Fiber-based optical path structure for wavelength-switchable narrow-linewidth single-frequency ytterbium-doped fiber source and fiber-based listening

Abstract

The invention discloses an optical fiber listening optical path structure based on a wavelength switchable narrow linewidth single-frequency ytterbium-doped optical fiber source, belonging to the technical field of non-intrusive broadband optical fiber listening devices. A laser light source is connected to an input port of a wavelength division multiplexer through a single-mode optical fiber, the wavelength division multiplexer is connected to a high-doped ytterbium ion gain optical fiber through a single-mode optical fiber, the high-doped ytterbium ion gain optical fiber is connected to a circulator through a single-mode optical fiber, the circulator is connected to a polarization controller through a single-mode optical fiber, the polarization controller is connected to the ytterbium-doped optical fiber, the ytterbium-doped optical fiber is connected to a Bragg grating, the circulator is connected to a coupler through a single-mode optical fiber, the output end of the coupler has two loops, one is a single-mode optical fiber output loop, and the other is a single-mode optical fiber connected to the wavelength division multiplexer to form a closed loop. The invention does not require any additional components, and as long as there is an ordinary single-mode optical fiber on site, the mode hopping phenomenon can be effectively suppressed, thereby stabilizing the laser light source, improving the optical signal-to-noise ratio, and being used for technical reconnaissance, non-intrusive reconnaissance, and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of non-intrusive broadband optical fiber monitoring devices, and in particular is an optical fiber monitoring optical path structure based on a wavelength switchable narrow line width single frequency ytterbium-doped optical fiber source. Background Art

[0002] Today's eavesdropping devices include micro-eavesdroppers, micro-recorders, dedicated microphone eavesdroppers, wireless eavesdroppers, telephone eavesdroppers, infrared laser eavesdroppers, microwave eavesdroppers, etc. All of these technologies are invasive techniques, which are subject to the constraints of the use environment, scenes, and actual combat sites, and their effectiveness is greatly affected. The non-invasive and installation-free eavesdropping system based on fiber optic phonon detection technology uses existing household optical fibers to collect and process acoustic signals, and has the characteristics of anti-detection, non-invasive, high sensitivity, distributed, and strong robustness.

[0003] At present, the eavesdropping industry uses micro-eavesdroppers, micro-recorders, dedicated microphone eavesdroppers, wireless eavesdroppers, telephone eavesdroppers, infrared laser eavesdroppers, microwave eavesdroppers, etc. All of the above technologies are invasive technical means of detection, which are restricted by the use environment, scenes, and actual combat sites, and their use effects are greatly affected.

[0004] The above listening products belong to intervention listening and are electronic products. This type of product is composed of sound sensors, signal collection and transmission circuits, batteries, shells and other parts. The method of use is to place the listening module in the listening environment in advance, collect voice signals and transmit them wirelessly. The receiving end uses another communication module for reception, and the receiving distance is greatly affected by the environment. Summary of the invention

[0005] The present invention does not require any additional parts. As long as there is an ordinary single-mode optical fiber on site, it can be connected to the laser light source and other equipment of the present invention. Since the designed laser light source has the characteristic of dynamic self-adaptation of the central wavelength, the mode hopping phenomenon can be effectively suppressed, thereby stabilizing the laser light source and improving the optical signal-to-noise ratio. It can realize the pickup and restoration of sound signals around the optical fiber and be used for technical reconnaissance, non-intrusive detection, etc., and has a simple structure.

[0006] The technical solution of the present invention is as follows: based on a wavelength-switchable narrow-linewidth single-frequency ytterbium-doped fiber source fiber listening optical path structure, the optical path structure comprises: a laser light source, a wavelength division multiplexer, a highly doped ytterbium ion gain fiber, a circulator, a polarization controller, an ytterbium-doped fiber, a Bragg grating and a coupler; the laser light source is connected to port a of the wavelength division multiplexer through a single-mode fiber; port b of the wavelength division multiplexer is connected to port a of the highly doped ytterbium ion gain fiber through a single-mode fiber; port b of the highly doped ytterbium ion gain fiber is connected to port a of the circulator through a single-mode fiber; port b of the circulator is connected to port b of the polarization controller through a single-mode fiber; port a of the polarization controller is connected to port a of the ytterbium-doped fiber; port b of the ytterbium-doped fiber is connected to the Bragg grating; port c of the circulator is connected to port b of a 10 / 90 coupler through a single-mode fiber; an output end of the coupler has two loops, one is a single-mode fiber output loop, and the other is a single-mode fiber; the single-mode fiber is connected to port a of the wavelength division multiplexer to form a closed loop.

