CN102636888A - Electro-optic tuning multi-wavelength FIR (Finite Impulse Response) filter and all-level voltage determining method - Google Patents

Abstract

The invention relates to an electro-optic tuning multi-wavelength FIR (Finite Impulse Response) filter and an all-level voltage determining method. The electro-optic tuning multi-wavelength FIR filter comprises a three-port polarization beam splitter with one input port and two output ports, wherein one output port of the three-port polarization beam splitter is connected with an upper polarization conversion unit through an upper-arm polarization maintaining optical fiber while the other output port of the three-port polarization beam splitter is connected with a lower polarization conversion unit through a lower-arm polarization maintaining optical fiber; output ports of the upper polarization conversion unit and the lower polarization conversion unit are respectively connected with two input ports of a four-port polarization beam splitter; and two output ports of the four-port polarization beam splitter are output ports of the electro-optic tuning multi-wavelength FIR filter. According to the filter and the method, multiple wavelengths can be filtered at the same time in a free spectral range (FSR) by adjusting input voltages of electrode assemblies of all levels. By utilizing electro-optic tuning, the tuning speed of submicrosecond level is achieved, so that the requirements of high capacity and high speed of an optical network are satisfied.

Description

Electro-optical tuning multi-wavelength FIR wave filter and each step voltage are confirmed method

Technical field

The present invention relates to a kind of wave filter.Particularly relate to a kind of be used for optical network node, can select arbitrarily a wavelength and fast electro-optical tuning multi-wavelength FIR wave filter and each step voltage of tuned speed to confirm method simultaneously.

Background technology

Along with increasing substantially of optical fiber transmission network capacity, wavelength-division multiplex technique (WDM) is used widely, and optical filter technology receives much concern.Optical filter can be used for realizing the multiplexing and demultiplexing of light wave, the cross connection of network node, the power equalization of interchannel, the dispersion compensation of transmission signals etc.The implementation of the adjustable light wave-filter that therefore, the searching reconfigurability is strong, tuned speed is fast, tuning precision is high, the insertion loss is little, simple in structure becomes one of emphasis of Recent study.

At present; The optic tunable filter of main flow mainly contains: based on piezoelectric effect; Utilize the effect of voltage to ceramic pipe, the cavity length that changes the resonator cavity that optical reflection film constitutes of parallel placement realizes Fabry-Perot (Fabry-Perot) adjustable filter of filtering; Based on acoustooptic effect, utilize the interaction of surface acoustic wave and acousto-material to change the acousto-optic tunable filter (AOTF) that polarization state of light realizes filtering; Based on elasto-optical effect, utilize fiber grating adjustable filter that the stress sensitivity of Bragg grating reflection wavelength makes etc.

Existing multi-wavelength filtering mainly is that the cascade through wave filter realizes.This structure has inevitably been brought too problem such as complicacy of the excessive and multiplexing port design of node of insertion loss.Filtering when acousto-optic tunable filter can be realized a plurality of wavelength through the sound wave that encourages a plurality of frequencies, but its tuning speed is well below electro-optical filter (EOTF).

Patent " but periodicity optical superlattices multiple wavelengths filter of thermal tuning (CN101162342) " is set up two temperature control equipments below the dielectric wafer of common electrical photoperiodism polarized ferroelectric crystal list wavelength filter, comprehensively can be realized the output of multi-wavelength by temperature controlled each zone.It is simple in structure, and tuning range can reach tens nanometers.But this method tuned speed is slower, and the number that increases filter wavelength need increase temperature control equipment, has increased the complexity of element manufacturing.

The patent method for making (CN1529196) of optical superlattices multiple wavelengths filter " non-periodic " is positioned over wafer in the middle of two orthogonal polaroids, obtains optical superlattices multiple wavelengths filter non-periodic, and its filtering centre wavelength is tuning by working temperature.This multiple wavelengths filter is easy to integrated, is convenient to carry out light path and regulates.But the speed of thermal tuning is slower, and carries out the transmissivity that four wavelength select and be merely 14%.

Patent " can be extracted the adjustable optical wavelength filter (CN101846815A) of bandwidth of dual wavelength " simultaneously through on titanium diffusion lithium niobate substrate; Utilize the electrode sputtering technology to prepare phase shift electrode and polarization conversion electrode structure, can realize the tunable bandpass filtering of bandwidth of dual wavelength.This method is utilized electrooptical effect, has higher tuning speed, but the selection distribution that can leach wavelength is had more restriction.

Patent " two-way adjustable FIR wave filter of a kind of electric light and discrete voltages thereof are confirmed method (CN102324910A) " is through the interdigital electrode group structure of fabrication cycle property distribution at the bottom of the lithium niobate base; And adopt the method for undetermined coefficients to find the solution magnitudes of voltage at different levels, obtained the BPF. that the rectangle degree is good, side mode suppression ratio is high.This wave filter can be realized comb filtering, but the filtering multi-wavelength that can not be distributed arbitrarily the time.

