CN1697993A - Multichannel integrated tunable thermo-optic lens and dispersion compensator - Google Patents

Abstract

A thermo-optic lens of the present invention includes a plurality of parallel heating elements having substantially constant center-to-center spacing and respective dimensions varying from the outermost heating elements to the innermost heating elements, and at least two conductive elements for providing a potential across the heating elements. The dimensions of the heating elements are varied such that a parabolic temperature distribution is generated within the thermo-optic lens. A dispersion compensator of the present invention includes a first and a second waveguide grating, each of the waveguide gratings having a first star coupler, an array of waveguides of increasing path lengths, a first end of each of the waveguides of the array of waveguides optically coupled to the first star coupler, and a second star coupler, a second end of each of the waveguides of the array of waveguides optically coupled to the second star coupler. The dispersion compensator further includes a lens having a parabolic refractive index distribution, the lens optically coupling the second star coupler of the first waveguide grating and the second star coupler of the second waveguide grating.

Description

Multichannel integrated tunable thermo-optic lens and dispersion compensator

The cross reference of related application

Present patent application requires the U.S. Provisional Application No.60/364 of application on March 15th, 2002, and 930 right of priority is quoted it as a reference by integral body here.

Technical field

The present invention relates to the dispersion compensator field, relate more specifically to use the Tunable Dispersion Compensator field of thermo-optic lens.

Background technology

High speed transmission system as the data system of 40Gb/s and higher rate has the big bandwidth of every passage dispersion compensator of requirement.Advantage in this High Speed System is that these dispersion compensators are adjustable.Proposed various Tunable Dispersion Compensators (TDC), comprised optical fiber, full optical fiber (bulk-optic) and based on the TDC of waveguide.

Under the situation of optical fiber TDC, realized hot adjustable chirped optical fiber Bragg raster for its structure.Optical fiber TDC adjustable extent is big, but each equipment all can only be used for one or two wavelength channel.They also typically can not adjust to zero chromatic dispersion, and also need considerable time to adjust (being about several seconds).

For full optical fiber TDC, based on the TDC and the Gires-Tournois of virtual image phased array, realized interferometer for its structure.The grating that the TDC of virtual image phased array is used for the shaping ultrashort pulse before having adds the phase-plate configuration, with the calibrating device that tilts as grating, with curved reflectors as phase-plate.The TDC based on Gires-Tournois that also was used for the shaping ultrashort pulse in the past is the multi-cavity calibrating device that series connection is used more than two.Can use these two kinds of full TDC (being known as " colourless " TDC) for nearly all wavelength channel, still, these two kinds of TDC adjust very slow (being about tens seconds).

For TDC, toroidal cavity resonator and thermo-optic lens waveguide grating router (WGR) TDC have been proposed based on waveguide.Different with full optical fiber solution, based on the TDC of waveguide can large-scale production, automatically and non-tight ground packing, rapid adjustment (several milliseconds), and integrated other function.Toroidal cavity resonator TDC exquisiteness, compactness and colourless, but need very high index step (index-step) waveguide and some electric control.Based on the TDC of thermo-optic lens be colourless, use low index step waveguide and have only a control, but not too compact.

Summary of the invention

The present invention has advantageously provided a kind of colourless (integrated) thermo-optic lens and Tunable Dispersion Compensator (TDC) based on waveguide, can use low index step waveguide, low-loss, only need an electric drive signal, have the Millisecond adjustment regularly and the setting range that has increased.

In one embodiment of the invention, thermo-optic lens comprises: a plurality of parallel heating elements, and the interval constant of this heating element center to center, and size separately changes to the most inboard heating element from outermost heating element; And at least two conducting elements are used to provide the electromotive force at heating element two ends.The change in size of heating element makes to produce parabolic temperature distribution in thermo-optic lens.

