CN103776393A - Method and device for evaluating splicing angle error of optical axes of polarization maintaining optical fibers - Google Patents

Abstract

The invention discloses a method and a device for evaluating the splicing angle error of optical axes of polarization maintaining optical fibers. Based on the direct dependency relationship between the change of polarization state of monochromatic polarized light during transmission of the monochromatic polarized light in polarization maintaining optical fibers and the 0-degree or 45-degree splicing angle error of the optical axes of two sections of polarization maintaining optical fibers, the 0-degree or 45-degree splicing angle error of the optical axes of the polarization maintaining optical fibers is measured by detecting the degree of polarization of output light of the polarization maintaining optical fibers after splicing. The splicing performance of the polarization maintaining optical fibers can be accurately evaluated, and an effective evaluation method and an effective evaluation device are provided for development and performance of optical fiber sensors.

Description

Evaluation method and the device of polarization maintaining optical fibre optical axis welding angular error

Technical field

The present invention relates to optical precision measurement and sensory field, especially the evaluation method of polarization maintaining optical fibre optical axis welding angular error.

Background technology

Be a basic job by the optical axis of two sections of polarization maintaining optical fibres according to special angle welding, particularly 0 ° or 45 ° of welding schemes are widely used in optical precision measurement and sensory field.For example protect bias tyre optical fibre gyro and the polarization maintaining fiber pigtail of the polarization maintaining fiber pigtail of Y waveguide optical chip and fiber optic loop need to be carried out to 0 ° of welding, and in depolarized type optical fibre gyro, form 45 ° of weldings of two sections of polarization maintaining optical fibre needs of Lyot depolarizer.Above system all has high requirement to the precision at welding angle.

After 0 ° or 45 ° weldings of actual two sections of polarization maintaining optical fibre optical axises, due to the existence of welding angular error, be not no longer fully strict 1:1 along the power ratio on transmission axle propagation or two optical axises by causing the light after fusion point, this in the system of utilizing Through Optical Interference Spectra to measure (as interference optical fiber top) can introduce very large error.

Conventionally Polarization Maintaining Optical Fiber Fusion Splicer self is with the function of estimation welding angular error, the overwhelming majority is the stress axis direction that uses the two sections of polarization maintaining optical fibres in observation by light microscope fusion point place, then estimate welding angular error, this method precision is lower, the best magnitude that also can only reach 0.1 °, cannot meet the requirement at 0 ° or 45 ° welding angle of high precision.Therefore need a kind of method that precision is higher to evaluate the error of 0 ° or 45 ° welding angle of polarization maintaining optical fibre optical axis.

Summary of the invention

The object of the invention is for the deficiencies in the prior art, evaluation method and the device of polarization maintaining optical fibre optical axis welding angular error is provided.

The present invention is achieved through the following technical solutions:

One aspect of the present invention, the evaluation method of polarization maintaining optical fibre optical axis welding angular error, while transmission in polarization maintaining optical fibre based on monochromatic polarized light, the variation of polarization state and 0 ° or 45 ° welding angular errors of two sections of polarization maintaining optical fibre optical axises have direct dependence, export polarisation of light degree by polarization maintaining optical fibre after detecting welding, realize the measurement to 0 ° or 45 ° welding angular error of polarization maintaining optical fibre.

Described evaluation method, concrete steps are as follows:

1) measure the tail optical fiber one of exit end of Y waveguide integrated optics chip and the length of the tail optical fiber two of exit end, be designated as respectively l ₁, l ₂, establish l ₁> l ₂if, l ₁=l ₂, cut the tail optical fiber two of the exit end of suitable length with optical fiber cutter, make to meet l ₁> l ₂, now length is l ₁the tail optical fiber one of exit end be reference arm, length is l ₂the tail optical fiber two of exit end be gage beam;

2) get the linear birefrigence, fibre core of one section of material, the polarization maintaining optical fibre that cladding radius parameter is consistent with the tail optical fiber one of the exit end of Y waveguide integrated optics chip and the tail optical fiber two of exit end, use the tail optical fiber of Polarization Maintaining Optical Fiber Fusion Splicer and gage beam to carry out 0 ° or 45 ° of weldings, obtain fusion point to be measured, the length of measuring additional polarization maintaining optical fibre, is designated as l ₃, cut away redundance with optical fiber cutter, make l ₂+ l ₃=l ₁, now gage beam and reference arm are equal in length;

