CN112038878B - Distributed fiber optic acoustic wave sensing system based on remote pump amplifier and Raman amplifier - Google Patents

Abstract

The invention discloses a distributed optical fiber acoustic wave sensing system based on a far pump amplifier and a Raman amplifier, which comprises: a vibration detection unit providing signal light; a first laser source providing a first pump light; the head end of the first sensing optical fiber receives the beam combining light of the first pump light and the signal light; a far pump amplifier module connected to a tail end of the first sensing fiber, the far pump amplifier including an erbium-doped fiber for amplifying the signal light in an input; a second sensing fiber having a head end receiving the output of the far pump amplifier module. The invention effectively increases the sensing distance of the system.

Description

Distributed fiber optic acoustic wave sensing system based on remote pump amplifier and Raman amplifier

technical field

The invention belongs to the field of optical fiber sensing, in particular to a distributed optical fiber acoustic wave sensing system based on a remote pump amplifier and a Raman amplifier.

Background technique

The Distributed Fiber Acoustic Sensing System (DAS for short) transmits pulsed laser light into the sensing fiber, and receives the spontaneous back-Rayleigh scattered coherent light in the fiber at the light injection end. The vibration information can be obtained by sensing the external disturbance received by the fiber by detecting the coherent light intensity change caused by external vibration. This technical method has high sensitivity, fast measurement response speed, and can realize long-distance and fully distributed sensing. It is suitable for monitoring the micro-disturbance time. .

In the actual engineering application of the fiber optic acoustic wave sensing system, the signal light needs to be amplified because the actual loss of the fiber optic cable is relatively large, or the length of the fiber optic cable exceeds the farthest distance that the DAS can reach. The sensing measurement is generally carried out by using the already laid optical cable. The length of the optical cable in some engineering sites is relatively long, which exceeds the maximum length that can be measured by DAS. Or even if the length of the optical cable is within the maximum length that can be measured by DAS, the transmission loss of the optical cable is relatively large due to various reasons.

The Brillouin amplifier is also a distributed amplifier, but the bandwidth of the Brillouin amplifier is very narrow and is greatly affected by temperature, which affects the amplification of the transmitted signal, and is not suitable for use in DAS sensing systems.

SUMMARY OF THE INVENTION

In view of the problems existing in the prior art, the present invention provides a distributed optical fiber acoustic wave sensing system based on a remote pump amplifier and a Raman amplifier. Raman amplifiers are used in fiber optic acoustic wave sensing systems. These two technologies can greatly increase the capacity of existing fiber optic systems, increase the detection distance of sensing systems, and reduce system costs, so they are widely used in long-distance fiber optic communication systems, fiber optic At the same time, these two technologies are applied to the optical fiber acoustic wave sensing system to improve the sensing distance of the system.

To achieve the above object, the present invention adopts the following technical solutions:

A distributed optical fiber acoustic wave sensing system based on a remote pump amplifier and a Raman amplifier, the optical fiber acoustic wave sensing system includes: a vibration detection unit, providing signal light; a first laser source, providing a first pump light; a first sensor an optical fiber, the head end of the first sensing fiber receives the combined beam of the first pump light and the signal light; a remote pump amplifier module, the remote pump amplifier module and the tail end of the first sensing fiber The remote pump amplifier includes an erbium-doped fiber for amplifying the signal light in the input; a second sensing fiber, the head end of the second sensing fiber receives the output of the remote pump amplifier module.

Preferably, the optical fiber acoustic wave sensing system includes: a second laser source, which provides a second pump light and is input to the second sensing fiber. The first pump light is 1480 nm, and the second pump light is 1455 nm. The remote pump amplifier includes a wavelength division multiplexer for separating the first pump light and signal light, an attenuator for adjusting the separated first pump light, and the adjusted first pump light and Another wavelength division multiplexer that combines the signal light again, and the first pump light and the signal light after the recombination are input into the erbium-doped fiber.

Preferably, the first pump light is 1455 nm. The optical fiber acoustic wave sensing system includes: a third laser source, which provides a third pump light, which is used for recombining with the combining light and then inputting the erbium-doped optical fiber. The third pump light is 1480 nm.

Preferably, a first circulator is connected between the first sensing fiber and the remote pump amplifier module, the first end of the first circulator is connected to the tail end of the first sensing fiber, and the first circulator is connected to the tail end of the first sensing fiber. The second end of a circulator is connected to the input end of the remote pump amplifier, the first circulator further includes a third end, and the incident light at the first end of the first circulator is derived from the second end thereof, Incident light at the third end of the first circulator is directed away from the first end thereof.