In another embodiment of the invention, dispersion compensator comprises first and second waveguide optical gratings, each waveguide optical grating comprises that first end that first star-type coupler, increase each waveguide in the waveguide duct array of path, the waveguide duct array all couples light to first star-type coupler, and second star-type coupler, second end of each waveguide all couples light to second star-type coupler in the waveguide duct array.Dispersion compensator also comprises the lens with parabolic refractive index distribution, and lens light is coupled to second star-type coupler of first waveguide optical grating and second star-type coupler of second waveguide optical grating.

Description of drawings

Think over following detailed in conjunction with the drawings, but easy to understand instruction of the present invention, wherein:

Fig. 1 has shown the high level block diagram according to an embodiment of Tunable Dispersion Compensator of the present invention;

Fig. 2 a has shown the high level block diagram of an embodiment of the thermo-optic lens of the Tunable Dispersion Compensator that is applicable to Fig. 1;

Fig. 2 b has shown another of thermo-optic lens of the Tunable Dispersion Compensator that is applicable to Fig. 1

The high level block diagram of embodiment;

Fig. 3 a has shown the alternate embodiment of the thermo-optic lens that comprises parabolic temperature distribution;

Fig. 3 b has shown another embodiment of the thermo-optic lens that comprises parabolic temperature distribution;

Fig. 3 c has shown another embodiment of the thermo-optic lens that comprises parabolic temperature distribution;

Fig. 4 a has shown that the double star of the Tunable Dispersion Compensator of Fig. 1 when thermo-optic lens is closed reaches the wherein high level block diagram of principle of work;

Fig. 4 b has shown that the double star of the Tunable Dispersion Compensator of Fig. 1 when thermo-optic lens is opened reaches the wherein high level block diagram of principle of work;

Fig. 5 a has shown the transmissivity-wavelength of the Tunable Dispersion Compensator of Fig. 1 for the measurement of three kinds of different capacities of thermo-optic lens;

Fig. 5 b has shown the group delay-wavelength of the Tunable Dispersion Compensator of Fig. 1 for the measurement of three kinds of different capacities of thermo-optic lens;

Fig. 6 graphic presentation the bit error rate of measurement of three kinds of dispersion values of 40Gb/s CSRZ data of the Tunable Dispersion Compensator transmission by Fig. 1; And

Fig. 7 has shown the alternate embodiment according to Tunable Dispersion Compensator of the present invention.

For the ease of understanding, use identical reference numerals to represent that to figure be the similar elements that has in possible place.

Embodiment

Though will describe each embodiment of the present invention with respect to the Tunable Dispersion Compensator of realizing thermo-optic lens here, but can realize that in Tunable Dispersion Compensator of the present invention other equipment with parabolic refractive index distribution substitutes thermo-optic lens, such as using the electro-optic lens that for example in the silicon waveguide, injects charge carrier.

Fig. 1 has shown the high level block diagram according to an embodiment of Tunable Dispersion Compensator of the present invention (TDC).The TDC100 of Fig. 1 comprises two waveguide grating routers (WGR) 110 ₁With 110 ₂(be generically and collectively referred to as WGR110, be also referred to as waveguide optical grating), adjustable filter 140, comprise adjustable lens (exemplary is thermo-optic lens) 150 and the circulator/polarization separator (CPS) 160 of parabolic refractive index distribution.

WGR110 ₁With 110 ₂Each comprises the waveguide 120 of a plurality of increase paths respectively ₁-120 _nWith 122 ₁-122 _n(exemplary is that 18 waveguides are respectively arranged) (being generically and collectively referred to as waveguide 120 and 122) and first and second star-type couplers 130 separately ₁, 130 ₂With 132 ₁, 132 ₂

Adjustable filter 140 is exemplary comprises three adjustable Mach-Zehnder interferometers (MZI) wave filter 142 ₁, 142 ₂With 142 ₃Though in the TDC100 of Fig. 1, adjustable filter is shown as and comprises three MZI wave filters, but according to principle of the present invention, can in TDC, realize the MZI wave filter and the element other quantity and type, that carry out roughly the same function of other quantity, for example Optical Equalizer or toroidal cavity resonator are used to filter the spontaneous emission of amplifying type (ASE).In addition, comprise a CPS160 though the TDC100 of Fig. 1 is shown as, TDC can realize under the situation of CPS not having in accordance with the principles of the present invention.Equally, comprise an adjustable filter 140 though the TDC100 of Fig. 1 is shown as, TDC can realize under the situation that does not have adjustable filter 140 in accordance with the principles of the present invention.

