CN103743551A - Method for measuring optical performance of multi-functional lithium niobate integrator - Google Patents
Method for measuring optical performance of multi-functional lithium niobate integrator Download PDFInfo
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- 230000010287 polarization Effects 0.000 claims abstract description 143
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- 229910000530 Gallium indium arsenide Inorganic materials 0.000 description 1
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Abstract
本发明属于光学器件测量技术领域，具体涉及到一种多功能铌酸锂集成器件的光学性能测量方法。本方法包括：测量波导器件输入保偏尾纤的长度；测量波导芯片的长度；测量波导器件输出保偏尾纤的长度；对准输入/输出尾纤慢轴与波导芯片的传输轴；获取第一次分布式偏振串音测量结果；变换波导器件的光注入条件；获取第二次分布式偏振串音测量结果；通过对数据的分析和计算，获得波导器件光学参量。该方法可以准确地获得波导芯片的消光比和线性双折射，还能够同时获得芯片波导输入/输出端尾纤的耦合串音、线性双折射，输入/输出延长光纤焊点，以及波导芯片和连接尾纤内部光学缺陷；降低了信号读取与识别的难度，简化了数据分析与处理的过程。
The invention belongs to the technical field of optical device measurement, and in particular relates to a method for measuring the optical performance of a multifunctional lithium niobate integrated device. The method includes: measuring the length of the input polarization-maintaining pigtail of the waveguide device; measuring the length of the waveguide chip; measuring the length of the output polarization-maintaining pigtail of the waveguide device; aligning the slow axis of the input/output pigtail with the transmission axis of the waveguide chip; A distributed polarization crosstalk measurement result; transforming the light injection conditions of the waveguide device; obtaining the second distributed polarization crosstalk measurement result; and obtaining the optical parameters of the waveguide device through data analysis and calculation. This method can accurately obtain the extinction ratio and linear birefringence of the waveguide chip, and can also simultaneously obtain the coupling crosstalk and linear birefringence of the pigtail fiber at the input/output end of the chip waveguide, the input/output extension fiber solder joint, and the waveguide chip and connection Optical defects inside the pigtail; reduce the difficulty of signal reading and identification, and simplify the process of data analysis and processing.
Description
Technical field
The invention belongs to optical device field of measuring technique, be specifically related to a kind of optical property measuring method of multi-functional lithium niobate integrated device.
Background technology
Fiber optical gyroscope is commonly called as " Y waveguide ", the general lithium niobate material that adopts is as substrate, it has carried out monomode optical waveguide, beam splitter, photomodulator and optical polarizator highly integrated, be the core devices that forms interference optical fiber top (FOG) and optical fiber current mutual inductor, determining measuring accuracy, stability, volume and the cost of optical fiber sensing system.
Waveguide chip extinction ratio is the Important Parameters of Y waveguide device, as: the Y waveguide of the use in high precision micron order optical fibre gyro, more than its chip extinction ratio requires to reach 80dB.For example: a kind of method (CN 201310185490.2) that improves optical fibre gyro use Y waveguide chip extinction ratio that the Hua Yong of No.44 Inst., China Electronical Science and Technology Group Co., the equality people of relaxing propose, more than waveguide chip extinction ratio having been brought up to 80dB.But be limited to testing tool performance and method of testing, also cannot realize at present High Extinction Ratio Y waveguide chip extinction ratio Measurement accuracy.Conventional polarization property detecting instrument---extinction ratio tester, the development Model4810 of the U.S. dBm Optics company type polarization extinction ratio measuring instrument that resolution is the highest also only has 72dB, in addition, the ER2200 type of the ERM102 type of U.S. General Photonics company, Korea S Fiberpro company, the High Extinction Ratio of the PEM-330 type of Japan Santec company all can only reach 50dB left and right, cannot meet the testing requirement of the above High Extinction Ratio Y waveguide of 80dB device.
The people such as Alfred Healy of U.S. Fibersense Technology Corporation company in 2002 disclose a kind of coupling process (US6870628) of I/O optical fiber of integrated waveguide chip, utilize white light interferometry method to realize the measurement of the coupling cross-talk of waveguide chip I/O optical fiber; The people such as the Yi little Su of BJ University of Aeronautics & Astronautics in 2004, Xiao Wen disclose integrated optical modulator on-line testing method and proving installation (CN 200410003424.X) thereof for a kind of optical fibre gyro, can realize the measurement of the optical parametrics such as loss, splitting ratio of device; The people such as the Yi little Su of BJ University of Aeronautics & Astronautics in 2007, Xu little Bin disclose a kind of Y waveguide chip and polarization maintaining optical fibre online to shaft device and online to axle method (CN 200710064176.3), utilize interferometric spectrometry to realize equally the measurement of waveguide chip and waveguide I/O fiber crosswalk.Above-mentioned patent does not all design the measurement of waveguide chip extinction ratio.
Y waveguide is comprised of input optical fibre, waveguide chip and output optical fibre three parts, traditional extinction ratio test is lump type and measures, can only obtain the extinction ratio numerical value of Y waveguide device integral body, be all extinction ratio sums of device, waveguide chip extinction ratio (50～80dB) has been submerged among the extinction ratio (30～40dB) of optical fiber pigtail and chip coupling, cannot obtain the extinction ratio of chip.Therefore, the measurement difficult point of Y waveguide device chip extinction ratio mainly contains: 1) white light interferometer based on low relevant principle can be realized the measurement of distributed polarization cross-talk, can be to the measurement of (comprising chip extinction ratio) of Y waveguide device parameters, but how the resolution of polarization crosstalk can be brought up to-more than 90dB, realize the measurement up to the above waveguide chip of 80dB to extinction ratio; 2) in order to improve spatial resolution, white light interferometer generally adopts the wider SLD light source of spectrum, but light source light spectrum ripple (ripple) will cause relevant peak, its corresponding polarization crosstalk amplitude is greatly between-50～-70dB, if the polarization crosstalk peak value of waveguide chip overlaps, chip extinction ratio is very easily submerged in wherein, and how eliminating its impact is the problem that need to urgently connect solution; 3) waveguide device is as an assembly, and the accurate differentiation of each crosstalk signal forming such as chip, tail optical fiber, has suitable difficulty, and how accurately identifying white light interference signal is one of difficult point of device detection.
The invention discloses the optical property measuring method of a kind of multi-functional lithium niobate integrated optical device (Y waveguide), the length that comprises waveguide device I/O tail optical fiber is selected and measures, waveguide device light injection condition is selected, the measurement of waveguide chip geometric parameter, the distributed polarization cross talk characteristic of waveguide device is measured, and the step such as waveguide device optical performance parameter calculating, it is characterized in that utilizing white light interferometer (or low-coherence measuring device), input/output terminal at tested integrated waveguide device, by extending the length of input/output terminal tail optical fiber, to being injected into the presetting angle of the I/O detection light in device under test, set simultaneously, the difference polarization crosstalk Noise Background data of measurement mechanism and the distributed polarization cross-talk data of device, by the contrast to the two, can obtain some polarization crosstalk characteristic peaks of being introduced by waveguide chip, waveguide I/O tail optical fiber, I/O extended fiber, the measurement data of utilization to waveguide device geometrical length, comprise: the length of I/O extended fiber, waveguide I/O tail optical fiber length and waveguide chip length, can calculate the delustring of waveguide device chip, chip linear birefrigence, a plurality of optical parametrics such as the coupling cross-talk of waveguide input/output terminal tail optical fiber, I/O extended fiber solder joint.The method has been eliminated light source light spectrum ripple to the impact of measuring, improved the accuracy of measuring, can realize the measurement of the super large extinction ratio device performance of 0～85dB, there is the advantages such as high spatial resolution, can be widely used in the quantitative evaluation of the integrated optical device of chip extinction ratio more than 85dB, and whether waveguide chip and connection tail optical fiber inside there is the identification and analysis of optical defect.
