CN104180831A - Sensitivity-enhanced optical time domain reflection distributed Michelson interferometer based on two-core optical fiber - Google Patents
Sensitivity-enhanced optical time domain reflection distributed Michelson interferometer based on two-core optical fiber Download PDFInfo
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Abstract
The invention provides a sensitivity-enhanced optical time domain reflection distributed Michelson interferometer based on a two-core optical fiber, which can be used for distributed optical fiber sensing and measuring. The system is composed of a light source (1), a three-port optical fiber circulator (2), a 2*2 optical fiber coupler (3), a two-core optical fiber (4), a photoelectric detector (6), a photoelectric detector (7) and a differential signal amplifying and processing circuit (8). In the system, optical time domain reflection is used for realizing distributed measurement; interference characteristics can realize tiny disturbance measurement; the differential signal detection characteristics can offset the average signal intensity to enable the interference signals to be multiplied; the two fiber cores are located in the same optical fiber, changes of environmental temperature are the same, and influences of the temperature can be eliminated; and as the two fiber cores are symmetrically distributed outside the axis, transverse disturbance enables mechanical transformation with amplifying differential to be formed between the two fiber cores, and the system sensitivity is enhanced. Thus, the use of the two-core optical fiber can greatly enhance the ability of response to tiny vibration signals.
Description
(1) technical field
One of the present invention, based on the distributed Michelson interferometer of twin-core fiber Sensitivity enhancement type optical time domain reflection, can be used for distributing optical fiber sensing and measurement, belongs to optical fiber technology field.
(2) background technology
Utilize backward Rayleigh scattering light in Transmission Fibers to carry the feature of the information such as fiber position, extraneous vibration, adopt twin-core fiber differential signal detection method, can construct distributed Michelson-interference-type light time domain reflectometer, this for distributed interference sensing and measurement provide may.
1976, the optical time domain reflectometer (OTDR-Optical Time Domain Reflectmeter) of M.K.Barnoski and S.M.Jensen invention, by means of the distribution measuring of the detection of rear orientation light in optical fiber having been realized to fibre loss.In the time that burst pulse light is injected to testing fiber, this system can check over time the continuity in optical fiber and measure its decay by measuring back scattering light intensity, thus the length of definite testing fiber and loss distribution situation along the line thereof.Because OTDR method of testing has non-destructive, only needs one end access and advantage fast directly perceived, become that optical fiber cable is produced, construction, safeguard in indispensable instrument.But traditional OTDR technology is only backscatter intensity signal due to what measure, thus only sensitiveer to end face, breakpoint or larger stationary curved loss ratio, for example, to the time dependent small sample perturbations of optical fiber: vibration signal is but not too sensitive.For this reason, the invention technical patent that publication number is CN101290235A has provided a kind of interfere type optical time domain reflectometer, on original OTDR basis, adopt 2 × 2 coupling mechanisms, increase Liao Yi road reference optical fiber, thereby realized on the basis of backscatter intensity signal, distributed interference information has superposeed.But due to one side, detection optical fiber separates with reference optical fiber, temperature impact is difficult to overcome; On the other hand, less interference signal is superimposed upon on larger strength signal, causes the detection sensitivity of system not high.The shortcoming separating with reference optical fiber in order to solve detection optical fiber, publication number is that the invention technical patent of CN102809421A is on traditional OTDR basis, adopt polarising beam splitter, rear orientation light is carried out to the orthogonal separation of polarization state and amplifies in differential mode.This has lost the feature of interferometry on the one hand; On the other hand, due to the impact of variation of ambient temperature on fiber birefringence, also can make the positioning precision of vibration detecting decline.
In order to overcome above-mentioned shortcoming and defect, the present invention proposes a kind of based on the distributed Michelson interferometer of twin-core fiber Sensitivity enhancement type optical time domain reflection.It adopts two fiber cores independent of each other in same optical fiber, forms the backward Rayleigh scattering signal of two-way light, and formation can be carried out the Michelson interferometer of distribution measuring.By means of two anti-phase features of detection port interference signal of 2 × 2 fiber coupler, carry out differential detection and the amplification of two signals, this on the other hand, also makes interference signal realize multiplication at the bottom of having eliminated larger backscatter intensity code book on the one hand simultaneously.There is the advantages such as highly sensitive, dynamic range is large, fast response time, long transmission distance due to optical interferometry, in addition the environment temperature of the twin-core light path in same optical fiber can be considered identical, temperature variation is identical on two light path impacts, and this has just realized the auto-compensation of temperature impact.Therefore the interferometer that, this Novel double-core optical fiber forms is expected to realize detection and the location to long-distance distributed small sample perturbations.
