CN1035344C - Polarizing direct current optical fibre sensor compensation method - Google Patents

Abstract

The present invention provides a polarizing direct current optical fiber sensor compensation method; signal light is split by a light splitter after passing through sensing material and then is transmitted to a photoelectric detector. The present invention is characterized in that compensation light is split by the light splitter after passing through compensation material and then is transmitted to the photoelectric detector. The present invention has the advantages of high stabilization, high measure precision, etc., and the present invention can avoid the influence of various factors. The present invention can be used for the compensation of various direct current optical fiber sensors.

Description

The compensation method of polarization type direct current component opitical fiber sensor

The present invention relates to a kind of compensation method of direct current component opitical fiber sensor, particularly about a kind of compensation method of polarization type direct current component opitical fiber sensor.

In order to make the polarization type direct current component opitical fiber sensor can work steady in a long-term when the telemeasurement, to its light source luminescent power, the variation of fiber transmission attenuation and photodetector responsiveness must be compensated, and its mode of the compensation method of existing polarization type direct current component opitical fiber sensor has:

(1), Wheatstone bidge type network: the at present best implementation method of this Fibre Optical Sensor is that four optical fiber couplers are connected across respectively between sensing head front and back and the reference path, the light that two root receiving fibers is successively conducted send, reach the compensation purpose by the ratio computing then from two light sources, but the optical fiber coupler splitting ratio has stronger dependence to the incident light pattern, makes this method still can not satisfy high-precision measurement requirement.

(2), single light source sensing head polarization spectro: adopt the device structure of this method simple, but can not guarantee the unanimity that two root receiving fiber losses change, the variation of photodetector responsiveness can not compensate, so its precision is lower.

(3), two light source sensing head polarization spectros: the required polarization splitting prism of the equipment of this method costs an arm and a leg, and unstable properties.

High-precision direct current component opitical fiber sensor will step into the industrial practicability stage, only compensate the illuminating source luminous power, the photodetector responsiveness, the fiber transmission attenuation variation is not enough far away, in order to make direct current component opitical fiber sensor really reach high precision, the high stable performance is stepped into the industry practical stage, must compensation illuminating source center wavelength variation and sensing material characteristic variations.

The purpose of this invention is to provide a kind of compensation method that illuminating source luminous power, photodetector responsiveness, fiber transmission attenuation change, also can compensate the polarization type direct current component opitical fiber sensor of illuminating source center wavelength variation and sensing material characteristic variations that not only can compensate.

Technical solution of the present invention is: a kind of compensation method of polarization type direct current component opitical fiber sensor, its flashlight 10 collimates through Optical Fiber Transmission to the GRIN Lens 1 of optical cable 16,17 of the polarizers are inclined to one side, through sensing material 2 then through optical splitter 9 beam split, again through analyzer 6,7 analyzings, through GRIN Lens 5,8 injection fibres transfer to photodetector 12,13, it is characterized in that: be provided with compensation light 11, compensation light 11 collimates through Optical Fiber Transmission to the GRIN Lens 3 of optical cable 16,18 of the polarizers are inclined to one side, through compensative material 4, then through optical splitter 9 beam split, again through analyzer 6,7 analyzings are through GRIN Lens 5,8 injection fibres transfer to photodetector 12,13; Its compensation formula is: $S=\frac{i11-i12}{i11+i12}-K\left(\frac{i21-i22}{i21+i22}\right)$ In the formula: S: with measured relevant constant;

I11, i12: flashlight 10 luminous, the compensation light signals that light 11 is not luminous, photodetector 12,13 detects;

K: correction factor:

I21, i22: the photosignal that compensation light is 11 luminous, flashlight 10 is not luminous, photodetector 11,12 detects.

Described sensing material 2 is quartz glass or K9 glass, and described compensative material is quartz crystal or mica waveplate.

Described optical splitter 9 is a light splitting coupler, polarization splitting prism or common Amici prism.

The present invention compares with prior art has the measuring accuracy height, and compensation method is simple, and the degree of stability height can be avoided the advantages such as influence of various factors.

Fig. 1 is the compensation method synoptic diagram of the polarization type direct current component opitical fiber sensor of the two light source sensing head polarization spectros of the present invention.

Fig. 2 is a Wheatstone bidge type network compensation method synoptic diagram of the present invention.

