CN201903351U - Demodulation device for dynamic change of fiber bragg grating - Google Patents

Abstract

The utility model discloses a demodulation device for dynamic change of a fiber bragg grating, belonging to the technical field of fiber bragg grating sensors. The demodulation device for the dynamic change of the fiber bragg grating comprises a light source, an optical fiber splitter, a fiber bragg grating, a demodulation component, a photoelectric converter and a circuit processing system, wherein the demodulation component is an optical fiber semiconductor coating device. An incident light signal emitted by the light source is reflected at the fiber bragg grating, the reflected light is reflected again when passing through the optical fiber semiconductor coating device, and the reflected light at the moment passes through the photoelectric converter and the circuit processing system to obtain wavelength change quantity at the fiber bragg grating. By mainly utilizing the linear relation of the reflected light power and the wavelength change of the incident light of the optical fiber semiconductor coating device, the demodulation device is used for demodulating the phenomenon that centre wavelength is offset leftward and rightward after the fiber bragg grating is modulated by the outside, a light power signal convenient for measuring is obtained, and therefore the demodulation for the dynamic change of the fiber bragg grating is realized.

Description

A kind of fiber grating dynamic change demodulating equipment

Technical field

The utility model relates to the fiber grating sensing technology field, specifically, relates to fiber grating dynamic change demodulation field.

Background technology

Continuous development along with optical fiber sensing technology, fiber grating is owing to have the electromagnetic interference (EMI) of not being subjected to, not charged, corrosion-resistant, characteristics such as volume is little, in light weight, sensitivity height, by applicable industry scene widely, it is more crucial that the demodulation techniques of fiber grating also just become.The demodulation of fiber grating at present mainly contains spectrographic method, interferometer demodulation method, coupling raster method, adjustable F-P wave filter method etc.But spectrographic method resolution is lower, costs an arm and a leg, and demodulation speed is slow; The interferometer mode demodulation speed increases, but is subjected to the influence of extraneous factors such as temperature easily; Though coupling raster method cost is low, speed is fast, the demodulation narrow range can not satisfy the requirement of wide variation; Adjustable F-P wave filter method, though that the ratio of precision spectrographic method is wanted is high, but still can not engineering demands, and the cost height.

Summary of the invention

In order to solve the deficiencies in the prior art, the utility model provides a kind of fiber grating dynamic demodulation device, be used for demodulating fiber bragg grating owing to being subjected to the extraneous situation about being offset about the centre wavelength that produces takes place of modulating, demodulation speed is fast, only limit to employed bandwidth of a device, the parameter that is detected is only relevant with the variable quantity of fiber grating centre wavelength with the result who obtains, and is irrelevant with the absolute wavelength of fiber grating, also is not subjected to the influence of light source power variation and optical path loss.The package unit cost is low, is suitable for industrialization production.

A kind of fiber grating dynamic demodulation device described in the utility model, comprise light source, fiber optic branching device, fiber grating, restitution element, photoelectric commutator device and processing of circuit system, it is characterized in that: described restitution element is an optical fiber semiconductor coated film device, the light that light source sends reflects when inciding the fiber grating place by fiber optic branching device, because fiber grating is subjected to being offset about extraneous modulation makes the centre wavelength of light take place, reflect once more when the reflected light of skew was through optical fiber semiconductor coated film device about centre wavelength took place, reflected light enters photoelectric commutator device and processing of circuit system, makes the variable quantity of the light that the generation of fiber grating place is offset be demodulated into the physical quantity of easy measurement.

Of the present utility model being characterised in that: wideband light source sends continuous broadband light under the effect that drives, through had the narrow band light of external environment modulation intelligence behind the optical fiber splitter by fiber grating 3 reflected backs one, from the return terminal of optical fiber splitter through another optical fiber splitter to optical fiber semiconductor coated film device, after the reflection of optical fiber semiconductor coated film device, enter photoelectric commutator from the return terminal of this optical fiber splitter, light signal is converted to electric signal, again by going the DC coupling device that DC quantity is removed, only extract of ac with relative variation characteristic, wave filter carries out Filtering Processing, set the bandwidth of wave filter as required, export to data processing section, determine the variation of luminous power at last according to the variation of voltage, draw the wavelength variations of fiber grating again by the linear relationship of power and wavelength, thereby realize the dynamic change demodulation of fiber grating.

