CN2585502Y - Broad pass-band, low crosstalk wave division multiplexer using air-trough graduated output waveguide - Google Patents

Abstract

The utility model discloses a broad passing band and low crosstalk wave division multiplexer using a tapered air-trough output waveguide. An inlet of an output waveguide of the wave division multiplexer uses tapered waveguides having tapered structures, and an air trough is introduced between adjacent waveguides. The utility model has the advantages that due to the adoption of the tapered waveguides having tapered structures and the air trough introduced between adjacent waveguides, the utility model can use small power cost to cause a diffraction etched grating to have the obvious improved spectral response characteristics of broad passing band, low crosstalk, etc. as compared with traditional output via the adjustment of the width of the air trough and the width of the inlets of the tapered waveguides and the parametric optimization of contraction shapes, etc.

Description

Adopt the low wavelength division multiplex device of crosstalking of broad passband of air groove gradual change output waveguide

Technical field

The utility model belongs to optical communication wavelength-division multiplex technique field, particularly relates to a kind of have broad passband, extremely low wavelength division multiplex device of crosstalking.

Background technology

Wavelength division multiplexing/demultiplexing technology is the key technology of modern Fibre Optical Communication Technology.Wavelength division multiplexing/demultiplexing just is meant by special technique, with the light compositing complex light of different wave length, and the light of different wave length in the complex light separated.Wavelength division multiplexing (demultiplexing) device is exactly a device of realizing wavelength division multiplexing/demultiplexing technology.The diffraction etched grating is a kind of very typical integrated-type Wave decomposing multiplexer spare, compares with other Wave decomposing multiplexer, and the diffraction etched grating has the integrated level height, and volume is little, advantages such as wavelength resolution height.Another kind of typical integrated-type Wavelength division multiplexer/demultiplexer spare is an array waveguide grating.

Typical etched diffraction grating is made up of input waveguide 1, free propagation zone 2, diffraction grating 3, output waveguide 4.Complex light is from input waveguide 1 incident, freedom of entry transmission range 2 is freely dispersed propagation, after the diffraction grating diffraction, owing to have phase difference between the different teeth of grating,, the light of each wavelength is focused on positions different on the imaging curved surface once more by free propagation zone 2 focusing, and export by output waveguide, realize the chromatic dispersion function, the light that is about to different wave length is separated, and realizes the function of wavelength-division demultiplexing.The receiving unit of output waveguide is a straight wave guide in the traditional design.

Typical array waveguide grating is made up of input waveguide 6, free transmission range 7, Waveguide array 8, output waveguide 9.Complex light is from input waveguide 6 incidents, freedom of entry transmission range 7 is freely dispersed transmission, is coupled to each strip array waveguide in the waveguide array 8 then, and the adjacent array waveguide exists certain-length poor, thereby the light to each wavelength produces different phasic differences, realizes the chromatic dispersion function of grating.Behind second free transmission range, the optical convergence of different wave length difference on image planes places corresponding position with output waveguide 9, the light of different wave length can be separated, and realizes the function of wavelength-division demultiplexing.The receiving unit of output waveguide is a straight wave guide in the traditional design.

The band of the Wavelength division multiplexer/demultiplexer of traditional design (comprising diffraction etched grating, array waveguide grating) is logical to be Gaussian, and when this means the actual wavelength offset design centre wavelength when channel, device will descend rapidly through efficient to the transmission of this channel.This very strong wavelength selectivity makes traditional wavelength division multiplex device to the precision of the channel sources wavelength in the communication system very high requirement be arranged.But in actual conditions, a large amount of external factor may make operation wavelength drift about (comprise the drift of light source itself, temperature is floated, variations in refractive index or the like), and this has limited the application of Wavelength division multiplexer/demultiplexer spare greatly.

Solve Wavelength division multiplexer/demultiplexer spare passband flattening and huge meaning and value are arranged improving real system efficient.Therefore, a lot of methods are suggested and are used for realizing the wavelength division multiplex device flattened spectral response.Realize that at present the wavelength division multiplex device flattened spectral response has following several method:

1) based on the optimization of input structure:

As U.S. Patent No. 5,706,377. disclosed methods are to utilize Y branch to realize flattened spectral response.Wedge angle in the Y branch will increase the Insertion Loss of device.