Below in conjunction with description of drawings embodiment

Embodiment 1:

As shown in Figure 1:

Light-receiving emitter 14 is by illuminating source 10, compensation radiant 11 and photodetector 12,13 constitute, illuminating source 10 and compensation radiant 11 adopt the light emitting diode of two consistent wavelength, 15 of sensing heads are by GRIN Lens 1,3,5,8, the polarizer 17,18, quartz glass is as sensing material 2, rectangular parallelepiped is protected common partially Amici prism 9, the compensative material 4 that analyzer 6 and the employing quartz crystal between the polarizer 18 and the common partially Amici prism 9 of guarantor are made constitutes, and light-receiving emitter 14 adopts optical cable 16 to be connected with being connected of sensing head 15.Adopting quartz glass is as sensing material 2, quartz crystal is the pressure transducer that compensative material 4 is made, λ/2 wave plates that its quartz crystal is made, quartz glass sensing material 2 produces stress birefrin under stress, stress birefrin introducing phase differential: θ=2 π CL σ/go into, the quartz crystal compensative material is a birefringent material, introduces phase differential $\mathrm{\β}=\frac{2\mathrm{\π}{L}^{\′(\mathrm{ne}-n_0)}}{{\mathrm{\λ}}^{\′}}$ In the formula: C--quartz glass stress birefrin constant.

Ne, no--are respectively the refractive index of O light and e light.

L, L '--be respectively quartz glass, quartz crystal along optical propagation direction thickness.

σ--tested stress

λ, λ '--be optical wavelength.

Its compensation is calculated as follows:

Luminous when illuminating source 10, compensation radiant 11 is not luminous, and photodetector 12,13 may detect photosignal i11 and i12, and photosignal i11, i12 have the following relationship formula with variable θ: $i11=\left(\frac{1}{2}\right)I_{0}L11R11\mathrm{<figure-callout\; id="2"\; label="CO\; S"\; filenames="C9210987300081.png"\; state="\{\{state\}\}">CO</figure-callout>}{S}^{}{}^2\mathrm{\&theta;}----\left(1\right)$ $i12=\left(\frac{1}{2}\right)I_{0}L12\mathrm{<figure-callout\; id="12"\; label="R"\; filenames="C9210987300081.png"\; state="\{\{state\}\}">R</figure-callout>}12\mathrm{<figure-callout\; id="2"\; label="si\; n"\; filenames="C9210987300081.png"\; state="\{\{state\}\}">si</figure-callout>}{n}^{}{}^2\mathrm{\&theta;}----\left(2\right)$

(1) in (2) formula:

I ₀--the incident polarized light luminous power.

L11, L12--are respectively two root receiving fiber loss factors.

R11, R12--are respectively two photodetector responsivenesses.

θ--the transducing signal of the birefringence introducing that bring out in sensing material in tested outfield.

Luminous when compensation radiant 11, illuminating source 10 is not luminous, and photodetector 11,12 may detect photosignal i21 and i22, and photosignal i21, i22 have the following relationship formula with other amount: $i21=\left(\frac{1}{2}\right){I^{\&prime;}}_{0}L21R21\mathrm{<figure-callout\; id="2"\; label="CO\; S"\; filenames="C9210987300081.png"\; state="\{\{state\}\}">CO</figure-callout>}{S}^{}{}^2\mathrm{\&beta;}----\left(3\right)$ $i22=\left(\frac{1}{2}\right){I^{\&prime;}}_{0}L22R22\mathrm{<figure-callout\; id="2"\; label="Si\; n"\; filenames="C9210987300081.png"\; state="\{\{state\}\}">Si</figure-callout>}{n}^{}{}^2\mathrm{\&beta;}----\left(4\right)$ (3), in (4) formula:

I ' ₀--the incident light luminous power

L21, L22--are respectively the loss factor of optical fiber in the compensation 11 luminous moment of radiant.

R21, R22--are respectively the response of photodetector in the compensation 11 luminous moment of radiant and become.

Produce the compensating signal that birefringence is introduced in the 3--compensative material 4.

When illuminating source 10 and compensation radiant fluorescent lifetime enough have at interval in short-term:

L11＝L21、L12＝L22、R11＝R21、R12＝R22

Then have:

i11＝I ₀L11R11COS ²θ……(5)

i12＝I ₀L12R12Sin ²θ……(6)

i21＝I′ ₀L11R11COS ²β……(7)

i22＝I′ ₀L12R12Sin ²β……(8)