3) optical fiber integrally after Y waveguide integrated optics chip and welding is placed between the first micro objective and the second micro objective, open He-Ne LASER Light Source, adjust the first micro objective, light is coupled in the tail optical fiber of incident end of Y waveguide integrated optics chip, due to the optical characteristics of Y waveguide integrated optics chip, the light in the tail optical fiber one of its exit end and the tail optical fiber two of exit end has been the linearly polarized light of propagating along slow axis;

4) the second micro objective, fixture and light intensity detector are first positioned over reference arm one side, and the relative position of fine setting the second micro objective, fixture and light intensity detector, makes three's line overlap with the light of reference arm outgoing;

5) rolling clamp one week, the light transmission shaft direction of linear polarizer is rotated 360 ° thereupon, observes the reading of light intensity detector, records maximum light intensity readings value, is designated as I ₁;

6) then the second micro objective, fixture and light intensity detector are positioned over gage beam one side, and the relative position of fine setting the second micro objective, fixture and light intensity detector, makes three's line overlap with the light of gage beam outgoing;

7) repeating step 5), record the largest light intensity reading value of gage beam, be designated as I ₂, write down the scale value α of pointed on fixture now simultaneously;

8) rolling clamp, making the scale value of pointed on fixture is α+45 °, records light intensity detector readings I ₃;

9) data measured is calculated, can be obtained the value of M and C by following two formulas:

$M=\frac{{2I}_2-I_1}{I_1}$

$C=\frac{{2I}_3-I_1}{I_1}$

10) evaluate 0 ° of actual polarization maintaining optical fibre or 45 ° of welding angular errors by following formula:

11) repeat above-mentioned measuring process 4)-10), obtain AME:

$\stackrel{\‾}{\mathrm{\Δ\θ}}=\frac{1}{N}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\left|{\mathrm{\Δ\θ}}_i\right|$

In formula, N is for detecting number of times.

Another aspect of the present invention, polarization maintaining optical fibre optical axis welding angular error pick-up unit, comprises following part: there is polarization maintaining optical fibre optical fiber, the second micro objective, linear polarizer, fixture and the light intensity detector of 0 ° or 45 ° fusion point to be measured He-Ne LASER Light Source, the first micro objective, Y waveguide integrated optics chip, one end; He-Ne LASER Light Source, the first micro objective, Y waveguide integrated optics chip, the second micro objective, fixture, light intensity detector are connected in turn, linear polarizer is embedded in fixture, linear polarizer to pass through face vertical with the second micro objective, fixture, light intensity detector three's line.

Described Y waveguide integrated optics chip comprises tail optical fiber, the tail optical fiber one of exit end and the tail optical fiber two of exit end of incident end.

The invention has the beneficial effects as follows, the present invention has realized evaluation method and the pick-up unit of 0 °, a kind of polarization maintaining optical fibre optical axis or 45 ° of welding angular error sizes, the welding performance of this evaluation method energy exact evaluation polarization maintaining optical fibre is the effective evaluation method that provides of the development of Fibre Optical Sensor and performance.

Accompanying drawing explanation

Fig. 1 is the schematic diagram of two sections of polarization maintaining optical fibre weldings;

Fig. 2 is the device schematic diagram of measuring 0 ° or 45 ° welding angular error sizes of polarization maintaining optical fibre;

Fig. 3 is linear polarizer light transmission shaft direction schematic diagram;

In figure: tail optical fiber 26, polarization maintaining optical fibre fusion point 7, polarization maintaining optical fibre 8, the second micro objective 9, linear polarizer 10, fixture 11, the light intensity detector 12 of the tail optical fiber 1 of the exit end of the incident end tail optical fiber 3 of He-Ne LASER Light Source 1, the first micro objective 2, Y waveguide integrated optics chip, Y waveguide integrated optics chip 4, Y waveguide integrated optics chip, the exit end of Y waveguide integrated optics chip.

Embodiment

Principle of the present invention is: when the present invention is transmitted in polarization maintaining optical fibre by monochromatic line polarized light, the differentiation of polarization state and 0 ° or 45 ° welding angular errors of two sections of polarization maintaining optical fibres have direct dependence, export polarisation of light degree by polarization maintaining optical fibre after detecting welding, realize the measurement to 0 ° or 45 ° welding angular error of polarization maintaining optical fibre optical axis.Jones vector method and Stokes vector method that the present invention uses all relate to matrix computations, and can transmit in medium polarized light easily time, quantitative description is carried out in the differentiation of polarization state.