Summary of the invention
The object of the present invention is to provide a kind of light source light spectrum ripple of having eliminated on the impact of measuring, realize the automatic identification to axle of waveguide chip and tail optical fiber, improve the optical property measuring method of the multi-functional lithium niobate integrated device of the accuracy of testing.
The object of the present invention is achieved like this:
(1) measure the length l that inclined to one side tail optical fiber is protected in waveguide device input
w-i, detected transmission is protected the optical path difference S of light wave between inclined to one side tail optical fiber fast and slow axis in input
w-iwhether be greater than the light path S at the relevant peak of light source light spectrum ripple generation
ripple,
S
W-i>S
ripple，
S
w-i=l
w-i* Δ n
f, Δ n
fprotect the linear birefrigence of inclined to one side tail optical fiber;
(2) if the length l of inclined to one side tail optical fiber is protected in input
w-ido not meet step 2) in condition, in input, weld an elongated segment polarization maintaining optical fibre on tail optical fiber, solder joint to shaft angle degree, be 0 °-0 °, length is l
f-iinput extend polarization maintaining optical fibre and meet optical path difference S
f-ibe greater than the light path S at the relevant peak of light source light spectrum ripple generation
ripple,
S
f-i>S
ripple
S
f-i=l
f-i* Δ n
f, Δ n
fprotect the linear birefrigence of inclined to one side tail optical fiber, measure and record the length l that input extends polarization maintaining optical fibre
f-i;
(3) measure the length l of waveguide chip
w;
(4) measure the length l that inclined to one side tail optical fiber is protected in waveguide device output
w-o, detected transmission is protected the optical path difference S of light wave between inclined to one side tail optical fiber fast and slow axis in output
w-owhether be greater than the optical path difference S of transmission light wave between waveguide chip fast and slow axis
w,
S
w-o>S
w, S
w-o=l
w-o* Δ n
f, S
w=l
w* Δ n
w, Δ n
wthe linear birefrigence of waveguide chip;
(5) if the length l of inclined to one side tail optical fiber is protected in output
w-odo not meet the condition of step 4), in output, protect on inclined to one side tail optical fiber and weld an elongated segment polarization maintaining optical fibre, solder joint to shaft angle degree, be 0 °-0 °, length is l
f-ooutput extend the optical path difference S of polarization maintaining optical fibre
f-os
f-o>S
w, S
f-o=l
f-o* Δ n
f, measure and record the length l that output extends polarization maintaining optical fibre
f-o;
(6) aim to input or output and protect the slow axis of inclined to one side tail optical fiber and the transmission axle of waveguide chip, while extending polarization maintaining optical fibre without input, input protect inclined to one side tail optical fiber and white light interferometer export the polarizer tail optical fiber to shaft angle degree θ
1it is 0 °-0 °; While having input to extend polarization maintaining optical fibre, extended fiber and white light interferometer export the polarizer tail optical fiber to shaft angle degree θ
1also it is 0 °-0 °; When no-output extends polarization maintaining optical fibre, output protect inclined to one side tail optical fiber and white light interferometer input analyzer tail optical fiber to shaft angle degree θ
2it is 0 °-0 °; While having output to extend polarization maintaining optical fibre, output extend polarization maintaining optical fibre and white light interferometer input analyzer tail optical fiber to shaft angle degree θ
2also it is 0 °-0 °;
Aim at the accurate transmission axle of protecting the fast axle of inclined to one side tail optical fiber and waveguide chip that inputs or outputs, input protect inclined to one side tail optical fiber or input extend polarization maintaining optical fibre and white light interferometer export analyzer tail optical fiber to shaft angle degree θ
1it is 0 °-90 °; Output protect inclined to one side tail optical fiber or output extend polarization maintaining optical fibre and white light interferometer input analyzer tail optical fiber to shaft angle degree θ
2it is 90 °-0 °;
(7) obtain distributed polarization crosstalk measurement result for the first time, i.e. the instrument polarization cross-talk noise background data of white light interferometer, its horizontal ordinate is scan light number of passes value S, unit: μ m, ordinate is polarization crosstalk amplitude E, unit: dB; The light path sweep limit Δ S measuring
ΔS>2（S
f-i+S
W-i+S
W+S
W-o+S
f-o）
And the mid point of light path sweep limit is the position of the peak-peak of polarization crosstalk measurement data;
(8) the light injection condition of conversion waveguide device: while extending polarization maintaining optical fibre without input, input protect inclined to one side tail optical fiber and white light interferometer input the polarizer tail optical fiber to shaft angle degree θ
1it is 0 °-45 °; While having input to extend polarization maintaining optical fibre, input extend protect polarisation and white light interferometer input the polarizer tail optical fiber to shaft angle degree θ
1also it is 0 °-45 °; During no-output extended fiber, output protect inclined to one side tail optical fiber and white light interferometer export analyzer tail optical fiber to shaft angle degree θ
2it is 45 °-0 °; Have output during extended fiber, extended fiber and tail optical fiber to shaft angle degree θ
2also it is 45 °-0 °;
(9) obtain distributed polarization crosstalk measurement result for the second time, i.e. the optical polarization crosstalk measurement data of device, the requirement of its light path sweep limit Δ S is identical with step 7);
(10), by the analysis and calculation to data, obtain the chip delustring of waveguide device, the linear birefrigence of chip, the coupling cross-talk of waveguide input/output terminal tail optical fiber, the linear birefrigence optical parameter of tail optical fiber:
(10.1) the instrument polarization cross-talk background data of the white light interferometer that device distributed polarization crosstalk measurement result measuring process (9) being obtained and step (7) obtain contrasts, can obtain some polarization crosstalk characteristic peaks of protecting inclined to one side tail optical fiber, output or the introducing of output prolongation polarization maintaining optical fibre that inputed or outputed by waveguide chip, waveguide, the corresponding optical path difference S of horizontal ordinate of peak value, unit: μ m, the amplitude E of the corresponding polarization crosstalk of ordinate, unit: dB;
(10.2) according to the length l of input extended fiber
f-inumerical value, calculates the theoretical optical path delay numerical value S that input extends polarization maintaining optical fibre