Summary of the invention

Technical matters to be solved by this invention is; A kind of tuned speed that can improve light filtering is provided; Extract when realizing in the Free Spectral Range (FSR) arbitrarily wavelength; Thereby reduce the insertion loss of network node, strengthen wave filter and confirm method at electro-optical tuning multi-wavelength FIR wave filter and each step voltage of the applicability of OWDM network node.

The technical scheme that the present invention adopted is: a kind of electro-optical tuning multi-wavelength FIR wave filter and each step voltage are confirmed method.Electro-optical tuning multi-wavelength FIR wave filter; Include: three port polarization beam apparatus with an input port and two output ports; An output port of described three port polarization beam apparatus connects one through the upper arm polarization maintaining optical fibre and goes up the polarization conversion unit; Another output port of said three port polarization beam apparatus connects a following polarization conversion unit through the underarm polarization maintaining optical fibre; Described output of going up polarization conversion unit and following polarization conversion unit is connected two input ports of four port polarization beam apparatus respectively, and two output ports of said four port polarization beam apparatus are the output port of this electro-optical tuning multi-wavelength FIR wave filter.

It is described that upward the polarization conversion unit is identical with the structure of following polarization conversion unit; Include: X cuts at the bottom of the lithium niobate base of Y biography; Be arranged on X and cut the suprabasil titanium diffusion of the lithium niobate lithium niobate waveguide that Y passes; Be disposed with by N level interdigital electrode group to the output port of titanium diffusion lithium niobate waveguide from the input port of titanium diffusion lithium niobate waveguide; One end of said N level interdigital electrode group connects ground-electrode; In the described N level interdigital electrode group each grade interdigital electrode group be positioned at a side of output port corresponding a phase shift electrode is set, thereby with the corresponding N level shift electrode mutually that is provided with altogether of N level interdigital electrode group, the connection ground-electrode that each phase shift electrode pair is answered.

Described each grade interdigital electrode group constitutes by M interdigital electrode, and G is the gap length of every grade of phase shift electrode pair, and each grade interdigital electrode group length is made as L _c, relational expression is then arranged:

L _c=(M+1/4) Λ, Λ is the interdigital electrode cycle, L _dGap length for two-stage interdigital electrode group.

Definite method of discrete voltages at different levels comprises the steps: in the last polarization conversion unit of a kind of electro-optical tuning multi-wavelength FIR wave filter of the present invention/following polarization conversion unit

The first step: set filtering band center wavelength X ₀, working temperature is got normal temperature T, tries to achieve accurate TE mould with this understanding, the effective refractive index n of accurate TM mould _TE, n _TM,

$\left\{\begin{array}{c}{n}_{\mathrm{TM}}=\sqrt{4.9130+\frac{1.173\&times;{10}^5+1.65\&times;{10}^{-2}{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000153079030000013.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}{{{\mathrm{\&lambda;}}_0}^2\&times;{10}^6-{(2.12\&times;{10}^2+2.7\&times;{10}^{-5}{T}^2)}^2}-2.78\&times;{10}^{-2}{{\mathrm{\&lambda;}}_0}^2}\\ n_{\mathrm{TE}}=\sqrt{4.5567+2.605\&times;{10}^{-7}{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000153079030000013.png"\; state="\{\{state\}\}">T</figure-callout>}}^2+\frac{0.97{\&times;10}^5+2.70\&times;{10}^{-2}{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000153079030000013.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}{{{\mathrm{\&lambda;}}_0}^2\&times;{10}^6-{(2.01\&times;{10}^2+5.4\&times;{10}^{-5}{T}^2)}^2}-2.24\&times;{10}^{-2}{{\mathrm{\&lambda;}}_0}^2}\end{array}\right.;$

Second step: the concrete physical parameter of setting the polarization conversion unit: try to achieve interdigital electrode periods lambda=λ according to the value in the first step ₀/ (n _TE-n _TM) | _δ=0, the length L of every grade of interdigital electrode group _c=(M+1/4) Λ, wherein, M is any positive integer; The spacing of every grade of phase shift electrode pair is G, and cascade progression is N, and wherein, N is any positive integer; Confirm required Free Spectral Range FSR and the time delay Δ τ=1/FSR of unit, obtain interdigital electrode group gap length L _d=Δ τ c/ (n _TE-n _TM), wherein, c representes the light velocity 3 * 10 in the vacuum ⁸M/s;

The 3rd step: according to formula $\left\{\begin{array}{c}{\mathrm{\&beta;}}_{\mathrm{TE}}\left(\mathrm{\&lambda;}\right)=2\mathrm{\&pi;}*n_{\mathrm{TE}}\left(\mathrm{\&lambda;}\right)/\mathrm{\&lambda;}\\ {\mathrm{\&beta;}}_{\mathrm{TM}}\left(\mathrm{\&lambda;}\right)=2\mathrm{\&pi;}*n_{\mathrm{TM}}\left(\mathrm{\&lambda;}\right)/\mathrm{\&lambda;}\end{array}\right.,$ Wherein

