CN102519492B - Distributed single core feedback interference optical path structure having low background light - Google Patents
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Abstract
The invention, which belongs to the optical fiber sensing technology field, particularly relates to a distributed single core feedback interference optical path structure having low background light. According to the structure, a wave combination port of a polarization beam splitter is utilized as an interface of a distributed sensing optical fiber as well as a faraday rotating mirror that is used at an end of the sensing optical fiber is also cooperatively utilized, so that light that is returned along a same way is eliminated, a coherent light component in an interference optical path is improved and strip sharpness is enhanced. Besides, an application advantage in a traditional single core feedback sensing structure is preserved; and the sensing function can be realized only by using a common fiber in optical fiber communication. The distributed single core feedback interference optical path structure provided in the invention is especially suitable for long-distance line monitoring including security monitoring of communication trunk and a gas pipeline and the like.
Description
Technical field
The invention belongs to technical field of optical fiber sensing, be specifically related to a kind of distributed single core feedback interference optical path structure.
Background technology
In the contemporary society of scientific and technological high speed development, the development of Fibre Optical Communication Technology brings the revolution of sensing technology, Fibre Optical Sensor is day by day by people are paid close attention to, more and more emphasis becoming technical research, also each important application is more and more entered into, wherein distributing optical fiber sensing is far away with its monitoring distance, highly sensitive, environmental suitability is strong, special in the field being related to national economy, as tunnel fire hazard monitoring, optical cable security monitoring, oil and gas leakage monitoring etc. aspect obtains special concern and application.Distributed single core feedback interference structure only needs employing core as sensor fibre due to it, and it is convenient to realize, and thus becomes the important technology branch in distributed sensing.
Fig. 1 is common a kind of distributed single core feedback arrangement.
Optical interference circuit is integer by N*M(N, M) coupling mechanism 3, P*Q(P, Q be integer) coupling mechanism 4, fiber delay line 5, postpone for τ, optical fiber (optical cable) 6 and feedback assembly 2 are formed.3a1,3a2 ..., 3aN, 3b1,3b2 be the port of coupling mechanism 3,3a1,3a2 ..., 3aN is port in the same way, N number of altogether, 3b1,3b2 are two ports that another of coupling mechanism 3 organizes in port (altogether M) in the same way.4a1,4a2,4b1 are the port of coupling mechanism 4, and 4a1,4a2 are one group of coupling mechanism 2 two ports in the same way in port (altogether P), and 4b1 is two ports that another of coupling mechanism 4 organizes in port (altogether Q) in the same way.Optical fiber 6 is induction optical fiber.1 is the disturbance point on optical fiber 6.2 is feedback assembly, makes the light come along Optical Fiber Transmission reenter optical fiber 6 and turns back to coupling mechanism 4.Light source inputs through the port 3a1 of coupling mechanism 3, exports respectively after coupling mechanism 3 light splitting through port 3b1,3b2.Co-exist in four bundle light in the structure shown here, wherein two-way light:
Ⅰ：3b1→5→4a1→4b1→6→2→6→4b1→4a2→3b2；
Ⅱ：3b2→4a2→4b1→6→2→6→4b1→4a1→5→3b1。
At coupling mechanism 3, place joins again, interferes, interference signal respectively through port 3a1,3a2 ..., 3aN export.But due to the use of fiber coupler 4, when light returns from 4b1 port, when entering coupling mechanism 4, owing to all having light output from two ports 4a1,4a2, thus except forming above-mentioned interfering beam, also there is two-way light echo dorsad:
Ⅲ：3b1→5→4a1→4b1→6→2→6→4b1→4a1→5→3b1；
Ⅳ：3b2→4a2→4b1→6→2→6→4b1→4a2→3b2。
This two-way light due to light path, do not participate in interfere, only become bias light, show as direct current light, this two-way add ground unrest, reduce the sharpness of interference fringe.
For light echo dorsad, in the research of nautical receiving set, also encounter similar problem.