Waveguide 120,122 is exemplary comprises that index step is 0.80% imbeds silicon nuclear (sillica core) and be positioned on the silicon base.TDC100 comprise two similar substantially, at its second star-type coupler 130 separately ₂With 132 ₂The link together high raster stage WGR110 of (star-type coupler that has hereinafter connected is called " double star ") of end.Double star is retracted to the width of the optical grating diffraction level at its center, to distinguish the higher order of diffraction.Because reflection, this diffraction-order edges that is contracted in causes little spectral ripple, and for horizontal magnetic (TM) polarized light, spectral ripple is than laterally electrically (TE) polarized light is little.

Thermo-optic lens 150 among Fig. 1 mainly comprises and is arranged on its lip-deep metal heater structure.The back is described thermo-optic lens 150 in detail with reference to Fig. 2.

In order to realize and polarization irrelevant, realize polarization diversity scheme by realizing optional CPS160 as shown in Figure 1.In this case, only so that a polarization of using up.Otherwise in order to realize the polarization mode chromatic dispersion less than 0.5ps, wavelength (PDW) skew relevant with polarization in the grating must be less than 0.5ps/D _Max, D wherein _MaxIt is the maximum dispersion values that TDC100 will satisfy.For example, have ± TDC100 of 200ps/nm chromatic dispersion setting range for Fig. 1, grating PDW must be less than 2.5pm, and this is very inaccessible.

TDC100 uses optional adjustable filter 140 to suppress the spontaneous emission of amplifying type (ASE) of every passage light preamplifier generation of needs usually of 40Gb/s system.In the embodiment of the TDC100 of Fig. 1, three adjustable (MZI) wave filters 142 of adjustable filter 140 ₁, 142 ₂With 142 ₃Arranged in series has following three Free Spectral Ranges respectively: 3200,1600 and 800GHz.Like this, adjustable filter 140 has the clean Free Spectral Range of 3200GHz and the 3-dB bandwidth of 390GHz roughly.

The TDC100 of Fig. 1 utilizes the adjustable lens that comprises parabolic refractive index distribution (among Fig. 1 exemplary thermo-optic lens 150), can provide dispersion compensation to the input optical signal of dispersion values with variation in adjustable mode.

Fig. 2 a has shown the high level block diagram of an embodiment of the thermo-optic lens that uses among the TDC100 that is adapted at Fig. 1, and for example thermo-optic lens 150.The thermo-optic lens 150 of Fig. 2 a comprises that is positioned at two vertical conductors (potential plate) 220 ₁With 220 ₂Between parallel heating element 210 ₁-210 _nArray.Parallel heating element 210 ₁-210 _nThe interval that is equal in length and center to center all is constant, but has different width.That is, along with the center near the thermo-optic lens 150 shown in Fig. 2 a, heating element 210 ₁-210 _nWidth increase.Parallel heating element 210 in the thermo-optic lens 150 ₁-210 _nThe configuration parabolic refractive index distribution (being the parabolic temperature distribution of the present embodiment) that caused the present invention to wish.

