CN1488963A - Full optical fiber interference method formed by feedback loop and measuring system thereof - Google Patents
Full optical fiber interference method formed by feedback loop and measuring system thereof Download PDFInfo
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Abstract
The invention realizes functions of measuring vibration characteristic, modulating additional electric signal, and optical switch through a wave interference system obtained by using feedback loop method to form full optical fiber interference. Comparing with prior art, the invention is not dependent on laser light source (narrow spectrum) so as to be able to apply to laser interference, as well as interference of light source in wide spectrum. The system can adjust sensitivity of measuring disturbance source. The method also can test spectral characteristics. The system does not have the issue of frequency response, i.e. the system is not restricted by frequency of disturbance source, and frequency is only related to response of photo detector. The invention provides three routes of interference signals with fixed phase differences, possessing features of high sensitivity, accuracy, simple structure and easy adjustment.
Description
Technical field
The present invention utilizes the optical fiber backfeed loop to set up the method and the test macro thereof of full optical fiber interference.
Background technology
Interference of light has been widely used in the test and the communications field, traditional interference of light method depends on the coherent length of laser and complicated light path structure (often adopting prism, lens and beam splitter) and debugging, and its structure mainly contains: Michelson, Mach increase Dare and Fabry-Perot.Along with the maturation of development of fiber technology and photoelectric device, the fiber optic interferometric technology is developed in eighties of last century, but its structure and principle of work and traditional laser interference method are as broad as long.Because the phase differential that the interference signal that traditional interference technique can access exists generally by the structures shape of system, particularly utilizes the interference system of fiber coupler structure, the phase differential of output signal is by the parameter decision of coupling mechanism.In order to be tested physical parameter accurately, hope can access the two paths of signals of 90 degree phase differential, by being used alternatingly two paths of signals, and the fully sensitivity of safeguards system.Do not change the parameter of system's fiber coupler, by adding the change of light signal strength, change the phase differential of initialize signal, this all-fiber interferometer also seldom.The full light fiber white light interference method is in eighties of last century late nineteen nineties appearance, its structure mainly depends on many (more than two or two) fiber couplers and is combined into optical interference circuit, and be mainly used in sensory field of optic fibre, the initial phase difference of output signal is determined at the parameter of coupling mechanism fully, can not at will change, bring certain difficulty to test.
Summary of the invention
The purpose of this invention is to provide a kind of convenience, succinct full optical fiber interference method and the test macro thereof that utilizes feedback control loop to form.
Can provide a kind of system that can be widely used in Fibre Optical Sensor and optical fiber communication according to the inventive method, system adopts a fiber coupler to realize the white light interference method, and this system not only can be applied to sensory field of optic fibre, can also be applied to fiber optic communication field.
The full optical fiber interference method that the present invention is formed by feedback control loop, after the light that is sent by light source is coupled the device beam splitting, the backfeed loop that one road light constitutes by fibre delay line earlier, by fiber coupler, the arriving signal detection port is reflected back toward the coupling mechanism output terminal once more; Another Lu Guangxian is by the acquisition of signal port, after being reflected, pass through fiber coupler, enter the output port of coupling mechanism by backfeed loop, coherent ray forms clockwise and the two-way light that transmits counterclockwise, and under the situation that fibre delay line exists, two light beams are by the asynchronism(-nization) of disturbing source, corresponding disturbing signal is also inequality, and can be expressed as time delay:
C is the light velocity in the vacuum, and L postpones fiber lengths, n
EffIt is the equivalent refractive index of optical fiber;
Disturbing source is a refractive index n to the light path that two-beam forms