Preferably, a second circulator is connected between the second sensing fiber and the remote pump amplifier module, the first end of the second circulator is connected to the output end of the remote pump amplifier, and the second ring The second end of the circulator is connected to the head end of the second sensing fiber, the third end of the second circulator is connected to the third end of the first circulator, and the first The incident light of the end is led out from the second end, and the incident light of the second end of the second circulator is led out from the third end.

Compared with the prior art, the beneficial effects of the present invention are as follows: the main factor restricting the large-scale application of high-speed and ultra-long-distance communication systems is the optical signal-to-noise ratio (Optical Signal Noise Ratio, abbreviated as: OSNR). The system OSNR has unique advantages. Its low noise figure can significantly reduce the degradation speed of the optical signal-to-noise ratio in the optical fiber communication system, which is of great significance for extending the transmission distance, expanding the span distance, and reducing the system cost;

The remote pump amplifier module is an amplifier placed in the system circuit, which is different from the preamplifier and power amplifier used at the receiving end and the transmitting end; the so-called "remote pump" refers to the distance between the pump source of the amplifier as the gain medium. Erbium-doped fiber has a relatively long distance, so that the pump source can be placed at the transmitter or receiver. The far-pump erbium-doped fiber amplifier uses a 1480 nm laser as the pump source, which has higher efficiency than the 980-nm pump source, and the transmission loss of 1480 nm light in the line is much lower than that of 980 nm; the far-pump erbium-doped fiber amplifier can achieve continuous output, with High gain, low noise figure, extremely wide gain bandwidth and other excellent characteristics;

The Raman fiber amplifier uses a high-performance high-power 1455nm pump laser to achieve continuous output, uses the transmission fiber as the gain medium, and uses the energy transfer between the incident pump light and the medium molecules, that is, the amplification of weak signal light by the stimulated Raman scattering process. It is a fiber-based full-band amplifier and a distributed amplifier; it has excellent characteristics such as high gain, low noise figure, and extremely wide gain bandwidth;

After using the remote pump amplifier module and Raman amplifier, the transmission distance of the system is extended to 100km, thereby effectively increasing the sensing distance of the system.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative efforts.

FIG. 1 is a waterfall diagram of a DAS device in the prior art.

FIG. 2 is a schematic diagram of the first embodiment.

FIG. 3 is a 100km original graph of the first embodiment.

FIG. 4 is a 100km waterfall diagram of the first embodiment.

FIG. 5 is a waterfall diagram of the first 50km of the first embodiment.

FIG. 6 is a waterfall diagram of the last 50 km of the first embodiment.

FIG. 7 is a schematic diagram of the second embodiment.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

In the description of the present invention, it should be understood that the terms "portrait", "horizontal", "upper", "lower", "front", "rear", "left", "right", "vertical", The orientations or positional relationships indicated by "horizontal", "top", "bottom", "inside", "outside", etc. are based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than An indication or implication that the referred device or element must have a particular orientation, be constructed and operate in a particular orientation, is not to be construed as a limitation of the invention.

Example 1

As shown in Figure 2-6, the distributed optical fiber acoustic wave sensing system based on remote pump amplifiers and Raman amplifiers, the optical fiber acoustic wave sensing system includes: a vibration detection unit 1, which provides signal light; a first laser source 2, which provides a first pump light; the first sensing fiber 3, the head end of the first sensing fiber 3 receives the combined beam of the first pump light and the signal light; the remote pump amplifier module 4, the remote pump amplifier module 4 and the first sensor The end of the optical fiber 3 is connected, and the remote pump amplifier includes an erbium-doped fiber 5 for amplifying the signal light in the input; the second sensing fiber 6, the head end of the second sensing fiber 6 receives the output of the remote pump amplifier module 4 .

The fiber optic acoustic wave sensing system includes: a second laser source 7 , which provides a second pump light and is input to the second sensing fiber 6 .

The first pump light is 1480 nm, and the second pump light is 1455 nm.

The far pump amplifier module 4 includes a wavelength division multiplexer 8 that separates the first pump light and the signal light, and an attenuator 9 that adjusts the separated first pump light, and the adjusted first pump light and Another wavelength division multiplexer 8 that combines the signal light again, and the first pump light and the signal light after the recombination are input into the erbium-doped fiber 5 .

A first circulator 11 is connected between the first sensing fiber 3 and the remote pump amplifier module 4 , the first end of the first circulator 11 is connected with the tail end of the first sensing fiber 3 , and the first circulator 11 is connected to the tail end of the first sensing fiber 3 . The two ends are connected to the input end of the remote pump amplifier. The first circulator 11 further includes a third end. The incident light at the first end of the first circulator 11 is led out from the second end. Incident light exits from its first end. The first circulator 11 can also be arranged in the wavelength division multiplexer 8 that separates the first pump light and the signal light and another wavelength division multiplexer that combines the adjusted first pump light and the signal light again. 8 in between.

