CN204514460U - A kind of vibration sensing system based on optical fiber polarisation effect - Google Patents

Abstract

The utility model belongs to technical field of optical fiber sensing, discloses a kind of vibration sensing system based on optical fiber polarisation effect, comprising: light-pulse generator; Fibre Optical Sensor link, receives light pulse signal, produces feedback signal; Analyzer, carries out analyzing operation by feedback signal; Photo-detector, converts electric signal to and exports by light signal; Data collecting card, receives electric signal, transforms and stores and send to next stage circuit; Graphics art terminal, receives electric signal and conversion obtains the time domain beamformer of feedback signal, and carries out to it frequency domain collection of illustrative plates that Fourier transform obtains feedback signal; Wherein, Fibre Optical Sensor link comprises: input conduction optical fiber, and light pulse signal is transmitted in carrying; Sensor fibre, receive the light pulse signal of described input conduction optical fiber, induction vibration signal, produces feedback signal; Feedback conduction optical fiber, receives described feedback signal, passes to described analyzer.The utility model realizes multi-point sensing by multiple independently sensing branch road, avoids mutual interference, affects sensing efficiency.

Description

A kind of vibration sensing system based on optical fiber polarisation effect

Technical field

The utility model relates to technical field of optical fiber sensing, particularly a kind of vibration sensing system based on optical fiber polarisation effect.

Background technology

Optical fibre vibration sensor is generally used in circumference safety-security area, and typical apply place comprises: museum, stadiums, national defence communication cable, communication base station, airport, railway station, Along Railway, oil and gas pipes etc.

The flashlight of existing POTDR sensor-based system comes from the backward Rayleigh scattering of the pulsed light of propagated forward.Its subject matter is, because disturbance location have impact on the polarization state of the signal behind this positions all, so system can only locate first disturbing source, and the sensing operation of a functional positioning position, greatly have impact on operating accuracy and the efficiency of sensor-based system; Meanwhile, because the backward rayleigh scattering coefficient of general single mode fiber is very little, so the flashlight produced is very weak, at the order of magnitude of a few to tens of nanowatts; Because the frequency of flashlight is very high, tens to megahertz up to a hundred, so the noise equivalent power of photo-detector is also in tens of nanowatt; Finally cause the signal to noise ratio (S/N ratio) of system very low.

Utility model content

The utility model provides one to avoid disturbance mutually to disturb, and lifting multiposition is efficient, the subregion type optical fiber vibration sensing system of high-precision sensing.

For solving the problems of the technologies described above, the utility model provides a kind of vibration sensing system based on optical fiber polarisation effect, comprising: light-pulse generator, produces light pulse signal;

Fibre Optical Sensor link, receives described light pulse signal, and generates feedback signal according to described light pulse signal;

Analyzer and photo-detector, carry out analyzing operation by described feedback signal, and described feedback signal is converted to electric signal output;

Data collecting card, receives described electric signal, transforms and stores and send;

Graphics art terminal, obtains the data message of the transmission of described data collecting card, and draws time domain beamformer and the frequency domain collection of illustrative plates of feedback signal;

Wherein, described Fibre Optical Sensor link comprises:

Input conduction optical fiber, light pulse signal is transmitted in carrying;

Sensor fibre, receive the light pulse signal of described input conduction optical fiber, induction vibration signal, produces feedback signal;

Feedback conduction optical fiber, receives described feedback signal, passes to described analyzer.

Further, described sensor fibre is many, and arbitrary described sensor fibre two ends are communicated with described input conduction optical fiber and described feedback conduction optical fiber respectively by coupling mechanism, form many independently sensor measuring branch roads.

The vibration sensing system based on optical fiber polarisation effect that the utility model provides, by sensor fibre link, arranges multiple separate sensor fibre branch road, realizes the standalone probe sensing of multiple position; Simultaneously, the conduction optical fiber transmitted due to sensing branch road and light pulse signal is separate, make disturbance or the sensing operation of a certain position or multiple position, the pulse signal that can not affect the sensing branch road of other positions is propagated, and then other sensing branch road sensing operations can not be affected, thus the positioning precision of the sensor-based system greatly promoted and efficiency.

