CN104181635B - Intensity distribution type demodulation system and distribution type sensing optical fiber - Google Patents
Intensity distribution type demodulation system and distribution type sensing optical fiber Download PDFInfo
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Abstract
A distribution type sensing optical fiber is characterized in that thousands of fiber gratings with ultra-low reflectance are carved on a common single-mode fiber, so that the common single-mode fiber and the fiber gratings are integrated; the reflectance R of the fiber gratings is set to be 0.1-1%, and accordingly multi-path reflection is effectively lowered. An intensity distribution type demodulation system comprises a distribution type feedback semiconductor laser device, an acousto-optic modulator, a circulator, a coupler, the distribution type sensing optical fiber, a photoelectric detector and an intensity modulation device. The distribution type feedback semiconductor laser device sends out continuous laser into the acousto-optic modulator, the laser is modulated into pulse laser with the pulse width of W, the pulse laser enters the circulator and sequentially travels through a first grating, a second grating, a third grating to the Nth grating on the distribution type sensing optical fiber, reflected light enters an unbalance interferometer from the C3 end of the circulator for interference, interference light output by the unbalance interferometer enters the photoelectric detector, and the photoelectric detector outputs electric signals to an intensity demodulation device.
Description
Technical field
This programme is related to a kind of distributed sound wave monitoring technology, more particularly, to a kind of light distribution formula demodulating system and distribution
Formula sensor fibre.
Background technology
At present distributed fiber-optic sensor technology include optical fiber dual interferometer technology, the quasi-distributed sensing technology of fiber grating and
Optical time domain reflection technology.Optical fiber dual interferometer technology adopts Sagnac Sagnac, Sagnac MZ, Sagnac Michelson
Realize distributed testing Deng interference scheme, its light path design and demodulating algorithm are more complicated, exist relatively in practical implementation
The problem being difficult to overcome more.
The quasi-distributed sensing technology of fiber grating utilizes the reflection of fiber grating to realize the distributed prison to physical quantity
Survey, in conventional patent and application, and mainly use the wavelength variation information of fiber grating, traditional concatenated fiber grating
Sensor haves the shortcomings that solder joint is many, it is big to be lost and bad mechanical strength, is unfavorable for carrying out the large-scale networking of distance, therefore its
Become the bottleneck of engineer applied in the capacity of distributed sensing fiber and reusability, be exactly mainly that capacity is low.
Optical time domain reflection technology mainly use the Rayleigh that optical fiber produces under outside perturbation action, Raman,
The effects such as Briliouin measure, and it has the advantages that, and light path is simple, sensor is easy to lay, but the signal after its scattering
Energy is very weak, therefore as relatively low in the technical specification such as detecting distance, spatial resolution, if reaching higher technical specification, its demodulation
System design more complicates, and cost increases severely, and causes high cost in high precision.
Content of the invention
In order to solve the engineer applied convenience of distributed measurement, reach the high skills such as distance monitoring, high spatial resolution
Art index, the problem of high cost, we combine the advantage of optical time domain lift-off technology and the quasi-distributed sensing technology of fiber grating, carry
The distributed sensing fiber based on ultra-low reflectance fiber grating and light distribution formula demodulating system are gone out.
The technical measures that the application is taken are：A kind of distributed sensing fiber, is characterized in that distributed sensing fiber is
The fiber grating of thousands of ultra-low reflectance is inscribed on a general single mode fiber so that general single mode fiber and fiber grating
It is integrally formed, the reflectance R of fiber grating is set in 0.1%-1%, effectively reduces multipath reflection.
Ultra-low reflectance is defined as less than 1% reflectance, is characterized in reducing the multipath reflection of fiber grating, improves letter
Number signal to noise ratio.
