CN1588144A - Full optical fiber interference system - Google Patents
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- CN1588144A CN1588144A CNA2004100540237A CN200410054023A CN1588144A CN 1588144 A CN1588144 A CN 1588144A CN A2004100540237 A CNA2004100540237 A CN A2004100540237A CN 200410054023 A CN200410054023 A CN 200410054023A CN 1588144 A CN1588144 A CN 1588144A
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Abstract
The invention is a new-structural full-optical fiber interfering system and its interfering method, where the system is composed of a light source, 2 optical-fiber couplers, sensing optical fiber, transmission optical fiber, optical fiber delay line, reflector and so on, which are all interconnected by optical path. The light emitted by the light source is split by the optical-fiber couplers into two lights: one transmitted clockwise and the other transmitted anticlockwise, the interference signal of the two lights is detected by a detector and it obtains the physical property of the tested object through interference signal inversion. The invention can be applied to not only unimode optical fiber but also multimode optical fiber. It can test vibrating characteristic, modulate external electric signal and realize optical switching function. It can be widely applied to vibration test and communication field, and also to the sonar detection and voice signal transmission field. It has simple structure, debugging convenience and satisfying sensitivity and accuracy.
Description
Technical field
The present invention is all-fiber interferometer and the interference technique thereof that round trip utilizes fibre delay line to set up.
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, Sagnac interference ring.Wherein Sagnac interference ring structure can adopt broad spectrum light source work (being the white light interference principle), and characteristics are simple in structure, and temperature variation is insensitive to external world, is used in optical fiber communication and sensory field of optic fibre.Present white light interference system, majority utilize Sagnac interference ring structure.But, there is open defect in Sagnac interference ring structure, the sensitive zones and the fibre delay line zone that mainly show fibre system can not isolate, the physical quantity of sensitive zones test is subjected to the influence of the physical quantity of fibre delay line zone perception, and system utilizes the optical fiber one way to realize time delay, make and the insufficient sensitivity height of system therefore be greatly limited in actual applications.
Summary of the invention
The objective of the invention is to propose a kind of simple in structure, highly sensitive all-fiber interferometer.
The all-fiber interferometer that the present invention proposes is connected to form through light path by light source, two fiber couplers, sensor fibre, fibre delay line, Transmission Fibers and electro-optical detectors, and its structure as shown in Figure 1.Light path connects specific as follows: after the light source 1 is a fiber coupler 2, fiber coupler 2 connects sensor fibre 3 and Transmission Fibers 7 respectively, sensor fibre 3 is connected with another fiber coupler 4 respectively with Transmission Fibers 7 again, fiber coupler 4 is connected with fibre delay line 5 again, is connected with fiber reflector 6 then; Two outputs of fiber coupler 2 are connected with photodetector 8,9; The light that light source 1 sends forms two groups of interfering beams by fiber coupler 2 backs:
One road light after 6 reflections of optical fiber reflective mirror, once more by fibre delay line 5 and fiber coupler 4, arrives fiber coupler 2 through sensor fibre 7 by sensor fibre 3, fiber coupler 4 and fibre delay line 5 then;
A kind of light after fiber reflector 6 reflections, once more by fibre delay line 5 and fiber coupler 4, arrives fiber coupler 2 through sensor fibre 3 by Transmission Fibers 7, fiber coupler 4 and fibre delay line 5 then;
This two-way coherent light beam is received by photodetector 8 and 9 respectively.
Among the present invention, the light that sends by light source 1 by the fiber coupler beam splitting after, form 2 road coherent light beams, one road light passes through fibre delay line 5 twice then by sensor fibre 7 earlier, get back to fiber coupler from an other Transmission Fibers, one road light earlier by after the Transmission Fibers twice by fibre delay line 5, get back to fiber coupler from sensor fibre.This two-way light 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, and 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.
Light path (the refractive index n that the corresponding two-beam of disturbing source forms
sWith geometrical length L
sProduct), can represent 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)
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
λ is the interference light wavelength.
In the optical communication field modulating system, disturbing source is corresponding to crystal refractive index n (t), 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, (8) 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, I
0The incident light intensity,
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.
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 the mode of fusing, the connected mode of light source and interference system adopts FC/PC wire jumper connected mode, and the connected mode of interference system and detector also is a FC/PC wire jumper connected mode.
The disturbing source of sensor fibre of the present invention 3 positions inductions can be the device that the light path of sensor fibre is changed in time, therefore, can be vibrating device, for example the vibration that produces such as loudspeaker, sound wave, shaking platform, bridge machinery etc.; Perhaps light by the time, the crystal that optical fibre refractivity can change with the impressed voltage signal is as lithium columbate crystal etc.
The fiber coupler of system of the present invention can be tapered fiber coupler.
The luminous power of fiber coupler of the present invention is divided equally, and promptly 3 * 3 fiber coupler luminous power splitting ratios are 1: 1: 1, and 1 * 2 fiber coupler luminous power splitting ratio is 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 0.63 μ m, 0.85 μ m, 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.