2) based on the optimization of optical grating construction:

As U.S. Patent No. 5,926,587. disclosed methods are to utilize the method for two cascaded fiber gratings to realize flattened spectral response.

3) based on the optimization of export structure:

Be entitled as " Phased-array wavelengthdemultiplexer with flattened wavelength response " as what people such as M.R.Amersfoort delivered, Electron.lett., 1994,30, (4), in the article of pp.300-302, adopt the multimode output waveguide to realize flattened spectral response, directly be connected the occasion of using with detector but this method only is suitable for Wavelength division multiplexer/demultiplexer spare.

Can find that most planarization design often has bigger Power penalty.Therefore, the high-power cost that planarization brought is very disadvantageous to the overall performance that improves device.

Summary of the invention

The purpose of this utility model is the low wavelength division multiplex device of crosstalking of broad passband that a kind of inlet in output waveguide of design adopts air groove gradual change output waveguide, Power penalty that can be enough very little makes grating have significantly improved spectral response characteristics such as broad passband, extremely low string hold together.

The technical solution adopted in the utility model is as follows: it comprises input waveguide, free propagation zone, diffraction grating or Waveguide array, output waveguide composition, adopt the tapered waveguide of pyramidal structure respectively at the inlet of output waveguide, between adjacent waveguide, introduce air groove.

The useful effect that the utlity model has: owing to adopt the tapered waveguide of pyramidal structure, simultaneously between adjacent waveguide, introduce air groove, by adjusting the width of air groove, the throat width of tapered transmission line, the isoparametric optimization of contraction shape, compare with traditional output, the Power penalty that the utility model can be enough very little makes wavelength division multiplex device have broad passband, extremely low significantly improved spectral response characteristic such as crosstalk.

Description of drawings

Fig. 1 is the etched diffraction grating structural representation;

Fig. 2 is the array wave-guide grating structure schematic diagram;

Fig. 3 is the structural representation of output waveguide part of the present utility model;

Fig. 4 is a tapered transmission line structural representation of the present utility model;

Fig. 5 is an air groove structural representation of the present utility model;

Fig. 6 is that air groove is eliminated coupled mode graphoid (figure (a) is for before adding air groove, and figure (b) is for after adding air groove);

Fig. 7 is that (solid line is the spectral response that this patent is realized for the comparison diagram of the spectral response and the spectral response of the present utility model of traditional etched diffraction grating, dotted line is the spectral response of traditional design, chain-dotted line is for only introducing the spectral response of tapered transmission line, and dotted line is for only introducing the spectral response of air groove).

Embodiment

As Fig. 1, shown in Figure 3, it comprises that input waveguide 1, free propagation zone 2, diffraction grating 3, output waveguide 4 form, and adopts the tapered waveguide 11 of pyramidal structures at the inlet 5 of output waveguide 4, introduces air groove 12 between adjacent waveguide.

As Fig. 2, shown in Figure 3, it comprises that input waveguide 6, free propagation zone 7, Waveguide array 8, output waveguide 9 form, and adopts the tapered waveguide 11 of pyramidal structures at the inlet 10 of output waveguide 9, introduces air groove 12 between adjacent waveguide.

As shown in Figure 3, Figure 4, adopting the tapered waveguide 10 of pyramidal structure at the inlet of output waveguide 9 is by throat width W, exit width w and the decision of convergent function curve:

1) to go into be a fixed value for exit width w and throat width W, and throat width W satisfies: w≤W≤W _c-a _Min, unit is micron, wherein W _cBe device adjacent channel output spacing, a _MinAir groove minimum widith for the technology decision;

2) the convergent angle θ of linear convergence function curve satisfies: $\mathrm{\θ}=\arctan \left(\frac{W-w}{2l}\right),$ Wherein, l is a tapered transmission line length.