f-i(is theoretical), S
f-i(is theoretical)=l
f-i* Δ n
f(is theoretical), Δ n
f(is theoretical)by 5 * 10
-4meter; In device polarization crosstalk test data, the definite optical path delay amount that meets S being caused by input prolongation polarization maintaining optical fibre and the solder joint of inputting the inclined to one side tail optical fiber of guarantor
f-i(is theoretical)polarization crosstalk peak value, the corresponding solder joint cross-talk of its Y value value E
f-i, horizontal ordinate corresponds to input and extends the real optical path delay amount of polarization maintaining optical fibre S
f-i(measures);
(10.3) length l of protecting inclined to one side tail optical fiber according to waveguide input
w-inumerical value, calculates the theoretical optical path delay numerical value S that inclined to one side tail optical fiber is protected in waveguide input
w-i(is theoretical), S
w-i(is theoretical)=l
w-i* Δ n
f(is theoretical), Δ n
f(is theoretical)by 5 * 10
-4meter; In device detection data, determine by input and protect the optical path delay amount that the meets S that inclined to one side tail optical fiber sound causes
f-i(measures)+ S
w-i(is theoretical)polarization crosstalk peak value, its ordinate coupling cross-talk value E
w-i, the corresponding real optical path delay amount S of horizontal ordinate
f-i(measures)+ S
w-i(measures);
(10.4) according to the length l of waveguide input coupled fiber
w-itrue optical path delay amount S with its correspondence
w-i(measures), can accurate Calculation obtain the linear birefrigence Δ n that polarization maintaining optical fibre is inputted in waveguide
f-i(measures),
Δ n
f-i(measures)=S
w-i(measures)/ l
w-i
(10.5) with step 2)～step 4) is identical, extends the length l of polarization maintaining optical fibre according to output
f-o, waveguide output optical fibre length l
w-o, can determine and extend polarization maintaining optical fibre and export the solder joint cross-talk value E that protects inclined to one side tail optical fiber
f-o, output optical fibre and waveguide chip power coupling cross-talk value E
w-o, and the linear birefrigence Δ n of waveguide output polarization maintaining optical fibre
w-o;
Δ n
f-o(measures)=S
w-o(measures)/ l
w-o
(10.6) according to the length l of waveguide chip
w, calculate that waveguide chip is fast, the optical path delay amount S between slow axis
w(is theoretical), S
w(is theoretical)=l
w* Δ n
w(is theoretical), linear birefrigence Δ n
w(is theoretical)by 8 * 10
-2meter; In device polarization crosstalk test data, can input protect inclined to one side tail optical fiber, input extend polarization maintaining optical fibre, output protect inclined to one side tail optical fiber, output extend polarization maintaining optical fibre fast with waveguide chip, between working shaft, produce light path sum S slowly
f-i(measures)+ S
w-i(measures)+ S
w(is theoretical)+ S
w-o(measures)+ S
f-o(measures)or the difference S of light path
f-i(measures)+ S
w-i (measurement)+ S
w-o(measures)+ S
f-o(measures)-S
w(is theoretical)corresponding horizontal ordinate place, finds the polarization crosstalk peak value of waveguide chip, its amplitude E
wabsolute value be the extinction ratio of waveguide chip; Waveguide chip cross-talk peak value appears at light path sum S
f-i(measures)+ S
w-i(measures)+ S
w (measurement)+ S
w-o(measures)+ S
f-o(measures)place, can determine that the fast axle of waveguide tail optical fiber aims at the fast axle of waveguide, and appears at the difference S of light path
f-i(measures)+ S
w-i(measures)+ S
w-o(measures)+ S
f-o(measures)-S
w(is theoretical)the slow axis of determining waveguide tail optical fiber is aimed at the fast axle of waveguide; According to the optical path delay amount S of the waveguide chip measuring
w(measures)true length l with waveguide chip
w, calculate the linear birefrigence Δ n of waveguide chip
w(measures)
Δ n
w(measures)=S
w(measures)/ l
w.
Beneficial effect of the present invention is:
The method not only can obtain extinction ratio and the linear birefrigence of waveguide chip exactly, can also obtain coupling cross-talk, the linear birefrigence of chip waveguide input/output terminal tail optical fiber simultaneously, I/O extended fiber solder joint, and waveguide chip and connection tail optical fiber internal optics defect; The method allows by the selection to I/O fiber lengths, has avoided dexterously wide spectrum light source spectrum ripple (ripple) and has caused that relevant peak, on the impact of measuring, has increased realizability and stability; The method can be passed through the polarization crosstalk data of comparative device and the cross-talk noise background of measurement mechanism, make the polarization crosstalk peak value for the treatment of the generations such as waveguide chip, I/O tail optical fiber, extended fiber solder joint be more prone to differentiate, reduced the difficulty of signal-obtaining and identification, simplify the process of data analysis and processing, can realize the measurement of the above integrated waveguide device of extinction ratio 85dB.
Accompanying drawing explanation
Fig. 1 is the method for testing process flow diagram of the optical parameters such as chip extinction ratio of Y waveguide device;
Fig. 2 is the Y waveguide device detection schematic diagram based on white light interferometric device;
Fig. 3 is 0 °～45 ° schematic diagram of aiming at, exporting 45 °～0 ° of aligning of input for the treatment of between side device and proving installation;
Fig. 4 is 0 °～0 ° schematic diagram of aiming at, exporting 0 °～0 ° of aligning of input for the treatment of between side device and proving installation;
Fig. 5 is that waveguide tail optical fiber slow axis is aimed at the fast axle of waveguide chip, during 0 °～0 ° of access proving installation of device, and the distributed polarization cross-talk data that measure (the polarization interference noise of measurement mechanism);
Fig. 6 is that waveguide tail optical fiber slow axis is aimed at the fast axle of waveguide chip, when 0 °～45 ° of the inputs of device, 45 °～0 ° of access measurement mechanism of output, and the distributed polarization cross-talk data (optical characteristics of Y waveguide device) that measure;
Fig. 7 is that the fast axle of waveguide tail optical fiber is aimed at the fast axle of waveguide chip, during 0 °～90 °, 90 °～0 ° of access proving installation of device, and the distributed polarization cross-talk data that measure (the polarization interference noise of measurement mechanism);
Fig. 8 is that the fast axle of waveguide tail optical fiber is aimed at the fast axle of waveguide chip, when 0 °～45 ° of the inputs of device, 45 °～0 ° of access measurement mechanism of output, and the distributed polarization cross-talk data (optical characteristics of Y waveguide device) that measure.