A second circulator 12 is connected between the second sensing fiber 6 and the remote pump amplifier module 4, the first end of the second circulator 12 is connected to the output end of the remote pump amplifier, and the second end of the second circulator 12 is connected to the output end of the remote pump amplifier. The head end of the second sensing fiber 6 is connected, the third end of the second circulator 12 is connected to the third end of the first circulator 11, the incident light of the first end of the second circulator 12 is led out from the second end, Incident light at the second end of the second circulator 12 is led out from the third end.

The length of the detection fiber in the system is 100km, which consists of two 50km optical fibers. The working principle of the system is: the 1480nm laser at one end of the vibration detection unit is used as a remote pump source, and the light output by the pump source passes through the isolator (the function of the isolator: to prevent the reflected light from the end face of the fiber from damaging the laser ), and the 1550nm signal light output from the vibration detection unit enters the wavelength division multiplexer 1 at the same time, and then enters the 50km detection fiber. The devices in the dotted box behind the 50km fiber and the erbium-doped fiber constitute a far-pump amplifier module. The light output by the module enters the second section of 50km detection fiber after passing through the second circulator. A 1455nm laser is used as a Raman pump source and is connected to the end of the second 50km fiber.

The fiber optic circulator works in the 1550nm band and has 3 ports in total. The working principle of the circulator is as follows: the light input to the port of the first circulator is directly output to port 2, and the light input to the port of the second circulator is directly output to port 3.

The working process of the second circulator is as follows: the signal light output by the remote pump amplifier enters port 1 of the second circulator and directly enters port 2, and then enters the second 50km fiber. The spontaneous back-Rayleigh scattered coherent light generated in the second 50km probe fiber enters port 2 of the second circulator and directly to port 3, and then enters the remote pump amplifier module, the first 50km fiber and wavelength division multiplexer 1 , and finally enter the optical fiber distributed vibration detection unit for signal processing to detect the micro-perturbation along the optical fiber.

The 1480nm remote pump source plays two roles, one is as a Raman pump source, injected into a long-distance optical fiber to achieve distributed amplification of optical signals, and the other is as a pump source, a remote pump amplifier module after transmission to a 50km optical fiber It can be used as a pump source, thereby effectively increasing the sensing distance of the system.

It can be seen that the waterfall diagram of each fiber segment is very clear. After using the far-pump erbium-doped fiber amplifier and Raman amplifier, the transmission distance of the system is extended from 40km to 100km, thereby effectively increasing the sensing distance of the system.

Unlike optical communication systems, optical sensing systems are prone to nonlinear effects such as four-wave mixing and stimulated Raman effects as the power of optical pulses increases. The longer the fiber, the lower the critical optical power for stimulated Raman. As mentioned above, the 1480nm remote pump source plays two roles. When the transmitting end is used as the Raman pump source, the higher the power, the greater the signal gain, but the high-power 1480nm laser enters the first 50km fiber The signal light generated in the remote pump amplifier module is very large and it is easy to cause nonlinear effects. To this end, the present invention designs a remote pump amplifier module as shown in the dashed box in FIG. 2 . The most critical part of this module is to use two wavelength division multiplexers to separate the pump light and the signal light for transmission. Its working principle is: after the 1480nm pump light and signal light transmitted in the first 50km fiber enter the wavelength division multiplexer 2, the 1480nm pump light and 1550nm signal light are separated, and an adjustable optical attenuator is added to the pump light side. Thus, the power of the pump light entering the erbium-doped fiber is optimized. The 1550nm signal light enters port 2 of the first circulator and goes directly to port 3. The attenuated pump light and signal light simultaneously enter the wavelength division multiplexer 3 for beam combining, and then enter the erbium-doped fiber after passing through the isolator to amplify the 1550 nm signal light. As mentioned above, the spontaneous back-Rayleigh scattered coherent light generated in the second section of 50km fiber is output through the 3-port of the second circulator, and then enters the 1-port of the first circulator, and is directly output to the 2-port. Then enter the wavelength division multiplexer 2, the first 50km fiber and the wavelength division multiplexer 1, and finally enter the fiber distributed vibration detection unit for signal processing to detect the micro-perturbation along the fiber.

The invention applies the far-pump erbium-doped fiber amplifier and the Raman fiber amplifier from the field of optical communication to the field of sensing, and can extend the transmission distance of the fiber-optic acoustic wave sensing system from 40km to 100km, thereby effectively increasing the sensing capacity of the system. distance.