$\left\{\begin{array}{c}{n}_{\mathrm{TM}}\left(\mathrm{\&lambda;}\right)=\sqrt{4.9130+\frac{1.173\&times;{10}^5+1.65\&times;{10}^{-2}{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000153079030000013.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}{{\mathrm{\&lambda;}}^2\&times;{10}^6-{(2.12\&times;{10}^2+2.7\&times;{10}^{-5}{T}^2)}^2}-2.78\&times;{10}^{-2}{\mathrm{\&lambda;}}^2}\\ n_{\mathrm{TE}}\left(\mathrm{\&lambda;}\right)=\sqrt{4.5567+2.605\&times;{10}^{-7}{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000153079030000013.png"\; state="\{\{state\}\}">T</figure-callout>}}^2+\frac{0.97{\&times;10}^5+2.70\&times;{10}^{-2}{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000153079030000013.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}{{\mathrm{\&lambda;}}^2\&times;{10}^6-{(2.01\&times;{10}^2+5.4\&times;{10}^{-5}{T}^2)}^2}-2.24\&times;{10}^{-2}{\mathrm{\&lambda;}}^2}\end{array}\right.$

Ask for the transmission β of accurate TE mould and accurate TM mould respectively _TE(λ) and β _TM(λ), λ gets λ in the formula ₀, adopt the z conversion to represent the target filter function, z can be expressed as z=exp [j (β _TE-β _TM) L _d]; Be set in central wavelength lambda ₀FSR in the object transmission function $H\left(z\right)=\left({\mathrm{\&Sigma;}}_{i=1}^N{m}_i{z}^{-i}\right)z^{N/2},$ M wherein _iI level coefficient for H (z);

The 4th step: establish X (z) and be the arbitrary function of z, definition X _*(z)=X ^*(1/z ^*), X wherein ^*(1/z ^*) be z got complex conjugate, gets inverse after, X gets complex conjugate to function; The Jones matrix of polarization conversion unit is expressed as unitary matrix $S=\left(\begin{array}{cc}H\left(z\right)& -F_{*}\left(z\right)\\ F\left(z\right)& H_{*}\left(z\right)\end{array}\right),$ Wherein H (z) and F (z) they are the reciprocity filter transmission function of two polarization directions, and n _iI level coefficient for function F (z); Matrix S satisfies H (z) H _*(z)+F (z) F _*(z)=1.

The 5th step: in the i level filter network of N level cascading filter, the coupling coefficient of interdigital electrode group is used k _iRepresent that what driven phase shift electrode caused diverts from one use to another mutually

Expression; The utilization method of undetermined coefficients, the definition arbitrary number

The coefficient p of the n level of function in the expression m level cascade filtering network _n, n=1 wherein, 2 ... M obtains:

Thereby when trying to achieve progression n from N to 1, the expansion coefficient m of filter function H (z) and F (z) in each n level cascade device ^[n]And n ^[n] With

It is respectively the expansion coefficient of the n level of H (z) and F (z) in the n level cascade device; Thereby can be in the hope of the coupling coefficient k of interdigital electrode groups at different levels in the N level cascading filter _iAnd the phase shift that causes of phase shift electrodes at different levels Be the coupling coefficient k of the interdigital electrode group in the n level NE in the n level cascading filter _nAnd the phase shift that causes of phase shift electrode

Be expressed as respectively:

The 6th step: judge whether n is zero, is then to get into for the 7th step, otherwise, returned for the 5th step and continue circulation;

Step Seven: Determine discrete voltage levels

and

Wherein, Γ _TE-TM, Γ _TEAnd Γ _TMBe the normalization overlap integral factor that produces because of the electric field uneven distribution, all be made as 1 in this value; γ ₅₁, γ ₃₃And γ ₁₃Be each component of lithium columbate crystal electric light tensor, value is respectively: γ ₅₁=28 * 10 ^-12M/V, γ ₃₃=30.8 * 10 ^-12M/V, γ ₁₃=8.6 * 10 ^-12M/V.

Electro-optical tuning multi-wavelength FIR wave filter of the present invention and each step voltage are confirmed method, through regulating the input voltage of electrode groups at different levels, in Free Spectral Range (FSR), can realize filtering in any a plurality of wavelength.And tuned speed is fast.It is means that the present invention adopts electro-optical tuning, can reach the tuned speed of submicrosecond level.Thereby can better meet optical-fiber network high capacity, high-speed requirement.

Description of drawings

Fig. 1 is a N level electro-optical tuning multi-wavelength FIR filter construction synoptic diagram;

Fig. 2 is N level electro-optical tuning multi-wavelength FIR wave filter polarization conversion unit;

The filtering output intensity transmissivity spectrum of wave filter in Free Spectral Range (FSR) when Fig. 3 is N=16;

Fig. 4 is the algorithm flow chart that discrete voltages at different levels of the present invention is confirmed method.