Embodiment
The optical property measuring method of the multi-functional lithium niobate integrated optical device (Y waveguide) based on white light interferometer measurement mechanism that the present invention proposes, respectively at the fast axle of the inclined to one side tail optical fiber of guarantor of waveguide device and slow axis Injection Signal light equably, by measuring waveguide device transmission axle (fast axle) and the white light interference signal amplitude of cut-off axle (slow axis) and the ratio between transmission axle self interference signal amplitude, obtain the optical parametrics such as waveguide chip extinction ratio, waveguide-coupled cross-talk; Measuring process, the measurement of the length selection that comprises waveguide device I/O tail optical fiber and measurement, waveguide chip geometric parameter, waveguide device light injection condition are selected, the distributed polarization cross talk characteristic of waveguide device is measured, and waveguide device optical performance parameter calculates, detailed process as shown in Figure 1:
1) measure the length l that inclined to one side tail optical fiber 21 is protected in waveguide device input
w-i, the optical path difference S of requirement transmission light wave between tail optical fiber 21 fast and slow axis
w-i(S
w-i=l
w-i* Δ n
f, Δ n
fprotect the linear birefrigence of inclined to one side tail optical fiber) be greater than the light path S at the relevant peak that light source 11 spectrum ripples produce
ripple, meet
S
W-
i>S
ripple （1）
2) if the length l of input tail optical fiber 21
w-ido not meet (1) formula, weld an elongated segment polarization maintaining optical fibre 25, what require solder joint 24 is 0 °-0 ° to shaft angle degree, simultaneously the fiber lengths l of extended fiber 25
f-ineed to meet optical path difference S
f-i(S
f-i=l
f-i* Δ n
f, Δ n
fprotect the linear birefrigence of inclined to one side tail optical fiber) be greater than the light path S at the relevant peak that light source 11 spectrum ripples produce
ripple, meet
S
f-
i>S
ripple （2）
Measure and record the length l of extended fiber 25
f-i;
3) measure the length l of waveguide chip 22
w;
4) measure the length l that inclined to one side tail optical fiber 23 is protected in waveguide device output
w-o, the optical path difference S of requirement transmission light wave between tail optical fiber 23 fast and slow axis
w-o(S
w-o=l
w-o* Δ n
f) be greater than transmission optical path difference S of light wave between waveguide chip 22 fast and slow axis
w(S
w=l
w* Δ n
w, Δ n
wthe linear birefrigence of waveguide chip), meet
S
W-o>S
W （3）
5) if the length l of output tail optical fiber 23
w-odo not meet 3 formula requirements, weld an elongated segment polarization maintaining optical fibre 27; What require solder joint 25 is 0 °-0 ° to shaft angle degree, simultaneously length l
f-othe optical path difference S of extended fiber 27
f-o(S
f-o=l
f-o* Δ n
f) needs meet
S
f-o>S
W （4）
Measure and record the length l of extended fiber 27
f-o;
6) while testing waveguide device first, the transmission axle of its I/O tail optical fiber 21,23 slow axis and waveguide chip 22 (fast axle) is on time, the light injection condition of device should meet: without input during extended fiber 25, input protect inclined to one side tail optical fiber 21 and the white light interferometer output polarizer 15 tail optical fiber 16 to shaft angle degree θ
1it is 0 °-0 °; Have input during extended fiber 25, extended fiber 25 and tail optical fiber 16 to shaft angle degree θ
1also it is 0 °-0 °; During no-output extended fiber 27, output protect inclined to one side tail optical fiber 23 and tail optical fiber 31 to shaft angle degree θ
2it is 0 °-0 °; Have output during extended fiber 27, extended fiber 27 and tail optical fiber 31 to shaft angle degree θ
2also it is 0 °-0 °;
To on time, the light injection condition of device should meet the transmission axle of the fast axle of its I/O tail optical fiber 21,23 and waveguide chip 22 (fast axle): input protect inclined to one side tail optical fiber 21 or extended fiber 25 and tail optical fiber 16 to shaft angle degree θ
1it is 0 °-90 °; Output protect inclined to one side tail optical fiber 23 or input extended fiber 27 and tail optical fiber 31 to shaft angle degree θ
2it is 90 °-0 °;
7) start white light interferometer, obtain distributed polarization crosstalk measurement result for the first time, be the instrument polarization cross-talk noise background data of white light interferometer, its horizontal ordinate is scan light number of passes ZhiS(unit: μ m), ordinate is polarization crosstalk amplitude E(unit: dB); The light path sweep limit Δ S measuring need to meet
ΔS>2（S
f-i+S
W-i+S
W+S
W-o+S
f-o） （5）
And the mid point of light path sweep limit is chosen as the position of the peak-peak of polarization crosstalk measurement data as far as possible.
8) the light injection condition of conversion waveguide device: without input during extended fiber 25, input protect inclined to one side tail optical fiber 21 and the white light interferometer output polarizer 15 tail optical fiber 16 to shaft angle degree θ
1it is 0 °-45 °; Have input during extended fiber 25, extended fiber 25 and tail optical fiber 16 to shaft angle degree θ
1also it is 0 °-45 °; During no-output extended fiber 27, output protect inclined to one side tail optical fiber 23 and white light interferometer input analyzer 32 tail optical fiber 31 to shaft angle degree θ
1it is 45 °-0 °; Have output during extended fiber 27, extended fiber 27 and tail optical fiber 31 to shaft angle degree θ
2also it is 45 °-0 °;
9) start white light interferometer, obtain distributed polarization crosstalk measurement result for the second time, i.e. the optical polarization crosstalk measurement data of device, the requirement of its light path sweep limit Δ S is identical with step 7);
10) if the polarization crosstalk background data of known white light interferometer, can skip over measuring process 6) and 7) the optical polarization crosstalk measurement data of instrument directly obtained, by the analysis and calculation to data, can obtain once the chip delustring of waveguide device, the linear birefrigence of chip, the coupling cross-talk of waveguide input/output terminal tail optical fiber, the optical parameters such as linear birefrigence of tail optical fiber.
Input is protected inclined to one side tail optical fiber 21, exports the inclined to one side tail optical fiber 23 of guarantor and is extended polarization maintaining optical fibre 25, extends the length of polarization maintaining optical fibre 27 and selects foundation, it is characterized in that: the inclined to one side tail optical fiber 21 of input guarantor, output are protected the length of inclined to one side tail optical fiber 23 and selected according to exchanging, the length that extends accordingly polarization maintaining optical fibre 25, prolongation polarization maintaining optical fibre 27 is selected according to also need to exchange simultaneously.
The chip delustring of waveguide device, the linear birefrigence of chip, the calculation procedure of the coupling cross-talk of waveguide input/output terminal tail optical fiber, the linear birefrigence of tail optical fiber is:
1) by measuring process 9) the device distributed polarization crosstalk measurement result and the instrument polarization cross-talk background data of the white light interferometer of step 7) acquisition (or known) that obtain contrast, can obtain some polarization crosstalk characteristic peaks of being introduced by waveguide chip, waveguide I/O tail optical fiber, output/output extended fiber, the corresponding optical path difference of the horizontal ordinate S(unit of peak value: μ m), the amplitude E(unit of the corresponding polarization crosstalk of ordinate: dB);
2) length l of input extended fiber 25
f-inumerical value, can calculate the theoretical optical path delay numerical value S that inputs extended fiber 25
f-i(is theoretical)(S
f-i(is theoretical)=l
f-i* Δ n
f(is theoretical), Δ n
f(is theoretical)by 5 * 10
-4meter); In device polarization crosstalk test data, can determine and meet optical path delay amount S
f-i(is theoretical)polarization crosstalk peak value be to cause by extending the solder joint 24 that polarization maintaining optical fibre 25 and input protect inclined to one side tail optical fiber 21, the corresponding solder joint 24 cross-talk value E of its Y value
f-i, horizontal ordinate corresponds to and postpones the real optical path delay amount of optical fiber S
f-i (measurement);
3) according to the length l of waveguide input optical fibre 21
w-inumerical value, can calculate the theoretical optical path delay numerical value S of waveguide input optical fibre 21
w-i(is theoretical)(S
w-i(is theoretical)=l
w-i* Δ n
f(is theoretical), Δ n
f(is theoretical)by 5 * 10
-4meter); In device detection data, can determine and meet optical path delay amount S
f-i(measures)+ S