Embodiment 2

As shown in FIG. 7 , the distributed optical fiber acoustic wave sensing system based on the remote pump amplifier and Raman amplifier, the optical fiber acoustic wave sensing system includes: a vibration detection unit 1, which provides signal light; a first laser source 2, which provides a first pump light; the first sensing fiber 3, the head end of the first sensing fiber 3 receives the combined beam of the first pump light and the signal light; the remote pump amplifier module 4, the remote pump amplifier module 4 and the first sensing fiber 3 The remote pump amplifier includes an erbium-doped fiber 5 for amplifying the signal light in the input; the second sensing fiber 6, the head end of the second sensing fiber 6 receives the output of the remote pump amplifier module 4.

The first pump light is 1455 nm.

The optical fiber acoustic wave sensing system includes: a third laser light source 10 , which provides a third pump light, which is used for recombining with the combined beam and then inputting the erbium-doped fiber 5 .

The third pump light is 1480 nm.

A first circulator 11 is connected between the first sensing fiber 3 and the remote pump amplifier module 4 , the first end of the first circulator 11 is connected with the tail end of the first sensing fiber 3 , and the first circulator 11 is connected to the tail end of the first sensing fiber 3 . The two ends are connected to the input end of the remote pump amplifier. The first circulator 11 further includes a third end. The incident light at the first end of the first circulator 11 is led out from the second end. Incident light exits from its first end.

A second circulator 12 is connected between the second sensing fiber 6 and the remote pump amplifier module 4, the first end of the second circulator 12 is connected to the output end of the remote pump amplifier, and the second end of the second circulator 12 is connected to the output end of the remote pump amplifier. The head end of the second sensing fiber 6 is connected, the third end of the second circulator 12 is connected to the third end of the first circulator 11, the incident light of the first end of the second circulator 12 is led out from the second end, Incident light at the second end of the second circulator 12 is led out from the third end.

Although the above embodiments have specifically described the present invention, it should be understood by those skilled in the art that modifications or improvements can be made based on the disclosure of the present invention without departing from the spirit and scope of the present invention. and modifications are within the spirit and scope of the present invention.

Claims (6)

1. a distributed optical fiber acoustic wave sensing system based on far-pump amplifier and Raman amplifier, is characterized in that, described distributed optical fiber acoustic wave sensing system comprises: Vibration detection unit, providing signal light; a first laser source, providing a first pump light; a first sensing optical fiber, the head end of the first sensing optical fiber receives the combined beam of the first pump light and the signal light; a remote pump amplifier module, the remote pump amplifier module is connected to the tail end of the first sensing fiber, and the remote pump amplifier includes an erbium-doped fiber for amplifying the signal light in the input; a second sensing optical fiber, the head end of the second sensing optical fiber receives the output of the remote pump amplifier module; The remote pump amplifier module includes a wavelength division multiplexer for separating the first pump light and signal light, an attenuator for adjusting the separated first pump light, and the adjusted first pump light another wavelength-division multiplexer that is re-combined with the signal light, and the re-combined first pump light and signal light are input into the erbium-doped fiber; A first circulator is connected between the first sensing fiber and the remote pump amplifier module, the first end of the first circulator is connected to the tail end of the first sensing fiber, and the first circulator The second end of the first circulator is connected to the input end of the remote pump amplifier, the first circulator further includes a third end, and the incident light at the first end of the first circulator is derived from its second end, and the first circulator further includes a third end. Incident light at the third end of a circulator is derived from its first end; A second circulator is connected between the second sensing fiber and the remote pump amplifier module, the first end of the second circulator is connected to the output end of the remote pump amplifier, and the second circulator is connected to the output end of the remote pump amplifier. The two ends are connected to the first end of the second sensing fiber, the third end of the second circulator is connected to the third end of the first circulator, and the incident light of the first end of the second circulator is connected Light exits from the second end, and light incident at the second end of the second circulator exits from the third end. 2. The distributed optical fiber acoustic wave sensing system based on far-pump amplifier and Raman amplifier according to claim 1, is characterized in that, described optical fiber acoustic wave sensing system comprises: The second laser source provides the second pump light and is input to the second sensing fiber. 3 . The distributed optical fiber acoustic wave sensing system based on a remote pump amplifier and a Raman amplifier according to claim 2 , wherein the first pump light is 1480 nm, and the second pump light is 1455 nm. 4 . 4 . The distributed optical fiber acoustic wave sensing system based on a remote pump amplifier and a Raman amplifier according to claim 1 , wherein the first pump light is 1455 nm. 5 . 5. The distributed optical fiber acoustic wave sensing system based on far-pump amplifier and Raman amplifier according to claim 4, is characterized in that, described optical fiber acoustic wave sensing system comprises: The third laser source provides a third pump light, which is used for recombining with the combining light and then inputting it into the erbium-doped fiber. 6 . The distributed optical fiber acoustic wave sensing system based on a remote pump amplifier and a Raman amplifier according to claim 5 , wherein the third pump light is 1480 nm. 7 .

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