sWith geometrical length L
sProduct, can be expressed as A (t) and A (t-τ),
A(t)＝n
s(t)L
s(t) (2)
A(t-τ)＝n
s(t-τ)L
s(t-τ) (3)
Because remove the influence of disturbing source, the transmission light path that two light beams pass through is equal fully, so the optical path difference Δ L that two light beams form can be expressed as:
ΔL＝A(t)-A(t-τ) (4)
1. for the fiber-optic vibration test macro, disturbing source is corresponding to vibration displacement, i.e. A (t)～S (t), and light does not change in time by the refractive index of disturbing source, so formula (4) can be expressed as
ΔL＝n
s[S(t)-S(t-τ)] (5)
Utilize mean value theorem, following formula can be rewritten as
ΔL＝n
sS′(t-τ/2)τ (6)
Following formula corresponding to the phase place (t) of interference light is
2. or in the optical communication field modulating system, disturbing source is corresponding to crystal refractive index, i.e. A (t)～n (t), light are during by disturbing source, and the geometric distance of transmission light remains unchanged, so formula (4) can be expressed as
ΔL＝L
s[n(t)-n(t-τ)] (8)
Modulation signal m (t) can be expressed as with the relation of refractive index n (t):
n(t)＝f[m(t)] (9)
Utilize mean value theorem, following formula can be rewritten as
ΔL＝L
sf′[m(t)]τ (10)
Following formula corresponding to the phase place (t) of interference light is
The interference pattern of utilization 3 * 3 fiber couplers, at the detectable signal output terminal, interference signal can be expressed as respectively:
I
1(t)＝I
0cos[(t)+
0] (12)
I
2(t)＝I
0cos[(t)-
0] (13)
I
3(t)＝I
0cosφ(t) (14)。
In splitting ratio is 13 * 3 fiber couplers,
0=120 degree; If the splitting ratio of coupling mechanism is not 1, initial phase
0≠ 120 degree.(12) the interference signal amplitude peak in (13) formula is not equating.Above in two formulas,
0Be the initial phase of interference signal, in vibration test system and voice signal transmission system, (t) is shown in (7) formula; In the optical modulation and photoswitch application of fiber optic communication field, (t) is shown in (11) formula.Because initial phase is different, it is 0 that one tunnel light intensity will appear in two interference signals, and another road light intensity is not 0 situation, and promptly all-fiber interferometer shows the switching function to light.
If add another feedback control loop again, on the superincumbent analysis foundation, interference light will form other two optical interference circuits, just its interference strength than top interference light a little less than, luminous power is 1/9 of a last surface analysis interference light power.The interference fringe expression formula of Xing Chenging is identical with (12) (13) (14) at last, just initial phase
0No longer be 120 degree, its size is in close relations relevant with the interference light watt level that two parts coherent light forms.
With the structure among Fig. 1 is example, and the light that stabilized light source (13) sends connects through wire jumper FC/PC, is introduced into 1 * 2 fiber coupler (1), by 3 * 3 fiber couplers (2), has formed two pairs of interfering beams then.
A pair of interfering beam is formed by following two light beams:
Light beam I: after tested object (14) reflection earlier of one road light,, successively enter fiber coupler (2) by port (7), fibre delay line (3), fiber coupler (4) and port (5) by fiber coupler (2) beam splitting; Light beam II: other one road light enters fiber coupler (2) by port (5), fiber coupler (4), fibre delay line (3) and port (7) earlier, and tested object (14) reflects the laggard optical fiber coupling mechanism (2) of going into.This two light beam is when tested object remains static, and the light path that passes through is equal fully, forms the interfering beam of system.
Another is formed by following two light beams interfering beam:
Light beam I: after tested object (14) reflection earlier of one road light, by fiber coupler (2) beam splitting, successively enter fiber coupler (2) by port (7), fibre delay line (3), fiber coupler (4) and port (5), after beam splitting, enter fiber coupler (2) by fiber coupler (9) and port (6) from port 8; Light beam II: other one road light enters fiber coupler (2) by port (5), fiber coupler (4), fibre delay line (3) and port (7) earlier, after beam splitting, enter fiber coupler (2) once more by port (6), fiber coupler (9) and port (8), the tested object of the light after the beam splitting (14) reflection is laggard goes into optical fiber coupling mechanism (2).This two light beam is when tested object remains static, and the light path that passes through is equal fully, forms the interfering beam of system.Because the existence of fiber coupler makes the energy of interference light compare interfering beam with last, is 1/6 of its size.