Wherein, Jones vector represents polarized light in system

the complex amplitude of two quadrature components, be designated as [E _xe _y] ^t, the wherein transposition of superscript T representing matrix.And polarized light passes through after fusion point, polarisation of light state will change, if be expressed as by the polarization state before fusion point

the polarized light after fusion point can be expressed as:

${\stackrel{\→}{E}}_2=\left[\begin{array}{c}{E}_{x2}\\ E_{y2}\end{array}\right]=\left[\begin{array}{cc}\cos \mathrm{\θ}& -\sin \mathrm{\θ}\\ \sin \mathrm{\θ}& \cos \mathrm{\θ}\end{array}\right]\left[\begin{array}{c}{E}_{x1}\\ E_{y1}\end{array}\right]---\left(1\right)$

In formula, θ is the angle between two sections of fast axles in polarization maintaining optical fibre fusion point place (or slow axis).

Be after l, linear birefringence value are the polarization maintaining optical fibre of Δ β by length, suppose that its quick shaft direction is along x ₁axle, Jones vector can be written as:

${\stackrel{\→}{E}}_3=\left[\begin{array}{c}{E}_{x3}\\ E_{y3}\end{array}\right]=\left[\begin{array}{cc}\exp (-\mathrm{i\Δ\βl}/2)& 0\\ 0& \exp (\mathrm{i\Δ\βl}/2)\end{array}\right]\left.2\begin{array}{c}{E}_{x2}\\ E_{y2}\end{array}\right]---\left(2\right)$

Stokes vector is to utilize four parameters to describe light wave intensity and polarization state, is designated as [IMCS] ^t, these four time averages that parameter is all light intensity, this feature is very beneficial for using light intensity detector respectively four parameters to be measured.For complete polarized light, can specifically be written as:

$\left\{\begin{array}{c}I={E_x}^2+{E_y}^2\\ M={E_X}^2-{E_y}^2\\ C={2E}_x{E}_y\cos \mathrm{\δ}\\ S={2E}_x{E}_y\sin \mathrm{\δ}\end{array}\right.$

Wherein δ is E _x, E _ybetween phase differential.

If light by before fusion point completely along x ₀direction of principal axis polarization, and take the phase place at fusion point place as with reference to (establishing this some place phase place as 0),

by fusion point and through length l ₃polarization maintaining optical fibre after, its Jones vector is expressed as:

$\left[\begin{array}{c}{E}_{x3}\\ E_{y3}\end{array}\right]\begin{array}{c}=\left[\begin{array}{cc}\exp (-\mathrm{i\Δ\β}{l}_3/2)& 0\\ 0& \exp (\mathrm{i\Δ\β}{l}_3/2)\end{array}\right]\left[\begin{array}{cc}\cos \mathrm{\θ}& -\sin \mathrm{\θ}\\ \sin \mathrm{\θ}& \cos \mathrm{\θ}\end{array}\right]\left[\begin{array}{c}1\\ 0\end{array}\right]\\ =\begin{array}{c}\left[\begin{array}{c}\cos \mathrm{\θexp}(-\mathrm{i\Δ\β}{l}_3/2)\\ \sin \mathrm{\θexp}(\mathrm{i\Δ\β}{l}_3/2)\end{array}\right]\end{array}\end{array}---\left(4\right)$

Therefore, four corresponding stokes parameters are: [1 cos (2 θ) sin (2 θ) cos (Δ β l ₃) sin (2 θ) sin (Δ β l ₃)] ^t.According to polarization optics theory, the general type of the light of propagating in polarization maintaining optical fibre is elliptically polarized light, transverse and x ₁the angle of axle

can represent with the M in stokes parameter and C:

Wherein

value can measure M in stokes parameter and the value of C obtains by light intensity detector, and θ is real welding angle.Although due to cos (Δ β l ₃) this existence, under normal circumstances might not equate with θ, but when θ=0 ° or θ=45 ° two in particular cases, when two sections of polarization maintaining optical fibres adopt 0 ° or 45 ° of weldings, formula (5) will reach respectively 0 or two limit of ∞, now cos (Δ β l ₃) this can not have influence on result of calculation, can directly use

value characterize θ.

Further illustrate the present invention below in conjunction with drawings and Examples.

The present invention realizes on polarization maintaining optical fibre optical axis welding angular error pick-up unit, as shown in Figures 2 and 3, polarization maintaining optical fibre optical axis welding angular error pick-up unit, comprises following part: there is polarization maintaining optical fibre optical fiber 8, the second micro objective 9, linear polarizer 10, fixture 11 and the light intensity detector 12 of 0 ° or 45 ° fusion point 7 to be measured He-Ne LASER Light Source 1, the first micro objective 2, Y waveguide integrated optics chip 4, one end; He-Ne LASER Light Source 1, the first micro objective 2, Y waveguide integrated optics chip 4, the second micro objective 9, fixture 11, light intensity detector 12 are connected in turn, linear polarizer 10 is embedded in fixture 11, linear polarizer 10 to pass through face vertical with the second micro objective 9, fixture 11, light intensity detector 12 threes' line.