A kind of manufacture method of distributed sensing fiber comprises the steps：
The pulse frequency of first step initial setting excimer laser and time of exposure, adopt phase on general single mode fiber
Position mask plate method inscribes fiber grating；As shown in figure 1, under guidance first according to Theoretical Calculation and empirical value, initial setting is accurate
The pulse frequency of molecular laser and time of exposure, make fiber grating using phase mask plate legal system, fiber termination box 3 are put into biography
On moving axis B, optical fiber 4 is pulled out a part and is wrapped on winding box 5, winding box is fixed in rotary shaft C, laser controller 8
Excimer laser 1 is controlled to send pulsed light, through light path system 2, pulsed light inscribes grating on the optical fiber at A.
Second step accurately measures the ultra-low reflectance R of fiber grating according to interferometric method（R<1%）；
If the reflectance R recording is not the reflectance being pre-designed, adjust pulse frequency and the exposure of excimer laser
The light time inscribes fiber grating again, until completing the fiber grating of a ultra-low reflectance being pre-designed；By above two
Individual step completes ultra-low reflectance R and the pulse frequency of excimer laser and the one-to-one relationship of time of exposure；
As shown in figure 1, wideband light source sends firm power（Luminous power is 1mW）Laser enter into the first isolator, warp
Entering into splitting ratio after crossing the first isolator is 50:The P of 50 the first bonder11End, beam splitting light enters into isometric two-arm, one point
Shu Guang enters into P13End, the master grating being 90% through reflectance, reflected light returns to the P of the first bonder12End, transmitted light
Enter into the second isolator, second half beam splitting light enters into P14End, through test gratings, reflected light returns to the first bonder
P12End, transmitted light enters into the 3rd isolator, two-beam P12End is interfered, and enters into high accuracy light power meter, respectively recording light work(
Rate value maximum WmaxWith minima Wmin,
(1)
(2)
By formula（1）With（2）Draw
If the reflectance R recording is not the reflectance being pre-designed, adjust pulse frequency and the exposure of excimer laser
The light time inscribes fiber grating again, until completing the fiber grating of a ultra-low reflectance being pre-designed.
3rd step makes distributed sensing fiber；Determined between fiber grating according to the parameter request of distributed sensing system
Away from d and number N, wherein spacing d determines the spatial distribution rate of light distribution demodulating system, and d*N determines light distribution solution
The detecting distance of adjusting system；
（1）Adjusting the distance between power transmission shaft and rotary shaft is 2d, and makes power transmission shaft and the midpoint A of rotary shaft be located at standard
At the inscription fiber grating of molecular laser, fiber termination box is put on power transmission shaft, an optical fiber pull-out part is wrapped in take-up
On box；
（2）Optical fiber at fiber grating to be inscribed goes to cover method removing coat, the arteries and veins determining according to second step using heat
Rush frequency and time of exposure inscribes fiber grating, inscribe and carry out optical fiber coating after finishing；
（3）Control program on computer controls motor to drive rotary shaft that winding box is rotated, and length is d rice
Optical Fiber Winding on winding box, and the control program on computer guarantee inscribe fiber grating spacing be d rice；
（4）Repeated execution of steps（2）With（3）, until completing the ultra-low reflectance light in length L rice distributed sensing fiber
The inscription of fine grating, completes the making of distributed sensing fiber.
Wire-drawer-tower makes the technology of fiber grating online because inscribing fiber grating under the tangible kinestate of optical fiber, exists
Reflectance controls inaccurate and grating fringe broadening, and the distributed sensing fiber that this patent makes utilizes precise control arteries and veins
Rush frequency and time of exposure so that ultra-low reflectance is precisely controlled and there is not striped broadening phenomenon.
The method that the good fiber grating of pre-production is welded on optical fiber is suitable for the higher situation of reflectance, because thousands of
The light distribution formula demodulating system that the splice loss, splice attenuation of individual optical fiber makes cannot normal work, therefore the phase of the distributed sensing fiber of this patent
The relatively conventional fiber grating being welded on optical fiber has and does not have splice loss, splice attenuation, improves mechanical fiber optic intensity, realizes Large Copacity
Fiber grating（N>1000）Advantage.
