CN100501468C - Stress compensation method of athermal arrayed waveguide gratings and gratings - Google Patents

Abstract

This invention relates to stress compensation method of array wave guide without heat, which is characterized by the following: selecting two force points along array wave guide direction or along array wave guide; exerting pulling or stretch force in AWG chip plane and exerting pressure force on AWG array wave guide area.

Description

The stress compensation method and the grating thereof of non-heat array wave guide grating

Technical field

The invention belongs to optical communication device.

Background technology

As the best means of building the high capacity Optical Transmission Network OTN, the DWDM technology has obtained tremendous development.Multiplexer and demodulation multiplexer are the Primary Components in the dwdm system, and the device that can finish this function at present mainly contains array waveguide grating (AWG), Thin Film Filter and fiber grating.On existing market and technology, AWG and Thin Film Filter account for absolute leading position, and AWG is having the trend that replaces Thin Film Filter and monopolize whole multiplexing demultiplexing device market in the future greatly.The more important thing is the gordian technique of AWG---optical planar circuit technology (PLC)---function that can realize runs far deeper than multiplexing and demultiplexing, it can also realize functions such as power division, exchange, monitoring and light intensity variable attenuation.At present, the PLC chip that can realize 100 multinomial functions simultaneously comes out.Just as integrated circuit replaces triode discrete device circuit, following optical communication system will make up on the basis of this integrated monolithic photosystem.

Communication system requires the wavelength of each passage of AWG and the consistent wavelength of ITUT (International Telecommunications Union (ITU)) regulation, but because AWG is fabricated on the silicon chip, the refractive index of silicon dioxide changes with variation of temperature, thereby causes the wavelength of each passage of AWG to change with temperature.For the centre wavelength that compensates causes is drifted about, adopt two kinds of schemes at present: 1, use temperature control circuit and well heater, make the AWG chip be in the isoperibol about 70 degrees centigrade, each channel wavelength of AWG will keep stable like this, and this AWG is exactly the so-called hot AWG that has; 2, on the chip structure of AWG, adopt particular design and technology, make centre wavelength not change, do not adopt any heating arrangement and control circuit, Here it is Heatless AWG with ambient temperature.Because Heatless AWG is smaller on package dimension, characteristics that need not auxiliary circuit give system development with bigger design freedom, and cost is lower, so domestic and international many major companies and research institution have launched the further investigation to Heatless AWG.

There are several schemes can realize Heatless AWG at present, according to its feature branch, can reduce following four classes: 1, the automatic motion compensation technology of input port: change input waveguide and import the position of planar waveguide (change of this position realizes by a hot telescopic material) relatively, the position that input waveguide is imported planar waveguide has relatively compensated centre wavelength with variation of temperature with variation of temperature.Because input waveguide has changed mobile optical fiber into as input, in order to realize the AWG flat spectral response, must design and develop special Heatless AWG chip.2, adding the thermal refractive index coefficient material different with the silicon dioxide thermal refractive index coefficient in AWG compensates.As opening leg-of-mutton groove on the Waveguide array or on planar waveguide, opening the groove and the filling temp compensative material of moon shape.3, the AWG that leads based on no heat wave, the waveguide top covering is made the Polymer material, or changes the doping of silicon dioxide, and by suitable selection waveguide cross-sectional dimensions, perhaps adds the way of transition bed in waveguide, makes the light path of waveguide not be subjected to extraneous thermal effect.4, utilize piezooptical effect compensation thermo-optic effect, such as on AWG, pasting stress plate.

In above-mentioned each scheme, based on the Heatless AWG of the automatic mobile technology of input waveguide, the IGNIS company in Corning Incorporated and Europe all researchs and develops.In the scheme of other several realization Heatless AWGs, the 2nd kind of scheme adopts grooving on Waveguide array, and shortcoming is restricted to the number of Waveguide array, so also restricted to the number of output channel; Though grooving can be avoided this problem on planar waveguide, can cause loss excessive, and after adding macromolecular material, the stability of device is difficult to guarantee.Adopt macromolecular material to do top covering in the 3rd kind of scheme, can introduce the Polarization Dependent Loss problem, and the bonding problem between glue and the chip, main problem is that the waveguide effective refractive index of this structure is non-linear with variation of temperature, so just can not compensate the drift of centre wavelength in whole temperature range.And the scheme of change mixing in glass may make the softening temperature step-down of sandwich layer, thereby has increased the technology manufacture difficulty of waveguide; The 4th kind of scheme is to paste stress plate, and shortcoming is that stress can't be controlled flexibly.