Described optical fiber semiconductor coated film device, its catoptrical power changes with the variation of lambda1-wavelength, and is linear.

Employed fiber grating is a kind of device that reflects narrow band light, and its spectral width is generally several nanometers at zero point.

Employed light source is a kind of light source of broadband, and promptly the light source light spectrum width is tens nanometers.

Described optical fiber splitter is fiber coupler or the circulator with beam split function.

Demodulation principle of the present utility model is shown in Fig. 2,3, and Fig. 2 is the reflectance spectrum of optical fiber semiconductor coated film device, and the power and the wavelength of its reflectance spectrum are linear, establishes its linear equation and is:

P＝k·λ+b 1

Wherein P is the performance number that reflects, and λ is a wavelength value, and k is slope or sensitivity, and b is an intercept.

Can obtain by formula 1:

ΔP＝k·Δλ 2

$\mathrm{\Δ\λ}=\frac{\mathrm{\ΔP}}{k}---3$

Order Then

Δλ＝k′·ΔP 4

Centre wavelength is λ ₀Fiber grating, when the wavelength change amount is Δ λ, can cause the optical power change Δ P that reflects during the optical fiber semiconductor coated film, the variation of power causes the variation of whole device output voltage.And the slope k of optical fiber semiconductor coated film device is fixed, so,, can obtain the variable quantity of luminous power by detecting photoelectric commutator and filtered voltage variety, finally obtain the variable quantity of fiber grating centre wavelength, realize the purpose of demodulation according to formula 4.

The utility model discloses a kind of fiber grating dynamic change demodulating equipment, it is compared with other fiber grating demodulation method and apparatus, and the utility model has following advantage and good effect:

1, apparatus structure is simple, and cost is low;

2, this device demodulating fiber bragg grating dynamic variable quantity is not subjected to the influence of light source power variation and optical path loss.

3, the change in voltage of demodulating equipment output just can demodulate the wavelength variations of fiber grating;

4, because the reflectance spectrum of optical fiber semiconductor coated film device has the bigger range of linearity, so the range and the dynamic range of this device are big

5, used in the demodulating equipment and gone the measure of DC coupling device, eliminated influence because of temperature on fiber semiconductor coated film device.

Description of drawings

Fig. 1 is the structural representation of the utility model device

Fig. 2 is the reflectance spectrum synoptic diagram of the utility model optical fiber semiconductor coated film device.

Fig. 3 is demodulation principle figure of the present utility model;

Embodiment

Be described in further detail below in conjunction with the enforcement of specific embodiment technical scheme:

The utility model device relates to a kind of fiber grating dynamic change demodulating equipment, mainly comprises wideband light source 1, coupling mechanism 2, fiber grating 3, circulator 4, optical fiber semiconductor coated film device 5, photoelectric commutator 6, removes DC coupling device 7, wave filter 8, data processing 9, drives 10.The input end of the output termination coupling mechanism 2 of wideband light source 1, the input end of the output termination fiber grating 3 of coupling mechanism 2, the return terminal of coupling mechanism 2 connects the input end of circulator 4, the input end of the output terminated optical fiber semiconductor coated film device 5 of circulator 4, the input end that returns termination photoelectric commutator 6 of circulator 4, the output termination of photoelectric commutator 6 is removed the input end of DC coupling device 7, remove the input end of the output termination wave filter 8 of DC coupling device, the output termination of wave filter 8 connects the input end of data processing 9.

Wideband light source 1 sends continuous broadband light under the effect of driving 10, the narrow band light that is had the external environment modulation intelligence through coupling mechanism 2 backs by fiber grating 3 reflected backs one, from the return terminal of coupling mechanism 2 through circulator 4 to optical fiber semiconductor coated film device 5, after 5 reflections of optical fiber semiconductor coated film device, enter photoelectric commutator 6 from the return terminal of circulator 4, light signal is converted to electric signal, again by going DC coupling device 7 that DC quantity is removed, only extract of ac with relative variation characteristic, wave filter 8 carries out Filtering Processing, set the bandwidth of wave filter 8 as required, export to data processing section 9, determine the variation of luminous power at last according to the variation of voltage, draw the wavelength variations of fiber grating again by the linear relationship of power and wavelength, thereby realize the dynamic change demodulation of fiber grating.