Distributed sensing fiber used by this patent is same reflection wavelength, N number of optical fiber of same ultra-low reflectance
Grating is scribed on optical fiber so that optical fiber is integrally formed with fiber grating, and the reflectance R of grating is set in 0.1%-1%, effectively drops
Low multipath reflection.
A kind of light distribution formula demodulating system, it includes distributed Feedback semiconductor laser, acousto-optic modulator, annular
Device, bonder, distributed sensing fiber, photodetector and light intensity demodulating system；Narrow linewidth（<10KHz）Distributed Feedback
Semiconductor laser sends continuous laser and enters into acousto-optic modulator, is modulated to repetition rate and isf rep =n/2Lc, wherein n are
Optical fibre refractivity, L is fiber lengths, and c is the speed in vacuum for the light, and pulsewidth is the pulse laser of W, and pulse laser enters into annular
The C of device1End, through the C of circulator2End enters into sensor fibre, travels through the first grating, the second grating, the 3rd grating successively, and one
Until N grating, because the reflectance of optical fiber is in 0.1%-1%, most light transmission gratings continue to propagate forward, only on a small quantity
Light by the C of optical grating reflection to circulator3End, reflected light is from the C of circulator3End enters non-equilibrium interferometer and is interfered, non-flat
The interference light of weighing apparatus interferometer output enters into photodetector, and the photodetector output signal of telecommunication is to light intensity demodulating system.
Described non-equilibrium interferometer includes the second bonder and the first Faraday rotation being connected with the second bonder
Mirror and the second faraday rotation mirror；Reflected light is from the C of circulator3End enters into the P of the second bonder21It is divided into two tunnels behind end, one
Road is from the P of the second bonder23End reflects back into P through the first faraday rotation mirror23End forms P2Signal, P as shown in Figure 42
Signal；Another road is from the P of the second bonder24End is anti-through the second faraday rotation mirror after length is for the time delay optical fiber of D rice
It is emitted back towards P24End forms P4Signal, 0.1m<D<The size of 100m, D is determined by the spatial distribution rate of light distribution formula demodulating system
, that is, between grating away from d from determine, i.e. D=d.P as shown in Figure 44Signal, P4Signal and P2Signal is in the second bonder
P22End interferes generation P3Signal, P as shown in Figure 43Signal, P3Signal is from the P of the second bonder22End is sent to photoelectricity
Detector, P3Signal is exactly the intensity signal between two gratings, i.e. light distribution formula demodulating system minimum space resolution
Intensity signal.
The 4th bonder that described non-equilibrium interferometer is included the 3rd bonder and is connected with the 3rd bonder；, instead
Penetrate the C from circulator for the light3End enters into the P of the 3rd bonder31It is divided into two-way, the P of a road the 3rd bonder behind end32End enters
The P of the 4th bonder41End, the P of another Lu Zi tri- bonder33The time delay optical fiber through D rice for the end enters into the P of the 4th bonder42
End, 0.1m<D<100m, two-beam is in the P of the 4th bonder43Photodetector is sent into after interfering in end.
The 3rd Faraday rotation that described non-equilibrium interferometer is included the 5th bonder and is connected with the 5th bonder
Mirror；Reflected light is from the C of circulator3End enters into the P of the 5th bonder51It is divided into two-way, the P of a road the 5th bonder behind end54
The P of the 5th bonder is entered into after the time delay optical fiber of end feeding D rice52End, 0.1m<D<100m, another Lu Jing five bonder
P55End reaches the P that the 3rd faraday rotation mirror back reflection returns the 5th bonder55End, the P of the 5th bonder52The light letter of end output
Number with the 5th bonder P55The return light at end is in the P of the 5th bonder53Photodetector is sent into after being interfered in end.