Domestic and international patent retrieval situation:

(1) U.S. Pat 6470119 of Siemens company, patent name is the optical couping device of light between two Waveguide end faces of coupling.An optical fiber is fixed on an end of a bar, and an other end of bar is fixed on above the device, it is complete that the end face that will comprise the fiber device of bar and device is aimed at coupling.

(2) European patent EP 0922973 of JDS Fitel company, FurukawaElectric company comprises the multinomial patent of patent US2002/0009263; Chinese patent: CN 1302131A and CN 1392961A (patent of company of Furukawa Electronic application).The technology that these patents are introduced is with the Rowland circle of AWG (SLAB part) lateral dissection, with half Rowland circle with respect in addition half laterally relatively moves.

(3) patent US 673854B1, US 2004/0208417A1, WO2005/114288A1, to the effect that in planar waveguide position or the Waveguide array position of AWG, digging a groove or dig a ditch along chip surface, is boundary with the AWG chip with this groove or ditch again, is divided into two parts A and B.The A and the B of AWG chip partly are separately fixed at the two ends on the metal support that can stretch, and when metal support was flexible, chip A part and B part can relatively move, and compensate the compensate for temperature drift characteristic of AWG.The shortcoming of this method is: dig groove or dig a ditch along chip surface difficult realizing that technology difficulty is big, cost height, and can the index of AWG itself being had a negative impact, big or the like as inserting loss meeting change.

(4) the patent retrieval situation of other Heatless AWG:

In AWG, add the thermal refractive index coefficient material different and compensate the following representative patents: the European patent EP 0919840 of NTT company with the silicon dioxide thermal refractive index coefficient, the U.S. Pat 6169838 of private application, the U.S. Pat 6549696 of Hitachi Cable company; Based on the AWG that no heat wave is led, the waveguide top covering is made the Polymer material, or changes the doping of silicon dioxide, and by suitable selection waveguide cross-sectional dimensions, perhaps adds the way of transition bed in waveguide, makes the light path of waveguide not be subjected to extraneous thermal effect.The following representative patents is arranged: the European patent EP 0849231 of Corning company, the European patent EP 1262805 of Hoya company, the Chinese patent CN1402070 of the Central China University of Science and Technology; Utilize piezooptical effect compensation thermo-optic effect, as the U.S. Pat 2003021567 of NEC Corporation.

Utilize and paste the patent that stress plate realizes that Heatless AWG has two pieces of article reports and Wuhan GuangXun Co., Ltd applying for.These reports and patent all pass through in the method realization of AWG back side stickup stress plate or stress bar the AWG temperature compensation.Each channel wavelength of AWG must coincide with the ITUT wavelength, so the initial wavelength of Heatless AWG must be transferred to the ITUT wavelength, accuracy of the wavelength, will be controlled at below 10 micromicrons.Above-mentioned document of mentioning or patent are adjusted on the link of ITUT wavelength very difficult at the initial wavelength with AWG.Generally speaking, AWG need be put in the high temperature furnace and heat, monitor the wavelength of AWG simultaneously, when the initial wavelength of AWG and ITUT wavelength coincide, just begin to solidify, stress plate and AWG chip are stained with are connected together.This method has two shortcomings: when the wavelength of AWG satisfied the ITUT wavelength, the solidification temperature of each AWG was different, and glue has been proposed very high requirement, because the solidification temperature relative fixed of glue.In addition, in case because fabrication error causes the initial wavelength of AWG and ITUT wavelength not to be aimed at, so whole AWG device must be scrapped.

Summary of the invention

The stress compensation method and the grating thereof that the purpose of this invention is to provide a kind of non-heat array wave guide grating, its processing and making are simple, and cost is low, and array waveguide grating reliability and good reproducibility help producing in batches.