3) (z)=(W-w) f (z/l)+w 0≤z≤l of non-linear convergent function curve w ', then convergent angle θ satisfies: θ (z)=arctan (W-w) f ' is (z/l)), wherein, l is a tapered transmission line length.

As Fig. 3, shown in Figure 5:

1) width (a) of air groove (12) satisfies: a _Min≤ a≤W _c-W, unit are micron, wherein a _MinBe the attainable air groove minimum widith of technology;

2) width (b) of air groove (12) must be greater than tapered transmission line length l: b＞l.For easy to process, general capping is 2 double-length degree tapered transmission line l:b＜2l.

One, the tapered transmission line structure is determined

Fig. 3 has represented the structural representation of tapered transmission line, and the major parameter of tapered transmission line is by throat width W, exit width w and the decision of contracting function curve.For the linear convergence function, major parameter is convergent angle θ.

Generally, the incident duct width of exit width w and device correspondence is identical, is a fixed value.Throat width W satisfies:

W≤W≤W _c-a _Min(unit: micron) wherein, W _cBe device adjacent channel output spacing, a _MinAir groove minimum widith for the technology decision.For the linear convergence function, convergent angle θ satisfies: $\mathrm{\θ}=\arctan \left(\frac{W-w}{2l}\right)$

Wherein, l is a tapered transmission line length.For nonlinear convergent function $w^{\′}\left(z\right)=(W-w)\·f\left(\frac{z}{l}\right)+w---0\≤z\≤l,$ Then have: $\mathrm{\θ}\left(z\right)=\arctan ((W-w)\·f^{\′}\left(\frac{z}{l}\right))$

For the incident of almost plane ripple, when θ less than a thresholding θ _cThe time, the loss that whole pyramidal structure is introduced will be less than 1dB, thresholding angle θ _cMain relevant with the refringence of material, refringence is more little, thresholding angle θ _cAlso more little.For earth silicon material, general 0 °＜θ _c＜1 °.

Also there is a thresholding angle for nonplanar wave incident.In concrete earth silicon material example, the angle of employing is θ=arctan (1/250)=0.2292 °.

The channel output spacing of diffraction etched grating can change easily according to the trim structure.Certain for the input waveguide width, less spacing can obtain bigger effective passband.Therefore, we wish to adopt less channel width when design.

Show that by the analysis to different pyramidal structure throat width W quality factor and effective bandwidth are proportional to W than all, loss and W are non-linear relation, and it changes near W equals single mode waveguide width and maximum permissible value slowly.Therefore, under the condition that loss allows, suitable choose bigger throat width.

The introducing of pyramidal structure makes the optical field distribution of off-center image space can more be coupled into output waveguide, increases coupling efficiency; Air groove can make the coupling effect of interchannel reduce (as shown in Figure 6) greatly, thereby obtains extremely low channel interference, and the combination of two structures makes the spectral response center broadening of device, and the edge is precipitous.

Other waveguiding structures of tapered transmission line and entire device are finished making simultaneously.

Two, the structure of air groove is determined

Because the coupling phenomenon between smooth sea is led is comparatively obvious, make and be easy to generate bigger crosstalking (shown in Fig. 6 (a)) between the output waveguide of dense arrangement, simultaneously, because the introducing of pyramidal structure has further aggravated to crosstalk, make the spectral performance of diffraction etched grating worsen.Therefore, the suitable air groove of introducing between adjacent waveguide can be good at stoping coupling (shown in Fig. 6 (b)) between waveguide, and reduction is crosstalked.

The principle of air groove mainly is based on the highly reflective energy of big refringence waveguide, and it is mainly eliminates interchannel because the coupling that short distance causes is crosstalked.Studies show that, the change width of air groove for the influence of crosstalking not quite the tapered transmission line throat width with fixed situation under, the air groove width satisfies:

a _Min≤ a≤W _c-W (unit: micron)

Wherein, a _MinFor the attainable air groove minimum widith of technology, for earth silicon material, a _MinGenerally greater than 2 microns.Simultaneously, the air groove of broad helps realizing the steep limit of spectral response, therefore, often chooses the Breadth Maximum that is allowed and designs.