Among the figure:

101: input port 102,103: output port

105: four port polarization beam apparatus of 104: three port polarization beam apparatus

106: upper arm polarization maintaining optical fibre 107: the underarm polarization maintaining optical fibre

108: go up polarization conversion unit 109: following polarization conversion unit

201:X cuts at the bottom of the lithium niobate base that Y passes 202: the waveguide of titanium diffusion lithium niobate

203: input port 204: output port

210: ground-electrode 211-21N:N level interdigital electrode group

221-22N:N level phase shift electrode 220: ground-electrode

Λ: interdigital electrode cycle G: the gap length of every grade of phase shift electrode pair

Embodiment

Below in conjunction with embodiment and accompanying drawing electro-optical tuning multi-wavelength FIR wave filter of the present invention and each step voltage are confirmed that method makes detailed description.

Electro-optical tuning multi-wavelength FIR wave filter of the present invention is cut the titanium diffusion lithium niobate (Ti:LiNbO that Y passes at X ₃) in the waveguide; N level interdigital electrode group and the periodically alternately cascade distribution of shift electrode mutually of N level by discrete voltages control; Through the periodicity perturbation of refractive index in the electric field change generation waveguide of Y direction and Z direction, thereby constitute corresponding Mode Coupling unit, phase-shift unit in the FIR network.Through finding the solution the discrete voltages value of each unit of control, realize corresponding many filtering output.

As shown in Figure 1; Electro-optical tuning multi-wavelength FIR wave filter of the present invention; Include: three port polarization beam apparatus 104 with an input port 101 and two output ports; An output port of described three port polarization beam apparatus 104 connects one through upper arm polarization maintaining optical fibre 106 and goes up polarization conversion unit 108; Another output port of said three port polarization beam apparatus 104 connects a following polarization conversion unit 109 through underarm polarization maintaining optical fibre 107; Described output of going up polarization conversion unit 108 and following polarization conversion unit 109 is connected two input ports of four port polarization beam apparatus 105 respectively, and two output ports 102,103 of said four port polarization beam apparatus 105 are the output port of this electro-optical tuning multi-wavelength FIR wave filter.

With λ 0 is the center; Light signal in the FSR through three port polarization beam apparatus 104, divides be as the criterion TE mould and these two kinds of mutually orthogonal polarization modes of accurate TM mould from input port 101 inputs; Wherein accurate TE mould gets into upper arm polarization maintaining optical fibre 106, and accurate TM mould gets into underarm polarization maintaining optical fibre 107.Signal gets into/following polarization conversion unit 108/109 (being structure as shown in Figure 2) then, meets the polarization conversion of light emergence pattern in this element of the wavelength of phase-matching condition, that is: the accurate TE mould conversion TM mould that is as the criterion, the accurate TM mould conversion TE mould that is as the criterion.Signal converges at four port polarization beam apparatus, 105 places, and accurate TM mould gets into crossing waveguide, and accurate TE mould gets into straight-through waveguide, thereby band hinders signal from output port 102 outputs, and bandpass signal is realized light filtering from output port 103 outputs.

As shown in Figure 2, described upward polarization conversion unit 108 is identical with the structure of following polarization conversion unit 109, includes: X cuts the lithium niobate (LiNbO that Y passes ₃) substrate 201, be arranged on X and cut at the bottom of the lithium niobate base that Y passes the titanium diffusion lithium niobate (Ti:LiNbO) on 201 ₃Waveguide 202; Be disposed with by N level interdigital electrode group 211-21N to the output port 204 of titanium diffusion lithium niobate waveguide 202 from the input port 203 of titanium diffusion lithium niobate waveguide 202; The end of said N level interdigital electrode group 211-21N connects ground-electrode 210; Among the described N level interdigital electrode group 211-21N each grade interdigital electrode group be positioned at a side of output port 204 corresponding a phase shift electrode is set; Thereby with the corresponding N level shift electrode 221-22N mutually that is provided with altogether of N level interdigital electrode group 211-21N, connection one ground-electrode 220 that each phase shift electrode pair is answered.

Described each grade interdigital electrode group constitutes by M interdigital electrode, and G is the gap length of every grade of phase shift electrode pair, and each grade interdigital electrode group length is made as L _c, relational expression is then arranged:

L _c=(M+1/4) Λ, Λ is the interdigital electrode cycle, L _dGap length for two-stage interdigital electrode group.

Last polarization conversion unit 108 and following polarization conversion unit 109 are at the bottom of X cuts the lithium niobate base that Y passes 201, titanium spreads lithium niobate (Ti:LiNbO) ₃In the waveguide 202, we have adopted N level interdigital electrode group and the N level shift electrode structure that distributes of cascade periodically alternately mutually.From waveguide input port 203 to output port 204; The discrete voltages of waveguide

joins among the N level interdigital electrode group 211-21N successively; Discrete voltages joins among the N level phase shift electrode 221-22N successively, ground-electrode 210 and ground-electrode 220 equal ground connection.