Outstanding advantage of the present invention is to have changed in the past the Sagnac interference ring fibre delay line to be separated with induction optical fiber, is subjected to the external environmental interference important disadvantages thereby overcome system testing; The double fibre delay line that utilized has simultaneously reduced the cost of system, and the sensitivity that has improved system simultaneously is useful especially to the test of small-signal.Simultaneously, system compatible the advantage of white light interference system, promptly overcome the defective that the interference of light 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.It not only can be used for sensory field of optic fibre, also can be applicable to optical-fibre communications field.
Description of drawings
Fig. 1 is a system architecture synoptic diagram of the present invention.Wherein, fiber coupler 2 adopts 3 * 3 fiber couplers.
Fig. 2 be system of the present invention structural representation two.Wherein, fiber coupler 2 adopts 2 * 2 fiber couplers.
Fig. 3 is the interference signal waveform of all-fiber interferometer in audio test signal that utilizes the present invention to realize.Middle base, the corresponding formula (12) of top curve, the corresponding formula (13) of following curve.
Number in the figure: 1 is light source, and 2 is fiber coupler, and 3 is sensor fibre, and 4 is fiber coupler, and 5 is fibre delay line, and 6 is fiber reflector, and 7 is Transmission Fibers, and 8 is photodetector, and 9 is photodetector.
Embodiment
Embodiment
In the present embodiment, used laser instrument is SO3-B type super radiation light emitting tube (SLD) the type stabilized light source 1 that 44 research institutes of main office of electronics group produce.Fiber coupler 2,4 is a single-mode optical-fibre coupler.Wherein fiber coupler 2 is 3 * 3 types, fiber coupler 4 employings 1 * 2 type.Photodetector 8,9 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 is the music that the general semiconductor radio is play.System architecture connects coupling mechanism, optical fiber, fibre delay line with the mode of fusing as shown in Figure 1.Light source is that the FC/PC wire jumper is connected with interference system, interference system with the connected mode of detector.
The light that stabilized light source sends connects through wire jumper FC/PC, enter 3 * 3 fiber couplers 2, after beam split, one road light is earlier by sensor fibre 3, by 1 * 2 fiber coupler 4 and optical fibre optical fibre lag line 3, be reflected after minute surface 6 reflections,, get back to the other end of fiber coupler 2 from Transmission Fibers 7 once more by fibre delay line 5 and fiber coupler 4; Other one road light, is reflected after minute surface 6 reflections by 1 * 2 fiber coupler 4 and optical fibre optical fibre lag line 3 through Transmission Fibers 7, once more by fibre delay line 5 and fiber coupler 4, gets back to an end of fiber coupler 2 from sensor fibre 3.The interference signal that two-way light interferes the back to produce by fiber coupler 2 is detected by Photodetection system 8,9.By the inverting interference signal, finally obtain the tested object physical characteristics that sensor fibres 3 are caught by formula 12,13.The results are shown in shown in Figure 3ly with this system testing, this interference curve is described by formula (12), (13), and expression is to the test result of sound signal.
The system architecture of another embodiment as shown in Figure 2.Wherein, fiber coupler 2 employings 2 * 2 types, fiber coupler 4 employings 1 * 2 type.All the other are with embodiment 1.In structure shown in Figure 2, the light that stable light source 1 sends is through 2 * 2 fiber couplers 2, after beam split, one road light is earlier by sensor fibre 3, by 1 * 2 fiber coupler 4 and optical fibre optical fibre lag line 3, be reflected after minute surface 6 reflections,, get back to the other end of fiber coupler 2 from Transmission Fibers 7 once more by fibre delay line 5 and fiber coupler 4; Other one road light, is reflected after minute surface 6 reflections by 1 * 2 fiber coupler 4 and optical fibre optical fibre lag line 3 through Transmission Fibers 7, once more by fibre delay line 5 and fiber coupler 4, gets back to an end of fiber coupler 2 from sensor fibre 3.The interference signal that two-way light interferes the back to produce by fiber coupler 2 is detected by Photodetection system 8.By the inverting interference signal, finally obtain the tested object physical characteristics that sensor fibres 3 are caught by formula 14.
Claims (9)
1, a kind of all-fiber interferometer, it is characterized in that connecting to form through light path by light source, two fiber couplers, sensor fibre, fibre delay line, Transmission Fibers and electro-optical detectors, light path connects specific as follows: light source (1) is a fiber coupler (2) afterwards, fiber coupler (2) connects sensor fibre (3) and Transmission Fibers (7) respectively, sensor fibre (3) is connected with another fiber coupler (4) respectively with Transmission Fibers (7) again, fiber coupler (4) is connected with fibre delay line (5) again, is connected with fiber reflector (6) then; Two outputs of fiber coupler (2) are connected with photodetector (8), (9); The light that light source (1) sends forms two groups of interfering beams by fiber coupler (2) back:
One road light, once more by fibre delay line (5) and fiber coupler (4), passes through Transmission Fibers (7) then and arrives fiber coupler (2) after optical fiber reflective mirror (6) reflection by sensor fibre (3), fiber coupler (4) and fibre delay line (5);
One road light, once more by fibre delay line (5) and fiber coupler (4), passes through sensor fibre (3) then and arrives fiber coupler (2) after fiber reflector (6) reflection by Transmission Fibers (7), fiber coupler (4) and fibre delay line (5);
This two-way coherent light beam is received by photodetector (8) and (9) respectively.