Described Y waveguide integrated optics chip 4 comprises tail optical fiber 3, the tail optical fiber 1 of exit end and the tail optical fiber 26 of exit end of incident end.

Embodiment

1), measure the tail optical fiber 1 of exit end of Y waveguide integrated optics chip 4 and the length of the tail optical fiber 26 of exit end, be designated as respectively l ₁, l ₂, establish l ₁> l ₂if, l ₁=l ₂, cut the tail optical fiber two of the exit end of suitable length with optical fiber cutter, make to meet l ₁> l ₂, now length is l ₁the tail optical fiber 1 of exit end be reference arm, length is l ₂the tail optical fiber 26 of exit end be gage beam;

2), get the linear birefrigence, fibre core of one section of material, the polarization maintaining optical fibre 8 that cladding radius parameter is consistent with the tail optical fiber 1 of the exit end of Y waveguide integrated optics chip 4 and the tail optical fiber 26 of exit end, use the tail optical fiber of Polarization Maintaining Optical Fiber Fusion Splicer and gage beam to carry out 0 ° or 45 ° of weldings, suppose to carry out 0 ° of welding, obtain fusion point 7 to be measured, the length of measuring additional polarization maintaining optical fibre 8, is designated as l ₃, cut away redundance with optical fiber cutter, make l ₂+ l ₃=l ₁, now gage beam and reference arm are equal in length;

3), the optical fiber integrally after Y waveguide integrated optics chip 4 and welding is placed between the first micro objective 2 and the second micro objective 9, open He-Ne LASER Light Source 1, adjust the first micro objective 2, light is coupled in the tail optical fiber 3 of incident end of Y waveguide integrated optics chip 4, due to the optical characteristics of Y waveguide integrated optics chip 4, the light in the tail optical fiber 1 of its exit end and the tail optical fiber 26 of exit end has been the linearly polarized light of propagating along slow axis;

4), the second micro objective 9, fixture 11 and light intensity detector 12 be first positioned over reference arm one side, the relative position of fine setting the second micro objective 9, fixture 11 and light intensity detector 12, makes three's line overlap with the light of reference arm outgoing;

5), rolling clamp 11 1 weeks, the light transmission shaft direction of linear polarizer 10 is rotated 360 ° thereupon, observes the reading of light intensity detector 12, records maximum light intensity readings value, is designated as I ₁, suppose I ₁=1mW;

6), then the second micro objective 9, fixture 11 and light intensity detector 12 be positioned over gage beam one side, the relative position of fine setting the second micro objective 9, fixture 11 and light intensity detector 12, makes three's line overlap with the light of gage beam outgoing;

7), repeating step 5, record the largest light intensity reading value of gage beam, be designated as I ₂, suppose I ₂=0.002mW writes down the scale value α of pointed on fixture 11 now simultaneously, supposes α=60 °;

8), rolling clamp 11, the scale value that makes pointed on fixture 11 is α+45 °=60 °+45 °=105 °, records light intensity detector 12 reading I ₃, suppose I ₃=0.499mW;

9), data measured is calculated, can be obtained the value of M and C in Stokes vector by following two formulas:

$M=\frac{{2I}_2-I_1}{I_1}=\frac{2\×0.002-1}{1}=-0.996---\left(6\right)$

$C=\frac{{2I}_3-I_1}{I_1}=\frac{2\×0.499-1}{1}=-0.002---\left(7\right)$

10), evaluate 0 ° of welding angular error of actual polarization maintaining optical fibre by following formula:

11), repeat above-mentioned measuring process 4)-10).Suppose to repeat 10 times, obtain average angle error:

$\stackrel{\‾}{\mathrm{\Δ\θ}}=\frac{1}{10}\underset{i=1}{\overset{10}{\mathrm{\Σ}}}\left|{\mathrm{\Δ\θ}}_{\text{i}}\right|---\left(9\right)\·$

Claims (4)

1. the evaluation method of a polarization maintaining optical fibre optical axis welding angular error, it is characterized in that, while transmission in polarization maintaining optical fibre based on monochromatic polarized light, the variation of polarization state and 0 ° or 45 ° welding angular errors of two sections of polarization maintaining optical fibre optical axises have direct dependence, export polarisation of light degree by polarization maintaining optical fibre after detecting welding, realize the measurement to 0 ° or 45 ° welding angular error of polarization maintaining optical fibre optical axis.