Though heating element 210 in Fig. 2 a ₁-210 _nWidth be shown as along with they near the center of thermo-optic lens 150 and width increases, but in alternate embodiment of the present invention, the sign inversion of the length by will being used for determining heating element or the parabolic function of width can dispose the thermo-optic lens of last figure in addition.That is, heating element 210 ₁-210 _nWidth can be configured to along with they reduce near the center of thermo-optic lens 150.In addition, heating element 210 ₁-210 _nWidth can be configured to respect to them at parallel heating element 210 ₁-210 _nRelative position in the array increases symmetrically equably or reduces, perhaps, and heating element 210 ₁-210 _nCan be configured to increases or reduces in uneven and asymmetrical mode, for example in order to correct heating element 210 ₁-210 _nBetween electric potential difference.This for describe below about the increase of the heating element length of the alternate embodiment of thermo-optic lens of the present invention or reduce same being suitable for.

Later referring to Fig. 2 a, configuration thermo-optic lens 150 is so that produce parabolic temperature distribution in double star.Because the electric power that temperature and per unit area consume is proportional, and the electric power of every heating element and V ²W proportional (wherein V is a voltage, and W is a heater width) is so pass through at parallel heating element 210 ₁-210 _nThe array two ends apply electromotive force and obtain parabolic temperature distribution, parallel heating element 210 ₁-210 _nThe width of variation cause parabolic temperature distribution.The parabolic temperature distribution of thermo-optic lens 150 of the present invention is compared with the lens design of prior art, favourable minimizing maximum lens temperature, and increased the long-term reliability of thermo-optic lens 150.

Parallel heating element 210 ₁-210 _nBetween center to center compare with the thermal diffusion width at thermo-optic lens 150 core places at interval must be relatively little.For example, for a wafer that comprises the thermal diffusion core of about 80 μ m, heating element 210 ₁-210 _nBetween the interval of center to center can adopt 16 μ m.Heating element 210 ₁-210 _nBetween heat crosstalk and in fact reduced the total power consumption of thermo-optic lens 150, therefore preferably keep the width of thermo-optic lens 150 narrow as far as possible.

Fig. 2 b has shown the high level block diagram of the alternate embodiment of the thermo-optic lens that uses among the TDC100 that is adapted at Fig. 1.In the thermo-optic lens 250 of Fig. 2 b, for the thermo-optic lens 150 of Fig. 2 a has increased by two vertical buss 260 ₁With 260 ₂These two vertical buss 260 ₁With 260 ₂Function be the constant cross-section of sustaining voltage along thermo-optic lens 250, similarly, increased the lens homogeneity.Though thermo-optic lens 150 is shown as and comprises two vertical conduction bars 260 in Fig. 2 b ₁With 260 ₂, but in thermo-optic lens of the present invention, can realize the vertical conduction bar of other quantity.

Fig. 3 a-3c has shown various other embodiments according to thermo-optic lens of the present invention.The parabolic temperature distribution that the arrangement of the heating element of Fig. 3 a-3c also obtains wishing in the thermo-optic lens 150 of Fig. 2 a and 2b.For example, the width of heating element reduces along with the center of their close thermo-optic lens in Fig. 3 a.

In the thermo-optic lens of Fig. 3 b and 3c, change the width of heating element, thus the parabolic temperature distribution that obtains wishing.For example, in Fig. 3 b, the length of heating element reduces along with the center of their close thermo-optic lens.Like this, the Temperature Distribution of the thermo-optic lens of Fig. 3 b comprises parabolic distribution.

In Fig. 3 c, the length of heating element increases along with the center of their close thermo-optic lens.The Temperature Distribution of the thermo-optic lens of Fig. 3 c also comprises parabolic distribution.Though Fig. 2 a and 2b and Fig. 3 a-3c have shown the different embodiments according to thermo-optic lens of the present invention, but those those skilled in the art that instruct according to the present invention can understand, and various other that can design heating element length and width disposes to be realized according to parabolic refractive index distribution of the present invention.In addition, utilize instruction of the present invention can dispose the lens of other type, for example inject the electro-optic lens of charge carrier such as use in the silicon waveguide, thereby have parabolic refractive index distribution, like this, TDC of the present invention is not limited to the realization of thermo-optic lens.