The signal that (5) to (8) formula is represented carries out following computing: $S_1=\frac{i11-i12}{i11+\mathrm{<figure-callout\; id="12"\; label="i"\; filenames="C9210987300081.png"\; state="\{\{state\}\}">i</figure-callout>}12}=\frac{L11R11\mathrm{<figure-callout\; id="2"\; label="CO\; S"\; filenames="C9210987300081.png"\; state="\{\{state\}\}">CO</figure-callout>}{S}^{}{}^2\mathrm{\&theta;}-L12\mathrm{<figure-callout\; id="12"\; label="R"\; filenames="C9210987300081.png"\; state="\{\{state\}\}">R</figure-callout>}12\mathrm{<figure-callout\; id="2"\; label="Si\; n"\; filenames="C9210987300081.png"\; state="\{\{state\}\}">Si</figure-callout>}{n}^{}{}^2\mathrm{\&theta;}}{L11R11\mathrm{<figure-callout\; id="2"\; label="CO\; S"\; filenames="C9210987300081.png"\; state="\{\{state\}\}">CO</figure-callout>}{S}^{}{}^2\mathrm{\&theta;}+L12\mathrm{<figure-callout\; id="12"\; label="R"\; filenames="C9210987300081.png"\; state="\{\{state\}\}">R</figure-callout>}12\mathrm{<figure-callout\; id="2"\; label="Si\; n"\; filenames="C9210987300081.png"\; state="\{\{state\}\}">Si</figure-callout>}{n}^{}{}^2\mathrm{\&theta;}}$ ${\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="C9210987300081.png"\; state="\{\{state\}\}">S</figure-callout>}}_2=\frac{i21-i22}{i21+i22}=\frac{L11R11\mathrm{<figure-callout\; id="2"\; label="CO\; S"\; filenames="C9210987300081.png"\; state="\{\{state\}\}">CO</figure-callout>}{S}^{}{}^2\mathrm{\&beta;}-L21\mathrm{<figure-callout\; id="12"\; label="R"\; filenames="C9210987300081.png"\; state="\{\{state\}\}">R</figure-callout>}12\mathrm{<figure-callout\; id="2"\; label="Si\; n"\; filenames="C9210987300081.png"\; state="\{\{state\}\}">Si</figure-callout>}{n}^{}{}^2\mathrm{\&beta;}}{L11R11\mathrm{<figure-callout\; id="2"\; label="CO\; S"\; filenames="C9210987300081.png"\; state="\{\{state\}\}">CO</figure-callout>}{S}^{}{}^2\mathrm{\&beta;}+L12R12\mathrm{<figure-callout\; id="2"\; label="Si\; n"\; filenames="C9210987300081.png"\; state="\{\{state\}\}">Si</figure-callout>}{n}^{}{}^2\mathrm{\&beta;}}$

In order to compensate wavelength, sensing material characteristic variations, loss factor, responsiveness changes, once more by computing:

S=S1-KS2 ... K is a correction factor in the formula, and S is and measured relevant constant.

Because θ=2 π CL σ (/ λ, $\mathrm{\&beta;}=\frac{2\mathrm{\&pi;}{L}^{\&prime;}(\mathrm{\&eta;e}-\mathrm{\&eta;}0)}{{\mathrm{\&lambda;}}^{\&prime;}}$ And obtain the one-to-one relationship of S value and tested value, by the linear interpolation compensation of computing machine, obtain the S value only with measured relevant result, eliminated optical source wavelength, the sensing material characteristic variations, fibre loss, the variation of photodetection responsiveness and illuminating source power are to the influence of measurement result.

Embodiment 2

Accompanying drawing 2 is Wheatstone bidge type network compensation method synoptic diagram of the present invention.Among the figure: 1,3,5,8 is GRIN Lens, and 2 is that sensing material, 4 is that compensative material, 10 is that flashlight illuminating source, 11 is compensatory light, and 12,13 is photodetector, and 19 are the beam split coupling device, and its compensation computing method are identical with embodiment 1.

Claims (3)

1, a kind of compensation method of polarization type direct current component opitical fiber sensor, its flashlight (10) collimates through Optical Fiber Transmission to the GRIN Lens (1) of optical cable (16), the polarizer (17) rises partially, through sensing material (2) then through optical splitter (9) beam split, again through analyzer (6), (7) analyzing, through GRIN Lens (5), (8) injection fibre transfers to photodetector (12), (13), it is characterized in that: be provided with compensation light (11), compensation light (11) collimates through Optical Fiber Transmission to the GRIN Lens (3) of optical cable (16), the polarizer (18) rises partially, through compensative material (4), then through optical splitter (9) beam split, again through analyzer (6), (7) analyzing is through GRIN Lens (5), (8) injection fibre transfers to photodetector (12), (13); Its compensation formula is: $S=\frac{i11-i12}{i11+i12}-K\left(\frac{i21-i22}{i21+i22}\right)$ In the formula: S: with measured relevant constant;

I11, i12: the light signal that flashlight (10) is luminous, compensation light (11) is not sent out, photodetector (12), (13) detect;

K: correction factor:

I21, i22: the photosignal that compensation light (11) is luminous, flashlight (10) is not luminous, photodetector (11), (12) detect.

2, the compensation method of polarization type direct current component opitical fiber sensor according to claim 1 is characterized in that: described sensing material (2) is quartz glass or K9 glass, and described compensative material is quartz crystal or mica waveplate.

3, the compensation method of polarization type direct current component opitical fiber sensor according to claim 1 and 2 is characterized in that: described optical splitter (9) is light splitting coupler or polarization splitting prism or common Amici prism.

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