w-i(is theoretical)polarization crosstalk peak value be to be caused by input optical fibre 21 and the power coupling cross-talk of waveguide chip 22, its ordinate coupling cross-talk value E
w-i, the corresponding real optical path delay amount S of horizontal ordinate
f-i(measures)+ S
w-i(measures);
4) according to the length l of waveguide input coupled fiber 21
w-itrue optical path delay amount S with its correspondence
w-i(measures), can accurate Calculation obtain the linear birefrigence Δ n that polarization maintaining optical fibre 21 is inputted in waveguide
f-i(measures), it is determined by (6) formula:
Δ n
f-i(measures)=S
w-i(measures)/ l
w-i(5)
5) with 2)～4) step is similar, the length l that extends polarization maintaining optical fibre 27 according to output
f-o, waveguide output optical fibre 23 length l
w-o, can determine and extend polarization maintaining optical fibre (27) and export the solder joint 26 cross-talk value E that protect inclined to one side tail optical fiber 23
f-i, output optical fibre 23 and waveguide chip 22 power coupling cross-talk value E
w-o, and the linear birefrigence Δ n of waveguide output polarization maintaining optical fibre 23
f-o;
Δ n
f-o(measures)=S
w-o(measures)/ l
w-o(6)
6) according to the length l of waveguide chip 22
w, can calculate that it is fast, the optical path delay amount S between slow axis
w(is theoretical)(S
w(is theoretical)=l
w* Δ n
w(is theoretical), linear birefrigence Δ n
w(is theoretical)by 8 * 10
-2meter); In device polarization crosstalk test data, can protect inclined to one side tail optical fiber 21 in input, extend polarization maintaining optical fibre 25, inclined to one side tail optical fiber 23 is protected in output, extend polarization maintaining optical fibre 27 fast with waveguide chip 22, between working shaft, produce optical path difference sum (S slowly
f-i(measures)+ S
w-i(measures)+ S
w(is theoretical)+ S
w-o(measures)+ S
f-o(measures)) or the poor (S of light path
f-i (measurement)+ S
w-i(measures)+ S
w-o(measures)+ S
f-o(measures)-S
w(is theoretical)) corresponding horizontal ordinate place, find the polarization crosstalk peak value of waveguide chip 22, its amplitude E
wabsolute value be the extinction ratio of waveguide chip 22; Waveguide chip 22 cross-talk peak values appear at above-mentioned light path sum (S
f-i(measures)+ S
w-i(measures)+ S
w(measures)+ S
w-o(measures)+ S
f-o(measures)) locate, can determine that the fast axle of waveguide tail optical fiber aims at the fast axle of waveguide, and appear at the poor (S of above-mentioned light path
f-i(measures)+ S
w-i(measures)+ S
w-o(measures)+ S
f-o(measures)-S
w(measures)) determine that the slow axis of waveguide tail optical fiber aims at the fast axle of waveguide; According to the optical path delay amount S of the waveguide chip 22 measuring
w(measures)true length l with waveguide chip 22
w, can accurate Calculation obtain the linear birefrigence Δ n of waveguide chip 22
w(measures)
Δ n
w(measures)=S
w(measures)/ l
w(7)
The optical property measuring method of a kind of multi-functional lithium niobate integrated optical device (Y waveguide) based on white light interferometer measurement mechanism, its test philosophy as shown in Figure 2.The detection light being sent by light source module 1 is through device under test 2, flashlight with device optical signature is admitted in white light measurement mechanism 3, by means of photodetection, processing module 4, can obtain once a plurality of optical parameters such as waveguide chip extinction ratio, linear birefrigence.The concrete function of measurement mechanism is:
Wide spectrum light source 11 sends flashlight through 2/98 coupling mechanism 12,2% power is fed to detector (PD0) 13, for detection of light source power, all the other are 98% after isolator (ISO) 14, be polarized the wide range polarized light that device (LP) 15 becomes high stable, output tail optical fiber 16 through the polarizer, by solder joint (or connector) 17, is injected into detection light in waveguide device 2 to be measured;
Waveguide device 2 is at least comprised of input optical fibre, waveguide chip and output optical fibre 3 parts, the some optics point of discontinuity that exist in device, comprise: waveguide chip, optical fiber and waveguide-coupled point, optical fiber solder joint, and the defect of other waveguides inside and inside of optical fibre etc., can make a part for transmission flashlight energy of a feature axis (for example fast axle) in treating side integrated optical device for example be coupled to, in the another one feature axis (slow axis) of quadrature, form a series of coupled light beam, the intensity of coupled light beam and light path position are corresponding one by one with the optical property of device.
Above-mentioned coupled light beam outputs in white light measurement mechanism 3 by solder joint (or connector) 30 together with remaining transmitting beam, because optical fiber and lithium niobate waveguide exist linear birefrigence, the refractive index official post transmission light and the coupling light that between two feature axis, exist occur discrete on light path; Above-mentioned light beam, after the polarization polarization of analyzer 32, is divided into respectively two parts equably by fiber coupler 33, in the reference arm that half transmission of energy forms at optical fiber 34, arrives fiber coupler 38; Other half transmission of energy is in the scan arm being comprised of fiber optical circulator 35, GRIN Lens 36 and mobile mirror 37, same coupling mechanism 38 and the reference arm light beam white light interference signal of arriving, is received and light signal is converted to electric signal by differential detector 391,392.This signal, after signal demodulating circuit 41 is processed, is sent in metering computer 42; Metering computer 42 also will be responsible in addition controlling mobile mirror 37 and realize light path scanning.
When the mobile mirror 37 of M-Z interferometer carries out light path scanning, transmission light is mated with coupling light generation light path, will produce white light interference signal, the amplitude of the corresponding coupling light of its peak amplitude; The locus that the corresponding coupling light of light path difference between white light interference signal peak occurs, therefore by the detection to a series of coupling light white light interference signal intensities and light path position in waveguide device, can obtain the measurement of the optical characteristics such as device inside extinction ratio, coupling fiber point, optical fiber solder joint.
As shown in Figure 3, when the alignment angle of waveguide device to be measured 2 and wide spectrum light source 1 and white light measurement mechanism 3 be 0 °～45 °, 45 °～0 ° on time, the amplitude of the white light interference signal of acquisition and optical path delay amount, can be as shown in the formula expression:
In formula: S represents light path delayed sweep amount, the normalization self-coherence function that R (S) is wide spectrum light source, R (0)=1, the white light interference peak signal amplitude of transmission light, optical path difference is zero; R (S)=0(S>S
0time, S
0coherent length for wide spectrum light source); S
f-i, S
f-o, S
w-i, S
w-o, S
wbe respectively the optical path delay amount of I/O extended fiber, I/O tail optical fiber and waveguide chip, when slow axis light path is ahead of fast axial light journey, above-mentioned retardation is defined as+; When slow axis light path lags behind fast axial light journey, above-mentioned retardation is defined as-, each optical path delay amount can be expressed as successively:
S
f-i＝l
f-i×Δn
f
S
W-i＝l
W-i×Δn
f
S
f-o＝l
f-o×Δn
f
S
W-o＝l
W-o×Δn
f （9）
S
W＝l
W×Δn
W
S
ripple＝2l
SLD×n
S
S
i＝l
i×Δn
i
In formula, l
f-i, l
f-o, l
w-i, l
w-o, l
wbe respectively the length of I/O extended fiber, I/O tail optical fiber and waveguide chip, Δ n
f, Δ n
wbe respectively the linear birefrigence of polarization maintaining optical fibre and waveguide chip; S
ripplefor the optical path difference of the relevant peak value of light source light spectrum ripple, it is directly proportional to active area and the refractive index length of SLD light source, S
ithe optical path delay amount of the interference peak causing for other optical defects that exist in white light interference proving installation 3; ρ
f-i, ρ
f-obe respectively the cross-talk amplitude amplitude of the solder joint of solder joint, output extended fiber and the waveguide output optical fibre of inputting extended fiber and waveguide input optical fibre, ρ
w-i, ρ
w-o, be respectively the coupling cross-talk amplitude amplitude of waveguide I/O optical fiber and waveguide chip, ε
chipfor the amplitude amplitude of Y waveguide extinction ratio, ρ
ripplethe relevant peak amplitude causing for light source light spectrum ripple; ρ
ithe interference peak amplitude causing for the optical defect existing in white light interference proving installation 3.