In the sagnac ring structure of nautical receiving set, in order to reduce the susceptibility of the noise to external world of lag line, can adopt as Fig. 2 the mode that adopts form delay winding, namely 1 × 2 coupling mechanism 8 is adopted to add one section of fibre delay line 9, and connect a catoptron 10 at the end of 9, the function of lag line in former sagnac ring is jointly realized with this.In Fig. 2,7 is fiber coupler, and 9 for postponing optical fiber, and 11 is induction optical fiber.But this lag line constituted mode have also been introduced the light echo dorsad that non-existent two-way in former Sagnac ring does not participate in interfering.In order to address this problem, Benjamin J. Vakoc etc. are at " Demonstration of a folded Sagnac sensor array immune to polarization-induced signal fading " (Applied Optics Vol. 42, No. 36,7132-7136) structure adopting polarization beam apparatus and faraday rotation mirror to share is proposed in.Fig. 3 is the frame mode presented in this article, the conjunction ripple end of polarization beam apparatus (PBS) is connected with delay winding (Delay Coil), the other end of delay winding (Delay Coil) is connected with faraday rotation mirror (FRM), and polarization spectro end c and g of polarization beam apparatus (PBS) is connected in Sagnac ring.The operating characteristic of beam splitter is: when light inputs from conjunction ripple port (optical fiber) d, light is divided into two orthogonal polarization states, working shaft respectively along partial wave port (optical fiber) c and g exports, thus when only having a polarization mode corresponding to decomposing polarization state from the light closing the input of ripple end, to only export from corresponding partial wave port, another partial wave port does not have light output.In the structure shown here, from the light that port c inputs, exported by port d, port d is input to through FRM reflection, due to the effect of FRM, this polarisation of light direction with relative to the polarisation of light exported from port d, have rotated 90 degree, thus, it is vertical with the transmission polarization mode of port c that light transmits polarization mode through port g() export, and port c does not export light, vice versa, thus, this structure by polarization beam apparatus and faraday rotator mirror with the use of, eliminate the problem of light echo dorsad utilizing coupling mechanism formation lag line to bring, make only to exist in light path the light that two-way is interfered mutually, there is low bias light, thus improve interference fringe sharpness.
Summary of the invention
The object of the present invention is to provide a kind of long range propagation that is applicable to, light echo dorsad can be eliminated, there is the distributed single core feedback interference optical path structure of low bias light.
The distributed single core feedback interference light path that the present invention proposes, make use of the characteristic that polarization beam apparatus and faraday rotator mirror share; In polarization light path, the conjunction ripple end of polarization beam apparatus is connected with one end of sensor fibre, the other end of sensor fibre is connected with faraday rotator mirror, and fiber delay line is directly made up of an optical fiber, or reflects rotating mirror by polarization beam apparatus, optical fiber and faraday and jointly form.Basic comprising as shown in Figure 4, Figure 5.Specifically comprise:
A fiber coupler 12,12a1,12a2 ..., 12aN, 12b1,12b2 be the port of fiber coupler 12,12a1,12a2 ..., 12aN is one group of fiber coupler 12 port in the same way, altogether N number of, 12b1,12b2 are two ports that another of fiber coupler 12 organizes in port (altogether M) in the same way;
First polarization beam apparatus 13,13a1,13a2,13b1 are the port of the first polarization beam apparatus 13, and port one 3a1,13a2 are partial wave port, port one 3b1 is for closing ripple port, from the light that port one 3b1 inputs, two orthogonal polarization states will be divided into, export from 13a1,13a2 respectively;
First faraday rotator mirror 14,14a1 is its light input/output port mouth;
One sensor fibre 15;
One fiber delay line 20.
Sensor fibre 15 one end is connected with the conjunction ripple port one 3b1 of the first polarization beam apparatus 13, and sensor fibre 15 other end is connected with the first faraday rotator mirror 14, and fiber delay line 20 is connected between port one 2b1 and port one 3a1, and port one 2b2 is connected with port one 3a2.Light inputs from the port of coupling mechanism 12, and interference signal also exports from the port of fiber coupler 12.
Wherein, fiber delay line 20 adopts the first delay optical fiber 16(to play delayed-action); As shown in Figure 4.
