CN103760732B - A kind of cascade and frequency and difference frequency AOWC and conversion method - Google Patents

Abstract

The present invention is a kind of cascade and frequency and difference frequency AOWC and conversion method, two pump lights of this transducer dual-laser device are after Polarization Controller, line polarized light conversion equipment, the first photo-coupler, the second photo-coupler, erbium-doped fiber amplifier, optical circulator is accessed to PPLN ridge waveguide together with flashlight, forward direction light beam is reflected by 90 ° of rotating mirrors of faraday, backward light beam enters again ridge waveguide, and conversion ideler frequency light exports from optical circulator.This conversion method is: is adjusted to the online polarized light conversion device of pump light of TM mould through Polarization Controller and is changed into that polarization direction is parallel with the cross section of PPLN ridge waveguide and the line polarized light of X-axis angulation θ, TE and the TM mould that amplitude ratio is tg θ it is decomposed in ridge waveguide, pump light occurs cascade and frequency to react with difference frequency with the TM mould of flashlight, produces conversion ideler frequency light TM mould, other forward light is through the reflection of faraday's reflecting mirror and patten transformation, then returns ridge waveguide.The present invention realizes the wavelength convert unrelated with flashlight polarization state.

Description

A kind of cascade and frequency and difference frequency AOWC and conversion method

Technical field

The invention belongs to technical field of photo communication, relate to a kind of cascade and frequency and difference frequency all-optical wave-length The all-optical wave-length of transducer and conversion method, a kind of cascade based on PPLN fiber waveguide and frequency with difference frequency type Transducer and conversion method, be primarily adapted for use in dense wave division multipurpose optical communication system.

Background technology

In technical field of photo communication, the data of Large Copacity and two-forty are needed to transmit.In optical fiber telecommunications system In, dense wave division multipurpose (DWDM) energy its transmission capacity of especially significant raising, dense wave division multipurpose light Communication system is the technology that current development future is expected most.AOWC is dense wave division multipurpose One of key performance device of optical communication network, AOWC realizes the information light from a wavelength Carrier wave, to the duplication of the light carrier of another wavelength, contributes to wavelength recycling, effectively carries out dynamic routing Select, reduce network blocking probability, and then motility and the expandability of optical-fiber network can be improved, it is achieved open Put the forwarding of optical signal in formula dwdm system.

The most conventional All-Optical Wavelength Conversion Techniques specifically includes that XGM (XGM), intersection phase Position modulation (XPM), laser gain saturated absorption, electro-absorption modulation (EA), nonlinear optics ring Shape mirror (NOLM), four-wave mixing (FWM), second order nonlinear effect etc..In existing scheme, based on week Phase poled lithium niobate fiber waveguide, the All-Optical Wavelength Conversion Techniques of referred to as PPLN fiber waveguide, because of PPLN light wave The second order nonlinear effect led has the superiority of uniqueness, as the most saturating to signal bit rate and modulation format Bright, multi-wavelength transfer capability simultaneously, mirroring wavelength conversion characteristics, noise figure are extremely low, fast response time, And switching bandwith is the widest etc., thus All-Optical Wavelength Conversion Techniques based on PPLN fiber waveguide is subject in recent years The great attention of various countries scientific worker.

Carry out in terms of wavelength convert based on PPLN fiber waveguide second order nonlinear effect both at home and abroad at present Many significant work, mainly include based on direct difference frequency (DFG), based on cascade frequency multiplication and difference frequency (SHG+DFG), based on cascade and frequency and second order and the cascaded second order nonlinearity such as difference frequency (SFG+DFG) The wavelength conversion technology of effect.But these technology all also exist defect.

Although DFG type AOWC conversion efficiency is higher, but due to its pump light used (0.775 μm) and flashlight (1.5 μm) are in different-waveband, and differ greatly, the full light of DFG type Wavelength shifter is difficult to well pump light and flashlight are coupled into waveguide simultaneously, it is difficult to realize simultaneously Pump light and the flashlight single mode transport in fiber waveguide.