From (8), (9) formula, if length and the birefringence thereof of known I/O extended fiber, I/O waveguide tail optical fiber and waveguide chip scan by white light interferometric device light path, at optical path delay amount ± S
f-i, ± S
f-o, ± (S
f-i+ S
w-i), ± (S
f-o+ S
w-o), ± (S
f-o+ S
w-o+ S
f-i+ S
w-i+ S
w) can obtain white light interference peak value, by the calculating to amplitude, can obtain ρ by single pass
f-i, ρ
f-o, ρ
w-i, ρ
w-o, ε
chipdeng optical parametric.
From (9) formula, the polarization crosstalk peak value being only difficult to existing in waveguide device and light source light spectrum ripple, proving installation 3 from light path and cross-talk amplitude is distinguished, because this latter can produce considerable influence to measuring.Generally, I/O extended fiber solder joint cross-talk, I/O waveguide pigtail coupling cross-talk etc., its amplitude can not surpass-and extinction ratio that 50dB(is corresponding is less than 50dB), and the amplitude at the relevant peak that wide spectrum light source spectrum ripple (ripple) produces is between-60～-70dB, therefore, light source can not exert an influence to the measurement of above-mentioned parameter substantially; But quite different for waveguide chip extinction ratio, its amplitude is conventionally all more than 50dB, and the higher corresponding polarization crosstalk of 80dB(that reaches is at-80dB) more than, if the interference light path (S of waveguide chip
f-i+ S
w-i+ S
w-o+ S
f-o+ S
w) (on light path territory, there is wider scope with the relevant peak of light source light spectrum ripple, be generally several mm) overlaid, can cause and cannot differentiate, because for the realizability that guarantees to measure, must carry out requirement to the length of input optical fibre (or output optical fibre), meet formula (1), or input optical fibre (or output optical fibre) is extended, meet formula (2).
Because the extinction ratio of waveguide chip to be measured may be up to more than 80dB, in order to determine more accurately amplitude and the light path position of each characteristic peaks, eliminate light source light spectrum ripple, other optic fibre light path defects of white light interference proving installation to the impact of measuring, can first obtain the noise of instrument background of light source 1 and white light interference proving installation 3, then by the contrast of noise and signal, determine the polarization crosstalk peak value of the generations to be measured such as waveguide chip, coupling fiber point, specifically can realize with the alignment angle of light source 1 and proving installation 3 by changing device under test 2.
As shown in Figure 4, when I/O tail optical fiber 21,23 slow axis of waveguide device and the transmission axle of waveguide chip 22 (fast axle) are on time, inject light signal for 0 °～0 ° aligning of input, export 0 °～0 ° on time, at θ
1≈ 0, θ
2under the condition of ≈ 0, amplitude and the optical path delay amount of the white light interference signal of acquisition are expressed as approx:
In formula: θ
1, θ
2alignment angle for input, output.
When the fast axle of I/O tail optical fiber 21,23 of waveguide device and the transmission axle of waveguide chip 22 (fast axle) are on time, inject light signal for 0 °～90 ° alignings of input, export 90 °～0 ° on time, can be same to (10) identical result, only need angle to become θ
1≈ θ
1 hurry up-90 °, θ
2≈ θ
2 hurry up-90 °.
Contrast (8) formula and (10) are known, as alignment angle θ
1, θ
2during change, in device under test, the light path position of the interference peak of each point (polarization crosstalk) does not change, but interference signal (cross-talk amplitude) has been subject to the modulation of soldering angle, works as θ
1≈ 0, θ
2≈ 0(or θ
1≈ θ
1 hurry up-90 °, θ
2≈ θ
2 hurry up-90 °) time, polarization crosstalk peak value will be greatly weakened substantially; And measurement noise comprises: the cross-talk peak value that in light source 1 spectrum ripple, white light interferometric device 3, other optical defects produce, due to irrelevant with the angle of device under test injection light, its amplitude substantially can be constant.Therefore,, by the contrast to (9), twice measurement result of (10) formula, can be distinguished signal and noise.
For the optical property measuring method of integrated waveguide modulator of the present invention (Y waveguide) is clearly described, the invention will be further described with accompanying drawing in conjunction with the embodiments, but should not limit the scope of the invention with this.
Embodiment 1---the measurement of the Y waveguide device of the fast axle of tail optical fiber slow axis and waveguide chip
Device measurement mechanism as shown in Figure 2, select with parameter as follows by the device of white light interferometric device:
(1) the centre wavelength 1550nm of wideband light source 11, half spectral width are greater than 45nm, and fiber power is greater than 2mW, be approximately-60dB of light source light spectrum ripple <0.05dB(peak amplitude), the scope 4～7mm at relevant peak; Half spectral width of DFB light source 311 is less than 50MHz, and fiber power is greater than 1mW;
(2) 2/98 fiber coupler 12 operation wavelength 1550nm, splitting ratio 2:98;
(3) fibre optic isolater 14 operation wavelength 1550nm, insertion loss 0.8dB;
(4) operation wavelength of the optical fiber polarizer 15, optical fiber analyzer 32 is 1550nm, and extinction ratio is 30dB, and insertion loss is less than 1dB;
The insertion loss of the (5) the 1st, the 2nd fiber rotation connector 17,30 is 1dB, and extinction ratio is better than 18dB;
The operation wavelength 1310/1550nm of the (6) the 1st, the 2nd coupling mechanism 33,38, splitting ratio 50:50;
(7) fiber optical circulator 35 is three-port circulator, insertion loss 1dB, and return loss is greater than 55dB;
(8) operation wavelength of collimation lens 36 is 1550nm, and it and removable optical mirror 37(reflectivity are more than 92%) between light path scanning distance between 0～200mm, change greatly, average insertion loss is 2.0dB;
The photochromics of the (9) the 1st, the 2nd, the 3rd photodetector 13,391,392 is InGaAs, and photodetection scope is 1100～1700nm, and responsiveness is greater than 0.85;
(10) the operation wavelength 1550nm of Y waveguide device to be measured, waveguide tail optical fiber slow axis is aimed at the fast axle of waveguide chip, waveguide chip length 20mm.