The inventor also determines, when being placed on thermo-optic lens 150 between the double star, by with its beam optical axis slight inclination with respect to expection, shown in Fig. 2 a-2b, can significantly reduce refractive index fluctuation.The inclination of thermo-optic lens 150 can be ignored to the influence of lens strength, but has significantly reduced the refractive index fluctuation that produces in thermo-optic lens 150.That is, when thermo-optic lens of the present invention did not tilt, distributing along the medial temperature of lens comprised the little fluctuation that produces owing to heating element.These fluctuations cause fluctuation in the chromatic dispersion of thermo-optic lens.Thereby, significantly reduced fluctuation by beam optical axis inclination thermo-optic lens with respect to expection.Thermo-optic lens according to the present invention reduces refractive index fluctuation though can tilt, but in alternate embodiment of the present invention, can be by the heating element of constructing with respect to the minute angle of expection beam optical axis in the thermo-optic lens in the thermo-optic lens of the present invention, with in the above-mentioned inclination of textural realization, the direction that keeps thermo-optic lens simultaneously is straight substantially between double star.

Fig. 4 a and 4b respectively graphic presentation the principle of work of thermo-optic lens 150 TDC100 of Fig. 1 when closing and opening.Fig. 4 a has shown that the double star of TDC100 when thermo-optic lens 150 is closed (not having making alive) reaches the wherein high level block diagram of principle of work.In Free Spectral Range, left side WGR110 ₁The light of the shorter wavelength that sends is had the WGR110 of longer path by the right side ₂Waveguide 122 receive left side WGR110 ₁The light of the longer wavelength that sends has WGR110 than short path length by the right side ₂Waveguide 122 receive.Therefore TDC100 presents negative dispersion.Described the characteristic of dispersion measure during " lens cut out " state according to equation (1), equation is as follows:

$D_0=\frac{2\mathrm{Mb}{c}_0}{\mathrm{\α}{\left({\mathrm{\λ}}_0\mathrm{\Δ}{f}_{\mathrm{FSR}}\right)}^2}$

Wherein M equals the quantity of grating arm, α is the interval of center to center between the double star incoming wave conduit, b is space " passage " width (for example, b=(space Brillouin (Brillouin) sector width of double star center WGR)/M), the λ of double star center ₀Be interested optical wavelength, c ₀Be the vacuum value of velocity of light, Δ f _FSRIt is Free Spectral Range.

Fig. 4 b has shown that the double star of TDC100 when thermo-optic lens 150 is opened (making alive) reaches the wherein high level block diagram of principle of work.When electric current was flowed through the heating element of thermo-optic lens 150, thermo-optic effect changed the refractive index of lens, thereby the focal length of thermo-optic lens 150 also can change.Therefore, by the voltage that control applies, light can be accurately converged at precalculated position (WGR110 for example ₂Specific waveguides 122).When thermo-optic lens 150 is opened, chromatic dispersion increase along with lens strength and increase and become on the occasion of.The focal power of thermo-optic lens 150 is defined as the phase shift difference between lens center and its upper and lower edge, and it is proportional with the needed hot luminous power of driving lens.Adjustment TDC100 has been described by its dispersion range D according to equation (2) ₀To-D ₀The characteristic of needed lens strength, equation is as follows:

$\frac{\mathrm{\π}{D}_0{\left({\mathrm{\λ}}_0\mathrm{\Δ}{f}_{\mathrm{GDBW}}\right)}^2}{2c_0}---\left(2\right)$

Δ f wherein _GDBWThe bandwidth that is the linear part of TDC100 group delay (is Δ f _GDBW/ Δ f _FSRBe the sub-fraction in the Brillouin district, double star center that takies of thermo-optic lens 150).