Since the air groove effect be mainly reduce string around, so the length of air groove must satisfy the coupling effect between basic elimination adjacent waveguide.For general tapered transmission line, air groove length need be greater than tapered transmission line length; Simultaneously, because consideration easy to make generally is limited to 2 times of tapered transmission line length: 2l＞b＞l on it.

Three, spectral response

The spectral response function to a certain position output waveguide of diffraction etched grating can be expressed as: $I=\frac{|\∫{\hat{F}}_{\mathrm{wg}}{E}_{\mathrm{out}}(x,z_c)\mathrm{dx}{|}^2}{\∫E_{\mathrm{in}}\left(x^{\′}\right)\·E_{\mathrm{in}}^{*}\left(x^{\′}\right){\mathrm{dx}}^{\′}}$ Wherein, operator

The expression output waveguide is to the coupled characteristic of grating image.

Because the dichroism of diffraction etched grating has determined that in local wavelength's scope, outgoing position and wavelength are linear change.Suppose simultaneously that for the wavelength in the channel spacing scope its single mode transverse field distributes identical.For output waveguide also is the traditional design of single mode waveguide, and the spectral response of diffraction etched grating can be tried to achieve by the overlap integral formula: $I\left(\mathrm{\λ}\right)=\frac{|\∫E_{\mathrm{out}}(\mathrm{\λ},x)\·E_{\mathrm{wg}}^{*}(\mathrm{\λ},x)\mathrm{dx}{|}^2}{\∫E_{\mathrm{in}}(\mathrm{\λ},x^{\′})\·E_{\mathrm{in}}^{*}(\mathrm{\λ},x^{\′}){\mathrm{dx}}^{\′}\·{\∫E}_{\mathrm{wg}}(\mathrm{\λ},x)\·E_{\mathrm{wg}}^{*}(\mathrm{\λ},x)\mathrm{dx}}$

E wherein _OutBe the field distribution of grating in output face, E _InAnd E _WgIt is respectively the mould field distribution function of input and output waveguide.When both are equal, can further obtain one from convolution function.

For tapered transmission line and air groove design, can re-use overlap integral at settling position then and calculate coupling efficiency, and then obtain spectral response with the transmission of beam propagation method simulation light field.

Fig. 7 is that the utility model is applied to the planarization frequency spectrum (solid line) of etched diffraction grating realization and the frequency spectrum (dotted line) of ordinary construction, and the comparison of the frequency spectrum of the utility model part-structure introducing.The parameter that this figure uses is:

n core	n clad	Duct width	Operation wavelength	The tapered transmission line throat width	Tapered transmission line length	Air groove length	The air groove width
								1.4674	1.46	6μm	1.55μm	18μm	2250μm	2500μm	2μm

Though pyramidal structure can increase pass band width, also introduced very big crosstalking (shown in Fig. 7 chain-dotted line) simultaneously; Air groove can reduce crosstalks, but the effect little (shown in Fig. 7 dotted line) to increasing bandwidth.When both in conjunction with after, the 1dB bandwidth has increased by 47.4%, simultaneously crosstalking of adjacency channel reduced about 15dB, reach-50dB about, satisfied the requirement of dense wavelength division multiplexing.Simultaneously, after the tapered transmission line structure was optimized, the power loss that the utility model is introduced had only 0.65dB, was significantly less than the Power penalty of other planarization designs.

In addition, the utility model also is applicable to other wavelength division multiplex devices, as reflection type array wave-guide grating etc.

Claims (9)

1. adopt the low wavelength division multiplex device of crosstalking of broad passband of air groove gradual change output waveguide, it comprises: input waveguide (1), free propagation zone (2), diffraction grating (3), output waveguide (4) are formed, it is characterized in that: adopt the tapered waveguide (11) of pyramidal structure at the inlet (5) of output waveguide (4), between adjacent waveguide, introduce air groove (12).

