CN2552017Y - High-flat low-crosstalk wavelength division multiplexing device with optimization input - Google Patents

Abstract

The utility model discloses a high-flat low-crosstalk wavelength division multiplexing device with an optimization input end, which comprises an input wave-guide free spreading area, a corrosion concave face grating and an output wave-guide array. The end of the input wave-guide is connected with a curve shape multi-mold interfering component with a pre-widening input. The utility model has the advantages that the conical wave-guide of the pre-widening input can pre-widen the mold field of the input wave-guide to ensure that the flat frequency spectrum gains very steep descending edge so as to effectively reduce the crosstalk. The multi-mold interfering area is designed according to the self image theory and mold field inspiration can be produced through the wave-guide input of the pre-widening input so as to form multi-mold interfering, and two images with a certain distance is gained at the output at last so as to realize flatness. The utility model can effectively reduce the bandpass ripple and increase the 1dB bandwidth through the line type optimization adjusting of parabola. The utility model has a plurality of commonness, thereby being suitable for any one of AWG and EDG components.

Description

Optimize the high smooth low wavelength division multiplex device of harassing of input end

Technical field

The utility model belongs to optical communication wavelength-division multiplex field, particularly a kind of have low harass, the broadband is logical, the wavelength division multiplex device of the logical ripple of low strap, big 1dB bandwidth.

Background technology

Wavelength-division multiplex/demultiplexing is one of core technology of modern optical mechanics of communication, and it is meant the light of different wave length become and makes complex light and the light of respectively forming wavelength in the complex light is separated.Wavelength division multiplex device is exactly the device that is used for realizing wavelength-division multiplex/demultiplexing.There is very much now the Wavelength division multiplexer/demultiplexer spare of development potentiality to mainly contain two kinds of array waveguide grating (AWG) and etched diffraction gratings (EDG).

The band of traditional Wavelength division multiplexer/demultiplexer spare is logical to be Gaussian, when this makes practical center wavelength departure design centre, causes transmitance to descend greatly.This must increase the requirement to the strict control of optical source wavelength, and the extraneous factors such as tolerance that exist in the aging and device etching process of environment temperature change simultaneously, material all can cause big infringement to device performance.The influence that these factors cause device performance can be effectively eliminated in smooth spectral response.

Existing certain methods is used for realizing the planarization of Wavelength division multiplexer/demultiplexer spare frequency spectrum, for example:

United States Patent (USP) NO.5412744 proposes to use y branch waveguide to realize flattened spectral response, because the mould field leakage of Y branch wedge angle can cause big loss.

K.Okamoto etc. have delivered one piece and have been entitled as " Eight-Channel flat spectralresponse Arrayed-waveguide multiplexer with asymmetrical Mach-Aehnder filters ", IEEEPhot.Tech.Lett., vo1.8, no.3, march 1996, and the pp.373-374. article relates to a kind of use M-Z interferometer and realizes planarization, but this method can cause big device size, big Insertion Loss also might cause the distortion of mould spot simultaneously.

Y.P.Ho etc. delivered one piece of article, " Flat channel-passband-wavelength multiplexingand demultiplexing devices by multiple Rowland circles ", IEEEPhot.Tech.Lett., (9), pp.342-344 mentions in 1997 and uses two Rowland circles to realize planarization.

A.Rigney etc. have delivered and have made one piece of article, " Double-phased array for a flattened spectralresponse ", Proc.23 ^RdECOC, Edinburgh, UK, pp.79-82, Sept.1997, in mention and use the quarter-phase array to realize planarization, this method and last a kind of method are similar, the planarization effect is relatively limited, and complexity increases.

M.R.Amersfoort etc. have delivered and have made one piece and be entitled as " Phased-arrayed wavelengthdemultiplexer with flattened wavelength response ", Electron.Lett., 1994,30, (4), the article of pp.300-302 proposes to use multimode waveguide to export and realizes planarization, but this method only is applicable to the situation that Wavelength division multiplexer/demultiplexer directly links to each other with detector.