SHG+DFG type wavelength shifter based on cascade frequency multiplication and difference frequency solves DFG type wavelength shifter and meets The difficulty arrived, the pump light of injection and flashlight are in 1.5 mu m wavebands together, can realize 1.5 mu m wavebands All Optical Wavelength Conversion.But, owing to during cascade frequency multiplication and difference frequency, pump light occupies the ripple of flashlight Section, this is not permitted in a lot of dwdm system.And frequency multiplication (SHG) process quasi-phase matched (QPM) Pump wavelength responsive bandwidth at wavelength is the narrowest, for the flashlight of fixing input, traditional SHG+DFG type wavelength shifter is difficult to change the tunable output of ideler frequency light, and tunable wavelength turns It is again very important for changing the motility for strengthening network management.

Based on cascade and frequency and the AOWC of difference frequency (SFG+DFG) can solve simultaneously DFG type and Tradition cascade frequency multiplication and the SHG+DFG type wavelength shifter problem encountered of difference frequency.The most all incidences Light is in 1.5 mu m wavebands, and on the other hand the flashlight even for fixed wave length input can also facilitate Realize tunable wavelength conversion.With difference frequency (SFG+DFG), there is Two-orders non-thread based on cascade and frequency Property effect, be placed in the wavelength approximation of first pump light on the both sides of flashlight wave band window and the second pump light Symmetrical about frequency multiplication (SHG) process quasi-phase matched wavelength, the wavelength of the first pump light is λ₁, frequency For ω₁, the wavelength of the second pump light is λ₂, frequency be ω₂.Pumping wavelength is close easily with signal wavelength Realizing Best Coupling again will not Seize ACK message wave band.Regulate first, second pump light, make the first pump light Wavelength and the second pump wavelength meet or approximation meets and the quasi-phase matched condition of frequency (SFG) process, Now first, second pump light occurs and frequency (SFG) reaction, produces and frequency light, and the frequency a length of λ of light wave_SF, frequency be ω_SF, ω_SF=ω_p1+ω_p2.Meanwhile, (wavelength is λ to flashlight_S, frequency be ω_S) With and frequency light generation difference frequency (DFG) interact and obtain changing ideler frequency light (wavelength is λ_i, frequency be ω_i), ω_i=ω_SF-ω_s.According to conservation of energy principle, flashlight, the first pump light, the second pump light, and frequency The wavelength of light and conversion ideler frequency light meets relationship below:

SFG:1/λ_SF=1/λ_p1+1/λ_p2

DFG:1/λ_i=1/λ_SF-1/λ_s

SFG+DFG:1/ λ_i=1/λ_p1+1/λ_p2-1/λ_s

λ_p1The wavelength of the first pump light

λ_p2The wavelength of the second pump light

λ_sThe wavelength of flashlight

λ_SFWavelength with frequency light

λ_iThe wavelength of conversion ideler frequency light

But existing AOWC based on cascade with frequency with difference frequency (SFG+DFG) type has polarization Dependency, when flashlight inputs with polarization state, and the conversion ideler frequency light intensity finally exported will be inclined with flashlight Shake the change in direction and change, thus wavelength conversion efficiency is relatively low in the wave-length coverage of some.

Summary of the invention

It is an object of the invention to provide a kind of cascade and frequency and difference frequency AOWC, this full light wave The PPLN fiber waveguide of long transducer is PPLN ridge waveguide, and is connected to line polarized light conversion equipment, simple in construction, Conversion efficiency is higher, and especially polarization independence performance is good, and can carry out fine tune.

Another object of the present invention is to the conversion providing a kind of cascade and frequency with difference frequency AOWC Method, injects PPLN ridge waveguide linear polarization pump light, is decomposed into TM and TE mould, method in PPLN ridge waveguide The 90th ° of rotating mirror is drawn to make again TE and the TM mould of flashlight and pump light exchange and reflect to participate in level Connection and the pump light that react with difference frequency of frequency and flashlight can make up various damage in forward, backward transmission Consumption, when making output, the conversion efficiency of TE mould and TM mould is equal.

A kind of cascade and frequency and the difference frequency AOWC of present invention design, including laser instrument, polarization Controller, photo-coupler, erbium-doped fiber amplifier, optoisolator, optical circulator, PPLN fiber waveguide, 90 ° of rotating mirrors of faraday, the first laser instrument and second laser are tunable external cavity laser, send out The first pump light gone out and the second pump light are respectively connected to the first Polarization Controller and the second Polarization Controller, After the output of the first Polarization Controller and the second Polarization Controller accesses the first photo-coupler, polarize with passing through The flashlight of the random polarization state of controller accesses the second photo-coupler, the output of the second photo-coupler together Accessing erbium-doped fiber amplifier, the output of amplifier accesses optical circulator the first port, light through optoisolator The light beam of the fl transmission of circulator the second port output is after PPLN fiber waveguide, and light beam is by faraday 90 ° Rotating mirror reflect, the light beam of reverse transfers enters again PPLN fiber waveguide, the conversion ideler frequency light of generation from 3rd port of optical circulator is output as the output of this wavelength shifter.