2, all-fiber interferometer according to claim 1 is characterized in that the connected mode between being connected of fiber coupler and optical fiber, the optical fiber adopts the mode that fuses, the employing wire jumper mode that is connected of being connected of light source and optical fiber, detector and optical fiber.
3, all-fiber interferometer according to claim 1 is characterized in that the disturbing source tested object of described sensor fibre (3) induction is a vibrating device, or the optical fibre refractivity crystal that can change with the impressed voltage signal, or the shock wave sniffer.
4, all-fiber interferometer according to claim 1 is characterized in that described fiber coupler is tapered fiber coupler, and coupling mechanism is a single mode, or multimode.
5. all-fiber interferometer according to claim 4 is characterized in that the luminous power of described fiber coupler is divided equally.
6, all-fiber interferometer according to claim 1 is characterized in that described optical fiber or fibre delay line are single-mode fibers, or multimode optical fiber.
7, all-fiber interferometer according to claim 1 is characterized in that fiber coupler (2) is 3 * 3 or 2 * 2 fiber couplers.
8, all-fiber interferometer according to claim 1, it is characterized in that described light source (1) is the semiconductor laser diode of 0.63 μ m, 0.85 μ m, 1.31 μ m or 1.55 μ m for operation wavelength, or semiconductor light-emitting-diode laser instrument, or super-radiance light emitting diode laser instrument.
9, a kind of full optical fiber interference method according to the described all-fiber interferometer of claim 1, after it is characterized in that the light that sent by light source (1) is by the fiber coupler beam splitting, form 2 road coherent light beams, one road light passes through fibre delay line (5) twice then by induction optical fiber earlier, get back to fiber coupler from an other Transmission Fibers, one road light earlier by after the Transmission Fibers twice by fibre delay line (5), get back to fiber coupler from sensor fibre, this two-way light forms clockwise and the two-way light that transmits counterclockwise, these two groups of coherent light beams form the light signal that carries the disturbing source physical features in coupling mechanism (2), received by signal sensor, by the inverting interference signal, by formula (12), (13), (14) obtain the physical quantity that sensor fibre (3) is tested:
I
1(t)＝I
0cos[(t)+
0] (12)
I
2(t)＝I
0cos[(t)-
0] (13)
I
3(t)＝I
0cosφ(t) (14)
Wherein, I
0The incident light intensity,
0Initial phase for interference signal;
When in disturbance test macro voice signal transmission system, φ (t) is:
When in the optical modulation of fiber optic communication field or photoswitch, φ (t) is:
Wherein, n
sBe the interference light refractive index, Ls is for interfering optical path length, and λ is the interference light wavelength, τ is the time delay of two-beam when passing through disturbing source, S (t) is the optical fiber disturbance displacement, and m (t) is a modulation signal, f[m (t)]=n (t) is the relation function of modulation signal m (t) and crystal refractive index n (t).
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|---|---|---|---|
| CNA2004100540237A CN1588144A (en) | 2004-08-26 | 2004-08-26 | Full optical fiber interference system |
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|---|---|---|---|
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Cited By (5)
| 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 |
| CN101951289A (en) * | 2009-03-04 | 2011-01-19 | 弗兰克公司 | The EPON tester |
| CN105023643A (en) * | 2014-04-29 | 2015-11-04 | 上海威尔泰仪器仪表有限公司 | Theft-proof power cable and anti-theft detection system thereof |
| CN113686812A (en) * | 2021-07-23 | 2021-11-23 | 复旦大学 | Gas sensing method and system for eliminating different-path interference noise |
| CN116105848A (en) * | 2023-04-13 | 2023-05-12 | 北京信维科技股份有限公司 | Method and device for improving quality of optical fiber sensing signal |
-
2004
- 2004-08-26 CN CNA2004100540237A patent/CN1588144A/en active Pending
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 |
| CN101951289A (en) * | 2009-03-04 | 2011-01-19 | 弗兰克公司 | The EPON tester |
| CN101951289B (en) * | 2009-03-04 | 2015-06-03 | 弗兰克公司 | Passive optical network testing instrument |
| CN105023643A (en) * | 2014-04-29 | 2015-11-04 | 上海威尔泰仪器仪表有限公司 | Theft-proof power cable and anti-theft detection system thereof |
| CN113686812A (en) * | 2021-07-23 | 2021-11-23 | 复旦大学 | Gas sensing method and system for eliminating different-path interference noise |
| CN116105848A (en) * | 2023-04-13 | 2023-05-12 | 北京信维科技股份有限公司 | Method and device for improving quality of optical fiber sensing signal |
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