T.Chiba etc. are in OECC (2000), mention in the 13B2-2 and use interleaver to realize that the signal complex conjugate realizes planarization, but this method makes device size excessive, are unsuitable for integratedly, and price is also relatively costly simultaneously.

M.R.Amersfoort etc. have delivered one piece and have been entitled as; " Passband broadening of integratedarrayed waveguide filter using multimode interference couplers "; Electron.Lett.; vol.32 (1996); PP.1661-1662; propose to use the MMI coupling mechanism to realize planarization, because MMI is simple in structure, process allowance is big, can be used to realize flattened spectral response easily.But can bring in the time of simple use MMI planarization big harass, unfavorable factors such as Insertion Loss and the logical ripple of band.

Summary of the invention

The purpose of this utility model be development a kind of interband is harassed drop to very low value, the logical ripple of band is reduced to high smooth the hanging down of approaching zero optimization input end harasses wavelength division multiplex device.

The technical solution adopted in the utility model is as follows:

It comprises input waveguide, free diffusion region, etching concave grating, output waveguide array.End at input waveguide is connected to the shaped form multiple-mode interfence parts that have pre-broadening input.

Pre-broadening area size determines:

The final purpose of pre-broadening is high-order mode time to occur, changes the mould field distribution, therefore, by the mould field distribution in this process of BPM sunykatuib analysis, finds to make the structural parameters of broadening mould field edge decline steepest.

The width in pre-broadening zone can be expressed as on arbitrary cross section: $d\left(z\right)={\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="Y0221814600111.png"\; state="\{\{state\}\}">d</figure-callout>}}_2+(d_1-d_2)(1-\frac{z}{L_1})$ Wherein z is transmission direction, d ₁, d ₂Be respectively pre-broadening zone head and the tail width, L ₁Be the length in pre-broadening zone. $C=\frac{\mathrm{\&lambda;}}{\mathrm{\&pi;}}\&CenterDot;{\left(\frac{n_c}{n_r}\right)}^{2\mathrm{\&sigma;}}{(n_r^2-n_c^2)}^{(-1/2)},$ Wherein Can represent that then pre-broadening region design length is: ${\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="Y0221814600111.png,Y0221814600141.png"\; state="\{\{state\}\}">L</figure-callout>}}_1=\frac{3}{8}{L}_{\mathrm{\&pi;eff}}=\frac{{\mathrm{<figure-callout\; id="2"\; label="n\; r"\; filenames="Y0221814600111.png"\; state="\{\{state\}\}">n</figure-callout>}}_r}{2\mathrm{\&lambda;}}({\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="Y0221814600111.png"\; state="\{\{state\}\}">d</figure-callout>}}_2+C)({\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="Y0221814600111.png,Y0221814600141.png"\; state="\{\{state\}\}">d</figure-callout>}}_1+C)$ Cladding index rate n wherein _c, the sandwich layer refractive index n _r, central wavelength lambda, L _{π eff}For clapping length;

Find out three parameter d in pre-broadening zone from top analysis ₁, d ₂, L ₁In, length L ₁Be initial end width d ₁Width d with end ₂Function, therefore, only need to determine the width d in pre-broadening zone ₁And d ₂, fixedly original width is d earlier ₁, find out suitable terminal width d ₂According to calculating spectrum and inserting the method for loss, find out d below the different in width respectively ₂With the relation of quality factor, insertion loss, make curve, along with d ₂Increase, quality factor and insert loss and all can increase thereupon, purpose are that will to obtain quality factor big as far as possible, and insert the relatively little project organization of loss, so according to the actual bandwidth needs, comprehensively both select the most suitable d ₂Size.

Shaped form multiple-mode interfence district is the parabolic type interference region, its structural design:

To this partial design, original width d ₃Its main measurement index of optimization quality factor that are the planarization frequency spectrum, its size is the ratio of 1dB bandwidth and 33dB bandwidth.At the wide degree of given preview d ₂Change initial interference sector width d down, ₃, make d ₃With the variation relation curve of quality factor, then should be able to find the original width d of an optimum mutually ₃, this moment, quality factor had maximal value, the d that this moment is corresponding ₃Size is the designing optimal value.