The beneficial effect of the program is：
First, the beneficial effect of distributed sensing fiber
In sensor fibre pulling process, directly ultra-low reflectance fiber grating is scribed in sensor fibre, with sensing
Optical fiber combines together, it is to avoid the splice loss, splice attenuation of the fiber grating in previous patent or application.
2nd, the beneficial effect of light distribution formula demodulating system（Distributed sensing fiber is linked in light intensity demodulating equipment
Form distributed demodulating system）
（1）Application different from the past, this patent demodulation is the light intensity signal that fiber grating reflects, and is not wavelength letter
Breath, the capacity of grating and reflectance are closely related, the ultra-low reflectance fiber grating that this patent adopts, and its reflectance is in 0.1%-
Between 1%, and wavelength be Same Wavelength it is ensured that thousand of fiber gratings can be multiplexed on the sensor fibre of upper km, protect
Demonstrate,prove the high power capacity of grating it is ensured that the requirement of the distance of Distributed Detection.
（2）Grating space in distributed sensing fiber in this patent reflects the spatial resolution of system, different from the past
The quasi-distributed system of fiber grating can only information at demodulating fiber bragg grating, this patent demodulation is between two fiber gratings
Sensor fibre at intensity signal, increased the spatial resolution of distributed detection system.Demodulation scheme be demodulation grating it
Between intensity signal can accomplish very little with reference to the grating space of distributed sensing fiber, thus improve the spatial distribution of system
Rate.
（3）By the energy of the light after optical grating reflection compare transmitted through energy be faint, but with optical fiber in Rayleigh
Scattering or Brillouin scattering are eager to excel 100-1000 times, so system is higher than the signal to noise ratio based on Rayleigh scattering, precision will height.
Light intensity demodulating equipment demodulation principle：
According to the relevant principle of light, light intensity I on electric explorer is represented by：
I=A+BcosΦ(t) (3)
In formula (1)：A is the average light power of interferometer output, and B is interference signal amplitude, B=κ A, and κ≤1 is to interfere bar
Stricture of vagina visibility.Φ (t) is the phase contrast of interferometer.If Φ (t)=Ccos ω 0t+ φ (t), then formula (1) can be written as：
I=A+Bcos[Ccosω0t+φ(t)] (4)
In formula (2), Ccos ω 0t is phase carrier, and C is amplitude, and ω 0 is carrier frequency;φ(t) =Dcosωst +Ψ
T (), Dcos ω st is the phase place change that sensor fibre acoustic field signal causes, and D is amplitude, and ω s is acoustic field signal frequency, Ψ (t)
It is the slowly varying of initial phase that environmental perturbation etc. causes.Formula (4) is obtained with Bessel functional expansion：
（5）
In formula (5), Jn (m) is the n rank Bessel functional value under m modulation depth；As shown in figure 5, phase carrier modulation is illustrated
Desire to make money or profit and carry out fundamental frequency signal (amplitude is G), two frequency-doubled signals with the interferometer output detector signal I after Bessel functional expansion
(amplitude is H) is multiplied, in order to overcome the blanking that signal occurs and distortion phenomenon with the fluctuation of outside interference signal, to two-way
Signal has carried out differential multiplication cross (DCM), and the signal after differential multiplication cross turns after differential amplification, integral operation are processed
It is changed to
B2GHJ1(C)J2(C)φ(t) (6)
φ (t)=Dcos ω st+Ψ (t) is substituted into formula (4) to be had
B2GHJ1(C)J2(C)[Dcosωst+Ψ(t)] (7)
It can be seen that, the signal obtaining after integration contains measured signal Dcos ω st and extraneous environmental information. Hou Zhetong
It is often slow varying signal, and amplitude can be very big, can be filtered by high pass filter. being finally output as of system
B2GHJ1(C)J2(C)Dcosωst (8)
The Dcos ω st signal of the phase place change that sensor fibre acoustic field signal causes can be solved by formula (8).
