made of fluorine-doped quartz material, and the refractive index of the cladding is lower than that of the fiber core. Coating layer; Outer protective layer.

[0006] Furthermore, the doping concentration of the rare earth element is 0.5%-5%.

[0007] Furthermore, the rare earth element is selected from at least one of erbium, ytterbium, and thulium.

[0008] Furthermore, the coating layer is made of polyimide material with a thickness of 10-50µm.

[0009] Furthermore, the outer sheath is reinforced with Kevlar fibers, and the spiral winding density is 200-300 fibers / mm. 2 Tensile strength greater than 500MPa.

[0010] The present invention also discloses a cable comprising, from the outside to the inside, an outer sheath, a wrapping tape, a mechanical reinforcement layer, an electromagnetic interference protection layer, and a cable core, wherein the cable core comprises a rare earth doped scattering enhancement optical fiber as described above and several conductor units, and the gaps in the cable core are filled with a filling structure.

[0011] Furthermore, each conductor unit includes a conductor and an insulating layer extruded over the conductor.

[0012] This invention also discloses a real-time cable monitoring system, comprising: The laser source module is used to inject laser light into a rare-earth-doped scattering enhancement fiber as described above to excite Brillouin scattering and Raman scattering signals. The detection module is used to acquire and amplify the backscattered signal; The signal processing module, connected to the detection module, is used to analyze the temperature and strain data in the scattered signal uploaded by the detection module in real time, and generate real-time distributed monitoring results of temperature and strain along the cable. The communication module, connected to the signal processing module, is used to transmit the monitoring data uploaded by the signal processing module to the cloud platform or remote monitoring terminal in real time. Temperature signals are detected by the detection module and transmitted to the signal processing module for processing and analysis. The results are transmitted to the cloud platform or remote monitoring terminal via the communication module, and then to the alarm terminal to trigger a multi-level alarm mechanism to respond to abnormal events.

[0013] Furthermore, the performance indicators of the system include: Monitoring distance ≥ 50km, optical signal loss ≤ 0.2dB / km, scattering coefficient 0.2-0.3m -1 Temperature measurement accuracy is ±0.1℃, vibration monitoring accuracy is 0.1m / Hz; fault location accuracy is ≤10m, response time is ≤1s; temperature monitoring frequency is once per minute, strain monitoring frequency is 20 times per second, and strain measurement accuracy is ±10 microstrain.

[0014] This invention also discloses a method for using a real-time cable monitoring system, comprising the following steps: In application, a rare-earth-doped scattering-enhancing optical fiber as described above is twisted together with several conductor units, and then an anti-electromagnetic interference layer, a mechanical reinforcement layer, a wrapping tape, and an outer sheath are sequentially fabricated to form the required cable. A laser source module, a detection module, and a signal processing module are installed at the end of the cable. The signal processing module is connected to a cloud platform or remote monitoring terminal via a communication module. The detection module detects the temperature signal and transmits it to the signal processing module for processing and analysis. The results are transmitted to the cloud platform or remote monitoring terminal via the communication module, and then to the alarm terminal to trigger a multi-level alarm mechanism to respond to abnormal events.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention discloses a rare-earth-doped scattering-enhancing optical fiber, a cable incorporating it, a system, and a method. The scattering-enhancing optical fiber is integrated into a cable, and a laser source module, a detection module, and a signal processing module are installed at the cable end. The signal processing module is connected to a cloud platform or remote monitoring terminal via a communication module, enabling the cable to perform both power transmission and fiber optic sensing monitoring functions. It can achieve real-time data acquisition and analysis of temperature and vibration, and can display the cable's temperature, strain distribution, and alarm information in real time. The monitoring distance is ≥50km, the optical signal loss is ≤0.2dB / km, and the scattering coefficient is 0.2-0.3m. -1 With a temperature measurement accuracy of ±0.1℃, vibration monitoring accuracy of 0.1m / Hz, fault location accuracy of ≤10m, response time of ≤1s, and strain measurement accuracy of ±10 microstrain, it is suitable for high temperature, high humidity, and corrosive environments. It can solve the problems of weak scattered signals, severe signal attenuation over long distances, and poor environmental adaptability in traditional fiber optic sensing technology, break through the performance boundaries of existing DOFS technology, and provide a high-reliability, high-precision, long-life, long-distance, real-time online full life cycle monitoring solution for high-voltage cables. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a rare-earth-doped scattering-enhancing optical fiber according to the present invention. Figure 2 A schematic diagram illustrating the working principle of Brillouin scattering signal enhancement; Figure 3 A schematic diagram illustrating the working principle of Raman scattering signal enhancement; Figure 4 This is a schematic diagram of the structure of a cable according to the present invention; Figure 5 This is a schematic diagram of a real-time cable monitoring system according to the present invention. Detailed Implementation