Two pairs of interfering beams form the light signal that carries the disturbing source physical features in 3 * 3 fiber couplers (2), be detected device (10), (11) and (12) reception.By the inverting interference signal, finally obtain the physical characteristics of disturbing source (14).Its expression formula is corresponding formula (12) (13) and (14) respectively.
Fig. 2,3,4 compares with structure shown in Figure 1, and its principle of work is the same with method, by reducing by a fiber coupler, makes the interfering beam energy double.Just detectable signal has also reduced one the tunnel.The interference signal expression formula is corresponding formula (13) and (14), (12) and (14), (12) and (13) respectively.
Compared to Figure 1 Fig. 5 has only formed single feedback operation light path, has formed a pair of interfering beam, and its principle of work is the same to the last analysis to interfering beam of system shown in Figure 1 with the front.The interference signal expression formula is corresponding to formula (12), (13) and (14).
Fig. 6 compares with Fig. 5, and 2 * 2 fiber couplers have replaced 3 * 3 fiber couplers, and principle of work is the same with system shown in Figure 5.The interference signal power that forms has increased by 3/2.Have only the output of two-way interference signal, its expression formula one tunnel is with the same shown in the formula (14), and another road interference signal is reverse with it.
According to (7) and (11) formula, as can be seen, the interferometric phase size is directly proportional with optical fiber time τ, promptly is directly proportional with fibre delay line length.According to these characteristics,, can increase the effect that fibre delay line length reaches increases modulation amplitude for little disturbing signal; For big modulation signal, can adopt the method that reduces fibre delay line length, reduce requirement to the signal acquiring system frequency bandwidth.Can adjust the phase modulation radian as the case may be, be a distinguishing feature of the present invention.
All-fiber interferometer of the present invention, connected mode between being connected of fiber coupler and optical fiber, the optical fiber is that the mode of fusing connects, light source is connected with the connected mode FC/PC wire jumper of interference system, and interference system also is that the FC/PC wire jumper is connected with the connected mode of detector.
Disturbing source of the present invention is the device that changes in time of light path that makes transmission light, therefore, can be vibrating device, for example the vibration that produces such as loudspeaker, shaking platform, bridge machinery etc.; Perhaps light by the time, the crystal that fine refractive index can change with the impressed voltage signal is as lithium columbate crystal etc.
The fiber coupler of system of the present invention is tapered fiber coupler.
The luminous power of coupling mechanism is divided equally, and promptly 3 * 3 fiber coupler luminous power splitting ratios are 1: 1: 1, and 2 * 2 fiber coupler luminous power splitting ratios are 1: 1.
Single-mode fiber, multimode optical fiber all are applicable to system of the present invention.
Stabilized light source can be any in following: operation wavelength is the semiconductor laser diode (LD) of 1.31 μ m or 1.55 μ m; Semiconductor light-emitting-diode (LED) laser instrument; Super-radiance light emitting diode (SLD) laser instrument etc.
The inventive method realizes white light interference (broad spectrum light source interference) method with fiber coupler and optical fiber backfeed loop structure optical interference circuit, not only can be applied to sensory field of optic fibre, can also be widely used in fiber optic communication field.Light intensity control by backfeed loop, phase differential that can realization system output interference signal.The present invention can application, be embodied in: vibration (shock wave) test, microstrain test, voice signal transmission, laser external modulation, photoswitch, functions such as light path logic coding.So no matter from structure of the present invention and range of application, this method was with any fiber optic interferometric method was all inequality in the past.
The inventive method has changed the defective that the interference of light in the past must depend on laser (narrow spectrum) light source, can not only be applied to the interference of laser, can also be applied to the interference of broad spectrum light source; Simultaneously, this interference technique can also realize the laser external modulation to electric signal, also can realize distribution adjusted and light switch function to light intensity, will be applied to the external modulation and the full optical routing exchange network of light signal; System can adjust easily to the measurement sensitivity of disturbing source, can be applicable to the test in strong disturbance source, also can be applicable to the test in weak disturbance source; System is not subjected to the restriction of disturbance source frequency, and frequency is only relevant with the response of photodetector, and there is not the frequency response problem in light path system.The present invention can access the interference signal that two-way has fixed skew, will improve the sensitivity and the precision of system.Interference system of the present invention, simple in structure, debugging is convenient, sensitivity and precision height.