The number that can leach wavelength in the value of cascade progression N and the FSR simultaneously is relevant, can obtain through checking, and the N value is big more, and the filtering number is many more, and this also means reducing of three dB bandwidth that each leaches wavelength.The increase of N value has also increased the length and the manufacture difficulty of device but simultaneously.The value of interdigital electrode periods lambda is by the central wavelength lambda of institute's filter section ₀Decision.Receive periodically electric field effects, there is phase mismatch to a certain degree in two kinds of polarization modes in coupling process, are expressed as with the single order phase mismatch degree δ of the interior two kinds of patterns of unit length: δ=[β _TM(λ)-β _TE(λ)]/2-π/Λ.Realize the polarization conversion of maximal efficiency, in wavelength X ₀The phase place of the two kinds of patterns in place is mated fully, satisfies

Be interdigital electrode periods lambda=λ ₀/ (n _TE-n _TM) | _δ=0

We get λ ₀=1550nm obtains Λ=20.5 μ m.The gap length L of interdigital electrode group _dConfirm by the Free Spectral Range that sets (FSR): L _d=c/ [FSR (n _TE-n _TM)].Set FSR=1000GHz, L _dBe about 4mm.If 5 groups of interdigital electrodes are arranged in every grade of interdigital electrode group, obtain L _c=0.11mm.Take all factors into consideration the number and the element manufacturing difficulty of Wavelength-selective, choose cascade progression N=16.

The present invention has introduced the algorithm of finite impulse response (FIR) in the electricity (FIR) digital filtering.In fact light signal can be regarded as the synergistic effect that light transmits in the transmission of the cascade polarized converting unit of N level (structure shown in Figure 2) in the light path of different length.Adopt the FIR network to represent its transition function and Jones matrix, the Jones matrix S of i level _iCan be decomposed into by discrete voltages

Drive the phase shift matrix that the phase shift electrode is constituted By voltage

Drive the coupled matrix that the interdigital electrode group is constituted

And by the time delay matrix of FSR value control

Therefore, can between target filter function and the discrete voltages that is added, set up one to one relation, output when realizing a plurality of wavelength.

As shown in Figure 4, definite method of discrete voltages at different levels comprises the steps: in the last polarization conversion unit of electro-optical tuning multi-wavelength FIR wave filter of the present invention/following polarization conversion unit

The first step: set filtering band center wavelength X ₀, working temperature is got normal temperature T, tries to achieve accurate TE mould with this understanding, the effective refractive index n of accurate TM mould _TE, n _TM, select λ in the present embodiment ₀=1550nm, T=24 ℃

$\left\{\begin{array}{c}{n}_{\mathrm{TM}}=\sqrt{4.9130+\frac{1.173\&times;{10}^5+1.65\&times;{10}^{-2}{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000153079030000013.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}{{{\mathrm{\&lambda;}}_0}^2\&times;{10}^6-{(2.12\&times;{10}^2+2.7\&times;{10}^{-5}{T}^2)}^2}-2.78\&times;{10}^{-2}{{\mathrm{\&lambda;}}_0}^2}\\ n_{\mathrm{TE}}=\sqrt{4.5567+2.605\&times;{10}^{-7}{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000153079030000013.png"\; state="\{\{state\}\}">T</figure-callout>}}^2+\frac{0.97{\&times;10}^5+2.70\&times;{10}^{-2}{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000153079030000013.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}{{{\mathrm{\&lambda;}}_0}^2\&times;{10}^6-{(2.01\&times;{10}^2+5.4\&times;{10}^{-5}{T}^2)}^2}-2.24\&times;{10}^{-2}{{\mathrm{\&lambda;}}_0}^2}\end{array}\right.;$

Second step: the concrete physical parameter of setting the polarization conversion unit: try to achieve interdigital electrode periods lambda=λ according to the value in the first step ₀/ (n _TE-n _TM) | _δ=0, select Λ=λ in the present embodiment ₀/ (n _TE-n _TM) | _δ=0=20.5 μ m.The length L of every grade of interdigital electrode group _c=(M+1/4) Λ, wherein, M is any positive integer, selects L in the present embodiment _c=(5+1/4) Λ=0.11mm; The spacing of every grade of phase shift electrode pair is G, and cascade progression is N, and wherein, N is any positive integer, G=10 μ m in the present embodiment, N=16; Confirm required Free Spectral Range FSR and the time delay Δ τ=1/FSR of unit, FSR=1000GHz in the present embodiment obtains interdigital electrode group gap length L _d=Δ τ c/ (n _TE-n _TM), wherein, c representes the light velocity 3 * 10 in the vacuum ⁸M/s, L in the present embodiment _d=Δ τ c/ (n _TE-n _TM) ≈ 4mm;

