CN202221353U

CN202221353U - Conical fiber grating sensing demodulating system based on CCD

Info

Publication number: CN202221353U
Application number: CN2011203728826U
Authority: CN
Inventors: 周倩; 宁提纲; 袁博
Original assignee: Beijing Jiaotong University
Current assignee: Beijing Jiaotong University
Priority date: 2011-09-27
Filing date: 2011-09-27
Publication date: 2012-05-16
Anticipated expiration: 2021-09-27

Abstract

The utility model relates to a conical fiber grating sensing demodulating system based on a CCD, belonging to the technical field of the fiber grating sensing. The conical fiber grating sensing demodulating system solves the problem that the temperature affects the demodulating system. The output of a broadband light source (1) of the system is connected with a first port (21) of a three-port coupler, a second port (22) of the three-port coupler is connected with a conical fiber grating (3), the light output from a third port (23) of the three-port coupler comes into a collimation reflector (4), the radiated parallel light is reflected on a diffraction grating (5), the diffractive light is radiated on a convergent lens (6) and then converged on the CCD (7), the CCD (7) is connected with the input of an amplification circuit (8), the output of the amplification circuit (8) is connected with the input of an A/D conversion module (9), the output of the A/D conversion module (9) is connected with the input of a processor (10), the output of the processor (10) is connected with a computer (11) and a CCD drive circuit (12) drives the CCD (7). The system has features of simple structure, easy implement, high demodulating speed and capability of simultaneously demodulating the temperature and the stress.

Description

Cone optical-fiber grating sensing demodulating system based on CCD

Technical field

The utility model relates to the cone optical-fiber grating sensing demodulating system based on CCD, is applicable to fields such as optical fiber sensing technology, civil engineering, track traffic.

Background technology

The advantage that fiber-optic grating sensor has many Fibre Optical Sensors not have, measuring-signal do not receive factor affecting such as light source fluctuating, bending loss of optical fiber, junction loss and surveying instrument are aging; The phase measurement of having avoided existing in the interference-type optical fiber sensing technology is unintelligible and to the needs of permanent datum, can realize long-term absolute measurement; Can in an optical fiber, be connected in series a plurality of fiber gratings, utilize wavelength-division multiplex technique that parameters such as the strain of structure and temperature are carried out high resolving power, distributed measurement on a large scale easily.

But also there is restriction in fiber-optic grating sensor in actual application in engineering.At first, fiber grating can both cause the drift of fiber grating reflected light centre wavelength to variation of temperature and strain, when fiber grating is used for sensing measurement, is difficult to distinguish the variation of the reflected light centre wavelength that temperature and stress causes.Secondly, the output quantity of fiber-optic grating sensor is a wavelength information, and the device that is used for Wavelength demodulation at present more complicated all costs an arm and a leg the practicability difficulty.

For this reason, proposed sensing demodulating system, but the wavelength coverage of its demodulation speed and demodulation is restricted all, and is not suitable for the needs of distributed sensing and kinetic measurement based on narrow band filter scanning.Simultaneously, because the utilization of Fiber Bragg Grating FBG and F-P wave filter all receives Influence of Temperature easily, thereby has also limited sensing demodulating system to a certain extent in actual application in engineering.

Summary of the invention

The utility model technical matters to be solved provide a kind of demodulation speed soon, not temperature influence, be applicable to the cone optical-fiber grating sensing demodulating system based on CCD of distributed measurement and kinetic measurement.

The technical scheme of the utility model:

A kind of cone optical-fiber grating sensing demodulating system based on CCD, the output of the wideband light source of this system connects first port of three port coupler, and second port of three port coupler connects cone optical-fiber grating;

Be placed on the light path of the 3rd port output of three port coupler opposing parallel placement on diffraction grating and the collimating mirror on the collimating mirror;

Convergent lens is placed on the reflected light path of diffraction grating, and convergent lens and CCD opposing parallel are placed;

CCD connects the input of amplifying circuit, and the output of amplifying circuit connects the input of A/D modular converter, and the output of A/D modular converter connects the input of processor, and the output of processor connects computing machine, and the CCD driving circuit is connected with CCD.

The beneficial effect of the utility model:

A kind of cone optical-fiber grating sensing demodulating system that the utility model proposes based on CCD, simple in structure, be easy to realize; Demodulation speed is high, temperature influence not; Carry out the signal demodulation through cone optical-fiber grating sensor, measure when can realize temperature-stress; The sweep velocity of CCD is fast, and this system both can satisfy static state, also can satisfy the demodulation requirement of kinetic measurement.

Description of drawings

A kind of cone optical-fiber grating sensing demodulating system synoptic diagram of Fig. 1 based on CCD.

Embodiment

Below in conjunction with accompanying drawing the present invention is further described.