Description of drawings
Fig. 1 is a system architecture synoptic diagram of the present invention.1 is 1 * 2 fiber coupler, and 2 is 3 * 3 fiber couplers, the 3rd, and fibre delay line, 4 is 1 * 2 fiber couplers, the 5, the 6th, and the output port of optical fiber, the 7, the 8th, the input port of optical fiber, 9 is 1 * 2 fiber couplers, the 10,11, the 12nd, and photodetector, the 13rd, LASER Light Source, the 14th, tested object.
Fig. 2 be system of the present invention structural representation two.1 is 1 * 2 fiber coupler, and 2 is 3 * 3 fiber couplers, the 3rd, and fibre delay line, the 5, the 6th, the output port of optical fiber, the 7, the 8th, the input port of optical fiber, 9 is 1 * 2 fiber couplers, the 10, the 12nd, photodetector, the 13rd, LASER Light Source, the 14th, tested object.
Fig. 3 be system of the present invention structural representation three.1 is 1 * 2 fiber coupler, and 2 is 3 * 3 fiber couplers, the 3rd, and fibre delay line, 4 is 1 * 2 fiber couplers, the 5, the 6th, the output port of optical fiber, the 7, the 8th, the input port of optical fiber, the 11, the 12nd, photodetector, the 13rd, LASER Light Source, the 14th, tested object.
Fig. 4 be system of the present invention structural representation four.1 is 1 * 2 fiber coupler, and 2 is 3 * 3 fiber couplers, the 3rd, and fibre delay line, 4 is 1 * 2 fiber couplers, the 5, the 6th, and the output port of optical fiber, the 7, the 8th, the input port of optical fiber, 9 is 1 * 2 fiber couplers, the 10, the 11st, and photodetector, the 13rd, LASER Light Source, the 14th, tested object.
Fig. 5 is a system architecture synoptic diagram five of the present invention.1 is 1 * 2 fiber coupler, and 2 is 3 * 3 fiber couplers, the 3rd, and fibre delay line, 4 is 1 * 2 fiber couplers, the 5, the 6th, and the output port of optical fiber, the 7, the 8th, the input port of optical fiber, 10, the 11, the 12nd, photodetector, the 13rd, LASER Light Source, the 14th, tested object.
Fig. 6 is a system architecture synoptic diagram of the present invention.1 is 1 * 2 fiber coupler, and 2 is 2 * 2 fiber couplers, the 3rd, and fibre delay line, 4 is 1 * 2 fiber couplers, the 5th, the output port of fiber coupler, the 7th, the input port of optical fiber, the 11, the 12nd, photodetector, the 13rd, LASER Light Source, the 14th, tested object.
Fig. 7 is the interference signal oscillogram of all-fiber interferometer in vibration-testing of utilizing the inventive method to realize, corresponding formula (12).
Fig. 8 utilizes two of the interference signal oscillogram of all-fiber interferometer in vibration-testing that the inventive method realizes, corresponding formula (13).
Fig. 9 utilizes three of the interference signal oscillogram of all-fiber interferometer in vibration-testing that the inventive method realizes, corresponding formula (14).
Embodiment
Embodiment
In the present embodiment, used laser instrument is SO3-B type super radiation light emitting tube (SLD) the type stabilized light source (3) that 44 research institutes of main office of electronics group produce.Fiber coupler (1) (2) (4) (9) is the single-mode optical-fibre coupler that Wuhan post and telecommunications research institute produces.Photodetector (10) (11) (12) is that 44 models of being produced are the InGaAs photodetector of GT322C500.Used optical fiber is " healthy and free from worry " G652 type single-mode fiber produced in USA.Tested object (14) is the DZT-10 permanent magnetic vibration platform that new vibration measuring instrument company of Bei Dai River section produces.Connect pale pinkish purple device, optical fiber, fibre delay line by Fig. 1 mode with the mode of fusing.Light source is that the FC/PC wire jumper is connected with interference system, interference system with the connected mode of detector.The results are shown in Figure 7,8,9 with this system testing, this interference curve is described by formula (12), (13), (14), and expression is to the test result of vibration source.