(3) summary of the invention
The present invention is directed to the deficiency that prior art exists, proposed one based on the distributed Michelson interferometer of twin-core fiber Sensitivity enhancement type optical time domain reflection, can be used for distributing optical fiber sensing and measurement.It is characterized by, this system is by light source (1), three fiber port circulators (2), 2 × 2 fiber couplers (3), twin-core fiber (4), photodetector (6) and photodetector (7) and differential wave amplification treatment circuit (8) composition.Light source (1) is connected with the signal input part of three fiber port circulators (2), three fiber port circulators (2) in addition two-port are connected with 2 × 2 fiber couplers (3) and photodetector (6) respectively, 2 × 2 fiber coupler (3) two signal output parts are connected with two fibre cores of twin-core fiber (4) respectively, another input port of 2 × 2 fiber couplers (3) is connected with photodetector (7), photodetector (6) is connected with differential wave amplification treatment circuit (8) two input ends respectively with photodetector (7).
The light pulse of being sent by light source (1), after three fiber port circulators (2), arrive at 2 × 2 fiber couplers (3), this pulsed light is evenly divided into two-way by 2 × 2 fiber couplers, be sent to twin-core fiber (4), because Rayleigh scattering can occur the two ways of optical signals of transmitting forward along twin-core fiber, the backward Rayleigh scattering light of this two-way will be passed coupling mechanism (3) back along twin-core fiber (4), because two-way incident light amplitude is suitable, frequency is all identical with incident light, Rayleigh scattering light mechanism of production is identical, under the condition that meets phase matching, will produce interference, coherent signal is received by two-way photodetector (6) and photodetector (7) respectively.Because the received two-way coherent signal of two detectors is to be exported by two ports of 2 × 2 fiber couplers, so its phase place is just the opposite, after differential wave amplification treatment circuit (8), the mean intensity signal irrelevant with interferometry has been cancelled, meanwhile, measured coherent signal but obtains differential enhancing.In addition, because two fibre cores are in same optical fiber, it is identical that variation of ambient temperature can be considered, this has just eliminated the impact being brought by environment temperature.
The twin-core fiber that this system is used can be that centering type twin-core fiber, symmetrical expression twin-core fiber and hollow are protected any in inclined to one side double-core optical fiber.In addition, due to the selected twin-core fiber of the present invention, can to realize two-way light path roughly equal, and the light source that therefore this system adopts can be both the LASER Light Source with good spatial coherence, can be also wide-spectrum white-light light source.In order to ensure two-way rear orientation light time, survey, the Transmission Fibers length of the two-way receiving optical signals of this system should equate.In addition, make the intensity equilibrium of two ways of optical signals to obtain larger dynamic range and higher detection sensitivity.Therefore, wherein a road light signal need to add an optical attenuator (5) and carries out preconditioning.In order to improve the Discern and judge ability of this system for disturbing signal, the present invention can also increase twin-core fiber end reverberator (9), as shown in Figure 6, two light pulse signals are reflected back in optical fiber end, formed the long-armed Michelson interferometer of twin-core fiber.The one,, this signal is the reflected signal of fiber end face reverberator, and it is for rear orientation light, and signal amplitude is larger, can be used as compartment system and whether completed the label signal of the dynamic interference scanning of an overall process; The 2nd,, the disturbance information of this signal is included in a certain group of back scattering interference signal before this signal, thereby this signal confirmation verification criterion signal that can whether occur as the disturbance event of recognition system.
The object of the present invention is achieved like this:
Principle of work based on the distributed Michelson interferometer of twin-core fiber Sensitivity enhancement type optical time domain reflection as shown in Figure 1, the pulsed light sending from light source, after 2 × 2 coupling mechanisms that are 1: 1 through splitting ratio, be divided into the two bundle coherent lights that power is suitable, they are accessed respectively in twin-core fiber two separately independently in fiber core with single-mold.Suppose that two fibre core parameters in twin-core fiber are approximate identical, the attenuation coefficient of light is α, when light signal transmits in twin-core fiber, is respectively for the back scattering light intensity at z place apart from coupling mechanism distance
Suppose that the attenuation coefficient in optical fiber is constant, above formula is reduced to
The backward Rayleigh scattering of two bundles of passing back along two fibre cores of optical fiber is after coupling mechanism, because the two frequency is all identical with incident light, two-way incident optical power is suitable, Rayleigh scattering light mechanism of production is identical, polarization direction is roughly the same, the phase differential of supposing two-way Rayleigh scattering light changes the frequency far below light wave electric field, and phase differential variation is relatively slowly.Therefore they will be equivalent to the Michelson interferometer of motion, at the each self-forming interference signal of two ports of coupling mechanism, so arrive photo-detector PD
1and PD
2light signal be respectively
Distributed dynamic interference signal after differential amplification is
I in formula
s0(z)=P
0exp[-2 α z],
for the external disturbance phase differential of ordering along optical fiber z
a is signal amplification factor.
