CN103776393B - The evaluation method of polarization maintaining optical fibre optical axis welding angular error and device - Google Patents

Abstract

The invention discloses a kind of evaluation method and device of polarization maintaining optical fibre optical axis welding angular error.When transmitting in polarization maintaining optical fibre based on monochromatic polarized light, the change of polarization state and two sections of polarization maintaining optical fibre optical axises, 0 ° or 45 ° welding angular errors have direct dependence, export polarisation of light degree by polarization maintaining optical fibre after detection welding, realize the measurement to polarization maintaining optical fibre optical axis 0 ° or 45 ° welding angular error.The welding performance of energy exact evaluation polarization maintaining optical fibre of the present invention, provides effective evaluation method device for the development of Fibre Optical Sensor and performance.

Description

The evaluation method of polarization maintaining optical fibre optical axis welding angular error and device

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.Such as protect bias tyre optical fibre gyro to need the polarization maintaining fiber pigtail of the polarization maintaining fiber pigtail of Y waveguide optical chip and fiber optic loop to carry out 0 ° of welding, and the two sections of polarization maintaining optical fibres forming Lyot depolarizer in depolarized type optical fibre gyro need 45 ° of weldings.Above system all has high requirement to the precision at welding angle.

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

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

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 are 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, when transmitting in polarization maintaining optical fibre based on monochromatic polarized light, the change of polarization state and two sections of polarization maintaining optical fibre optical axises, 0 ° or 45 ° welding angular errors have direct dependence, export polarisation of light degree by polarization maintaining optical fibre after detection welding, realize the measurement to polarization maintaining optical fibre 0 ° or 45 ° welding angular error.

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 l respectively ₁, l ₂if, l ₁> l ₂if, l ₁=l ₂, then 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) linear birefrigence of one section of material, fibre core, 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 is got, the tail optical fiber of Polarization Maintaining Optical Fiber Fusion Splicer and gage beam is used to carry out 0 ° or 45 ° of weldings, obtain fusion point to be measured, measure the length of additional polarization maintaining optical fibre, be designated as l ₃, cut away redundance with optical fiber cutter, make l ₂+ l ₃=l ₁, namely now gage beam is equal with reference arm 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, coupling light is entered in the tail optical fiber of the incidence 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 propagated along slow axis;

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

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

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

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

8) rolling clamp, makes the scale value of pointed on fixture be α+45 °, record light intensity detector readings I ₃;

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

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

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

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

11) above-mentioned measuring process 4 is repeated)-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 as lower part: He-Ne LASER Light Source, the first micro objective, Y waveguide integrated optics chip, one end have the polarization maintaining optical fibre optical fiber of 0 ° or 45 ° fusion point to be measured, the second micro objective, linear polarizer, fixture and light intensity detector; 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 vertical with the line of the second micro objective, fixture, light intensity detector three by face.

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

The invention has the beneficial effects as follows, present invention achieves 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, provides effective evaluation method for 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 measuring polarization maintaining optical fibre 0 ° or 45 ° of welding angular error sizes;

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

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

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

Wherein, polarized light in Jones vector expression 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 is by after fusion point, polarisation of light state will change, if be expressed as by the polarization state before fusion point polarized light then 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 the two sections of fast axle in polarization maintaining optical fibre fusion point places (or slow axis).

Be l by length, after linear birefringence value is the polarization maintaining optical fibre of Δ β, suppose that its quick shaft direction is along x ₁axle, then 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 then utilize four parameters to describe light wave intensity and polarization state, is designated as [IMCS] ^t, these four parameters are all the time averages of light intensity, and this feature is very beneficial for using light intensity detector to measure four parameters respectively.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 is by complete in x before fusion point ₀direction of principal axis polarization, and with the phase place at fusion point place for reference (namely setting this some place phase place as 0), then 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: [1cos (2 θ) sin (2 θ) cos (Δ β l ₃) sin (2 θ) sin (Δ β l ₃)] ^t.Theoretical according to polarization optics, the general type of the light propagated in polarization maintaining optical fibre is elliptically polarized light, transverse and x ₁the angle of axle can represent with M and C in stokes parameter:

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

The present invention is further illustrated 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 as lower part: He-Ne LASER Light Source 1, first micro objective 2, Y waveguide integrated optics chip 4, one end have polarization maintaining optical fibre optical fiber 8, second micro objective 9 of 0 ° or 45 ° fusion point 7 to be measured, linear polarizer 10, fixture 11 and light intensity detector 12; He-Ne LASER Light Source 1, first micro objective 2, Y waveguide integrated optics chip 4, 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 vertical with the line of the second micro objective 9, fixture 11, light intensity detector 12 three by face.

Described Y waveguide integrated optics chip 4 comprises the tail optical fiber 26 of the tail optical fiber 3 of incidence end, the tail optical fiber 1 of exit end and exit 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 l respectively ₁, l ₂if, l ₁> l ₂if, l ₁=l ₂, then 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) linear birefrigence of one section of material, fibre core, 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, is got, the tail optical fiber of Polarization Maintaining Optical Fiber Fusion Splicer and gage beam is used to carry out 0 ° or 45 ° of weldings, suppose to carry out 0 ° of welding, obtain fusion point 7 to be measured, measure the length of additional polarization maintaining optical fibre 8, be designated as l ₃, cut away redundance with optical fiber cutter, make l ₂+ l ₃=l ₁, namely now gage beam is equal with reference arm 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, coupling light is entered in the tail optical fiber 3 of the incidence 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 propagated along slow axis;

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

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

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

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

8), rolling clamp 11, make the scale value of pointed on fixture 11 be °+45 °=105 °, α+45 °=60, record light intensity detector 12 reading I ₃, suppose I ₃=0.499mW;

9), to data measured calculate, the value of M and C in Stokes vector can be obtained 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), actual polarization maintaining optical fibre 0 ° of welding angular error is evaluated by following formula:

11), above-mentioned measuring process 4 is repeated)-10).Suppose repetition 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 (2)

1. the evaluation method of a polarization maintaining optical fibre optical axis welding angular error, it is characterized in that, when transmitting in polarization maintaining optical fibre based on monochromatic polarized light, the change of polarization state and two sections of polarization maintaining optical fibre optical axises, 0 ° or 45 ° welding angular errors have direct dependence, export polarisation of light degree by polarization maintaining optical fibre after detection welding, realize the measurement to polarization maintaining optical fibre optical axis 0 ° or 45 ° welding angular error ;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 l respectively ₁, l ₂if, l ₁> l ₂if, l ₁=l ₂, then 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) linear birefrigence of one section of material, fibre core, 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 is got, the tail optical fiber of Polarization Maintaining Optical Fiber Fusion Splicer and gage beam is used to carry out 0 ° or 45 ° of weldings, obtain fusion point to be measured (7), measure the length of additional polarization maintaining optical fibre (8), be designated as l ₃, cut away redundance with optical fiber cutter, make l ₂+ l ₃=l ₁, namely now gage beam is equal with reference arm 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), coupling light is entered in the tail optical fiber (3) of the incidence 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 propagated along slow axis;

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

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

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

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

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

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

$M=\frac{2I_2-I_1}{I_1}$

$C=\frac{2I_3-I_1}{I_1}$

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

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

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

In formula, N is for detecting number of times.

2. one kind adopts the polarization maintaining optical fibre optical axis welding angular error pick-up unit of evaluation method according to claim 1, it is characterized in that, comprise as lower part: He-Ne LASER Light Source (1), the first micro objective (2), Y waveguide integrated optics chip (4), one end have the polarization maintaining optical fibre (8) of 0 ° or 45 ° fusion point (7) to be measured, the second micro objective (9), linear polarizer (10), fixture (11) and light intensity detector (12); 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) vertical with the line of the second micro objective (9), fixture (11), light intensity detector (12) three by face;

Described Y waveguide integrated optics chip (4) comprises the tail optical fiber two (6) of the tail optical fiber (3) of incidence end, the tail optical fiber one (5) of exit end and exit end.