2. evaluation method as claimed in claim 1, is characterized in that, concrete steps are as follows:

1) measure the tail optical fiber one (5) of exit end of Y waveguide integrated optics chip (4) and the length of the tail optical fiber two (6) of exit end, be designated as respectively l ₁, l ₂, establish l ₁> l ₂if, l ₁=l ₂, cut the tail optical fiber two (6) of the exit end of suitable length with optical fiber cutter, make to meet l ₁> l ₂, now length is l ₁the tail optical fiber one (5) of exit end be reference arm, length is l ₂the tail optical fiber two (6) of exit end be gage beam;

2) get the linear birefrigence, fibre core of one section of material, the polarization maintaining optical fibre (8) that cladding radius parameter is consistent with the tail optical fiber one (5) of the exit end of Y waveguide integrated optics chip (4) and the tail optical fiber two (6) of exit end, use the tail optical fiber of Polarization Maintaining Optical Fiber Fusion Splicer and gage beam to carry out 0 ° or 45 ° of weldings, obtain fusion point to be measured (7), the length of measuring additional polarization maintaining optical fibre (8), is designated as l ₃, cut away redundance with optical fiber cutter, make l ₂+ l ₃=l ₁, now gage beam and reference arm are equal in length;

3) optical fiber integrally after Y waveguide integrated optics chip (4) and welding is placed between the first micro objective (2) and the second micro objective (9), open He-Ne LASER Light Source (1), adjust the first micro objective (2), light is coupled in the tail optical fiber (3) of incident end of Y waveguide integrated optics chip (4), due to the optical characteristics of Y waveguide integrated optics chip (4), the light in the tail optical fiber one (5) of its exit end and the tail optical fiber two (6) of exit end has been the linearly polarized light of propagating along slow axis;

4) the second micro objective (9), fixture (11) and light intensity detector (12) are first positioned over reference arm one side, finely tune the relative position of the second micro objective (9), fixture (11) and light intensity detector (12), three's line is overlapped with the light of reference arm outgoing;

5) rolling clamp (11) weeks, the light transmission shaft direction of linear polarizer (10) is rotated 360 ° thereupon, observes the reading of light intensity detector (12), records maximum light intensity readings value, is designated as I ₁;

6) the second micro objective (9), fixture (11) and light intensity detector (12) are then positioned over gage beam one side, finely tune the relative position of the second micro objective (9), fixture (11) and light intensity detector (12), three's line is overlapped with the light of gage beam outgoing;

7) repeating step 5), record the largest light intensity reading value of gage beam, be designated as I ₂, write down the now scale value α of the upper pointed of fixture (11) simultaneously;

8) rolling clamp (11), making the scale value of the upper pointed of fixture (11) is α+45 °, records light intensity detector (12) reading I ₃;

9) data measured is calculated, can be obtained the value of M and C by following two formulas:

$M=\frac{{2I}_2-I_1}{I_1}$

$C=\frac{{2I}_3-I_1}{I_1}$

10) evaluate 0 ° of actual polarization maintaining optical fibre or 45 ° of welding angular errors by following formula:

11) repeat above-mentioned measuring process 4)-10), obtain AME:

$\stackrel{\‾}{\mathrm{\Δ\θ}}=\frac{1}{N}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\left|{\mathrm{\Δ\θ}}_i\right|$

In formula, N is for detecting number of times.

3. a polarization maintaining optical fibre optical axis welding angular error pick-up unit, it is characterized in that, comprise following part: there is polarization maintaining optical fibre optical fiber (8), the second micro objective (9), linear polarizer (10), fixture (11) and the light intensity detector (12) of 0 ° or 45 ° of fusion points (7) to be measured He-Ne LASER Light Source (1), the first micro objective (2), Y waveguide integrated optics chip (4), one end; He-Ne LASER Light Source (1), the first micro objective (2), Y waveguide integrated optics chip (4), the second micro objective (9), fixture (11), light intensity detector (12) are connected in turn, linear polarizer (10) is embedded in fixture (11), linear polarizer (10) to pass through face vertical with the second micro objective (9), fixture (11), light intensity detector (12) three's line.

4. device as claimed in claim 3, is characterized in that, described Y waveguide integrated optics chip (4) comprises the tail optical fiber one (5) of the tail optical fiber (3) of incident end, exit end and the tail optical fiber two (6) of exit end.

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