2. the low wavelength division multiplex device of crosstalking of employing air groove gradual change output waveguide broad passband according to claim 1 is characterized in that: it is by throat width W, exit width w and the decision of convergent function curve that the inlet (5) in output waveguide (4) adopts the tapered waveguide (11) of pyramidal structure:

1) to go into be a fixed value for exit width w and throat width W, and throat width W satisfies: w≤W≤W _c-a _Min, unit is micron, wherein W _cBe device adjacent channel output spacing, a _MinAir groove minimum widith for the technology decision;

2) the convergent angle θ of linear convergence function curve satisfies: $\mathrm{\θ}=\arctan \left(\frac{W-w}{2l}\right),$ Wherein, l is a tapered transmission line length.

3. according to the low wavelength division multiplex device of crosstalking of the broad passband of employing air groove gradual change output waveguide according to claim 1, it is characterized in that: adopting the tapered waveguide (10) of pyramidal structure at the inlet of output waveguide (4) is by throat width W, exit width w and the decision of convergent function curve:

1) to go into be a fixed value for exit width w and throat width W, and throat width W satisfies: w≤W≤W _c-a _Min, unit is micron, wherein W _cBe device adjacent channel output spacing, a _MinAir groove minimum widith for the technology decision;

2) (z)=(W-w) .f (z/l)+w 0≤z≤l of non-linear convergent function curve W ', then convergent angle θ satisfies: θ (z)=arctan ((W-w) f ' (z/l)), wherein, l is a tapered transmission line length.

4. the low wavelength division multiplex device of crosstalking of the broad passband of employing air groove gradual change output waveguide according to claim 1 is characterized in that:

1) the width a of air groove (12) satisfies: a _Min≤ a≤W _c-W, unit are micron, wherein a _MinBe the attainable air groove minimum widith of technology;

2) the length b of air groove (12) must satisfy the coupling effect between basic elimination adjacent waveguide.

5. adopt the low wavelength division multiplex device of crosstalking of broad passband of air groove gradual change output waveguide, it comprises: input waveguide (6), free propagation zone (7), Waveguide array (8), output waveguide (9) are formed, it is characterized in that: adopt the tapered waveguide (11) of pyramidal structure at the inlet (10) of output waveguide (9), between adjacent waveguide, introduce air groove (12).

6. the low wavelength division multiplex device of crosstalking of the broad passband of employing air groove gradual change output waveguide according to claim 5 is characterized in that: it is by throat width W, exit width w and the decision of convergent function curve that the inlet (10) in output waveguide (9) adopts the tapered waveguide (11) of pyramidal structure:

1) to go into be a fixed value for exit width w and throat width W, and throat width W satisfies: w≤W≤W _c-a _Min, unit is micron, wherein W _cBe device adjacent channel output spacing, a _MinAir groove minimum widith for the technology decision;

2) the convergent angle θ of linear convergence function curve satisfies: $\mathrm{\θ}=\arctan \left(\frac{W-w}{2l}\right),$ Wherein, l is a tapered transmission line length.

7. according to the low wavelength division multiplex device of crosstalking of broad passband of employing air groove gradual change output waveguide according to claim 5, it is characterized in that: it is by throat width W, exit width w and the decision of convergent function curve that the inlet (10) in output waveguide (9) adopts the tapered waveguide (11) of pyramidal structure:

1) to go into be a fixed value for exit width w and throat width W, and throat width W satisfies: w≤W≤W _c-a _Min, unit is micron, wherein W _cBe device adjacent channel output spacing, a _MinAir groove minimum widith for the technology decision;

2) (z)=(W-w) f (z/l)+w 0≤z≤l of non-linear convergent function curve w ', then convergent angle θ satisfies: θ (z)=arctan ((W-w) f ' (z/l)), wherein, l is a tapered transmission line length.

8. the low wavelength division multiplex device of crosstalking of the broad passband of employing air groove gradual change output waveguide according to claim 5 is characterized in that:

1) the width a of air groove (12) satisfies: a _Min≤ a≤W _c-W, unit are micron, wherein a _MinBe the attainable air groove minimum widith of technology;

2) the length b of air groove (12) must satisfy the coupling effect between basic elimination adjacent waveguide.

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