Claims (11)
1. the full optical fiber interference method that forms of a feedback control loop, after it is characterized in that being coupled the device beam splitting by the light that light source sends, the backfeed loop that one road light constitutes by fibre delay line earlier, by fiber coupler, the arriving signal detection port is reflected back toward the coupling mechanism output terminal once more; Another Lu Guangxian is by the acquisition of signal port, after being reflected, pass through fiber coupler, enter the output port of coupling mechanism by backfeed loop, coherent ray forms clockwise and the two-way light that transmits counterclockwise, and under the situation that fibre delay line exists, two light beams are by the asynchronism(-nization) of disturbing source, corresponding disturbing signal is also inequality, and can be expressed as time delay:
C is the light velocity in the vacuum, and L postpones fiber lengths, n
EffIt is the equivalent refractive index of optical fiber;
Disturbing source is a refractive index n to the light path that two-beam forms
sWith geometrical length L
sProduct, can be expressed as A (t) and A (t-τ),
A(t)＝n
s(t)L
s(t) (2)
A(t-τ)＝n
s(t-τ)L
s(t-τ) (3)
Because remove the influence of disturbing source, the transmission light path that two light beams pass through is equal fully, so the optical path difference Δ L that two light beams form can be expressed as:
ΔL＝A(t)-A(t-τ) (4)
1. for the fiber-optic vibration test macro, disturbing source is corresponding to vibration displacement, i.e. A (t)～S (t), and light does not change in time by the refractive index of disturbing source, so formula (4) can be expressed as
ΔL＝n
s[S(t)-S(t-τ)] (5)
Utilize mean value theorem, following formula can be rewritten as
ΔL＝n
sS′(t-τ/2)τ (6)
Following formula corresponding to the phase place (t) of interference light is
2. or in the optical communication field modulating system, disturbing source is corresponding to crystal refractive index, i.e. A (t)～n (t), light are during by disturbing source, and the geometric distance of transmission light remains unchanged, so formula (4) can be expressed as
ΔL＝L
s[n(t)-n(t-τ)] (8)
Modulation signal m (t) can be expressed as with the relation of refractive index n (t):
n(t)＝f[m(t)] (9)
Utilize mean value theorem, following formula can be rewritten as
ΔL＝L
sf′[m(t)]τ (10)
Following formula corresponding to the phase place (t) of interference light is
The interference pattern of utilization 3 * 3 fiber couplers, at the detectable signal output terminal, interference signal can be expressed as respectively:
I
1(t)＝I
0cos[(t)+
0] (12)
I
2(t)＝I
0cos[(t)-
0] (13)
I
3(t)＝I
0cosφ(t) (14)。
2. the test macro of the full optical fiber interference method that feedback control loop according to claim 1 forms, the light path that it is characterized in that this system is as follows: light source (13) is fiber coupler (1) afterwards, light forms two groups of interfering beams by behind the fiber coupler (1) (2), and is specific as follows;
(1) formation of coherent light beam one: one road light is from the optical fiber feedback control loop of port (5) through fiber coupler (4) and fibre delay line (3) composition, be transferred to port (7) clockwise, enter fiber coupler (2) once more, by disturbing source (14) reflected back optical fiber coupling mechanism (2); Another Lu Guangxian is reflected back toward fiber coupler (2) by disturbing source (14), and the feedback control loop from port (7) is formed by fibre delay line (3) and fiber coupler (4) enters fiber coupler (2) from port (5) counterclockwise;
(2) formation of coherent light beam two: one road light is transferred to port (8) from port (6) clockwise through fiber coupler (9), enter fiber coupler (2) once more, the feedback control loop entry port (7) that coordinates by fiber coupler (4) and fibre delay line (3) from port (5), through fiber coupler (2), by disturbing source (14) reflected back optical fiber coupling mechanism (2); Another Lu Guangxian is by disturbing source (14), be reflected back toward fiber coupler (2), arrive port (6) from port (8) clockwise through fiber coupler (9), after entering fiber coupler (2) once more, feedback control loop from port (7) is formed by fibre delay line (3) and fiber coupler (4) enters fiber coupler (2) from port (5) counterclockwise;
Above two groups of coherent light beams in 3 * 3 fiber couplers (2), form the light signal that carries the disturbing source physical features, this signal is detected device (10) (11) (12) and receives, by the inverting interference signal, obtain the physical characteristics of disturbing source (14) by formula (12) (13) (14).