3-dB transmissivity bandwidth when having described minimum dispersion (thermo-optic lens 150 power-offs) according to equation (3), equation is as follows:

$\mathrm{\Δ}{f}_{\mathrm{TBW}}=\mathrm{\α}\frac{a}{b}\mathrm{\Δ}{f}_{\mathrm{FSR}}---\left(3\right)$

Wherein α is a constant that depends on the efficiency shapes (efficiency shape) of power division and bistellate Brillouin district in the grating arm, and α typical case is in 0.28 scope.

In a embodiment according to thermo-optic lens of the present invention, select the design parameter of protruding thermo-optic lens, make that chromatic dispersion is at the negative terminal of usable range when closing thermo-optic lens.Thereby by changing the focal power of thermo-optic lens, thermo-optic lens can be adjusted in whole dispersion range.

In thermo-optic lens according to the present invention, the temperature of heating element is than thermo-optic lens core place height.Therefore, for the temperature with heating element minimizes and guarantees long-term reliability, make thermo-optic lens and should keep firmly in mind as far as possible, the length of thermo-optic lens is subjected to the restriction of equation (4), and equation is as follows:

$l<<\frac{2M{b}^{2}n}{{\mathrm{\&lambda;}}_0}---\left(4\right)$

Wherein M equals the quantity of grating arm, and b still is space " passage " width of double star center, λ ₀Be interested optical wavelength, n is the refractive index of the waveguide 120,122 of TDC100.

The impedance variation that increases along with temperature in the necessary in addition consideration heating element.Specifically, more along with the thermo-optic lens heating in center impedance increase, cause thermo-optic lens " to flatten voluntarily ".Therefore the second half adjustment by dispersion range is than by the first half the more hot luminous power of adjustment needs.In order to alleviate lens distortion, can by add the para-curve width distribution square less number percent, to the pre-weighting of the width of thermo-optic lens heating element.But, preferably utilize the heating element material (metal) low to the impedance sensitivity of temperature variation.

For design consideration TDC of the present invention, must at first select D ₀, Δ f _FSR, Δ f _GDBWWith Δ f _TBWValue.Lens can use top equation (2) and (4) to determine the value of b and l then, so that can be operated in the temperature of permission.Can use top equation (3) to determine α then, and the equation (1) above using is determined M.

Fig. 5 a graphic presentation for the measurement transmissivity-wavelength of three kinds of different capacities (0W, 2.9W and 7.3W) of the thermo-optic lens 150 of TDC100.Fig. 5 b has shown the measurement group delay-wavelength for three kinds of different capacities of Fig. 5 a (0W, 2.9W and 7.3W).Mean dispersion on these power levels is respectively-205ps/nm, 0ps/nm and+202ps/nm.Because lens flatten voluntarily, from 0 adjust to+power ratio of 200ps/nm from-that 200ps/nm adjusts to 0 desired power is high by 50%.Transmissivity bandwidth＞40GHz (+200ps/nm regularization condition place is limited), linear group postpones bandwidth＞48GHz (place is limited at the 0ps/nm regularization condition).Adjust the transmissivity maximization of three noise filter MZI with the TDC passband under will measuring.

In a test, return-to zero system (CSRZ) data of the 40Gb/s of 193.350THz carrier suppressed by dispersion values be+181ps/nm, 0 and-the fiber optic coils transmission of 220ps/nm, pass through TDC100 then.The corresponding adjustment imposes on the voltage of thermo-optic lens 150 with compensation of dispersion.Fig. 6 graphic presentation the luminous power of the measurement bit error rate (BER)-reception of three dispersion values of 40Gb/s CSRZ data.Find out obviously that from the measurement bit error rate (BER) that Fig. 6 shows TDC100 easily compensates the chromatic dispersion up to-220ps/nm under the situation that not have loss.Each illustration graphic presentation of Fig. 6 40Gb/s CSRZ data by have-during the transmission of the fiber optic coils of 220ps/nm chromatic dispersion not by TDC100 compensation (as seen scheme on top) with by the corresponding eye diagram of TDC100 compensation (as seen scheme the bottom).The inventor notices that the adjustment response of TDC100 is in the scope of 2ms.