Fiber delay line 20 also can reflect rotating mirror 19 by the second polarization beam apparatus 17, second delay optical fiber 18 and the second faraday and form; As shown in Figure 5.17a1,17a2,17b1 are the port of the second polarization beam apparatus 17, and port one 7a1,17a2 are partial wave port, and port one 7b1, for closing ripple port, from the light that port one 7b1 inputs, will be divided into two orthogonal polarization states, and export respectively from 17a1,17a2; Second postpones optical fiber 18 delayed-actions; The light input/output port mouth of the second faraday rotator mirror 19 is 19a1; Second postpones optical fiber 18, and one end is connected with the conjunction ripple port one 7b1 of the second polarization beam apparatus 17, and the other end is connected with the second faraday rotator mirror 19; Partial wave port one 7a1,17a2 of second polarization beam apparatus 17 are connected with port one 2b1 with 13a1 respectively.Fiber delay line 20 in Fig. 4 is owing to being only made up of an optical fiber, and thus this part can not bring light echo dorsad; The implementation that fiber delay line 20 in Fig. 5 shares owing to employing fibre optic polarizing beam splitter and faraday rotator mirror, therefore also can not bring light echo dorsad.
Light path trend (i.e. the transmission path of light) as shown in Figure 4 has 2, is respectively:
I: port one 2b1 → the first postpones optical fiber 16 → port one 3a1 → port one 3b1 → sensor fibre 15 → the first faraday rotator mirror 14 → sensor fibre 15 → port one 3b1 → port one 3a2 → port one 2b2;
II: port one 2b2 → port one 3a2 → port one 3b1 → sensor fibre 15 → the first faraday rotator mirror 14 → sensor fibre 15 → port one 3b1 → port one 3a1 → the first postpones optical fiber 16 → port one 2b1;
This two-beam is joined at coupling mechanism 12 place, interferes;
Light path trend (i.e. the transmission path of light) as shown in Figure 5 has 2, is respectively:
I: port one 2b1 → port one 7a1 → port one 7b1 → the second postpones optical fiber 18 → the second faraday rotator mirror 19 → the second and postpones optical fiber 18 → port one 7b1 → port one 7a2 → port one 3a1 → port one 3b1 → sensor fibre 15 → the first faraday rotator mirror 14 → sensor fibre 15 → port one 3b1 → port one 3a2 → port one 2b2;
II: port one 2b2 → port one 3a2 → port one 3b1 → sensor fibre 15 → the first faraday rotator mirror 14 → sensor fibre 15 → port one 3b1 → port one 3a1 → port one 7a2 → port one 7b1 → the second postpones optical fiber 18 → the second faraday rotator mirror 19 → the second and postpones optical fiber 18 → port one 7b1 → port one 7a1 → port one 2b1;
This two-beam is joined at coupling mechanism 12 place, interferes;
Visible, the distributed single core feedback interference structure shown in Fig. 4, Fig. 5 eliminates light echo dorsad.
In above-mentioned light path representation, arrow represents the direction that light transmits.
The outstanding advantages of this invention is, eliminates the light echo dorsad in traditional single core feedback sensing arrangement, has low bias light, can obtain high clear-cut texture degree, be conducive to the raising of measurement sensistivity, precision.The method remains the application advantage in traditional single core feedback sensing arrangement, uses ordinary optic fibre conventional in optical fiber communication, can realize sensing function.The present invention is specially adapted to long distance line monitoring, such as, can be used for the monitoring of fiber communication link, Safety monitoring of oil, natural gas line etc. field.
Accompanying drawing explanation
Fig. 1 is common a kind of distributed single core feedback arrangement.
Fig. 2 is a kind of sagnac ring structure of nautical receiving set, and this structure is the susceptibility in order to reduce lag line noise to external world.
Fig. 3 is the interference structure adopting polarization beam apparatus and faraday rotation mirror to share, and solves in light path with this problem that there is light echo dorsad.Wherein d is the conjunction ripple port (optical fiber) of polarization beam apparatus (PBS), c and g is partial wave port (optical fiber).
Fig. 4 is the distributed single core feedback interference optical path structure with low bias light of the present invention.Wherein, fiber delay line is directly made up of optical fiber.
Fig. 5 is the distributed single core feedback interference optical path structure with low bias light of the present invention.Wherein, fiber delay line is made up of jointly polarization beam apparatus, optical fiber and faraday rotator mirror.