Technical scheme of the present invention is: a kind of stress compensation method of non-heat array wave guide grating, it is characterized in that: on the AWG chip along the direction of Waveguide array, perhaps along the direction of partial array waveguide, select two forces, in the plane of AWG chip, apply pulling force or tension force, the Waveguide array place of AWG is applied compressive stress or tension stress.

The stress compensation method of aforesaid non-heat array wave guide grating is characterized in that: with the redundance excision of the Waveguide array periphery of AWG chip, make the border profile of AWG chip, and partly or entirely similar to the shape of its train wave guide path of going into battle.

Utilize the non-heat array wave guide grating of said method, it is characterized in that: the stress bar two ends are connected with the front or the back side of AWG chip, the plane coplanar of the force surface of stress bar and AWG chip or parallel.

Aforesaid non-heat array wave guide grating is characterized in that: the whole face of AWG chip is connected on the stress section, and the two ends of stress bar are connected on the stress section.

Aforesaid non-heat array wave guide grating is characterized in that: the border profile of stress section is similar to the shape of the Waveguide array light path of AWG chip.

Aforesaid non-heat array wave guide grating is characterized in that: apparatus for adjusting force is answered in the centre of stress bar.

The present invention adjusts AWG centre wavelength, the purpose that makes it to meet the ITUT standard and reach no thermal compensation by waveguide applies compressive stress or tension stress to the AWG chip array.Principle of work specifically describes as follows.

The central wavelength lambda of AWG is:

$\mathrm{\λ}=\frac{n_{\mathrm{eff}}\mathrm{\ΔL}}{m}---\left(1\right)$

N wherein _EffBe the effect refractive index that waveguide has, Δ L is the length difference of adjacent array waveguide, and m is the diffraction magnitude.For the AWG chip, the temperature sensitivity of centre wavelength is expressed as:

$\frac{\mathrm{d\λ}}{\mathrm{dT}}=\mathrm{\λ}(\frac{1}{n_{\mathrm{eff}}}\frac{{\∂n}_{\mathrm{eff}}}{\∂T}+\frac{1}{\mathrm{\ΔL}}\frac{\∂\mathrm{\ΔL}}{\∂T})---\left(2\right)$

Because the thickness of waveguide is far smaller than the thickness of substrate, the no-load voltage ratio of substrate plays conclusive effect, therefore can think

$\frac{1}{\mathrm{\ΔL}}\frac{\∂\mathrm{\ΔL}}{\∂T}\≈{\mathrm{\α}}_{\mathrm{sub}}$

α wherein _SubIt is the thermal expansivity of substrate.Formula (2) becomes:

$\frac{\mathrm{d\λ}}{\mathrm{dT}}=\mathrm{\λ}\left(\frac{1}{n_{\mathrm{eff}}}\frac{{\∂n}_{\mathrm{eff}}}{\∂T}{+\mathrm{\α}}_{\mathrm{sub}}\right)---\left(3\right)$

For silicon based silicon dioxide wave, the temperature dependency of centre wavelength is 0.012nm/ ° of c.

After having applied stress for the AWG chip in it is unilateral, waveguide is subjected to stress.Because central wavelength lambda also is the function of stress σ, the temperature sensitivity of centre wavelength is expressed as:

$\frac{\mathrm{d\λ}}{\mathrm{dT}}=\mathrm{\λ}(\frac{1}{n_{\mathrm{eff}}}\frac{{\∂n}_{\mathrm{eff}}}{\∂\mathrm{\σ}}+\frac{1}{\mathrm{\ΔL}}\frac{\∂\mathrm{\ΔL}}{\∂\mathrm{\σ}})\frac{\mathrm{d\σ}}{\mathrm{dT}}+\mathrm{\λ}(\frac{1}{n_{\mathrm{eff}}}\frac{{\∂n}_{\mathrm{eff}}}{\∂T}+{\mathrm{\α}}_{\mathrm{sub}})--\left(4\right)$

(4) the preceding binomial on the right is caused by stress in the formula.Wherein

$\frac{1}{n_{\mathrm{eff}}}\frac{{\∂n}_{\mathrm{eff}}}{\∂\mathrm{\σ}}$

Be the elasto-optical effect of waveguide,

$\frac{1}{\mathrm{\ΔL}}\frac{\∂\mathrm{\ΔL}}{\∂\mathrm{\σ}}=\frac{\∂\mathrm{\ϵ}}{\∂\mathrm{\σ}}$

It is the strain stress relation.As long as preceding two numerical value, just can obtain reduce or the insensitive AWG of centre wavelength susceptibility less than zero.