[0007] Furthermore, the laser light source is a 980 / 1060nm semiconductor laser.

[0008] Furthermore, the wavelength of the wavelength division multiplexer is 980 / 1060nm.

[0009] Furthermore, the coupler port ratio is 10 / 90.

[0010] Furthermore, the central wavelength of the circulator is 1064 nm.

[0011] Furthermore, the reflectivity of the Bragg grating is greater than 99%.

[0012] Furthermore, the longitudinal mode frequency interval of the circulator is 15-25 MHz.

[0013] The beneficial effects of the present invention are:

[0014] The invention provides a technology for monitoring using existing optical fibers, which does not require any changes to the optical cables entering the home, and does not affect the detection and identification of the existing communication system. It has strong anti-detection capabilities, the advantages of high sensitivity and low noise, and can still work reliably in harsh environments. The optical path used has the characteristics of dynamic adaptation of the central wavelength, which can effectively suppress the mode hopping phenomenon, thereby stabilizing the laser light source and improving the optical signal-to-noise ratio. It supports remote data access and real-time monitoring data release, is compact and easy to integrate, and can provide networking or independent rapid monitoring deployment. Utilize the existing home optical fiber, access the detection equipment, use advanced fiber optic radar technology to realize acoustic phonon distributed fixed-point detection and identification, listen to the sound signal in the room and perform intelligent processing, and use the room's broadband home optical cable to realize non-intrusive listening and identification, audio track tracking, automatic recording, automatic subtitle generation, etc.; there is no need to enter the room to deploy sensors, and it does not affect the quality of broadband data and other communication links; it has anti-detection, anti-identification, and no electromagnetic radiation. It is simple and easy to implement, highly reliable, and easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the structure of the present invention.

[0016] In the figure:

[0017] 1 laser light source, 2 wavelength division multiplexer, 3 highly doped ytterbium ion gain fiber, 4 circulator, 5 coupler, 6 polarization controller, 7 ytterbium-doped fiber, 8 Bragg grating, a port a, b port b, c port c. DETAILED DESCRIPTION

[0018] It should be noted that in the description of the present invention, the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", "clockwise", "counterclockwise", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction.

[0019] In the present invention, unless otherwise clearly specified and limited, the terms "set", "install", "connect", "connect" and the like should be understood in a broad sense. For example, "fixed" can be a fixed connection, a detachable connection, or an integral connection; the connection can be a mechanical connection or an electrical connection; the connection can be a direct connection or an indirect connection through an intermediate medium, and can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0020] By using the existing broadband optical fiber for households, a laser signal of a certain energy is injected, and the backscattering effect of the laser transmitted in the optical fiber is used to collect the acoustic signals inside the room. The disturbance process of the optical fiber caused by the sound signal fluctuation produces a photoelastic effect. The backscattered light produced by the photoelastic effect is received by the receiving end to restore the sound.

[0021] This type of technology is a special means of eavesdropping, a state action permitted by law, and is not aimed at eavesdropping on civilian communication optical cables.

[0022] Fiber-detecting optical path structure based on wavelength-switchable narrow-linewidth single-frequency ytterbium-doped fiber source.

[0023] The laser light source 1 is a 980 / 1060nm semiconductor laser, which is connected to the port a of the wavelength division multiplexer 2 (980 / 1060nm) through a single-mode optical fiber, and the port b of the wavelength division multiplexer 2 is connected to the port a of the highly doped ytterbium ion gain optical fiber 3 through a single-mode optical fiber. The port b of the highly doped ytterbium ion gain optical fiber 3 is connected to the port a of the circulator 4 through a single-mode optical fiber, and the port b of the circulator 4 is connected to the port b of the polarization controller 6 through a single-mode optical fiber, and the port a of the polarization controller 6 is connected to the port a of the ytterbium-doped optical fiber 7, and the port b of the ytterbium-doped optical fiber 7 is connected to the Bragg grating 8.

[0024] Port c of the circulator 4 is connected to port b of the 10 / 90 coupler 5 through a single-mode optical fiber. The output end of the coupler 5 has two loops, one is a single-mode optical fiber output loop, and the other is a single-mode optical fiber. The single-mode optical fiber is connected to port a of the wavelength division multiplexer 2 to form a closed loop.