Number in the figure: 3 for N*M(N, M be integer) coupling mechanism, 4 for P*Q(P, Q be integer) coupling mechanism, 5 is for fiber delay line, postpone for τ, 6 is optical fiber (optical cable), and 1 is the disturbance point on optical fiber 6, and 2 is feedback assembly.3a1,3a2 ..., 3aN, 3b1,3b2 be the port of coupling mechanism 3,3a1,3a2 ..., 3aN is port in the same way, N number of altogether, 3b1,3b2 are two ports that another of coupling mechanism 3 organizes in port (altogether M) in the same way.4a1,4a2,4b1 are the port of coupling mechanism 4, and 4a1,4a2 are one group of coupling mechanism 2 two ports in the same way in port (altogether P), and 4b1 is two ports that another of coupling mechanism 4 organizes in port (altogether Q) in the same way.7 is fiber coupler, and 8 is 1 × 2 coupling mechanism, and 9 for postponing optical fiber, and 10 is catoptron, and 11 is induction optical fiber.2 is fiber coupler, 12a1,12a2 ..., 12aN, 12b1,12b2 be the port of coupling mechanism 12,12a1,12a2 ..., 12aN is port in the same way, N number of altogether, 12b1,12b2 are two ports that another of coupling mechanism 12 organizes in port (altogether M) in the same way; 13 is the one one polarization beam apparatus, and 13a1,13a2,13b1 are the port of the first polarization beam apparatus 13, and port one 3a1,13a2 are partial wave port, port one 3b1 is for closing ripple port, from the light that port one 3b1 inputs, two orthogonal polarization states will be divided into, export from 13a1,13a2 respectively; 14 is the one one faraday rotator mirror, and 14a1 is its light input/output port mouth; 15 is sensor fibre; 16 is the first delay optical fiber; 17 is the second polarization beam apparatus, 17a1,17a2,17b1 are the port of polarization beam apparatus 17, port one 7a1,17a2 are partial wave port, port one 7b1 is for closing ripple port, from the light that port one 7b1 inputs, to be divided into two orthogonal polarization states, export from 17a1,17a2 respectively, 18 is the second delay optical fiber; 19 is the second faraday rotator mirror, and 19a1 is its light input/output port mouth, and 20 is fiber delay line.
Embodiment
Logical embodiment specifically describes the present invention below.
The optical interference circuit of the present embodiment adopts the structure shown in Fig. 4.
Fiber coupler 12 uses the equal branch/coupler of 3*3, for Wuhan post and telecommunications research institute produces; First delay optical fiber 16 is optical fiber loops that the healthy and free from worry single-mode fiber of G652 type turns to; The tail optical fiber of the first polarization beam apparatus 13 is all general single mode fiber, for Mianyang ultraphotic is produced.
Sensor fibre 15 is the core single-mode fiber in the optical cable that will monitor, and length is about 30km, and its one end is connected with the first polarization beam apparatus 13, and the other end is connected with faraday rotator mirror.
The light of optical interference circuit inputs from the port one 2a1 of fiber coupler 12, and interference signal obtains from port one 2a2,12a3.The light source used is the SO3-B type super luminescence diode (SLD) that research institute of main office of electronics group 44 produces.The InGaAs photodetector that the electrooptical device used in opto-electronic conversion and information processing is GT322C500 for 44 models of producing.
The interference unit that fiber coupler 12, first delay optical fiber delay 16, first polarization beam apparatus 13 is formed and the measurement mechanism such as light source, photodetection are placed in Control Room, and faraday rotator mirror is then positioned at the sensing cable other end away from Control Room.
Sensing optic cable is knocked, namely can be observed interference signal and export.
Test shows, background light echo is eliminated, the clear-cut texture degree obtained is about 50%, and when using structure shown in Fig. 1, replace with the 2*1 coupling mechanism divided equally by polarization beam apparatus 13, clear-cut texture degree is deteriorated, be about 25%, therefore aspect of the present invention brings and significantly interferes improvement, that is, clear-cut texture degree obviously increases.