Brief description
Fig. 1 is fiber grating ultra-low reflectance test block diagram；Fig. 2 is ultra-low reflectance distributed sensing fiber producing device
Schematic diagram；Fig. 3 is light distribution formula demodulating system embodiment 1 light path block diagram；Fig. 4 non-equilibrium interferometer interference signal schematic diagram；
Fig. 5 is light intensity demodulating equipment block diagram；Fig. 6 is embodiment 2 light distribution formula demodulating system block diagram；Fig. 7 is embodiment 3 light distribution
Formula demodulating system block diagram.
In Fig. 2：1- laser instrument；2- light path system；3- fiber termination box；4- optical fiber；5- winding box；6- motor；7- calculates
Machine；8- laser controller；9- power transmission shaft；10- rotary shaft；11- fiber grating.
Specific embodiment
Embodiment one：
As shown in figure 3, a kind of light distribution formula demodulating system, it includes distributed Feedback semiconductor laser, acousto-optic is adjusted
Device processed, circulator, bonder, distributed sensing fiber, photodetector and light intensity demodulating equipment；Narrow linewidth（<10KHz）Point
Cloth feedback semiconductor laser sends continuous laser and enters into acousto-optic modulator, is modulated to repetition rate and isf rep =n/2Lc,
Wherein n is optical fibre refractivity, and L is fiber lengths, and c is the speed in vacuum for the light, and pulsewidth is the pulse laser of W, and pulse laser enters
Enter the C to circulator1End, through the C of circulator2End enters into sensor fibre, travel through successively the first grating, the second grating, the
Three gratings, until N grating, because the reflectance of optical fiber is in 0.1%-1%, most light transmission gratings continue to forward pass
Broadcast, only a small amount of light is by the C of optical grating reflection to circulator3End, reflected light is from the C of circulator3End enters non-equilibrium interferometer and enters
Row is interfered, and the interference light of non-equilibrium interferometer output enters into photodetector, and the photodetector output signal of telecommunication is to light strong solution
Adjust device.
Described non-equilibrium interferometer includes the second bonder and the first Faraday rotation being connected with the second bonder
Mirror and the second faraday rotation mirror；Reflected light is from the C of circulator3End enters into the P of the second bonder21It is divided into two tunnels behind end, one
Road is from the P of the second bonder23End reflects back into P through the first faraday rotation mirror23End forms P2Signal, P as shown in Figure 42
Signal；Another road is from the P of the second bonder24End is anti-through the second faraday rotation mirror after the time delay optical fiber that length is 1 meter
It is emitted back towards P24End forms P4Signal, P as shown in Figure 44Signal, P4Signal and P2Signal is in the P of the second bonder22End occurs dry
Relate to generation P3Signal, P as shown in Figure 43Signal, P3Signal is from the P of the second bonder22End is sent to photodetector.
Photo detector signal as shown in Figure 3 enters in light intensity demodulating equipment as shown in Figure 5, described smooth strong solution
Device is adjusted to include multiplier, wave filter, differentiator, integrator.Detector signal and fundamental frequency signal the first multiplier be multiplied into
Enter to the first low pass filter, signal delivers to the first differentiator, the signal multiplication with after the second low-pass filtering enters into subtractor
Signal after one end, with the 4th multiplier carries out subtraction；Detector signal is multiplied in the second multiplier with frequency-doubled signal
Enter into the second low pass filter, signal delivers to the second differentiator, the signal multiplication with after the first low-pass filtering, enter into subtraction
Signal after device one end, with the 3rd multiplier carries out subtraction；Two paths of signals is simultaneously fed into subtractor, sends into long-pending after computing
After dividing device, high pass filter, demodulate transducing signal.
Distributed sensing fiber is the fiber grating inscribing thousands of ultra-low reflectance on a general single mode fiber, makes
Obtain general single mode fiber to be integrally formed with fiber grating, the reflectance R of fiber grating is set as 0.2%, effectively reduces multipath anti-
Penetrate.Ultra-low reflectance is defined as less than 1% reflectance, is characterized in reducing the multipath reflection of fiber grating, improves the letter of signal
Make an uproar ratio.