The 3rd step: according to formula $\left\{\begin{array}{c}{\mathrm{\&beta;}}_{\mathrm{TE}}\left(\mathrm{\&lambda;}\right)=2\mathrm{\&pi;}*n_{\mathrm{TE}}\left(\mathrm{\&lambda;}\right)/\mathrm{\&lambda;}\\ {\mathrm{\&beta;}}_{\mathrm{TM}}\left(\mathrm{\&lambda;}\right)=2\mathrm{\&pi;}*n_{\mathrm{TM}}\left(\mathrm{\&lambda;}\right)/\mathrm{\&lambda;}\end{array}\right.,$ Wherein

$\left\{\begin{array}{c}{n}_{\mathrm{TM}}\left(\mathrm{\&lambda;}\right)=\sqrt{4.9130+\frac{1.173\&times;{10}^5+1.65\&times;{10}^{-2}{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000153079030000013.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}{{\mathrm{\&lambda;}}^2\&times;{10}^6-{(2.12\&times;{10}^2+2.7\&times;{10}^{-5}{T}^2)}^2}-2.78\&times;{10}^{-2}{\mathrm{\&lambda;}}^2}\\ n_{\mathrm{TE}}\left(\mathrm{\&lambda;}\right)=\sqrt{4.5567+2.605\&times;{10}^{-7}{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000153079030000013.png"\; state="\{\{state\}\}">T</figure-callout>}}^2+\frac{0.97{\&times;10}^5+2.70\&times;{10}^{-2}{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000153079030000013.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}{{\mathrm{\&lambda;}}^2\&times;{10}^6-{(2.01\&times;{10}^2+5.4\&times;{10}^{-5}{T}^2)}^2}-2.24\&times;{10}^{-2}{\mathrm{\&lambda;}}^2}\end{array}\right.$

Ask for the transmission β of accurate TE mould and accurate TM mould respectively _TE(λ) and β _TM(λ), λ gets λ in the formula ₀, adopt the z conversion to represent the target filter function, z can be expressed as z=exp [j (β _TE-β _TM) L _d]; Be set in central wavelength lambda ₀FSR in the object transmission function $H\left(z\right)=\left({\mathrm{\&Sigma;}}_{i=1}^N{m}_i{z}^{-i}\right)z^{N/2},$ M wherein _iI level coefficient for H (z);

The 4th step: establish X (z) and be the arbitrary function of z, definition X _*(z)=X ^*(1/z ^*), X wherein ^*(1/z ^*) be z got complex conjugate, gets inverse after, X gets complex conjugate to function; The Jones matrix of polarization conversion unit is expressed as unitary matrix $S=\left(\begin{array}{cc}H\left(z\right)& -F_{*}\left(z\right)\\ F\left(z\right)& H_{*}\left(z\right)\end{array}\right),$ Wherein H (z) and F (z) they are the reciprocity filter transmission function of two polarization directions, and

n _iI level coefficient for function F (z); Matrix S satisfies H (z) H _*(z)+F (z) F _*(z)=1.

The 5th step: in the i level filter network of N level cascading filter, the coupling coefficient of interdigital electrode group is used k _iRepresent that what driven phase shift electrode caused diverts from one use to another mutually

Expression; The utilization method of undetermined coefficients, the definition arbitrary number

The coefficient p of the n level of function in the expression m level cascade filtering network _n, n=1 wherein, 2 ... M obtains:

Thereby when trying to achieve progression n from N to 1, the expansion coefficient m of filter function H (z) and F (z) in each n level cascade device ^[n]And n ^[n]

With

It is respectively the expansion coefficient of the n level of H (z) and F (z) in the n level cascade device; Thereby can be in the hope of the coupling coefficient k of interdigital electrode groups at different levels in the N level cascading filter _iAnd the phase shift that causes of phase shift electrodes at different levels

Be the coupling coefficient k of the interdigital electrode group in the n level NE in the n level cascading filter _nAnd the phase shift that causes of phase shift electrode

Be expressed as respectively:

The 6th step: judge whether n is zero, is then to get into for the 7th step, otherwise, returned for the 5th step and continue circulation;

Step Seven: Determine discrete voltage levels

and

Wherein, Γ _TE-TM, Γ _TEAnd Γ _TMBe the normalization overlap integral factor that produces because of the electric field uneven distribution, all be made as 1 in this value; γ ₅₁, γ ₃₃And γ ₁₃Be each component of lithium columbate crystal electric light tensor, value is respectively: γ ₅₁=28 * 10 ^-12M/V, γ ₃₃=30.8 * 10 ^-12M/V, γ ₁₃=8.6 * 10 ^-12M/V.