The utility model has solved the demodulation problem of fiber grating dynamic change, and the demodulation wide ranges, and the maximum that can satisfy fiber grating changes, and detection speed is fast, and real-time is good, and package unit is simple in structure, and cost is low.

In the specific implementation, the connection between wideband light source 1, coupling mechanism 2, fiber grating 3, circulator 4, optical fiber semiconductor coated film device 5, the photoelectric commutator 6 all is that optical fiber connects;

In the specific implementation, employed light source 1 is a wideband light source, and its spectral width is generally about 40nm, and has certain flatness;

In the specific implementation, the effect of driving 10 is to allow wideband light source 1 send the light of continous-stable;

In the specific implementation, employed fiber grating 3 is Fiber Bragg Grating FBGs, can reflect narrow-band spectrum;

In the specific implementation, employed coupling mechanism 2 and circulator 4 can location swaps or are coupling mechanism simultaneously or are circulator simultaneously;

In the specific implementation, described photoelectric commutator 6 is photoelectric commutator PIN pipes, and light signal is converted to electric signal;

In the specific implementation, described what go that DC coupling device 7 adopts is capacitive coupling, can remove direct current biasing and interference;

What in the specific implementation, described wave filter 8 adopted is quadravalence active band-pass filter, design bandwidth as required;

In the specific implementation, described data processing 9 is the processor modules with analog-digital conversion function and computing function.

Demodulation principle of the present utility model as shown in Figure 3, optical characteristics according to optical fiber semiconductor coated film device 5, its reflectance spectrum is that wavelength X and power P have linear relationship, the wavelength variations Δ λ of fiber grating 3, be transformed into variable power Δ P, Δ λ and Δ P are proportional, again the variation of luminous power are changed into the variation of electric signal, the variation that can draw fiber grating after treatment with photoelectric commutator 6.

The utility model adopts variable power to detect, and follows fast than the demodulation speed of spectrographic method; The variable quantity of this demodulating equipment demodulating fiber bragg grating has also used simultaneously and has gone DC coupling device and Filtering Processing, has removed the interferometer demodulation method and has been subjected to external influence factors such as temperature easily; Use wideband light source in this device, and the range of linearity broad of semiconductor coated film device, the restriction of mating the suffered demodulation scope of raster method solved.

Claims (5)

1. fiber grating dynamic change demodulating equipment, comprise light source, optical fiber splitter, fiber grating, restitution element, photoelectric commutator and processing of circuit system, it is characterized in that: described restitution element is an optical fiber semiconductor coated film device, the light that light source sends reflects when inciding the fiber grating place by fiber optic branching device, because fiber grating is subjected to being offset about extraneous modulation makes the centre wavelength of light take place, reflect once more when the reflected light of skew was through optical fiber semiconductor coated film device about centre wavelength took place, reflected light enters photoelectric commutator device and processing of circuit system, makes the variable quantity of the light that the generation of fiber grating place is offset be demodulated into the physical quantity of easy measurement.

2. a kind of fiber grating dynamic change demodulating equipment according to claim 1 is characterized in that: described optical fiber semiconductor coated film device, its catoptrical power changes with the variation of lambda1-wavelength, and is linear.

3. a kind of fiber grating dynamic change demodulating equipment according to claim 1 is characterized in that: employed fiber grating is a kind of device that reflects narrow band light, and its spectral width is generally several nanometers at zero point.

4. a kind of fiber grating dynamic change demodulating equipment according to claim 1, it is characterized in that: employed light source is a kind of light source of broadband, promptly the light source light spectrum width is tens nanometers.

5. a kind of fiber grating dynamic change demodulating equipment according to claim 1 is characterized in that: employed optical fiber splitter is a kind of in fiber coupler or the optical fiber circulator.

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