Under small sample perturbations is approximate, have
can be write as
Can see thus (referring to accompanying drawing 2), for twin-core fiber, be D because two fibre-optic waveguide fuses depart from central shaft spacing, thereby, small sample perturbations causes optical fiber generation minor bending to become, thereby make elongation of physical dimension of two fiber cores, another shortens, the phase differential being caused by light path obtains mechan-amplifier how much.Compare with common single-mode fiber, twin-core fiber is greatly strengthened for the detection sensitivity of the local disturbance of microvibration.
Compared with original technology, proposed by the invention thisly have following outstanding feature based on the distributed Michelson interferometer of twin-core fiber Sensitivity enhancement type optical time domain reflection: (1) optical time domain reflection characteristic---can realize distribution measuring; (2) interference pattern---can realize small sample perturbations and measure; (3) differential signal detection feature---when having offset mean intensity signal, make interference signal multiplication; (4) temperature self-compensation characteristic---because two fibre cores are co-located in same optical fiber, it is identical that variation of ambient temperature can be considered, eliminated the impact of temperature; (5) Sensitivity enhancement characteristic---because two fibre cores are all distributed in outside symmetrical axis, laterally disturbance makes to have formed between two fibre cores the mechanical deformation of differential amplification, therefore, the use of twin-core fiber has greatly strengthened the responding ability of microvibration signal.
(4) brief description of the drawings
Fig. 1 is based on the distributed Michelson interferometer system of twin-core fiber Sensitivity enhancement type optical time domain reflection structural representation;
Fig. 2 is that the phase place that twin-core fiber causes under micro-curved disturbance changes enhancing effect schematic diagram;
Fig. 3 is the twin-core fiber cross-sectional view that two fibre cores lay respectively at center and disalignment;
Fig. 4 is the twin-core fiber cross-sectional view that two fibre cores are symmetrically distributed in same covering;
Fig. 5 is the hollow twin-core polarization maintaining optical fibre cross-sectional view with oval fibre core polarization property;
Fig. 6 is the distributed Michelson interferometer system architecture schematic diagram that has increased the twin-core fiber of twin-core fiber end face reflection device.
(5) embodiment
Below in conjunction with accompanying drawing, the present invention is described in more detail:
By reference to the accompanying drawings 1, embodiments of the present invention are, send light pulse by light source, and the recurrence interval is
to guarantee in length in the twin-core fiber of L, after first light pulse back scattering light signal can be received, then send second inquiry light pulse.The light pulse being sent by light source is after three fiber port circulators, and the 3dB fiber coupler that is 1: 1 by splitting ratio is divided into two light signals that luminous power is roughly equal, two fibre cores of the twin-core fiber injecting respectively.Because Rayleigh scattering can occur the two ways of optical signals of transmitting forward along twin-core fiber, the backward Rayleigh scattering light of this two-way will transfer back in three-dB coupler along twin-core fiber, at this moment the catoptrical light amplitude of two bundles is suitable, frequency is all identical with incident light, Rayleigh scattering light mechanism of production is identical, under the condition that meets phase matching, will produce interference.One tunnel after three fiber port circulators (the about 1dB of loss) by photoelectric detector PD
1receive; Meanwhile, another road through after optical attenuator decay directly by photoelectric detector PD
2receive; Because the received two-way coherent signal of two detectors is to be exported by two ports of 2 × 2 fiber couplers, so its phase place is just the opposite, regulate optical attenuator to make two ways of optical signals size reach balance, at this moment after difference amplifier, the mean intensity signal irrelevant with interferometry has been cancelled, and two-way interference signal obtains differential multiplication.Meanwhile, because two fibre cores are in same optical fiber, it is identical that variation of ambient temperature can be considered, the light path of two-way fiber core waveguide is subject to the impact that uniform temp changes, and its change in optical path length is basic identical, and the phase differential causing thus remains unchanged.This has just eliminated the impact being brought by environment temperature.