The manufacture method of distributed sensing fiber comprises the steps：
The first step inscribes fiber grating on general single mode fiber；As shown in Fig. 2 first according to Theoretical Calculation and empirical value
Guidance under, the pulse frequency of initial setting excimer laser and time of exposure, optical fiber light is made using phase mask plate legal system
Grid, fiber termination box 3 is put on power transmission shaft 9, optical fiber 4 is pulled out a part and is wrapped on winding box 5, and winding box 5 is fixed on and turns
On moving axis 10, laser controller 8 controls excimer laser 1 to send pulsed light, and through light path system 2, pulsed light is at A
Fiber grating 11 is inscribed on optical fiber.
Second step accurately measures the ultra-low reflectance R of fiber grating（R<1%）, as shown in figure 1, wideband light source sends stablizing
Power（Luminous power is 1mW）Laser enter into the first isolator, enter into after the first isolator splitting ratio be 50:50
The P of the first bonder11End, beam splitting light enters into isometric two-arm, and a beam splitting light enters into P13End, the mark being 90% through reflectance
Quasi-optical grid, reflected light returns to the P of the first bonder12End, transmitted light enters into the second isolator, and second half beam splitting light enters into
P14End, through test gratings, reflected light returns to the P of the first bonder12End, transmitted light enters into the 3rd isolator, two-beam
P12End is interfered, and enters into high accuracy light power meter, respectively recording optical power value maximum WmaxWith minima Wmin,
(1)
(2)
By formula（1）With（2）Draw
If the reflectance R recording is not the reflectance being pre-designed, adjust pulse frequency and the exposure of excimer laser
The light time inscribes fiber grating again, until completing the fiber grating of a ultra-low reflectance being pre-designed.By above two
Step completes ultra-low reflectance R and the pulse frequency of excimer laser and the one-to-one relationship of time of exposure.
3rd step makes distributed sensing fiber.As shown in Fig. 2 light is determined according to the parameter request of distributed sensing system
Spacing d of fine grating and number N, such as monitoring distance L rice, spatial resolution is S rice, then d=S, N=L/S.
（1）Adjusting the distance between power transmission shaft 9 and rotary shaft 10 is in 2d, and the power transmission shaft 9 and rotary shaft 10 making
Point A is located at the inscription fiber grating of excimer laser, fiber termination box 3 is put on power transmission shaft 9, optical fiber 4 is pulled out one
Divide and be wrapped on winding box 5,
（2）Optical fiber at fiber grating to be inscribed goes to cover method removing coat, the arteries and veins determining according to second step using heat
Rush frequency and time of exposure inscribes fiber grating, inscribe and carry out optical fiber coating after finishing.
（3）Control program on computer 7 controls motor 6 to drive rotary shaft 10 winding box 5 to be rotated, by length
For d rice Optical Fiber Winding on winding box 5, and the control program on computer 7 guarantee inscribe fiber grating 11 spacing be d
Rice.
（4）Repeated execution of steps（2）With（3）, until completing the ultra-low reflectance light in length L rice distributed sensing fiber
The inscription of fine grating, completes the making of the distributed sensing fiber being applied to this demodulating system.
Wire-drawer-tower makes the technology of fiber grating online because optical fiber is inscription fiber grating under kinestate, exists
Reflectance controls inaccurate and grating fringe broadening, and the distributed sensing fiber that this patent makes is using in resting state
Lower inscription fiber grating is so that ultra-low reflectance is precisely controlled and there is not striped broadening phenomenon.
The method that the good fiber grating of pre-production is welded on optical fiber is suitable for the higher situation of reflectance, because thousands of
The light distribution formula demodulating system that the splice loss, splice attenuation of individual optical fiber makes cannot normal work, therefore the phase of the distributed sensing fiber of this patent
The relatively conventional fiber grating being welded on optical fiber has and does not have splice loss, splice attenuation, improves mechanical fiber optic intensity, realizes Large Copacity
Fiber grating（N>1000）Advantage.