According to said method, at progression N=16, when H (z) was taken as the filter function that obtains the 2nd, 6 and 8 three wavelength channel simultaneously arbitrarily, the output light transmission spectrum that obtains was as shown in Figure 3, and each side mode suppression ratio (SMSR) that leaches wavelength can reach more than the 10dB.Following table has provided the value of discrete voltages:

The present invention is aspect manufacture craft: at first X is cut LiNO ₃Wafer strip is as substrate, and twin polishing is also cleaned, and uses the rf magnetron sputtering machine after the surface plates titanium metal film, and substrate is placed in the diffusion furnace, and high temperature sintering obtains titanium diffusion LiNO ₃Slab guide.Then, the designed mask plate utilizes photoetching technique to make the titanium bar on the slab guide surface, and calcination is spread under the same high temperature, thereby accomplishes the making of light path.

At last, the mask plate of design metal electrode spreads the vacuum sputtering that carries out photoetching and metal electrode on the lithium niobate light path substrate at Ti, adopts gold wire bonder to make contact conductor, accomplishes the making of device.

In addition,,, adopt hardware description language (Verilog) to write FPGA, control the output of discrete voltages at different levels in order to improve its adaptivity about control voltages at different levels.

Claims (4)

1. electro-optical tuning multi-wavelength FIR wave filter; It is characterized in that; Include: three port polarization beam apparatus (104) with an input port (101) and two output ports; An output port of described three port polarization beam apparatus (104) connects one through upper arm polarization maintaining optical fibre (106) and goes up polarization conversion unit (108); Another output port of said three port polarization beam apparatus (104) connects a following polarization conversion unit (109) through underarm polarization maintaining optical fibre (107); Described output of going up polarization conversion unit (108) and following polarization conversion unit (109) is connected two input ports of four port polarization beam apparatus (105) respectively, and two output ports (102,103) of said four port polarization beam apparatus (105) are the output port of this electro-optical tuning multi-wavelength FIR wave filter.

2. electro-optical tuning multi-wavelength FIR wave filter according to claim 1; It is characterized in that; It is described that upward polarization conversion unit (108) is identical with the structure of following polarization conversion unit (109); Include: X cuts (201) at the bottom of the lithium niobate base that Y passes; Be arranged on X and cut the titanium diffusion lithium niobate waveguide (202) on (201) at the bottom of the lithium niobate base that Y passes; Be disposed with by N level interdigital electrode group (211-21N) to the output port (204) of titanium diffusion lithium niobate waveguide (202) from the input port (203) of titanium diffusion lithium niobate waveguide (202), an end of said N level interdigital electrode group (211-21N) connects ground-electrode (210), in the described N level interdigital electrode group (211-21N) each grade interdigital electrode group be positioned at output port (204) side correspondence a phase shift electrode is set; Thereby with corresponding N level shift electrode (221-22N) mutually, connection one ground-electrode (220) that each phase shift electrode pair is answered of being provided with altogether of N level interdigital electrode group (211-21N).

3. electro-optical tuning multi-wavelength FIR wave filter according to claim 2 is characterized in that described each grade interdigital electrode group constitutes by M interdigital electrode, and G is the gap length of every grade of phase shift electrode pair, and each grade interdigital electrode group length is made as L _c, relational expression is then arranged:

L _c=(M+1/4) Λ, Λ is the interdigital electrode cycle, L _dGap length for two-stage interdigital electrode group.

4. definite method of discrete voltages at different levels in the last polarization conversion unit/following polarization conversion unit of the described electro-optical tuning multi-wavelength of claim 1 a FIR wave filter is characterized in that, comprises the steps:

The first step: set filtering band center wavelength X ₀, working temperature is got normal temperature T, tries to achieve accurate TE mould with this understanding, the effective refractive index n of accurate TM mould _TE, n _TM,

$\left\{\begin{array}{c}{n}_{\mathrm{TM}}=\sqrt{4.9130+\frac{1.173\&times;{10}^5+1.65\&times;{10}^{-2}{T}^2}{{{\mathrm{\&lambda;}}_0}^2\&times;{10}^6-{(2.12\&times;{10}^2+2.7\&times;{10}^{-5}{T}^2)}^2}-2.78\&times;{10}^{-2}{{\mathrm{\&lambda;}}_0}^2}\\ n_{\mathrm{TE}}=\sqrt{4.5567+2.605\&times;{10}^{-7}{T}^2+\frac{0.97{\&times;10}^5+2.70\&times;{10}^{-2}{T}^2}{{{\mathrm{\&lambda;}}_0}^2\&times;{10}^6-{(2.01\&times;{10}^2+5.4\&times;{10}^{-5}{T}^2)}^2}-2.24\&times;{10}^{-2}{{\mathrm{\&lambda;}}_0}^2}\end{array}\right.;$