Linear and the interference region length L of para-curve ₂Optimization regulate and can eliminate the logical ripple of band effectively, at above-mentioned initial interference district original width d ₃Under the situation of Que Dinging, para-curve must pass through its marginal point, and its axis of symmetry must be the device central symmetry axis simultaneously, and therefore, three linear parameters of decision para-curve only have been left one.By changing this parameter, can obtain the logical ripple of minimum relatively band, near the interference region imaging point, further optimize length L in addition ₂, can find better interference region length L equally ₂, make band lead to ripple minimum, 1dB bandwidth maximum.

The useful effect that the utlity model has is:

1) tapered transmission line of pre-broadening input can be carried out pre-broadening to the mould field of input waveguide, makes the planarization frequency spectrum obtain very steep negative edge, harasses thereby effectively reduced;

2) the multiple-mode interfence district is according to the self-imaging effect design, produces the mould field excitation by pre-broadening input waveguide input, forms multiple-mode interfence, finally obtains separately two pictures of certain distance in output, thereby realizes planarization.

3) regulate by the linear optimization of para-curve, can effectively reduce the logical ripple of band, increase the 1dB bandwidth.The utlity model has more generality, can be applicable to any in AWG and the EDG device.

Description of drawings

Fig. 1 is a structural principle synoptic diagram of the present utility model;

Fig. 2 is the enlarged drawing that the input waveguide end has the parabolic type MMI structure of pre-broadening input among Fig. 1;

Fig. 3 is the MMI structure that has pre-broadening input;

Fig. 4 is common optimization MMI structure;

Fig. 5 is Fig. 3, and the Frequency spectrum ratio that two kinds of structures of Fig. 4 are used for planarization is (prove pre-broadening structure low harass characteristic);

Fig. 6 is to use that Fig. 3 structure obtains lowly harasses the characteristic frequency spectrum;

The MMI that Fig. 7 is to use parabolic structure is to the elimination of logical ripple and the increase of 1dB bandwidth;

Fig. 8 is the optimum spectral response under the band separation 200GHz;

Fig. 9 is the optimum spectral response under the band separation 100GHz;

Figure 10 is quality factor, the relation curve that the 1dB bandwidth changes with the wide degree of preview;

Figure 11 inserts the relation curve that loss changes with the wide degree of preview;

Figure 12 is quality factor, the relation curve that the 1dB bandwidth changes with multiple-mode interfence district original width.

Embodiment

The utlity model has more generality, be applicable to any in AWG and the EDG device, for convenience of description, is example with the EDG device only below.

All structural designs of the utility model are based on the SiO 2 waveguide of silicon base, cladding index n _c=1.445, the sandwich layer refractive index n _r=1.454, central wavelength lambda ₀=1.55 μ m.

The utility model comprises input waveguide 1 as shown in Figure 1, free diffusion region 2, etching concave grating 3, output waveguide array 4.Complex light is by input waveguide 1 incident, and transmission is dispersed in freedom of entry diffusion region 2, and then through the diffraction of over etching concave grating 3, different wavelength converges to corresponding output waveguide port 4.Be connected to the shaped form multiple-mode interfence parts of importing with pre-broadening 5 at input waveguide 1 end, be used for realizing planarization.

As shown in Figure 2, provide the enlarged drawing of parts 5, pre-broadening input waveguide 6 is first improvement of the present utility model.

Pre-broadening area size determines:

The final purpose of pre-broadening is high-order mode time to occur, changes the mould field distribution, therefore, can pass through the mould field distribution in this process of BPM sunykatuib analysis, finds to make the structural parameters of broadening mould field edge decline steepest.

