CN202614196U - Optical fiber strain sensor - Google Patents

Abstract

The utility model discloses an optical fiber strain sensor, comprising a tube, wherein an end cover is mounted on each of the two ends of the tube; an optical fiber grating is arranged in the tube; the two ends of the optical fiber grating are correspondingly fixed to the two end covers and pre-tensioned, respectively; a strain desensitizing beam is mounted in the tube, and composed of a middle fixed part and two mirror symmetrical edge strain desensitizing parts connected to the two sides of the middle fixed part; the middle fixed part is fixed to the inner wall of the tube; the free ends of the two edge strain desensitizing parts are fixedly connected with the optical fiber grating; and the length of the optical fiber grating between the bonding points of the two edge strain desensitizing parts and the optical fiber grating is a plurality of times of the transverse length of the middle fixed part. Besides, the optical fiber strain sensor provided by the utility model is capable of well protecting the optical fiber grating by using the strain desensitizing beam and thereby widened in measuring range therein.

Description

Fibre optic strain sensor

Technical field

The utility model relates to a kind of strain transducer, relates in particular to a kind of fibre optic strain sensor.

Background technology

Traditional strain transducer is to be the basis with strain-electric weight; With the electric signal is the carrier of conversion and transmission; Use the lead transmission of electric signals, therefore, be vulnerable to the influence of electromagnetic field and environment during use; Possibly cause fire hazardous or the like in short circuit, particularly high temperature and inflammable, the explosive environments as ambient humidity is too big.

Discover that when the strain of fiber grating changed, grating effective refractive index and grating cycle can change; Thereby cause the centre wavelength of fiber grating also can change; Be near the fiber grating the 1550nm for centre wavelength for example, 1 microstrain (i.e. 1 μ ε) will cause the wavelength change of about 1pm, through measuring the variation of fiber grating; The variation of strain can be pushed over out, thereby a kind of novel optical fiber and optical grating strain transducer can be constituted.Than the traditional strain transducer that is the basis with strain-electric weight; The noiseproof feature of fiber Bragg grating strain sensor is stronger; Therefore; Be widely used in industries such as civil engineering structure, aerospace, boats and ships shipping business, power industry, petrochemical industry, medical science, nuclear industry at present, especially in high voltage, strong-electromagnetic field, inflammable and explosive rugged surroundings, have very strong application advantage.

Because the limitation of self structure; The optical fiber of ordinary optic fibre grating strain transducer and the strain ratio between its shell body are about 1:1 usually at present; Its measurement range is generally about 0～2500 μ ε, but in a lot of occasions, like the rocket engine solid propellant; Lifting airscrews etc., dependent variable to be measured maybe be about 10000 μ ε even are higher.Therefore the measurement range of existing fiber Bragg grating strain sensor can't satisfy measurement requirement.

The utility model content

The purpose of the utility model is to provide a kind of fibre optic strain sensor of wide range.

For achieving the above object; The utility model provides a kind of fibre optic strain sensor; Comprise shell, the two ends of said shell are separately installed with an end cap, are provided with fiber grating in the said shell; The two ends of said fiber grating correspondence respectively are fixed on two said end caps and tensioning in advance; Strain is installed in the said shell subtracts quick beam, said strain subtracts quick beam and subtracts quick by the side strain of center fixed portion and two mirror images symmetry of being connected with its both sides and constitute, and said center fixed portion is fixed on the inwall of said shell; Two said side strains subtract quick free end and are fixedly connected with said optical fiber, and two said side strains subtract the several times that fiber grating length between the adhesive spots of quick and said fiber grating is said center fixed portion lateral length.

In the fibre optic strain sensor of the utility model; Because it is the several times (being assumed to be N times) of center fixed portion lateral length that two side strains subtract quick the fiber grating length between the adhesive spots with fiber grating; Then fibre optic strain sensor subtracts quick beam through its strain and is delivered to the strain on the fiber grating; 1/N for the measured object strain; Therefore, the fibre optic strain sensor of the utility model uses strain to subtract quick beam can the better protect fiber grating, and improves the measurement range of fibre optic strain sensor.

Description of drawings

Fig. 1 looks cut-open view for the master of the fibre optic strain sensor of the utility model.

