CN202255422U - Conical fiber bragg grating sensing demodulating system based on F-P filter - Google Patents

Abstract

A conical fiber bragg grating sensing demodulating system based on an F-P filter relates to the fiber sensing field and solves the problem of temperature-stress cross sensitivity of fiber bragg grating sensing. An output port of a broadband source (1) of the sensing demodulating 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 fiber bragg grating (3), and a third port (23) of the three-port coupler is connected with the F-P filter (4) which is pasted onto a piezoelectric ceramics (9). An output port of the F-P filter is connected onto a photoelectric detector (5) which is connected with an amplifier circuit (6), and the amplifier circuit is connected with a data acquisition card (7) which is connected with a computer (8). A piezoelectric ceramics controller (10) performs control to the piezoelectric ceramics, and an output port of the piezoelectric ceramics controller is connected with the computer. The fiber bragg grating is a conical fiber bragg grating. The conical fiber bragg grating sensing demodulating system is simple in structure, high in accuracy, good in stability, high in system signal noise ratio and resolution ratio and capable of achieving simultaneous demodulation of temperature and stress.

Description

Cone optical-fiber grating sensing demodulating system based on the F-P wave filter

Technical field

The utility model relates to the cone optical-fiber grating sensing demodulating system based on the F-P wave filter, 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.

As seen from the above analysis, solve temperature-stress cross sensitivity problem and the high precision of optical fiber grating sensing, demodulating system is the key point of present fiber grating sensing technology cheaply.

Summary of the invention

The utility model technical matters to be solved is the temperature-stress cross sensitivity problem of optical fiber grating sensing and a kind of high precision, demodulating system cheaply is provided.

The technical scheme of the utility model:

A kind of cone optical-fiber grating sensing demodulating system based on the F-P wave filter, this demodulating system comprises: wideband light source, three port coupler, fiber grating, F-P wave filter, photodetector, amplifying circuit, data collecting card, computing machine, piezoelectric ceramics, piezoelectric ceramics controller.

The output of wideband light source connects first port of three port coupler; Second port of three port coupler connects fiber grating, and the 3rd port of three port coupler connects the input of F-P wave filter, and the F-P wave filter sticks on the piezoelectric ceramics; The output of F-P wave filter connects the input of photodetector; The output of photodetector connects the input of amplifying circuit, and amplifying circuit output connects the input of data collecting card, and data collecting card output connects computing machine; The piezoelectric ceramics controller is connected with piezoelectric ceramics, and the piezoelectric ceramics controller also is connected with computing machine.Fiber grating is a cone optical-fiber grating.

The light that wideband light source sends is sent to cone optical-fiber grating through three port coupler, and the light that reflects from cone optical-fiber grating is introduced in the F-P wave filter after through three port coupler.The F-P wave filter is operated in scanning mode, and through piezoelectric ceramics controller drives piezoelectric ceramics device, the piezoelectric ceramics device applies sawtooch sweep voltage adjustment F-P chamber at interval, and the narrow passband of F-P wave filter is scanned within the specific limits.When wavelength components coupling that the scanning wavelength and the cone optical-fiber grating reflectance spectrum of F-P wave filter comprised, the F-P wave filter then provides output, otherwise the output of F-P wave filter is close to zero.Detect the output of F-P wave filter through photodetector, and then demodulate catoptrical initial wavelength of cone optical-fiber grating and bandwidth change amount thereof.

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.

The beneficial effect of the utility model: a kind of cone optical-fiber grating sensing demodulating system that the utility model proposes based on the F-P wave filter, simple in structure, be easy to realize; Higher, the good stability of precision; The F-P wave filter has narrower filter curve, and the signal to noise ratio (S/N ratio) of system is high, resolution is high; Carry out the signal demodulation through cone optical-fiber grating sensor, measure when can realize temperature-stress; The Free Spectral Range broad of F-P wave filter, this system can be used for the distributed cone optical-fiber grating sensor-based system.

Description of drawings

A kind of cone optical-fiber grating sensing demodulating system synoptic diagram of Fig. 1 based on the F-P wave filter.

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 the F-P wave filter; See Fig. 1, this demodulating system comprises: wideband light source 1, three port coupler, fiber grating 3, F-P wave filter 4, photodetector 5, amplifying circuit 6, data collecting card 7, computing machine 8, piezoelectric ceramics 9, piezoelectric ceramics controller 10.

The output of wideband light source 1 connects first port 21 of three port coupler; The 3rd port 23 that second port 22 of three port coupler connects fiber grating 3, three port coupler connects the input of F-P wave filter 4, and F-P wave filter 4 sticks on the piezoelectric ceramics 9; The output of F-P wave filter 4 connects the input of photodetector 5; The output of photodetector 5 connects the input of amplifying circuit 6, and amplifying circuit 6 outputs connect the input of data collecting card 7, and data collecting card 7 outputs connect computing machine 8; Piezoelectric ceramics controller 10 is connected with piezoelectric ceramics 9, and piezoelectric ceramics controller 10 also is connected with computing machine 8.Fiber grating 3 is a cone optical-fiber grating.

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

Because cone optical-fiber grating reflectance spectrum width has insensitivity to temperature variation, through catoptrical initial wavelength of cone optical-fiber grating and bandwidth change amount thereof, distinguishes the variation of temperature and stress, realize according to the following steps:

Step 1 is demarcated temperature-wavelength response, stress-wavelength response and three groups of relations of stress-bandwidth response of cone optical-fiber grating 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:

$\mathrm{\ΔT}=\frac{{\mathrm{\Δ\λ}}_B-K_{\mathrm{\ϵ}}\·\mathrm{\ϵ}}{K_T}$

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.

Claims (1)

1. cone optical-fiber grating sensing demodulating system based on the F-P wave filter, this demodulating system comprises: wideband light source (1), three port coupler, fiber grating (3), F-P wave filter (4), photodetector (5), amplifying circuit (6), data collecting card (7), computing machine (8), piezoelectric ceramics (9), piezoelectric ceramics controller (10);

The output of wideband light source (1) connects first port (21) of three port coupler; Second port (22) of three port coupler connects fiber grating (3), and the 3rd port (23) of three port coupler connects the input of F-P wave filter (4), and F-P wave filter (4) sticks on the piezoelectric ceramics (9); The output of F-P wave filter (4) connects the input of photodetector (5); The output of photodetector (5) connects the input of amplifying circuit (6), and amplifying circuit (6) output connects the input of data collecting card (7), and data collecting card (7) output connects computing machine (8); Piezoelectric ceramics controller (10) is connected with piezoelectric ceramics (9), and piezoelectric ceramics controller (10) also is connected with computing machine (8);

It is characterized in that: fiber grating (3) is a cone optical-fiber grating.

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