The width in pre-broadening zone can be expressed as on arbitrary cross section: wherein z is transmission direction, d ₁, d ₂Be respectively pre-broadening zone head and the tail width, L ₁Be the length in pre-broadening zone.If expression $C=\frac{\mathrm{\&lambda;}}{\mathrm{\&pi;}}\&CenterDot;{\left(\frac{n_c}{n_r}\right)}^{2\mathrm{\&sigma;}}{(n_r^2-n_c^2)}^{(-1/2)},$ Wherein

Can represent that then pre-broadening region design length is: ${\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="Y0221814600111.png,Y0221814600141.png"\; state="\{\{state\}\}">L</figure-callout>}}_1=\frac{3}{8}{L}_{\mathrm{\&pi;eff}}=\frac{{\mathrm{<figure-callout\; id="2"\; label="n\; r"\; filenames="Y0221814600111.png"\; state="\{\{state\}\}">n</figure-callout>}}_r}{2\mathrm{\&lambda;}}({\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="Y0221814600111.png"\; state="\{\{state\}\}">d</figure-callout>}}_2+C)({\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="Y0221814600111.png,Y0221814600141.png"\; state="\{\{state\}\}">d</figure-callout>}}_1+C)----\left(3\right)$ L wherein _{π eff}Expression is clapped long.Can find out three parameter d in pre-broadening zone from top analysis ₁, d ₂And L ₁In, length L ₁Be initial end width d ₁Width d with end ₂Function, therefore, only need to determine the width d in pre-broadening zone ₁, d ₂

For example, fixedly original width is d ₁=6 μ m find out suitable terminal width d ₂Process is according to calculating spectrum cited below and insert the method for loss, finds out d below the different in width respectively ₂With the relation of quality factor, insertion loss, make curve as shown in Figure 10 and Figure 11, as seen along with d ₂Increase, quality factor and insert loss and all can increase thereupon, and target is that will to obtain quality factor big as far as possible, inserts the relatively little project organization of loss, thus should be according to the actual bandwidth needs, comprehensively both select the most suitable d ₂Size.

The frequency spectrum that we will have the later MMI (as Fig. 4) of the MMI (as Fig. 3) of pre-broadening input waveguide and width optimization compares, and their spectral response is drawn among Fig. 5.

Wherein each parameter value of Fig. 3 is:

d ₀＝5μm；d ₁＝6μm；d ₂＝10μm；d ₃＝25μm；L ₁＝400μm；L ₂＝475μm。

Each parameter value of Fig. 4 is:

d ₀＝5μm；d ₃′＝18μm；L ₂′＝160μm。

Dotted line is common Gaussian spectrum response among Fig. 5, and dot-and-dash line is for using common optimization MMI spectral response, and solid line is then for using the later spectral response curve of structure that has pre-broadening input.Can see from figure, use the improved MMI that has the input of pre-broadening below 20dB, can effectively reduce and harass that as seen from Figure 6, use the EDG frequency spectrum of this structure to harass and can be reduced to about 50dB, this is the common unapproachable effect of planarization.

As shown in Figure 2, parabolic structure 8 is second important improvement of the present utility model, and the structural design of para-curve interference region is as follows:

Original width d ₃Its main measurement index of optimization quality factor that are the planarization frequency spectrum, its size is the ratio of 1dB bandwidth and 33dB bandwidth.At the wide degree of given preview d ₂Change initial interference sector width d down, ₃, make its variation relation curve with quality factor, then should be able to find the original width d of an optimum mutually ₃, this moment, quality factor had maximal value, the d that this moment is corresponding ₃Size is the designing optimal value.Corresponding search procedure example as shown in figure 12, the d of this moment ₂Size is 12 μ m, can see and work as d ₃During ≈ 24 μ m, have maximum quality factor.

Linear and the interference region length L of para-curve ₂Optimization regulate and can eliminate the logical ripple of band effectively, at above-mentioned initial interference district original width d ₃Under the situation of Que Dinging, para-curve must pass through its marginal point, and its axis of symmetry must be the device central symmetry axis simultaneously, and therefore, three linear parameters of decision para-curve only have been left one.By changing this parameter, can obtain the logical ripple of minimum relatively band, near the interference region imaging point, further optimize length L in addition ₂, can find better interference region length L equally ₂, make band lead to ripple minimum, 1dB bandwidth maximum.