Embodiment

Be described in detail below in conjunction with the embodiment of accompanying drawing the utility model:

With reference to shown in Figure 1, the fibre optic strain sensor of present embodiment comprises shell 1; The two ends of shell 1 seal the bonding end cap 2 that is connected to respectively, are provided with fiber grating 3 in the shell 1, and the two ends of fiber grating 3 are corresponding to respectively being adhesively fixed on two end caps 2 and tensioning in advance; Strain is installed in the shell 1 subtracts quick beam 4; It is to be the integrative-structure that the bar shaped corrosion resistant plate bending of 0.25～0.5mm forms by a thickness that this strain subtracts quick beam 4, and it comprises that center fixed portion 41 subtracts quick 42 with the symmetrical side strain of two mirror images that is connected with its both sides, wherein; Center fixed portion 41 is a rectangle flat-bottom slot structure; And two side strains to subtract quick 42 be the notch cuttype structures of two mirror images symmetries, center fixed portion 41 is adhesively fixed on the inwall of shell 1, two side strains subtract quick 42 free end and are fixedly connected with fiber grating 3.For guaranteeing that strain subtracts the quick requirement that reaches, and two side strains subtract fiber grating length between the adhesive spots of quick 42 and fiber grating 3 (i.e. L among the figure _f) be 5 times of center fixed portion 41 lateral lengths (i.e. figure in L), also appropriate change multiple as required.In addition, subtract quick effect, shell 1 and two full optical fiber factice for filling 5 of the interior filling of inner chamber that end cap 2 surrounds in order to improve strain.

Suppose when measured object receives pulling force generation deformation; Dependent variable is ε, because the bottom of center fixed portion 41 links together through shell 1 and measured object, then center fixed portion 41 produces strain stress simultaneously;

wherein; L is the raw footage of center fixed portion 41, and L' is the length of center fixed portion 41 when deformation takes place, and Δ L is a deformation quantity; Strain subtract quick beam 4 except that center fixed portion 41 remainders owing to do not contact with shell 1; Therefore deformation does not all take place, i.e. it is Δ L that strain subtracts quick beam 4 bulk deformation amounts, supposes that the strain that two side strains subtract the fiber grating between quick 42 is ε ':

Then ${\mathrm{\ϵ}}^{,}=({L_f}^{,}-L_f)/L_f$

$=\mathrm{\ΔL}/L_f$

$=\mathrm{\ΔL}/5L$

$=\frac{1}{5}\·\frac{\mathrm{\ΔL}}{L}$

$=\frac{1}{5}\mathrm{\ϵ}$

Wherein, L _fBe the raw footage that two side strains subtract the fiber grating between quick 42, L is the length of two side strains when subtracting the fiber grating generation deformation between quick 42.This shows that the fibre optic strain sensor of present embodiment subtracts quick beam through its strain and is delivered to the strain on the fiber grating, is 1/5 of measured object strain, when 15000 μ ε took place measured object, fiber grating only produced 3000 μ ε.

Above embodiment describes the preferred implementation of the utility model; Be not that scope to the utility model limits; Under the prerequisite that does not break away from the utility model design spirit; Various distortion and improvement that the common engineering technical personnel in this area make the technical scheme of the utility model all should fall in the protection domain that claims of the utility model confirm.

Claims (5)

1. fibre optic strain sensor; Comprise shell (1); The two ends of said shell (1) are separately installed with an end cap (2); Be provided with fiber grating (3) in the said shell (1); The two ends of said fiber grating (3) correspondence respectively are fixed on the last and tensioning in advance of two said end caps (2), it is characterized in that, strain is installed in the said shell (1) subtracts quick beam (4); Said strain subtracts quick beam (4) and subtracts quick (42) by the side strain of center fixed portion (41) and two mirror images symmetry of being connected with its both sides and constitute; Said center fixed portion (41) is fixed on the inwall of said shell (1), and the free end that two said side strains subtract quick (42) is adhesively fixed with said fiber grating (3) and is connected, and the fiber grating length that two said side strains subtract between the adhesive spots of quick (42) and said fiber grating (3) is the several times of said center fixed portion (41) lateral length.

2. fibre optic strain sensor according to claim 1 is characterized in that, it is said center fixed portion (41) 5 times along said shell (1) length radially along said shell (1) length sum radially that two said side strains subtract quick (42).

3. fibre optic strain sensor according to claim 1; It is characterized in that; It is the integrative-structure that is formed by bar shaped corrosion resistant plate bending that said strain subtracts quick beam (4); Said center fixed portion (41) is a rectangle flat-bottom slot structure, and two said side strains subtract the notch cuttype structure that quick (42) are two mirror image symmetries.

4. fibre optic strain sensor according to claim 3 is characterized in that the thickness of said bar shaped corrosion resistant plate is at 0.25～0.5mm.

5. fibre optic strain sensor according to claim 1 is characterized in that, said shell (1) is expired optical fiber factice for filling (5) with interior filling of inner chamber that two said end caps (2) surround.

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