Claims (6)
1. one kind based on the distributed Michelson interferometer of twin-core fiber Sensitivity enhancement type optical time domain reflection, it is characterized by, this system is by light source (1), three fiber port circulators (2), 2 × 2 fiber couplers (3), twin-core fiber (4), photodetector (6) and photodetector (7) and differential wave amplification treatment circuit (8) composition, light source (1) is connected with the signal input part of three fiber port circulators (2), three fiber port circulators (2) in addition two-port are connected with 2 × 2 fiber couplers (3) and photodetector (6) respectively, 2 × 2 fiber coupler (3) two signal output parts are connected with two fibre cores of twin-core fiber (4) respectively, another input port of 2 × 2 fiber couplers (3) is connected with photodetector (7), photodetector (6) is connected with differential wave amplification treatment circuit (8) two input ends respectively with photodetector (7).
2. one according to claim 1 is based on the distributed Michelson interferometer of twin-core fiber Sensitivity enhancement type optical time domain reflection, it is characterized in that: the twin-core fiber that this system is used can be centering type twin-core fiber, or symmetrical expression twin-core fiber or hollow are protected in inclined to one side double-core optical fiber.
3. one according to claim 1 is based on the distributed Michelson interferometer of twin-core fiber Sensitivity enhancement type optical time domain reflection, it is characterized in that: the light source that this system adopts can be both the LASER Light Source with good spatial coherence, can be also wide-spectrum white-light light source.
4. one according to claim 1, based on the distributed Michelson interferometer of twin-core fiber Sensitivity enhancement type optical time domain reflection, is characterized in that: the Transmission Fibers of the two-way receiving optical signals of this system is equal in length.
5. one according to claim 1, based on the distributed Michelson interferometer of twin-core fiber Sensitivity enhancement type optical time domain reflection, is characterized in that: carry out preconditioning at photodetector (6) or the front optical attenuator (5) that adds of photodetector (7).
6. one according to claim 1, based on the distributed Michelson interferometer of twin-core fiber Sensitivity enhancement type optical time domain reflection, is characterized in that: increase reverberator (9) at twin-core fiber end.
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| CN107036733A (en) * | 2017-04-21 | 2017-08-11 | 武汉理工大学 | The many reference amounts Distributed Measurement System and measuring method of twin-core dim light grid array based on dark pulse light source |
| CN108168728A (en) * | 2017-12-11 | 2018-06-15 | 哈尔滨工程大学 | Non-equilibrium polarization maintaining optical fibre dual interferometer temperature strain simultaneous measuring apparatus and method |
| CN109210385A (en) * | 2018-06-08 | 2019-01-15 | 张益平 | A kind of distributed optical fiber sensing system and method based on Phase-OTDR |
| CN109579886A (en) * | 2018-11-07 | 2019-04-05 | 桂林电子科技大学 | A kind of high integration fibre optic interferometer |
| CN109827601A (en) * | 2019-03-29 | 2019-05-31 | 重庆文理学院 | A kind of interference formula temperature based on special optical fiber and stress two-parameter measurement system |
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| CN113916326A (en) * | 2021-10-05 | 2022-01-11 | 桂林电子科技大学 | Inclined to one side double-core optic fibre level gauge |
| CN113984126A (en) * | 2021-11-04 | 2022-01-28 | 日照武汉理工大生物医药暨新材料研究院 | Temperature strain monitoring system and method based on different-doped double-core weak reflection FBG array |
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| CN111337057A (en) * | 2020-03-21 | 2020-06-26 | 哈尔滨工程大学 | Optical fiber interferometer temperature compensation device and method based on distributed temperature sensing |
| CN111337057B (en) * | 2020-03-21 | 2021-10-19 | 哈尔滨工程大学 | Optical fiber interferometer temperature compensation device and method based on distributed temperature sensing |
| CN113916326A (en) * | 2021-10-05 | 2022-01-11 | 桂林电子科技大学 | Inclined to one side double-core optic fibre level gauge |
| CN113984126A (en) * | 2021-11-04 | 2022-01-28 | 日照武汉理工大生物医药暨新材料研究院 | Temperature strain monitoring system and method based on different-doped double-core weak reflection FBG array |
| CN113984126B (en) * | 2021-11-04 | 2024-05-14 | 武汉理工大学威海研究院 | Temperature strain monitoring system and method based on differently doped double-core weak reflection FBG array |
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