For the ease of giving the Waveguide array place stress application of AWG, make it to reach positive effect, with the method for corrosion or Laser Curve cutting or other process technologies the AWG chip is cut, with the redundance excision of Waveguide array periphery.

The scheme of stress application has multiple, it mainly is direction along Waveguide array, perhaps along the direction of partial array waveguide, stress apply direction in line with following principle: 1, will be in the plane of chip or in the parallel surface, 2, can not introduce the polarization relevant issues to device, as Polarization Dependent Loss, the drift of polarization relevant wavelength.

Adjust the stress that AWG is applied by the regulating device of regulating stress section/bar, when the channel wavelength of AWG and ITUT wavelength coincide, just stop to regulate stress.

When environment temperature rose or descend, sheet metal/bar extension or contraction applied AWG respectively and presses or tension stress, causes equation 4 to approximate zero, thereby realizes the temperature benefit of AWG is tasted.

Stress section/bar can be selected suitable metal material, also can substitute by the nonmetallic materials that other functions meet the demands.Stress section/bar can be selected same material, also can select different materials according to regulating the stress needs.

Bonding stress section/bar and AWG chip can adopt various ultra-violet curing glue, and heat-curable glue also can adopt scolder or other adhesivess.

Stress section/bar end positions regulating device can be selected threaded rod and nut for use, selects various ultra-violet curing glue after also can regulating for use, and heat-curable glue, scolder or other adhesivess are directly fixing.

The invention has the beneficial effects as follows:

1, can be easily the initial wavelength of AWG be adjusted to the ITUT wavelength by stress section/bar.To the initial wavelength of AWG chip without limits.Reduce the cost of Heatless AWG greatly.

2, can under the prerequisite that does not increase device polarization relevant issues, realize Heatless AWG.Processing and fabricating is simple, and stability is high, favorable repeatability.

3, be expected to become a kind of suitability for industrialized production technology by stress compensation method manufacturing apyrexia arrayed waveguide grating technology, fundamentally opened up the bright prospects of various DWDM device production.

Description of drawings

Fig. 1, the embodiment of the invention 1 stress applies position view.Wherein, 1, the AWG chip, 2, the Waveguide array light path, 3, force.

Fig. 2, the embodiment of the invention 2 stress apply position view.

Fig. 3, the embodiment of the invention 3 stress apply position view.

Fig. 4, the embodiment of the invention 4 stress apply position view.

Fig. 5, the embodiment of the invention 5 stress sections/bar bonding location synoptic diagram.Wherein, 4, stress bar, the similar chip of 5 parts.

Fig. 6, the embodiment of the invention 6 stress sections/bar bonding location synoptic diagram.

Fig. 7, the embodiment of the invention 7 stress sections/bar bonding location synoptic diagram.Wherein, 6, whole similar chip.

Concrete embodiment

In order to give the Waveguide array place stress application of AWG, reach positive effect simultaneously, with the method for corrosion or curvilinear cut the AWG chip is cut, form Fig. 5, the shape shown in 6 or 7.The purpose of this shape is with the excision of the redundance of periphery, Waveguide array place, and what make that stress can be more concentrated is applied to the Waveguide array part.The scheme of stress application has multiple, mainly be the direction along Waveguide array, Fig. 1, and 2,3 and 4 have provided the canonical schema that stress applies direction.Fig. 5,6 and 7 have provided the exemplary position that sheet metal/bar is pasted, what pay special attention to is, Fig. 5,6 and 7 metal stresses bar has the adjusting position device at two ends, as rib-loop bar and nut etc., at these metal stresses plate/bars after good with the AWG chip attach, can also there be the adjusting position device to realize the dynamic change of counter stress at two ends by regulating the metal stresses bar, reaches till the needed stress.Adjust the stress that AWG is applied by regulating stress plate/bar end positions regulating device, when the channel wavelength of AWG and ITUT wavelength coincide, just stop to regulate stress.When environment temperature rose or descend, sheet metal/bar was upheld or is shunk, and AWG is applied press or tension stress respectively, caused equation 4 to approximate zero, thereby realized the temperature compensation to AWG.