The idiographic flow that device is measured is as shown in Figure 1:
Known according to step 501, measure Y waveguide input tail optical fiber l
w-ilength be: 1.53 meters;
Known according to step 502, input tail optical fiber l
w-itheoretical light path (Δ n
fby 5 * 10
-4meter) S
w-i=0.765mm; And S
ripple=4～7mm, visible, must weld input extended fiber;
Known according to step 503, connect extended fiber l
f-ilength at least want 7 * 10
-3/ 5 * 10
-4=14 meters, actually choose 15 meters;
Known according to step 504, the length of measuring waveguide chip is 20mm, its theoretical light path (Δ n
wby 8 * 10
-2meter) S
w=1.6mm, corresponding output tail optical fiber length l
w-o=1.6 * 10
-3/ 5 * 10
-4=3.2 meters;
Known according to step 505, measure output tail optical fiber length l
w-oit is 1.72 meters;
Known according to step 506～507, the light path S of output tail optical fiber
w-o<S
w, visible, must weld and input out prolongation fibre, welding extended fiber l
f-oat least want 3.2 meters, actually choose 5.6 meters;
According to step 508,509, device under test is linked in white light interferometric device 3 as shown in Figure 2, and because being measures device first, and device tail optical fiber slow axis is aimed at the fast axle of waveguide chip, adjusting I/O is 0 °-0 ° to shaft angle degree, as shown in Figure 4;
According to step 511, start white light interferometric device, obtain measurement result as shown in Figure 5,61 are expressed as the interference main peak of measurement, and it is measuring amplitude and light path position reference point; 62(62 '), 63(63 ') be the spuious interference peaks of measurement mechanism 3 light paths; 64(64 ') the relevant peak of high-order causing for light source light spectrum ripple; 65(65 ') be the polarization crosstalk Noise Background of measurement mechanism 3, represent the measuring limit of measurement mechanism;
According to step 512, adjusting I/O angle is 0 °-45 °, as shown in Figure 3;
According to step 513, again start proving installation, obtain measurement result as shown in Figure 6;
According to step 514, twice test result of comparison diagram 5 and Fig. 6,6A～6E is symmetrical respectively to obtain characteristic peak 6A～6E(6A '～6E ') totally 10 characteristic peaks;
By step 515～520, according to I/O extended fiber length, be respectively l
f-i=15.00 meters, l
f-o=5.60 meters, I/O tail optical fiber is respectively l
w-i=1.53 meters, l
w-o=1.72, waveguide chip length is 20mm, according to the light path calculating ± (S
f-i+ S
w-i), ± (S
f-i), ± (S
f-o+ S
w-o), ± (S
f-o), ± (S
f-i+ S
w-i+ S
w-o+ S
f-o-S
w), can determine characteristic peak 6A～6E(6A '～6E ') representative respectively, 6A, 6A ' they are input pigtail coupling cross-talk; 6B, 6B ' are input extended fiber solder joint cross-talk; 6C, 6C ' are output pigtail coupling cross-talk; 6D, 6D ' are output extended fiber solder joint cross-talk; 6E, 6E ' are waveguide chip cross-talk; The each point polarization crosstalk amplitude that it measures and the linear birefrigence of optical fiber and waveguide refer to table 1.
The measurement result of the Y waveguide device of the fast axle of watch 1 tail optical fiber slow axis and waveguide chip
As shown in Table 1 the measured value amplitude of each point cross-talk ± 0.2dB is measuring error, wherein the extinction ratio of waveguide chip is 55.2 ± 0.2dB.
Embodiment 2---the measurement of the Y waveguide device of the fast axle of the fast axle of tail optical fiber and waveguide chip
Equally as shown in Figure 2, the selection of measurement mechanism and parameter are with embodiment 1 for device measurement mechanism, and difference is that the fast axle of waveguide tail optical fiber of Y waveguide device to be measured is aimed at the fast axle of waveguide chip, waveguide chip length 30mm.
As shown in Figure 1, its test process and embodiment 1 are roughly the same for the idiographic flow that device is measured, and difference is:
(1) measure Y waveguide input tail optical fiber length l
w-i=6.11 meters, need equally to connect input extended fiber, get l
f-i=15.00 meters;
(2) measure output tail optical fiber length l
w-obe 0.90 meter, the length of waveguide chip is 30mm; Need to connect extended fiber equally, get l
f-o=5.60 meters;
(3) according to step 508,510, the fast axle of device tail optical fiber is aimed at the fast axle of waveguide chip, and adjusting I/O is 0 °-90 °, 90 °-0 ° to shaft angle degree, starts white light interferometric device, obtain measurement data for the first time, Noise Background result as shown in Figure 7; The 71 interference main peaks that are expressed as measurement in way, it is measuring amplitude and light path position reference point; 72(72 '), 73(73 '), 74(74 ') be the spuious interference peaks of measurement mechanism 3 light paths; 75(75 ') the relevant peak of high-order causing for light source light spectrum ripple; 76(76 ') be the polarization crosstalk Noise Background of measurement mechanism 3, represent measuring limit;
(4) according to step 512, adjusting alignment angle is 45 °-0 °, 0 °-45 °, obtains for the second time test result as accompanying drawing 8;
(5), according to step 514～520, twice test result of comparison diagram 7 and Fig. 8, according to l
f-i=15.00 meters, l
f-o=5.60 meters, l
w-i=6.11 meters, l
w-o=0.90 meter, l
w=30mm, determines in Fig. 8 ± (S
f-i+ S
w-i), ± (S
f-i), ± (S
f-o+ S
w-o), ± (S
f-o), ± (S
f-i+ S
w-i+ S
w-o+ S
f-o+ S
w), can determine characteristic peak 7A～7E(7A '～7E ') each point implication, cross-talk amplitude, linear birefrigence etc. refer to table 2.
The measured value amplitude of each point cross-talk is within ± 0.2dB (measuring error) as shown in Table 2, and the extinction ratio of waveguide chip is 47.7 ± 0.2dB.
The measurement result of the Y waveguide device of the fast axle of the watch fast axle of 2 tail optical fiber and waveguide chip
Claims (1)
1. an optical property measuring method for multi-functional lithium niobate integrated device, is characterized in that:
(1) measure the length l that inclined to one side tail optical fiber is protected in waveguide device input
w-i, detected transmission is protected the optical path difference S of light wave between inclined to one side tail optical fiber fast and slow axis in input
w-iwhether be greater than the light path S at the relevant peak of light source light spectrum ripple generation
ripple,
S
W-i>S
ripple，
S
w-i=l
w-i* Δ n
f, Δ n
fprotect the linear birefrigence of inclined to one side tail optical fiber;
(2) if the length l of inclined to one side tail optical fiber is protected in input
w-ido not meet step 2) in condition, in input, weld an elongated segment polarization maintaining optical fibre on tail optical fiber, solder joint to shaft angle degree, be 0 °-0 °, length is l
f-iinput extend polarization maintaining optical fibre and meet optical path difference S
f-ibe greater than the light path S at the relevant peak of light source light spectrum ripple generation
ripple,
S
f-i>S
ripple
S
f-i=l
f-i* Δ n
f, Δ n
fprotect the linear birefrigence of inclined to one side tail optical fiber, measure and record the length l that input extends polarization maintaining optical fibre
f-i;
(3) measure the length l of waveguide chip
w;
(4) measure the length l that inclined to one side tail optical fiber is protected in waveguide device output
w-o, detected transmission is protected the optical path difference S of light wave between inclined to one side tail optical fiber fast and slow axis in output
w-owhether be greater than the optical path difference S of transmission light wave between waveguide chip fast and slow axis
w,
S
w-o>S
w, S
w-o=l
w-o* Δ n
f, S
w=l
w* Δ n
w, Δ n
wthe linear birefrigence of waveguide chip;
(5) if the length l of inclined to one side tail optical fiber is protected in output
w-odo not meet the condition of step 4), in output, protect on inclined to one side tail optical fiber and weld an elongated segment polarization maintaining optical fibre, solder joint to shaft angle degree, be 0 °-0 °, length is l
f-ooutput extend the optical path difference S of polarization maintaining optical fibre
f-os
f-o>S
w, S
f-o=l
f-o* Δ n
f, measure and record the length l that output extends polarization maintaining optical fibre
f-o;