Described first pump light, the second pump light and flashlight are C-band.

The wavelength of described first pump light is λ_p1, the wavelength of the second pump light is λ_p2, produced by this device λ a length of with frequency light wave_SF, each wavelength meets: 1/ λ_SF=1/λ_p1+1/λ_p2。

PPLN fiber waveguide used by the present invention is PPLN ridge waveguide, and the substrate of this ridge waveguide is lithium niobate crystal chip, Ducting layer is that Z cuts and period polarized mixes zinc niobate lithium wafer, substrate and ducting layer Direct Bonding, ridge waveguide Cross section is the XOY plane being perpendicular to Z axis, referred to as Z tangent plane.PPLN ridge waveguide both can transmit TM mould, again may be used Transmission TE mould, it is not necessary to flashlight is divided into mutually orthogonal TE mould and TM mould with polarization beam apparatus, in output Hold without using polarization beam combiner that TE mould and the TM mould of conversion ideler frequency light are synthesized, reduce wavelength shifter Complexity.And PPLN ridge waveguide limits flashlight and pump light concentrates on transmission in waveguide, is conducive to Improve conversion efficiency.

Respectively through the first Polarization Controller and first, second pump light tie-in line of the second Polarization Controller Polarized light conversion device, then access the first photo-coupler.The TM that line polarized light conversion equipment polarizes X-direction The pump light of pattern is converted to another kind of line polarized light, the polarization direction of the line polarized light after conversion and PPLN The cross section (i.e. Z tangent plane) of ridge waveguide is parallel, and is at an angle of θ with vertical X-axis.

Described line polarized light conversion equipment includes the first faraday cell and the second faraday cell, based on faraday The principle of magnetic rotation effect, the magnetic rotation material in faraday cell makes the vibration of the line polarized light passed through Face turns over certain angle under its action of a magnetic field, the angle turned over by the line polarized light vibration plane of faraday cell Degree θ with the relational expression in the magnetic field of faraday cell is:

θ=VBL

Magnetic induction in B is faraday cell in formula, L is the length of magnetic rotation material, and V is ratio The temperature of coefficient Wei Erde constant, V and magnetic rotation material, character and lambda1-wavelength are relevant.

First pump light of the present invention and the second pump light, respectively enter the first of line polarized light conversion equipment Two pump lights are carried out the conversion of line polarized light by faraday cell and the second faraday cell respectively, to improve The accuracy of linear polarization pump light conversion.

The polarization direction of the linear polarization pump light after the conversion of described line polarized light conversion equipment and vertical X-axis Angulation θ, making TM mould that linear polarization pump light decomposes in PPLN ridge waveguide and TE mode amplitude ratio is 1 Ratio 1.

The output of the first Polarization Controller and the second Polarization Controller is each accesses the first optocoupler through polarization maintaining optical fibre Clutch, Polarization Controller is combined with polarization maintaining optical fibre to produce preferable pump light TM mould.

The optical fiber that optical circulator the 3rd port is connect is connected to the first fiber grating and the second fiber grating, The reflectance spectrum centre wavelength of the first fiber grating and the second fiber grating is respectively the first pump light and the second pump The wavelength of Pu light.Non-switched pump light will be reflected back the ring of light by the first fiber grating and the second fiber grating Row device, again entrance PPLN ridge waveguide recycling, improve the utilization rate of pump light, improve conversion efficiency.