Distributed sensing fiber used by this patent is same reflection wavelength, 1500 light of same ultra-low reflectance
Fine grating is scribed on optical fiber so that optical fiber is integrally formed with fiber grating, and the reflectance R of grating is set in 0.2%, effectively drops
Low multipath reflection.
Embodiment two：
The present embodiment part same as Example 1 repeats no more, and difference is：As shown in fig. 6, it is described non-equilibrium dry
Interferometer includes the 3rd bonder and the 4th bonder being connected with the 3rd bonder；Reflected light is from the C of circulator3End enters
P to the 3rd bonder31It is divided into two-way, the P of a road the 3rd bonder behind end32End enters the P of the 4th bonder41End, another
The P of Lu Zi tri- bonder33The time delay optical fiber through 10m for the end enters into the P of the 4th bonder42End, two-beam is in the 4th bonder
P43Photodetector is sent into after interfering in end.
Embodiment three：
The present embodiment part same as Example 1 repeats no more, and difference is：As shown in fig. 7, it is described non-equilibrium dry
Interferometer includes the 5th bonder and the 3rd faraday rotation mirror being connected with the 5th bonder；Reflected light is from the C of circulator3
End enters into the P of the 5th bonder51It is divided into two-way, the P of a road the 5th bonder behind end54After the time delay optical fiber of 80m is sent at end
Enter into the P of the 5th bonder52End, the P of another Lu Jing five bonder55End reaches the 3rd faraday rotation mirror back reflection and returns
The P of the 5th bonder55End, the P of the 5th bonder52The optical signal of end output and the 5th bonder P55The return light at end is the 5th
The P of bonder53Photodetector is sent into after being interfered in end.
Claims (5)
1. a kind of light distribution formula demodulating system, it include distributed Feedback semiconductor laser, acousto-optic modulator, circulator,
Bonder, distributed sensing fiber, photodetector and light intensity demodulating equipment；Distributed Feedback semiconductor laser sends continuously
Laser enters into acousto-optic modulator, is modulated to repetition rate and isf rep =n/2Lc, wherein n are optical fibre refractivities, and L is that optical fiber is long
Degree, c is the speed in vacuum for the light, and pulsewidth is the pulse laser of W, and pulse laser enters into the C of circulator1End, through circulator
C2End enters into distributed sensing fiber, the first grating on ergodic distribution formula sensor fibre, the second grating, the 3rd light successively
Grid, until N grating, because the reflectance of grating is in 0.1%-1%, most light transmission gratings continue to propagate forward, only
There is a small amount of light by the C of optical grating reflection to circulator3End, reflected light is from the C of circulator3End enters non-equilibrium interferometer and is done
Relate to, the interference light of non-equilibrium interferometer output enters into photodetector, and the photodetector output signal of telecommunication demodulates dress to light intensity
Put；Distributed sensing fiber is same reflection wavelength, and N number of fiber grating of same ultra-low reflectance is scribed on optical fiber.
2. light distribution formula demodulating system according to claim 1, is characterized in that described non-equilibrium interferometer includes second
Bonder and the first faraday rotation mirror being connected with the second bonder and the second faraday rotation mirror；Reflected light is from annular
The C of device3End enters into the P of the second bonder21It is divided into two tunnels, a road is from the P of the second bonder behind end23End is revolved through the first faraday
Tilting mirror reflect back into P23End forms P2Signal；Another road is from the P of the second bonder24Hold the time delay optical fiber for D rice through length,
0.1m<D<100m, reflects back into P by the second faraday rotation mirror24End forms P4Signal, P4Signal and P2Signal is second
The P of bonder22End interferes generation P3Signal, P3Signal is from the P of the second bonder22End is sent to photodetector.