Second step: the concrete physical parameter of setting the polarization conversion unit: try to achieve interdigital electrode periods lambda=λ according to the value in the first step ₀/ (n _TE-n _TM) | _δ=0, the length L of every grade of interdigital electrode group _c=(M+1/4) Λ, wherein, M is any positive integer; The spacing of every grade of phase shift electrode pair is G, and cascade progression is N, and wherein, N is any positive integer; Confirm required Free Spectral Range FSR and the time delay Δ τ=1/FSR of unit, obtain interdigital electrode group gap length L _d=Δ τ c/ (n _TE-n _TM), wherein, c representes the light velocity 3 * 10 in the vacuum ⁸M/s;

The 3rd step: according to formula $\left\{\begin{array}{c}{\mathrm{\&beta;}}_{\mathrm{TE}}\left(\mathrm{\&lambda;}\right)=2\mathrm{\&pi;}*n_{\mathrm{TE}}\left(\mathrm{\&lambda;}\right)/\mathrm{\&lambda;}\\ {\mathrm{\&beta;}}_{\mathrm{TM}}\left(\mathrm{\&lambda;}\right)=2\mathrm{\&pi;}*n_{\mathrm{TM}}\left(\mathrm{\&lambda;}\right)/\mathrm{\&lambda;}\end{array}\right.,$ Wherein

$\left\{\begin{array}{c}{n}_{\mathrm{TM}}\left(\mathrm{\&lambda;}\right)=\sqrt{4.9130+\frac{1.173\&times;{10}^5+1.65\&times;{10}^{-2}{T}^2}{{\mathrm{\&lambda;}}^2\&times;{10}^6-{(2.12\&times;{10}^2+2.7\&times;{10}^{-5}{T}^2)}^2}-2.78\&times;{10}^{-2}{\mathrm{\&lambda;}}^2}\\ n_{\mathrm{TE}}\left(\mathrm{\&lambda;}\right)=\sqrt{4.5567+2.605\&times;{10}^{-7}{T}^2+\frac{0.97{\&times;10}^5+2.70\&times;{10}^{-2}{T}^2}{{\mathrm{\&lambda;}}^2\&times;{10}^6-{(2.01\&times;{10}^2+5.4\&times;{10}^{-5}{T}^2)}^2}-2.24\&times;{10}^{-2}{\mathrm{\&lambda;}}^2}\end{array}\right.$

Ask for the transmission β of accurate TE mould and accurate TM mould respectively _TE(λ) and β _TM(λ), λ gets λ in the formula ₀, adopt the z conversion to represent the target filter function, z can be expressed as z=exp [j (β _TE-β _TM) L _d]; Be set in central wavelength lambda ₀FSR in the object transmission function $H\left(z\right)=\left({\mathrm{\&Sigma;}}_{i=1}^N{m}_i{z}^{-i}\right)z^{N/2},$ M wherein _iI level coefficient for H (z);

The 4th step: establish X (z) and be the arbitrary function of z, definition X _*(z)=X ^*(1/z ^*), X wherein ^*(1/z ^*) be z got complex conjugate, gets inverse after, X gets complex conjugate to function; The Jones matrix of polarization conversion unit is expressed as unitary matrix $S=\left(\begin{array}{cc}H\left(z\right)& -F_{*}\left(z\right)\\ F\left(z\right)& H_{*}\left(z\right)\end{array}\right),$ Wherein H (z) and F (z) they are the reciprocity filter transmission function of two polarization directions, and

n _iI level coefficient for function F (z); Matrix S satisfies H (z) H _*(z)+F (z) F _*(z)=1.

The 5th step: in the i level filter network of N level cascading filter, the coupling coefficient of interdigital electrode group is used k _iRepresent that what driven phase shift electrode caused diverts from one use to another mutually

Expression; The utilization method of undetermined coefficients, the definition arbitrary number

The coefficient p of the n level of function in the expression m level cascade filtering network _n, n=1 wherein, 2 ... M obtains:

Thereby when trying to achieve progression n from N to 1, the expansion coefficient m of filter function H (z) and F (z) in each n level cascade device ^[n]And n ^[n]

With

It is respectively the expansion coefficient of the n level of H (z) and F (z) in the n level cascade device; Thereby can be in the hope of the coupling coefficient k of interdigital electrode groups at different levels in the N level cascading filter _iAnd the phase shift that causes of phase shift electrodes at different levels

Be the coupling coefficient k of the interdigital electrode group in the n level NE in the n level cascading filter _nAnd the phase shift that causes of phase shift electrode

Be expressed as respectively:

The 6th step: judge whether n is zero, is then to get into for the 7th step, otherwise, returned for the 5th step and continue circulation;

Step Seven: Determine discrete voltage levels

and

Wherein, Γ _TE-TM, Γ _TEAnd Γ _TMBe the normalization overlap integral factor that produces because of the electric field uneven distribution, all be made as 1 in this value; γ ₅₁, γ ₃₃And γ ₁₃Be each component of lithium columbate crystal electric light tensor, value is respectively: γ ₅₁=28 * 10 ^-12M/V, γ ₃₃=30.8 * 10 ^-12M/V, γ ₁₃=8.6 * 10 ^-12M/V.

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