Use the structure of Fig. 5, the clear-cut texture degree of acquisition is also about 50%, is obviously better than the result using Fig. 1 structure.
Claims (2)
1. there is the distributed single core feedback interference optical path structure of low bias light, it is characterized in that comprising:
A fiber coupler (12), 12a1,12a2 ..., 12aN, 12b1,12b2 be the port of fiber coupler (12), 12a1,12a2 ..., 12aN is one group of fiber coupler (12) port in the same way, N number of altogether, 12b1,12b2 are two ports in the individual port in the same way of another group M of fiber coupler (12);
First polarization beam apparatus (13), 13a1,13a2,13b1 are the port of the first polarization beam apparatus (13), and port one 3a1,13a2 are partial wave port, port one 3b1 is for closing ripple port, from the light that port one 3b1 inputs, two orthogonal polarization states will be divided into, export from 13a1,13a2 respectively;
First faraday rotator mirror (14), 14a1 is its light input/output port mouth;
One sensor fibre (15);
One fiber delay line (20);
Sensor fibre (15) one end is connected with the conjunction ripple port one 3b1 of the first polarization beam apparatus (13), sensor fibre (15) other end is connected with the first faraday rotator mirror (14), fiber delay line (20) is connected between port one 2b1 and port one 3a1, and port one 2b2 is connected with port one 3a2; Light inputs from the port of coupling mechanism (12), and interference signal exports from the port of fiber coupler (12);
Described fiber delay line (20) reflects rotating mirror (19) by the second polarization beam apparatus (17), delay optical fiber (18) and the second faraday and forms; 17a1,17a2,17b1 are the port of the second polarization beam apparatus (17), and port one 7a1,17a2 are partial wave port, and port one 7b1, for closing ripple port, from the light that port one 7b1 inputs, will be divided into two orthogonal polarization states, and export respectively from 17a1,17a2; Described delay optical fiber (18) plays delayed-action; The light input/output port mouth of the second faraday rotator mirror (19) is 19a1; One end of described delay optical fiber (18) is connected with the conjunction ripple port one 7b1 of the second polarization beam apparatus (17), and the other end is connected with the second faraday rotator mirror (19); Partial wave port one 7a1,17a2 of second polarization beam apparatus (17) are connected with port one 2b1 with 13a1 respectively.
2. the distributed single core feedback interference optical path structure with low bias light according to claim 1, is characterized in that
In this optical interference circuit, the transmission of light has 2 paths, is respectively:
I: port one 2b1 → port one 7a1 → port one 7b1 → delay optical fiber (18) → second faraday rotator mirror (19) → delay optical fiber (18) → port one 7b1 → port one 7a2 → port one 3a1 → port one 3b1 → sensor fibre (15) → first faraday rotator mirror (14) → sensor fibre (15) → port one 3b1 → port one 3a2 → port one 2b2;
II: port one 2b2 → port one 3a2 → port one 3b1 → sensor fibre (15) → first faraday rotator mirror (14) → sensor fibre (15) → port one 3b1 → port one 3a1 → port one 7a2 → port one 7b1 → delay optical fiber (18) → second faraday rotator mirror (19) → delay optical fiber (18) → port one 7b1 → port one 7a1 → port one 2b1;
This two-beam is joined at coupling mechanism (12) place, interferes; In above-mentioned light path representation, arrow represents the direction that light transmits.
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| CN103018836B (en) * | 2012-12-26 | 2014-11-19 | 北京航天时代光电科技有限公司 | Optical fiber depolarizer with single-mode fiber serving as delay line |
| CN104748771B (en) * | 2015-04-17 | 2017-04-19 | 安徽师范大学 | Single-core fiber communicating and sensing device |
| CN111220881A (en) * | 2019-11-18 | 2020-06-02 | 南京航空航天大学 | Optical fiber detection device for detecting discharge fault of high-voltage bushing |
| CN113324568B (en) * | 2021-05-21 | 2022-04-12 | 复旦大学 | Distributed optical fiber sensing positioning system based on asymmetric fusion interferometer |
| CN116592922B (en) * | 2023-04-23 | 2024-10-01 | 复旦大学 | Branch distributed positioning system based on single-core feedback interferometer |
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