3. light distribution formula demodulating system according to claim 1, is characterized in that described non-equilibrium interferometer includes the 3rd
Bonder and the 4th bonder being connected with the 3rd bonder；Reflected light is from the C of circulator3End enters into the 3rd bonder
P31It is divided into two-way, the P of a road the 3rd bonder behind end32End enters the P of the 4th bonder41End, another Lu Zi tri- couples
The P of device33End enters into the P of the 4th bonder through D rice time delay optical fiber42End, 0.1m<D<100m, two-beam is in the 4th bonder
P43Photodetector is sent into after interfering in end.
4. light distribution formula demodulating system according to claim 1, is characterized in that described non-equilibrium interferometer includes the 5th
Bonder and the 3rd faraday rotation mirror being connected with the 5th bonder；Reflected light is from the C of circulator3End enters into the 5th
The P of bonder51It is divided into two-way, the P of a road the 5th bonder behind end54End enters into the 5th coupling after sending into D rice time delay optical fiber
The P of device52End, 0.1m<D<100m, the P of another Lu Jing five bonder55End reaches the 3rd faraday rotation mirror back reflection and returns the
The P of five bonders55End, the P of the 5th bonder52The optical signal of end output and the 5th bonder P55The return light at end is in the 5th coupling
The P of clutch53Photodetector is sent into after being interfered in end.
5. light distribution formula demodulating system according to claim 1, is characterized in that distributed sensing fiber is general at one
The fiber grating of thousands of ultra-low reflectance is inscribed on logical single-mode fiber so that general single mode fiber and fiber grating become one
Body, the reflectance R of fiber grating is set in 0.1%-1%, effectively reduces multipath reflection.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410403225.1A CN104181635B (en) | 2014-08-15 | 2014-08-15 | Intensity distribution type demodulation system and distribution type sensing optical fiber |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410403225.1A CN104181635B (en) | 2014-08-15 | 2014-08-15 | Intensity distribution type demodulation system and distribution type sensing optical fiber |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN104181635A CN104181635A (en) | 2014-12-03 |
| CN104181635B true CN104181635B (en) | 2017-02-22 |
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| CN105222884B (en) * | 2015-10-26 | 2018-07-27 | 浙江师范大学 | A kind of distributed vibration sensing method based on low light reflectivity fibre grating |
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| CN108896160B (en) * | 2015-05-27 | 2021-04-02 | 三峡大学 | Sensing method of fiber bragg grating ground sound sensing system |
| CN106066203B (en) * | 2016-05-25 | 2019-01-29 | 武汉理工大学 | The highly sensitive vibration-detection system of distribution and method based on ultrashort optical fiber optical grating array |
| CN106643837B (en) * | 2016-10-19 | 2019-04-02 | 武汉理工大学 | Bragg grating array demodulating equipment and method based on the reflection of incoherent frequency domain |
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| CN108981767B (en) * | 2018-08-17 | 2020-10-16 | 山东省科学院激光研究所 | Optical fiber distributed monitoring system and method |
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| CN102401666A (en) * | 2010-09-10 | 2012-04-04 | 北京邮电大学 | Method and device for demodulating reflection wavelength of fiber Bragg grating |
| CN102353394A (en) * | 2011-06-17 | 2012-02-15 | 武汉理工大学 | Time division multiplexing (TDM)-based low-reflectivity triangle spectrum-shaped fiber grating sensing system |
| CN102590929A (en) * | 2012-02-17 | 2012-07-18 | 武汉理工大学 | Method for continuously preparing fiber gratings on line |
| CN103411660B (en) * | 2013-08-29 | 2014-12-03 | 山东省科学院激光研究所 | Optical fiber distributed type sound wave monitor system |
| CN204101766U (en) * | 2014-08-15 | 2015-01-14 | 山东省科学院激光研究所 | Light distribution formula demodulating system and distributed sensing fiber |
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