Among Fig. 7, solid line is the spectral response behind the use parabolic structure, and dot-and-dash line is the optimum spectral response of using Fig. 3 structure under the same size, as we can see from the figure, uses improved parabolic structure 8 can effectively reduce the logical ripple of band; In addition as can also be seen from Figure, used structure 8 also to make the 1dB bandwidth obviously increase, thereby further improved planarization performance.

Multiple-mode interfence district 7 is according to the self-imaging effect design among Fig. 2, by pre-broadening input waveguide 6 input stimulus mould field excitation, forms multiple-mode interfence, finally obtains separately two pictures of certain distance in output, thereby realizes planarization.

Fig. 8 and Fig. 9 have provided respectively and have been applicable to that band separation is two kinds of optimization spectral responses under 200GHz and the 100GHz situation.

Wherein Fig. 8 works in Δ f=200GHz, and in the tapper received energy of output terminal with 15 μ m.Its concrete parameter is:

d ₀＝5μm；d ₁＝6μm；d ₂＝18μm；d ₃＝40μm；d ₄≈64μm；L ₁＝400μm；L ₂＝775μm。

Its performance parameter that obtains is as follows:

1dB bandwidth: 74.5600%; Quality factor F=0.8543; Insert the about 4dB of loss; Harass:

≤-120dB; Logical the ripple :≤0.1dB of band.

Because output terminal of the tapper received energy of 15 μ m, is made like this and is made and the corresponding increase of device size be applicable to the situation that port number is less, 200GHz for example, its frequency spectrum is corresponding to have approached desirable rectangular response, and its quality factor have about 85%, and the logical ripple of band has also approached zero.

Fig. 9 works in Δ f=100GHz, and directly comes received energy with the output waveguide of 6 μ m.Its concrete structure parameter is as follows:

d ₀＝5μm；d ₁＝6μm；d ₂＝12μm；d ₃＝24μm；d ₄≈31μm；L ₁＝400μm；L ₂＝550μm。

Its performance parameter that obtains is as follows:

1dB bandwidth: 53.4000%; Quality factor F=0.7744; Insert the about 4.2dB of loss; Harass :≤-70dB; Logical the ripple :≤0.3dB of band.

This moment is because output terminal is that directly to use width be that the output waveguide of 6 μ m is come received energy, do like this and make compact conformation, be applicable to multichannel dense wave division multipurpose, spectral response when being illustrated as band separation and being 100GHz, its Insertion Loss has also kept less level when having kept superior relatively planarization frequency spectrum.

The spectral response of device is calculated as follows:

Calculate the outgoing field distribution of passing through the MMI district by BPM, it is expressed as E ₀, to the initial field E of the freedom of entry diffusion region that obtains ₀Make fast fourier transform, its transformation results is designated as A (u)=FFT (E ₀), according to angular spectra theory, the propagation of a spatial mode field that distributes arbitrarily can be regarded as its angular spectrum with the additive process of plane wave form at the space each point.Therefore, more arbitrarily, we can calculate its value and are in the space: $U(x,z)=\underset{-\&infin;}{\overset{+\&infin;}{\&Integral;}}A\left(u\right)\exp \&lsqb;\mathrm{ikz}\sqrt{1-{\left(\mathrm{\&lambda;u}\right)}^2}]\exp \&lsqb;i2\mathrm{\&pi;}\left(\mathrm{ux}\right)\&rsqb;\mathrm{du}----\left(1\right)$ Output mould field after can being obtained by Kirchhoff's diffraction formula again is: $E\&prime;(x\&prime;z\&prime;)=\frac{1}{2}{\left(\frac{n}{\mathrm{\&lambda;}}\right)}^{\frac{1}{2}}\underset{\mathrm{Gratings}}{\&Integral;}\frac{U(x,z)}{\sqrt{r_0}}(\cos {\mathrm{\&theta;}}_i+\cos {\mathrm{\&theta;}}_d)\exp (-\mathrm{ik}{r}_0)\mathrm{ds}----\left(2\right)$ R wherein ₀Be output waveguide distance between a bit arbitrarily to the grating, n is a refractive index, and λ is a wavelength, θ _i, θ _dBe respectively incident angle and angle of diffraction on the grating flank of tooth.