A kind of cone optical-fiber grating sensing demodulating system based on CCD; See Fig. 1, this sensing demodulating system comprises: on wideband light source 1, three port coupler, cone optical-fiber grating 3, the collimating mirror 4, diffraction grating 5, convergent lens 6, CCD7, amplifying circuit 8, A/D modular converter 9, processor 10, computing machine 11, CCD driving circuit 12.

Second port 22 that the output of wideband light source 1 connects first port, 21, three port coupler of three port coupler in the system connects cone optical-fiber grating 3;

4 are placed on the light path of the 3rd port 23 output of three port coupler on the collimating mirror, and 4 opposing parallel are placed on diffraction grating 5 and the collimating mirror;

Convergent lens 6 is placed on the reflected light path of diffraction grating 5, and convergent lens 6 is placed with the CCD7 opposing parallel;

CCD7 connects the input of amplifying circuit 8, and the output of amplifying circuit 8 connects the input of A/D modular converter 9, and the output of A/D modular converter 9 connects the input of processor 10, and the output of processor 10 connects computing machine 11, and CCD driving circuit 12 is connected with CCD7.

The employed device of the utility model is commercially available device.

After the reflected light of cone optical-fiber grating 3 is through three port coupler 2, be admitted to collimating mirror 4; Shine on the diffraction grating 5 after becoming reflected light; Take place to shine on the convergent lens 6 of rear end behind many seam Fraunhofer diffractions through diffraction grating 5; Convergent lens 6 is assembled diffraction light, on the focal plane, demonstrates the spectrum that vertically has certain width.At this moment; To produce reaction to this spectrum during being placed on the CCD7 on the focal plane, convert light signal to electric signal, be sent to amplifying circuit 8; Sending into processor 10 behind the signal process A/D modular converter 9 after the amplification handles; The signal of output obtains the bandwidth and the variable quantity information thereof of cone optical-fiber grating 3 reflectance spectrums through computing machine 11 computational analysiss, and calculates stress to be measured, strain equivalence thus, accomplishes the demodulation of sensing wavelength.

Simultaneously, can also seek the maximal value in the CCD output through input related algorithm in the processor, thereby obtain the centre wavelength of cone optical-fiber grating reflectance spectrum and the variable quantity of bandwidth thereof, measure when realizing temperature and stress, strain.This is because cone optical-fiber grating reflectance spectrum width has insensitivity to temperature variation, through the variation of cone optical-fiber grating reflection bandwidth, distinguishes the variation of temperature and stress, realizes according to the following steps:

Step 1 is demarcated cone optical-fiber grating temperature-wavelength response, stress-wavelength response and three groups of relations of stress-bandwidth response respectively, confirms its stress sensitivity COEFFICIENT K _εWith the temperature control COEFFICIENT K _T

Step 2 is measured the centre wavelength drift value Δ λ of cone optical-fiber grating reflectance spectrum respectively in actual measurement _BWith bandwidth change amount Δ W;

Step 3 is confirmed its suffered stress value ε according to the variation of cone optical-fiber grating reflected light bandwidth;

Step 4 is confirmed the drift value of the foveal reflex wavelength of cone optical-fiber grating under stress according to the stress value and the stress-wavelength relationship that obtain:

Δλ _ε＝K _ε·ε

Step 5 is got rid of the caused variable quantity of stress in the center wavelength variation amount that records, can obtain the influence that simple temperature variation is brought:

ΔT＝Δλ _B-Δλ _ε

Step 6 obtains corresponding temperature variation according to temperature-wavelength relationship, thereby realizes utilizing the temperature of single cone optical-fiber grating and stress to measure simultaneously:

ΔT = \frac{Δ λ_{B} - K_{ϵ} \cdot ϵ}{K_{T}}

In the following formula, Δ T is the temperature change amount; Δ λ _BIt is bragg grating centre wavelength drift value; K _εIt is the stress sensitivity coefficient of this cone optical-fiber grating in the step 1; ε is the dependent variable that step 3 is surveyed; K _TIt is the temperature control coefficient of this cone optical-fiber grating in the step 1.

The cone optical-fiber grating of the utility model is that this cone optical-fiber grating is linear change along the cross-sectional area of the direction of grating through tapered along the corrosion of optical fiber axial linear.

Claims

1. cone optical-fiber grating sensing demodulating system based on CCD, it is characterized in that: the output of the wideband light source of this system (1) connects first port (21) of three port coupler, and second port (22) of three port coupler connects cone optical-fiber grating (3),

(4) are placed on the light path of the 3rd port (23) output of three port coupler on the collimating mirror, and (4) opposing parallel is placed on diffraction grating (5) and the collimating mirror;

Convergent lens (6) is placed on the reflected light path of diffraction grating (5), and convergent lens (6) is placed with CCD (7) opposing parallel;

CCD (7) connects the input of amplifying circuit (8); The output of amplifying circuit (8) connects the input of A/D modular converter (9); The output of A/D modular converter (9) connects the input of processor (10), and the output of processor (10) connects computing machine (11), and CCD driving circuit (12) is connected with CCD (7).