Fig. 1 applies the direction synoptic diagram for non-heat array wave guide light canopy stress, it is characterized in that stress is applied on the whole Waveguide array, stress applies direction and Waveguide array has certain included angle, change the size of this angle, can adjust the temperature variant linearity of centre wavelength.The variation counter stress of centre wavelength is relatively more responsive.

Fig. 2 is characterized in that for non-heat array wave guide grating stress applies the direction synoptic diagram stress is applied near in the partial array waveguide of input end Rowland circle, and the centre wavelength counter stress is reconciled susceptibility and reduced, and helps accurate control center wavelength.Change the length of the partial array waveguide of stress application, can change the susceptibility of centre wavelength counter stress accordingly.

Fig. 3 applies the direction synoptic diagram for non-heat array wave guide light canopy stress, it is characterized in that, stress is applied on the whole Waveguide array, stress is not that folk prescription is to stress, but, being parallel to Waveguide array along the direction of Waveguide array, the variation counter stress of centre wavelength is relatively more responsive.

Fig. 4 is characterized in that for non-heat array wave guide grating stress applies the direction synoptic diagram stress is applied near in the partial array waveguide of output terminal Rowland circle.

Fig. 5 is non-heat array wave guide grating stress section/bar bonding location synoptic diagram, it is characterized in that, method with corrosion or curvilinear cut becomes shape shown with the AWG chip cutting, excision is near the peripheral unnecessary part of input end Rowland circle partial array waveguide, by the bonding stress section/bar of graphic technique, direction and Waveguide array that stress applies have certain included angle, suitably regulate the position of setscrew nut according to four directions of arrow, when the channel wavelength of AWG and ITUT wavelength coincide, just stop to regulate.By the material and the length of rational selection stress section/bar, reaching does not have the purpose that heat is repaid.

Fig. 6 is non-heat array wave guide grating stress section/bar bonding location synoptic diagram, it is characterized in that excising near the peripheral unnecessary part of input end Rowland circle partial array waveguide, and direction and Waveguide array that stress applies have certain included angle, but angle is different from Fig. 5.

Fig. 7 is non-heat array wave guide light canopy stress section/bar bonding location synoptic diagram, it is characterized in that excising the peripheral unnecessary part of Rowland circle, stress is applied on the whole Waveguide array, and center wavelength variation is relatively more responsive, and the direction that stress applies constantly changes along Waveguide array.

Claims (6)

1, a kind of stress compensation method of non-heat array wave guide grating, it is characterized in that: on the AWG chip along the direction of Waveguide array, perhaps along the direction of partial array waveguide, select two forces, in the plane of AWG chip, apply pulling force or tension force, the Waveguide array place of AWG is applied compressive stress or tension stress.

2, the stress compensation method of non-heat array wave guide grating as claimed in claim 1, it is characterized in that: with the redundance excision of the Waveguide array periphery of AWG chip, make the border profile of AWG chip, partly or entirely similar to the shape of its train wave guide path of going into battle.

3, utilize the non-heat array wave guide grating of the method for claim 1 or 2, it is characterized in that: the stress bar two ends are connected with the front or the back side of AWG chip, the plane coplanar of the force surface of stress bar and AWG chip or parallel.

4, a kind of stress compensation method of non-heat array wave guide grating, it is characterized in that: the whole face of AWG chip is connected on the stress plate, the two ends of stress bar are connected on the stress plate, on stress plate along the direction of Waveguide array, perhaps along the direction of partial array waveguide, in the stress plate plane, apply pulling force or tension force, the Waveguide array place of AWG is applied compressive stress or tension stress.

5, the stress compensation method of non-heat array wave guide grating as claimed in claim 4 is characterized in that: the border profile of stress plate is similar to the shape of the Waveguide array light path of AWG chip.

6, as the stress compensation method of claim 4 or 5 described non-heat array wave guide gratings, it is characterized in that: apparatus for adjusting force is answered in the centre of stress bar.

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