3. the test macro of the full optical fiber interference method that feedback control loop according to claim 2 forms is characterized in that the fiber coupler and the detector joining with it that extract interference signal respectively reduce one.
4. the test macro of the full optical fiber interference method that feedback control loop according to claim 2 forms, the optical fiber and the fiber coupler (9) that it is characterized in that connecting (6) (8) port of coupling mechanism (2) can remove, form single loop work interference system, detector (10) directly is connected with port (8), and the serviceability of system is unaffected.
5. the test macro of the full optical fiber interference method that feedback control loop according to claim 2 forms is characterized in that coupling mechanism (2) is 2 * 2 fiber couplers.
6. the test macro of the full optical fiber interference method that feedback control loop according to claim 2 forms, it is characterized in that the connected mode between being connected of coupling mechanism and optical fiber, the optical fiber is that the mode of fusing connects, being connected of light source and optical fiber, detector adopt wire jumper to connect with being connected of optical fiber.
7. the test macro of the full optical fiber interference method that feedback control loop according to claim 2 forms is characterized in that disturbing source is a vibrating device, or the optical fibre refractivity crystal that can change with the impressed voltage signal, or the shock wave sniffer.
8. the test macro of the full optical fiber interference method that feedback control loop according to claim 2 forms is characterized in that fiber coupler is tapered fiber coupler.
9. the test macro of the full optical fiber interference method that feedback control loop according to claim 5 forms, the luminous power that it is characterized in that fiber coupler is to divide equally.
10. the test macro of the full optical fiber interference method that feedback control loop according to claim 2 forms is characterized in that used optical fiber or fibre delay line can be single-mode fibers, or multimode optical fiber.
11. the test macro of the full optical fiber interference method that forms according to the described feedback control loop of claim 1-5, it is characterized in that used laser works wavelength is semiconductor laser diode or the semiconductor light-emitting-diode laser instrument of 1.31 μ m or 1.55 μ m, perhaps super-radiance light emitting diode laser instrument.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100547365C (en) * | 2008-05-09 | 2009-10-07 | 东南大学 | The wide-field full-optical fiber perturbation sensing system high sensitivity perturbation detecting light path device |
| CN101769950B (en) * | 2009-12-30 | 2012-05-23 | 哈尔滨工业大学 | Full-optical fiber difference stream measuring device based on faraday effect |
| CN103229431A (en) * | 2012-12-26 | 2013-07-31 | 华为技术有限公司 | Crosstalk restraining method and device |
-
2003
- 2003-08-21 CN CN 03150468 patent/CN1236336C/en not_active Expired - Fee Related
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100547365C (en) * | 2008-05-09 | 2009-10-07 | 东南大学 | The wide-field full-optical fiber perturbation sensing system high sensitivity perturbation detecting light path device |
| CN101769950B (en) * | 2009-12-30 | 2012-05-23 | 哈尔滨工业大学 | Full-optical fiber difference stream measuring device based on faraday effect |
| CN103229431A (en) * | 2012-12-26 | 2013-07-31 | 华为技术有限公司 | Crosstalk restraining method and device |
| WO2014101004A1 (en) * | 2012-12-26 | 2014-07-03 | 华为技术有限公司 | Crosstalk suppression method and device |
| CN103229431B (en) * | 2012-12-26 | 2015-12-02 | 华为技术有限公司 | Cross talk restraining method and device |
| US9838074B2 (en) | 2012-12-26 | 2017-12-05 | Huawei Technologies Co., Ltd. | Crosstalk suppression method and apparatus |
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Granted publication date: 20060111 |