[0017] The present invention will now be described in detail so that its advantages and features can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0018] The following provides a brief overview of one or more aspects to offer a basic understanding of them. This overview is not an exhaustive summary of all conceived aspects, nor is it intended to identify key or decisive elements of all aspects, nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form to prepare for the more detailed descriptions that follow.

[0019] like Figure 1 As shown, this invention discloses a rare-earth-doped scattering-enhancing optical fiber 5, comprising the following four layers, from the inside out: The fiber core 1, preferably with a refractive index of 1.448, is composed of a high-refractive-index quartz glass matrix uniformly doped with rare earth elements. The doping concentration of rare earth elements is 0.5%-5% (weight percentage), which is used to enhance the intensity of Brillouin scattering and Raman scattering signals. Cladding 2, preferably with a refractive index of 1.444, is made of fluorine-doped quartz material, and its refractive index is lower than that of the fiber core 1, so as to achieve total internal reflection transmission of light waves; The cladding layer 3 is made of high-temperature and corrosion-resistant polyimide material with a thickness of 10-50µm. It is cured at high temperature to improve the stability of optical fiber in high-temperature, high-humidity and corrosive environments. Outer sheath 4 is reinforced with Kevlar fiber, with a spiral winding density of 200-300 fibers / mm. 2 With a tensile strength greater than 500 MPa and a breaking elongation ≤ 2.5%, it is used to improve the tensile strength of optical fibers.

[0020] Rare earth elements are selected from erbium (Er 3+ ), Yb 3+ ), Thulium (Tm 3+ It contains at least one of the following rare earth elements: (1%-3%) or other rare earth elements, with a doping concentration preferably of 1%-3%.

[0021] This invention employs special rare-earth elements to dope the fiber core 1 to enhance the intensity of Brillouin and Raman scattering signals, and improve sensitivity and resolution. Compared to traditional optical fibers, the signal intensity is increased by approximately 3-5 times. Specifically, Brillouin scattering enhancement introduces local density fluctuations through rare-earth doping, significantly increasing the Brillouin frequency shift signal intensity for temperature and strain monitoring. Raman scattering enhancement is achieved by the energy level transition effects of rare-earth elements, which enhance the Raman frequency shift signal for high-sensitivity temperature detection. Furthermore, rare-earth doping in the optical fiber can significantly reduce signal noise introduced by nonlinear effects.

[0022] like Figure 2 As shown, the working principle of Brillouin scattering signal enhancement is that rare earth doping causes distortion of the high refractive index quartz glass network, increasing the acoustic phonon density, thereby indirectly leading to an extension of phonon lifetime and significantly improving the intensity of the Brillouin frequency shift signal.

[0023] like Figure 3 As shown, the working principle of Raman scattering signal enhancement is as follows: due to the doping of rare earth elements (erbium ions), the pump light causes the erbium ions to transition from the ground state to the excited state. The erbium ions then transition from the excited state to a metastable state through "non-radiative transitions" such as the release of phonons. Under the induction of the signal light, the metastable erbium ions undergo stimulated emission, producing photons with the same frequency and phase as the signal light, thereby amplifying the signal light.