[0025] A 480mW 980nm single-mode fiber output semiconductor laser is used as a pump source, and the pump light is coupled by a 980 / 1060nm wavelength division multiplexer 2 into a highly doped ytterbium ion gain fiber in the resonant cavity; the gain fiber is connected to port a of a circulator 4 with a central wavelength of 1064nm, and port b of the circulator 4 is connected to an ytterbium-doped fiber 7, and a highly reflective fiber Bragg grating 8 (reflectivity greater than 99%) is connected to the other end. The polarization controller 6, the ytterbium-doped fiber 7 and the Bragg grating 8 with a bandwidth of 2nm and a reflectivity greater than 99% form a high-precision filter, which suppresses the number of modes in the resonant cavity and realizes the selection of a single longitudinal mode in the resonant cavity. The port c of the circulator 4 is connected to one end of the 1×2 coupler 5 (ratio is 10:90), and the 90% port of the other end of the coupler 5 is connected to one end of the wavelength division multiplexer 2 to form a single-frequency fiber laser ring cavity structure. The generated single-frequency laser is output from the 10% port of the coupler, and the corresponding longitudinal mode frequency interval is about 21.7MHz. The circulator has an isolation effect of more than 45dB, ensuring that the transmission process of light in the resonant cavity remains unidirectional. At the same time, it can further prevent the 980nm residual pump light passing through the highly doped ytterbium ion gain fiber from entering, so that the Bragg grating is not pumped. The light reflected back by the Bragg grating enters the ytterbium-doped fiber again to form a standing wave interference effect with the incident light; the light intensity of the antinode and the node at the standing wave is periodically distributed, thereby causing a periodic change in the refractive index, and finally a dynamic grating is formed in the unpumped ytterbium-doped fiber. The dynamic grating has an extremely narrow reflection bandwidth and the characteristics of center wavelength adaptation, which can effectively suppress the mode hopping phenomenon.

[0026] The above is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any modification, equivalent replacement and improvement made by any person skilled in the art within the technical scope disclosed by the present invention and within the spirit and principle of the present invention shall be covered within the protection scope of the present invention. At the same time, the contents not described in detail in this specification belong to the prior art known to those skilled in the art.

[0027] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

Claims

1. Based on the wavelength switchable narrow linewidth single frequency ytterbium-doped fiber source fiber listening optical path structure, it is characterized by: include: A laser light source, a wavelength division multiplexer, a highly doped ytterbium ion gain fiber, a circulator, a polarization controller, an ytterbium-doped fiber, a Bragg grating and a coupler. The laser light source is connected to port a of the wavelength division multiplexer through a single-mode fiber. Port b of the wavelength division multiplexer is connected to port a of the highly doped ytterbium ion gain fiber through a single-mode fiber. Port b of the highly doped ytterbium ion gain fiber is connected to port a of the circulator through a single-mode fiber. Port b of the circulator is connected to port b of the polarization controller through a single-mode fiber. Port a of the polarization controller is connected to port a of the ytterbium-doped fiber. Port b of the ytterbium-doped fiber is connected to the Bragg grating. Port c of the circulator is connected to port b of a 10 / 90 coupler through a single-mode fiber. The output end of the coupler has two loops, one is a single-mode fiber output loop, and the other is a single-mode fiber. The single-mode fiber is connected to port a of the wavelength division multiplexer to form a closed loop.

2. The optical fiber listening optical path structure based on wavelength switchable narrow linewidth single frequency ytterbium-doped optical fiber source according to claim 1 is characterized in that: The laser light source is a 980 / 1060nm semiconductor laser.

3. The optical fiber listening optical path structure based on wavelength switchable narrow linewidth single frequency ytterbium-doped optical fiber source according to claim 1 is characterized in that: The wavelength of the wavelength division multiplexer is 980 / 1060nm.

4. The optical fiber listening optical path structure based on wavelength switchable narrow linewidth single frequency ytterbium-doped optical fiber source according to claim 1 is characterized in that: The coupler port ratio is 10 / 90.

5. The optical fiber listening optical path structure based on wavelength switchable narrow linewidth single frequency ytterbium-doped optical fiber source according to claim 1 is characterized in that: The central wavelength of the circulator is 1064 nm.

6. The optical fiber listening optical path structure based on wavelength switchable narrow linewidth single frequency ytterbium-doped optical fiber source according to claim 1 is characterized in that: The reflectivity of the Bragg grating is greater than 99%.

7. The optical fiber listening optical path structure based on wavelength switchable narrow linewidth single frequency ytterbium-doped optical fiber source according to claim 1 is characterized in that: The circulator longitudinal mode frequency interval is 15-25MHz.

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