Accompanying drawing explanation

The optical fiber vibration sensing system structural representation that Fig. 1 provides for the utility model embodiment;

The time domain beamformer of the single feedback signal that Fig. 2 provides for the utility model embodiment;

The time domain beamformer of multiple feedback signals that Fig. 3 provides for the utility model embodiment;

The time dependent waveform of feedback signal that Fig. 4 provides for the utility model embodiment and carry out the spectrum waveform schematic diagram after Fourier transform.

Embodiment

See Fig. 1, a kind of vibration sensing system based on optical fiber polarisation effect that the utility model embodiment provides, comprising: light-pulse generator, produces light pulse signal;

Fibre Optical Sensor link, receives light pulse signal, produces feedback signal via Inductive links;

Online analyzer, carries out analyzing operation by feedback signal;

Photo-detector, receives the output signal of analyzer, converts electric signal to and exports;

Data collecting card, receives the electric signal of photo-detector, transforms and stores and send;

Graphics art terminal, receives data collecting card and exports data and time domain beamformer and the frequency domain collection of illustrative plates thereof of drawing feedback signal;

Wherein, Fibre Optical Sensor link comprises:

Input conduction optical fiber, light pulse signal is transmitted in carrying;

Sensor fibre, receives the light pulse signal of input conduction optical fiber, induction vibration signal, produces feedback signal;

Feedback conduction optical fiber, receiving feedback signals, passes to analyzer;

Data Control processing module and light-pulse generator set up real-time Communication for Power, realize the control of light source.

The course of work based on the vibration sensing system of optical fiber polarisation effect is: light-pulse generator produces light pulse signal, along the transmission of input conduction optical fiber, in transmittance process, enters sensor fibre; Sensor fibre produces light signal fed back and passes to analyzer via output conduction optical fiber, then arrive photodetector and convert electric signal to, stored by data collecting card conversion, export to graphics art terminal, draw the frequency domain collection of illustrative plates after feedback signal waveform figure and Fourier transform, the result result of detection of real-time sensing detection Vibration Condition.

In prior art, when a sensing location point action or after being disturbed, along on the pulse direction of propagation, the location of all sensing locations after this location point all will be affected, and have a strong impact on positioning precision and the work efficiency of sensor-based system.

In the present embodiment, many sensor fibres are separate, from the access of pulse signal, to the output of feedback signal, all independently carry out, avoid mutual interference.

Sensor fibre is many, and arbitrary described sensor fibre two ends are communicated with input conduction optical fiber and feedback conduction optical fiber respectively by coupling mechanism, form many independently sensor measuring branch roads.Wherein, arrange two corresponding coupling mechanisms respectively at input conduction optical fiber and feedback conduction optical fiber, the output of the access and feedback signal that directly realize pulse signal enters analyzer, and light channel structure is independent.And then avoid mutual interference, thus greatly improve positioning precision and work efficiency.Meanwhile, the signal to noise ratio (S/N ratio) of optical fiber vibration sensing system can be promoted, and there is not convolution problem and the coherent noise problem of signal completely.In view of, the disturbance of sensor fibre only affects the polarization state of the light signal through this sensor fibre, for the light signal through other sensor fibres without impact, achieves multiple spot and monitors simultaneously.

Simultaneously, in order to make up the phenomenon that the Dynamic Range that brings due to fibre loss reduces along with the increase of distance, can along with the increase of distance, the luminous power improving and enter sensor fibre is reached by the splitting ratio changing coupling mechanism, make the intensity of each reflection spot basically identical, the dynamic range of keeping system, promotes the fidelity of feedback signal, the efficiency of promotion signal process.

See Fig. 2, Fig. 3 and Fig. 4, if pulse width is δ T (ns, nanosecond), light velocity of propagation is in a vacuum c, and optical fibre refractivity is n, then light pulse length l is in a fiber:

$1=\mathrm{\δT}\×\frac{c}{n}$

Suppose that the fiber lengths between coupling mechanism 1 and light-pulse generator is L ₁, the fiber lengths between coupling mechanism 2 and coupling mechanism 1 is L ₂..., coupling mechanism m and coupling mechanism m-1, between fiber lengths be L _m.Sensor fibre 1 length is K ₁, sensor fibre 2 length is K ₂..., sensor fibre m length is K _m.The horizontal ordinate of the waveform that data collecting card collects is the time, and the relation of time and distance is by formula (2):

$T_j=\frac{\underset{i=1}{\overset{i=j}{\mathrm{\Σ}}}{L}_i+K_j}{c/n}$

Wherein j=1,2 ..., n.