Fig. 7 has shown the alternate embodiment according to TDC of the present invention.In the TDC700 of Fig. 7, replaced second waveguide grating router 110 among Fig. 1 with catoptron 710 ₂The TDC700 of Fig. 7 comprises waveguide grating router 110 ₁, comprise adjustable lens (exemplary is thermo-optic lens) 150 and the catoptron 710 of parabolic refractive index distribution.With the same among Fig. 1, waveguide grating router 110 ₁The waveguide and first and second star-type couplers 130 that comprise a plurality of increase paths ₁, 130 ₂

Because TDC of the present invention, for example the TDC of Fig. 1 is centrosymmetric, so the TDC700 of Fig. 7 is configured to include only a waveguide grating router 110 ₁, catoptron 710 is placed on after the thermo-optic lens 150.In the TDC700 of Fig. 7, from waveguide optical grating 110 ₁Input optical signal transmits by thermo-optic lens 150, and passes through thermo-optic lens 150 towards waveguide grating router 110 ₁Reflect.With respect to waveguide grating router 110 ₁With the operation of thermo-optic lens 150, the TDC100's of the operation of the TDC700 of Fig. 7 and function and Fig. 1 is roughly the same.In a kind of like this embodiment of the present invention, the TDC700 of Fig. 7 for example, catoptron is a polished surface at an end of the waveguide chip that forms TDC, on this face reflectance coating is arranged.The same with the TDC100 among Fig. 1, the TDC700 of Fig. 7 also may further include a CPS (not showing) and an adjustable filter (not showing).

Though various embodiments of the present invention have been pointed out in the front, under the situation that does not depart from base region of the present invention, can design other and more embodiment of the present invention.Thereby will determine proper range of the present invention according to attached claim.

Claims (20)

1. thermo-optic lens comprises:

A plurality of parallel heating elements (210 ₁-210 _n), the interval constant of heating element center to center, and size separately changes to the most inboard heating element from outermost heating element; And

At least two conducting elements (220 ₁, 220 ₂), be used to provide described heating element (210 ₁-210 _n) electromotive force at two ends;

Wherein, the size of described heating element changes, so that produce parabolic temperature distribution in described thermo-optic lens.

2. the thermo-optic lens in the claim 1, wherein said heating element (210 ₁-210 _n) size change equably and symmetrically.

3. the thermo-optic lens in the claim 1, wherein each described heating element (210 ₁-210 _n) same length, and width increases to the most inboard heating element from outermost heating element.

4. the thermo-optic lens in the claim 1, wherein each described heating element (210 ₁-210 _n) same length, and width reduces to the most inboard heating element from outermost heating element.

5. the thermo-optic lens in the claim 1, wherein each described heating element (210 ₁-210 _n) width is roughly the same, and length reduces to the most inboard heating element from outermost heating element.

6. the thermo-optic lens in the claim 1, wherein each described heating element (210 ₁-210 _n) width is roughly the same, and length increases to the most inboard heating element from outermost heating element.

7. the thermo-optic lens in the claim 1 wherein forms described a plurality of heating element (210 with the low-angle with respect to the expection beam optical axis in described thermo-optic lens ₁-210 _n) in each so that reduce the refractive index fluctuation that produces in the described thermo-optic lens, and the influence of the lens strength of described thermo-optic lens is ignored.

8. the thermo-optic lens in the claim 1 also comprises:

At least one conducting element (260 ₁, 260 ₂), its laterally place and with described a plurality of heating elements (210 ₁-210 _n) in each electrically contact, be used to keep constant potential along the thermo-optic lens xsect.