[0024] like Figure 4 As shown, the present invention also discloses a cable, comprising, from the outside to the inside, an outer sheath 10 made of cross-linked polyethylene, a wrapping tape 9 formed of non-woven fabric, a mechanical reinforcement layer formed of aluminum-plastic composite tape, an anti-electromagnetic interference layer, and a cable core, wherein the cable core includes a rare earth-doped scattering-enhancing optical fiber 5 as described above and several conductor units, each conductor unit including a conductor 6 (preferably a copper conductor) and an insulation layer 7 extruded outside the conductor 6, and the gaps in the cable core are filled with a filling structure 8 formed of inert filling paste.

[0025] The cable of this invention combines power transmission and fiber optic sensing monitoring functions, and is suitable for high temperature, high humidity and corrosive environments, providing a highly reliable and long-life online monitoring solution for smart grid cable safety.

[0026] like Figure 5 As shown, the present invention also discloses a real-time cable monitoring system, comprising: The laser source module uses a narrow-linewidth tunable laser with a wavelength of 1550nm and a pulse width of 10-100ns to inject laser light into the aforementioned scattering enhancement fiber 5 and excite Brillouin scattering and Raman scattering signals. The detection module includes a high-sensitivity photodetector, an adaptive gain amplifier circuit, and a bandpass filter arranged sequentially along the signal transmission direction. The passband of the bandpass filter covers the signal frequency bands corresponding to the Brillouin frequency shift (10-12 GHz) and the Raman frequency shift (13-15 THz), and is used to collect and amplify the backscattered signal. The signal processing module is configured to use an embedded processor combined with a neural network-based machine learning algorithm to analyze the temperature and strain data in the scattered signal uploaded by the detection module in real time, and generate real-time distributed monitoring results of temperature and strain along the cable. The algorithm has self-learning and adaptive functions to eliminate the cross-sensitivity error between temperature and strain. The communication module supports wireless transmission (such as 4G / 5G, LoRa) and wired transmission (such as Ethernet interface), and is used to transmit the monitoring data uploaded by the signal processing module to the cloud platform or remote monitoring terminal in real time. Temperature signals are detected by a high-sensitivity photodetector in the detection module. The signals are amplified by an adaptive gain amplifier circuit and filtered by a bandpass filter before being transmitted to a signal processing module for processing and analysis. The results are transmitted to a cloud platform or remote monitoring terminal via a communication module, and then to an alarm terminal to trigger a multi-level alarm mechanism to respond to abnormal events.

[0027] The performance metrics of the above system include: Monitoring distance ≥ 50km, optical signal loss ≤ 0.2dB / km, scattering coefficient 0.2-0.3m -1 Temperature measurement accuracy is ±0.1℃, vibration monitoring accuracy reaches 0.1m / Hz; real-time data acquisition and analysis of temperature and vibration are achieved, fault location accuracy is ≤10m, response time is ≤1s; temperature monitoring frequency is once per minute, strain monitoring frequency is 20 times per second, and strain measurement accuracy is ±10 microstrain.

[0028] This invention also discloses a method for using a real-time cable monitoring system, comprising the following steps: In application, the aforementioned scattering-enhancing optical fiber 5 is twisted together with several conductor units, and then an anti-electromagnetic interference layer, a mechanical reinforcement layer, a wrapping tape 9, and an outer sheath 10 are sequentially fabricated. A laser source module, a detection module, and a signal processing module are installed at the cable end. The signal processing module is connected to a cloud platform or remote monitoring terminal through a communication module. The detection module detects the temperature signal and transmits it to the signal processing module for processing and analysis. The results are transmitted to the cloud platform or remote monitoring terminal through the communication module, and then to the alarm terminal to trigger a multi-level alarm mechanism to respond to abnormal events. This enables real-time display of the cable's temperature, strain distribution, and alarm information.