Suppose that the output waveguide eigenmode is E ₂(x), the output waveguide end mould field that calculates through Kirchhoff's diffraction is E ₁(x), the spectral response that is coupled into so in the waveguide is: $T\left(u\right)=|{\&Integral;}_{-\&infin;}^{+\&infin;}{E}_1(x-u)\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="E"\; filenames="Y0221814600111.png"\; state="\{\{state\}\}">E</figure-callout>}}_2^{*}\left(x\right)\mathrm{dx}{|}^2$

Claims (3)

1. optimize the high smooth low wavelength division multiplex device of harassing of input end, it comprises input waveguide (1), free diffusion region (2), etching concave grating (3), output waveguide array (4) is characterized in that: the end at input waveguide (1) is connected to the shaped form multiple-mode interfence parts (5) that have pre-broadening input.

2. according to claim, the high smooth low of described optimization input end harassed wavelength division multiplex device, it is characterized in that determining of pre-broadening area size:

The final purpose of pre-broadening is high-order mode time to occur, changes the mould field distribution, therefore,, find to make the structural parameters of broadening mould field edge decline steepest by the mould field distribution in this process of BPM sunykatuib analysis,

The width in pre-broadening zone can be expressed as on arbitrary cross section: $d\left(z\right)=d_2+(d_1-d_2)(1-\frac{z}{L_1})$ Wherein z is transmission direction, d ₁, d ₂Be respectively pre-broadening zone head and the tail width, L ₁Be the length in pre-broadening zone. $C=\frac{\mathrm{\&lambda;}}{\mathrm{\&pi;}}\&CenterDot;{\left(\frac{n_c}{n_r}\right)}^{2\mathrm{\&sigma;}}{(n_r^2-n_c^2)}^{(-1/2)},$ Wherein

Can represent that then pre-broadening region design length is: $L_1=\frac{3}{8}{L}_{\mathrm{\&pi;eff}}=\frac{n_r}{2\mathrm{\&lambda;}}(d_2+C)(d_1+C)$ Cladding index n wherein _c, the sandwich layer refractive index n _r, central wavelength lambda, L _{π eff}For clapping length;

Find out three parameter d in pre-broadening zone from top analysis ₁, d ₂, L ₁In, length L ₁Be initial end width d ₁Width d with end ₂Function, therefore, only need to determine the width d in pre-broadening zone ₁And d ₂, fixedly original width is d earlier ₁, find out suitable terminal width d ₂,, find out d below the different in width respectively according to calculating spectrum and inserting the method for loss ₂With the relation of quality factor, insertion loss, make curve, along with d ₂Increase, quality factor and insert loss and all can increase thereupon, purpose are that will to obtain quality factor big as far as possible, and insert the relatively little project organization of loss, so according to the actual bandwidth needs, comprehensively both select the most suitable d ₂Size.

3. the high smooth low of optimization input end according to claim 1 harassed wavelength division multiplex device, it is characterized in that said shaped form multiple-mode interfence district is the parabolic type interference region, its structural design:

Original width d ₃Its main measurement index of optimization quality factor that are the planarization frequency spectrum, its size is the ratio of 1dB bandwidth and 33dB bandwidth, at the wide degree of given preview d ₂Change initial interference sector width d down, ₃, make d ₃With the variation relation curve of quality factor, then should be able to find the original width d of an optimum mutually ₃, this moment, quality factor had maximal value, the d that this moment is corresponding ₃Size is the designing optimal value;

Linear and the interference region length L of para-curve ₂Optimization regulate and can eliminate the logical ripple of band effectively, at above-mentioned interference district original width d ₃Under the situation of Que Dinging, para-curve must pass through its marginal point, its axis of symmetry must be the device central symmetry axis simultaneously, therefore, three linear parameters of decision para-curve only have been left one, by changing this parameter, can obtain the logical ripple of minimum relatively band, near the interference region imaging point, further optimize length L in addition ₂, can find better interference region length L equally ₂, make band lead to ripple minimum, 1dB bandwidth maximum.

Images