9. dispersion compensator comprises:

First and second waveguide optical gratings (110 ₁, 110 ₂), each described waveguide optical grating (110 ₁, 110 ₂) comprising:

First star-type coupler (130 ₁, 132 ₁),

Increase the waveguide duct array (120 of path ₁-120 _n, 122 ₁-122 _n), described waveguide duct array (120 ₁-120 _n, 122 ₁-122 _n) in first end of each waveguide couple light to described first star-type coupler (130 ₁, 132 ₁), and

Second star-type coupler (130 ₂, 132 ₂), described waveguide duct array (120 ₁-120 _n, 122 ₁-122 _n) in second end of each waveguide couple light to described second star-type coupler (130 ₂, 132 ₂),

And

Lens (150) that comprise parabolic refractive index distribution, these lens (150) couple light to described first waveguide optical grating (110 ₁) described second star-type coupler (130 ₂) and described second waveguide optical grating (110 ₂) described second star-type coupler (132 ₂).

10. the dispersion compensator of claim 9, wherein said lens (150) are thermo-optic lens.

11. the dispersion compensator of claim 10, wherein said thermo-optic lens (150) comprising:

A plurality of parallel heating elements (210 ₁-210 _n), the interval constant of described heating element center to center, and size separately changes to the most inboard heating element from outermost heating element; And

At least two conducting elements (220 ₁, 220 ₂), be used to be provided at described heating element (210 ₁-210 _n) electromotive force at two ends;

Wherein, described heating element (210 ₁-210 _n) size change so that in described thermo-optic lens (150), produce parabolic temperature distribution.

12. the dispersion compensator of claim 11 wherein, forms a plurality of heating elements (210 with the low-angle with respect to the expection beam optical axis in described thermo-optic lens (150) ₁-210 _n) in each so that reduce the refractive index fluctuation that produces in the described thermo-optic lens (150), and the influence of the lens strength of described thermo-optic lens (150) is ignored.

13. the dispersion compensator of claim 11, wherein, the refractive index of described thermo-optic lens (150) is added in heating element (210 by change ₁-210 _n) electromotive force at two ends is adjustable.

14. the dispersion compensator of claim 13, wherein, the refractive index of the described thermo-optic lens of described adjustment (150) is the chromatic dispersion compensation quantity that offers the light signal of transmission by described dispersion compensator adjustment.

15. the dispersion compensator of claim 9 also comprises an adjustable filter (140), is used to filter the spontaneous emission of amplifying type (ASE).

16. the dispersion compensator of claim 15, wherein said adjustable filter comprise at least one adjustable Mach-Zehnder interferometer filter (142 ₁, 142 ₂, 142 ₃).

17. the dispersion compensator of claim 9 comprises that also a circulator/polarization separator (160) is used for realizing and polarization irrelevant.

18. the dispersion compensator of claim 9, wherein, lens are placed on described first waveguide optical grating (110 with the low-angle with respect to the expection beam optical axis ₁) described second star-type coupler (130 ₂) and described second waveguide optical grating (110 ₂) described second star-type coupler (132 ₂) between, be used for reducing the refractive index fluctuation that these lens produce, so that the influence of the lens strength of described lens is ignored.

19. a dispersion compensator comprises:

A waveguide optical grating (110 ₁), this waveguide optical grating comprises:

First star-type coupler (130 ₁),

Increase the waveguide duct array of path, first end of each described waveguide couples light to described first star-type coupler (130 in this waveguide duct array ₁) first end, and

Second star-type coupler (130 ₂), second end of each described waveguide couples light to described second star-type coupler (130 in this waveguide duct array ₂) first end,

And

Lens (150) with parabolic refractive index distribution, first end of these lens (150) couples light to described second star-type coupler (130 ₂) second end; And

A catoptron (710) that couples light to these lens (150) second ends, thereby from described waveguide optical grating (110 ₁), the light signal by these lens (150) transmission by these lens (150) towards described waveguide optical grating (110 ₁) reflect.

20. the dispersion compensator of claim 19, wherein, described catoptron (710) is at the polished surface of the waveguide chip end that comprises described dispersion compensator, on this face reflectance coating is arranged.

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