(6) aim to input or output and protect the slow axis of inclined to one side tail optical fiber and the transmission axle of waveguide chip, while extending polarization maintaining optical fibre without input, input protect inclined to one side tail optical fiber and white light interferometer export the polarizer tail optical fiber to shaft angle degree θ
1it is 0 °-0 °; While having input to extend polarization maintaining optical fibre, extended fiber and white light interferometer export the polarizer tail optical fiber to shaft angle degree θ
1also it is 0 °-0 °; When no-output extends polarization maintaining optical fibre, output protect inclined to one side tail optical fiber and white light interferometer input analyzer tail optical fiber to shaft angle degree θ
2it is 0 °-0 °; While having output to extend polarization maintaining optical fibre, output extend polarization maintaining optical fibre and white light interferometer input analyzer tail optical fiber to shaft angle degree θ
2also it is 0 °-0 °;
Aim at the accurate transmission axle of protecting the fast axle of inclined to one side tail optical fiber and waveguide chip that inputs or outputs, input protect inclined to one side tail optical fiber or input extend polarization maintaining optical fibre and white light interferometer export analyzer tail optical fiber to shaft angle degree θ
1it is 0 °-90 °; Output protect inclined to one side tail optical fiber or output extend polarization maintaining optical fibre and white light interferometer input analyzer tail optical fiber to shaft angle degree θ
2it is 90 °-0 °;
(7) obtain distributed polarization crosstalk measurement result for the first time, i.e. the instrument polarization cross-talk noise background data of white light interferometer, its horizontal ordinate is scan light number of passes value S, unit: μ m, ordinate is polarization crosstalk amplitude E, unit: dB; The light path sweep limit Δ S measuring
ΔS>2（S
f-i+S
W-i+S
W+S
W-o+S
f-o）
And the mid point of light path sweep limit is the position of the peak-peak of polarization crosstalk measurement data;
(8) the light injection condition of conversion waveguide device: while extending polarization maintaining optical fibre without input, input protect inclined to one side tail optical fiber and white light interferometer input the polarizer tail optical fiber to shaft angle degree θ
1it is 0 °-45 °; While having input to extend polarization maintaining optical fibre, input extend protect polarisation and white light interferometer input the polarizer tail optical fiber to shaft angle degree θ
1also it is 0 °-45 °; During no-output extended fiber, output protect inclined to one side tail optical fiber and white light interferometer export analyzer tail optical fiber to shaft angle degree θ
2it is 45 °-0 °; Have output during extended fiber, extended fiber and tail optical fiber to shaft angle degree θ
2also it is 45 °-0 °;
(9) obtain distributed polarization crosstalk measurement result for the second time, i.e. the optical polarization crosstalk measurement data of device, the requirement of its light path sweep limit Δ S is identical with step 7);
(10), by the analysis and calculation to data, obtain the chip delustring of waveguide device, the linear birefrigence of chip, the coupling cross-talk of waveguide input/output terminal tail optical fiber, the linear birefrigence optical parameter of tail optical fiber:
(10.1) the instrument polarization cross-talk background data of the white light interferometer that device distributed polarization crosstalk measurement result measuring process (9) being obtained and step (7) obtain contrasts, can obtain some polarization crosstalk characteristic peaks of protecting inclined to one side tail optical fiber, output or the introducing of output prolongation polarization maintaining optical fibre that inputed or outputed by waveguide chip, waveguide, the corresponding optical path difference S of horizontal ordinate of peak value, unit: μ m, the amplitude E of the corresponding polarization crosstalk of ordinate, unit: dB;
(10.2) according to the length l of input extended fiber
f-inumerical value, calculates the theoretical optical path delay numerical value S that input extends polarization maintaining optical fibre
f-i(is theoretical), S
f-i(is theoretical)=l
f-i* Δ n
f(is theoretical), Δ n
f(is theoretical)by 5 * 10
-4meter; In device polarization crosstalk test data, the definite optical path delay amount that meets S being caused by input prolongation polarization maintaining optical fibre and the solder joint of inputting the inclined to one side tail optical fiber of guarantor
f-i(is theoretical)polarization crosstalk peak value, the corresponding solder joint cross-talk of its Y value value E
f-i, horizontal ordinate corresponds to input and extends the real optical path delay amount of polarization maintaining optical fibre S
f-i(measures);
(10.3) length l of protecting inclined to one side tail optical fiber according to waveguide input
w-inumerical value, calculates the theoretical optical path delay numerical value S that inclined to one side tail optical fiber is protected in waveguide input
w-i(is theoretical), S
w-i(is theoretical)=l
w-i* Δ n
f(is theoretical), Δ n
f(is theoretical)by 5 * 10
-4meter; In device detection data, determine by input and protect the optical path delay amount that the meets S that inclined to one side tail optical fiber sound causes
f-i(measures)+ S
w-i(is theoretical)polarization crosstalk peak value, its ordinate coupling cross-talk value E
w-i, the corresponding real optical path delay amount S of horizontal ordinate
f-i(measures)+ S
w-i(measures);
(10.4) according to the length l of waveguide input coupled fiber
w-itrue optical path delay amount S with its correspondence
w-i(measures), can accurate Calculation obtain the linear birefrigence Δ n that polarization maintaining optical fibre is inputted in waveguide
f-i(measures),
Δ n
f-i(measures)=S
w-i(measures)/ l
w-i
(10.5) with step 2)～step 4) is identical, extends the length l of polarization maintaining optical fibre according to output
f-o, waveguide output optical fibre length l
w-o, can determine and extend polarization maintaining optical fibre and export the solder joint cross-talk value E that protects inclined to one side tail optical fiber
f-o, output optical fibre and waveguide chip power coupling cross-talk value E
w-o, and the linear birefrigence Δ n of waveguide output polarization maintaining optical fibre
w-o;
Δ n
f-o(measures)=S
w-o(measures)/ l
w-o
(10.6) according to the length l of waveguide chip
w, calculate that waveguide chip is fast, the optical path delay amount S between slow axis
w(is theoretical), S
w(is theoretical)=l
w* Δ n
w(is theoretical), linear birefrigence Δ n
w(is theoretical)by 8 * 10
-2meter; In device polarization crosstalk test data, can input protect inclined to one side tail optical fiber, input extend polarization maintaining optical fibre, output protect inclined to one side tail optical fiber, output extend polarization maintaining optical fibre fast with waveguide chip, between working shaft, produce light path sum S slowly
f-i(measures)+ S
w-i(measures)+ S
w(is theoretical)+ S
w-o(measures)+ S
f-o(measures)or the difference S of light path
f-i(measures)+ S
w-i (measurement)+ S
w-o(measures)+ S
f-o(measures)-S
w(is theoretical)corresponding horizontal ordinate place, finds the polarization crosstalk peak value of waveguide chip, its amplitude E
wabsolute value be the extinction ratio of waveguide chip; Waveguide chip cross-talk peak value appears at light path sum S
f-i(measures)+ S
w-i(measures)+ S
w (measurement)+ S
w-o(measures)+ S
f-o(measures)place, can determine that the fast axle of waveguide tail optical fiber aims at the fast axle of waveguide, and appears at the difference S of light path
f-i(measures)+ S
w-i(measures)+ S
w-o(measures)+ S
f-o(measures)-S
w(is theoretical)the slow axis of determining waveguide tail optical fiber is aimed at the fast axle of waveguide; According to the optical path delay amount S of the waveguide chip measuring
w(measures)true length l with waveguide chip
w, calculate the linear birefrigence Δ n of waveguide chip
w(measures)
Δ n
w(measures)=S
w(measures)/ l
w.
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