In order to the convenience of signal transacting, following formula (3) can be met by the fiber lengths controlling each section:

T _j-T _j-1>δT

Wherein j=1,2 ..., n.

If the pulse repetition time of light-pulse generator is T (ms, millisecond), in order to prevent the mutual crosstalk of the signal between adjacent periods, T need meet formula (4):

$T>\frac{\underset{i=1}{\overset{i=m}{\mathrm{\Σ}}}{L}_i+K_m}{c/n}$

See Fig. 2, now add analyzer, due to polarization state random evolution process in a fiber, feedback signal is detected by photo-detector after analyzer, and data collecting card gathers the signal of photo-detector, by graphics art terminal or computer drawing oscillogram.

See Fig. 3, when external disturbance acts on sensor fibre, the change of the polarization state caused by disturbance can cause the intensity of light pulse signal to change.In view of multiple independent sensor fibre self contained function, so when sensor fibre is disturbed, do not affect the signal in other each points or region.The signal gathering multiple cycle can draw each reflection spot signal intensity waveform situation by processing further; By the signal waveform in multiple cycle by getting off with the change records of distance with the time.

See Fig. 4, get pulse signal i (i=1,2 ..., signal m) on the different recurrence interval, can draw the time dependent oscillogram of signal of reflection spot i.And then Fourier transform is carried out to data, the frequency domain collection of illustrative plates of this reflection spot signal can be obtained, by further analyzing the frequency information that can obtain disturbing signal source.Pulse repetition rate limits, so the sample frequency fs of single reflection spot signal is by formula (4):

$\mathrm{fs}=\frac{1}{T}$

According to nyquist sampling law, the highest frequency f of the signal that can detect _maxfor:

$f\max =\frac{\mathrm{fs}}{2}$

The vibration sensing system based on optical fiber polarisation effect that the utility model embodiment provides, by sensor fibre link, arranges multiple separate sensor fibre branch road, realizes the standalone probe sensing of multiple position; Simultaneously, the conduction optical fiber transmitted due to sensing branch road and light pulse signal is separate, make disturbance or the sensing operation of a certain position or multiple position, the pulse signal that can not affect the sensing branch road of other positions is propagated, and then other sensing branch road sensing operations can not be affected, thus the sensor-based system multiple affair greatly promoted station-keeping ability simultaneously.

It should be noted last that, above embodiment is only in order to illustrate the technical solution of the utility model and unrestricted, although be described in detail the utility model with reference to example, those of ordinary skill in the art is to be understood that, can modify to the technical solution of the utility model or equivalent replacement, and not departing from the spirit and scope of technical solutions of the utility model, it all should be encompassed in the middle of right of the present utility model.

Claims (2)

1. based on a vibration sensing system for optical fiber polarisation effect, it is characterized in that, comprising:

Light-pulse generator, produces light pulse signal;

Fibre Optical Sensor link, receives described light pulse signal, and generates feedback signal according to described light pulse signal;

Analyzer and photo-detector, carry out analyzing operation by described feedback signal, and described feedback signal is converted to electric signal output;

Data collecting card, receives described electric signal, transforms and stores and send;

Graphics art terminal, obtains the data message of the transmission of described data collecting card, and draws time domain beamformer and the frequency domain collection of illustrative plates of feedback signal;

Wherein, described Fibre Optical Sensor link comprises:

Input conduction optical fiber, light pulse signal is transmitted in carrying;

Sensor fibre, receive the light pulse signal of described input conduction optical fiber, induction vibration signal, produces feedback signal;

Feedback conduction optical fiber, receives described feedback signal, passes to described analyzer.

2. as claimed in claim 1 based on the vibration sensing system of optical fiber polarisation effect, it is characterized in that: described sensor fibre is many, arbitrary described sensor fibre two ends are communicated with described input conduction optical fiber and described feedback conduction optical fiber respectively by coupling mechanism, form many independently sensor measuring branch roads.