[0029] Any parts or structures not specifically described in this invention can be made using existing technologies or products, and will not be elaborated upon here.

[0030] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A rare-earth-doped, scattering-enhanced optical fiber, characterized in that, It comprises, from outside to inside, in sequence: a core made of high-refractive-index quartz glass doped with rare earth elements; a cladding made of fluorine-doped quartz material, the refractive index of which is lower than that of the core; a coating layer; an outer protective layer.

2. A rare-earth-doped scattering-enhanced optical fiber according to claim 1, wherein, The doping concentration of the rare earth elements is 0.5%-5%.

3. A rare-earth-doped scattering-enhanced optical fiber according to claim 1, wherein The rare earth elements are selected from at least one of erbium, ytterbium and thulium.

4. A rare-earth-doped scattering-enhanced optical fiber according to claim 1, wherein The coating layer is made of polyimide material and has a thickness of 10-50 µm.

5. A rare-earth-doped scattering-enhanced optical fiber according to claim 1, wherein The outer protective layer adopts a Kevlar fiber reinforced layer, and the spiral winding density is 200-300 roots / mm 2 The tensile strength is greater than 500 MPa.

6. A cable, characterized by It comprises, from outside to inside, in sequence, an outer sheath, a wrapping tape, a mechanical reinforcement layer, an electromagnetic interference resistant layer and a cable core, the cable core comprising a rare earth doped scattering enhanced optical fiber according to any one of claims 1-5 and a plurality of conductor units, and the gaps in the cable core are filled with a filling structure.

7. A cable according to claim 6, characterised in that Each conductor unit comprises a conductor and an insulating layer extruded outside the conductor.

8. A cable real-time monitoring system characterized by, It comprises: a laser source module for injecting laser into the rare earth doped scattering enhanced optical fiber according to any one of claims 1-5 to generate Brillouin scattering and Raman scattering signals; a detection module for collecting and amplifying the backscattering signals; a signal processing module connected to the detection module for real-time analysis of the temperature and strain data in the scattering signals uploaded by the detection module and generation of real-time distributed monitoring results of the temperature and strain along the cable; a communication module connected to the signal processing module for real-time transmission of the monitoring data uploaded by the signal processing module to a cloud platform or a remote monitoring terminal; The temperature signal is detected by the detection module and transmitted to the signal processing module for processing and analysis, and the results are transmitted to the cloud platform or the remote monitoring terminal through the communication module, and then to the alarm terminal, triggering a multi-level alarm mechanism to respond to abnormal events.

9. A cable real-time monitoring system according to claim 8, wherein, The performance indicators of the system include: The monitoring distance is greater than or equal to 50 km, the optical signal loss is less than or equal to 0.2 dB / km, and the scattering coefficient is 0.2-0.3 m -1 The temperature measurement accuracy is ±0.1℃, the vibration monitoring accuracy is 0.1 m / Hz, the fault positioning accuracy is less than or equal to 10 m, the response time is less than or equal to 1 s, the temperature monitoring frequency is once per minute, the strain monitoring frequency is 20 times per second, and the strain measurement accuracy is ±10 micro-strains.

10. A method of using a cable real-time monitoring system, characterized by, It comprises the following steps: In application, the rare earth doped scattering enhanced optical fiber according to any one of claims 1-5 is twisted together with a plurality of conductor units to form a cable, and then an electromagnetic interference resistant layer, a mechanical reinforcement layer, a wrapping tape and an outer sheath are sequentially made to form the required cable; The laser source module, the detection module and the signal processing module are installed at the end of the cable, the signal processing module is connected to the cloud platform or the remote monitoring terminal through the communication module, the temperature signal is detected by the detection module and transmitted to the signal processing module for processing and analysis, and the results are transmitted to the cloud platform or the remote monitoring terminal through the communication module, and then to the alarm terminal, triggering a multi-level alarm mechanism to respond to abnormal events.

Images