A kind of cascade of the present invention and frequency are as follows with the conversion method of difference frequency AOWC:

The first pump light that first tunable laser and the second tunable laser send and the second pump light It is respectively connected to the first Polarization Controller and the second Polarization Controller, adjusts its polarization direction, make first, Two pump lights are TM mould, and the output of the first Polarization Controller and the second Polarization Controller is each to be connect through polarization maintaining optical fibre Entering line polarized light conversion equipment, the TM mould pump light that line polarized light conversion equipment polarizes X-direction is changed into partially The direction that shakes is parallel with the cross section of PPLN ridge waveguide and be at an angle of the line polarized light of θ with vertical direction X-axis. The linear polarization pump light of 2 kinds of wavelength after conversion is after the first photo-coupler and through Polarization Controller The flashlight of random polarization state is coupled by the second photo-coupler together, then puts through erbium-doped fiber amplifier After great, the first port of optical circulator enter, from the second port output of optical circulator, for the first time Being coupled into PPLN ridge waveguide, in PPLN ridge waveguide, the linear polarization pump light after conversion is decomposed into TE simultaneously Mould and TM mould, the amplitude ratio of TE mould and TM mould is equal to tg θ.PPLN ridge waveguide transmits TM mould and TE mould simultaneously, Now the TM mould of flashlight and the TM mould of pump light occur cascade and frequency to react with difference frequency, produce conversion ideler frequency Light TM mould, the TE mould of flashlight is not involved in cascade during fl transmission and frequency reacts with difference frequency.PPLN Ideler frequency light TM mould, flashlight TE mould and pump light TE mould that ridge waveguide produces continue onwards transmission, arrive 90 ° of rotating mirrors of faraday.90 ° of rotating mirrors of described faraday, make flashlight, pump light and conversion There are 90 ° of rotations in the polarization state of ideler frequency light, completes the mutual phase transformation between TE and TM both of which and be allowed to anti- Penetrate, come back for reverse transfers.Produce when the rotary reflection of 90 ° of rotating mirrors of faraday makes fl transmission Raw ideler frequency light TM mould is changed into TE mould, flashlight TE mould is changed into the TE mould of TM mould, linear polarization pump light It is changed into TM mould, and transfers reverse transfers entrance PPLN ridge waveguide, the TM mould of flashlight new transition and pumping to The TM mould of light new transition occurs cascade and frequency to react with difference frequency, produces new conversion ideler frequency light TM mould, ideler frequency The TE mould that light is newly changed is not involved in cascade and frequency reacts with difference frequency, by PPLN ridge waveguide.Conversion ideler frequency light After TM and TE mould, reaction, remaining pump light continues the second port of reverse transfer entrance optical circulator, turns Change ideler frequency light TM and TE mould to be exported by optical circulator the 3rd port.After reaction, remaining pump light is through the ring of light Row device the first port continues to be stopped by optoisolator during reverse transfer, reflect, and will not return pump light and letter The input of number light, but again return to PPLN ridge waveguide further through optical circulator the second port.

After reacting with difference frequency with frequency, remaining pump light is with the conversion ideler frequency light the 3rd port from optical circulator Output, is recycled by the first fiber grating and the reflection of the second fiber grating, return PPLN ridge waveguide.Farad The magneto-optic memory technique of the 90th DEG C of rotating mirror can absorb approximation frequency doubled light and frequency light, play and frequency light wave The effect of wave filter.If produce in PPLN ridge waveguide during fl transmission and frequency light has residue, to reversely The cascade reaction of transmission is unfavorable.

Transmission and course of reaction in be perfect condition, i.e. entirely without loss in the case of, after conversion The polarization direction of line polarized light and vertical X-axis angulation θ=45 °, say, that the pumping of linear polarization Light resolve in PPLN ridge waveguide amplitude scale be 1 to 1 TM mould and TE mould.But due to PPLN ridge The loss of waveguide, the existence of the various losses such as coupling loss, θ will deviate 45 ° minutely.Another Aspect, TM mould participates in reaction when fl transmission；And during TE mould fl transmission, be not involved in reaction, but have one Fixed loss, reduces the conversion efficiency making TE mould participate in reaction when reverse transfers, causes The conversion efficiency of whole TE mould is less than the conversion efficiency of TM mould, therefore pump light when requiring to inject PPLN fiber waveguide TE mould power somewhat larger, to make up the loss of TE mould.Therefore the value of θ should be greater than 45 °, really Determine method as follows:.

According to pump light TE mould and TM mode amplitude than with ideler frequency polarization degree (polarized light intensity and total light intensity Ratio) graph of relation.

TE mould and the TM mode amplitude of the first pump light are respectively A_P1And A (TE)_P1(TM),

TE mould and the TM mode amplitude of the second pump light are respectively A_P2And A (TE)_P2(TM),

After conversion, TE mould and the TM mode amplitude of unused light are respectively A_iAnd A (TE)_i(TM),

Require that the TE mould often restrainting pump light is equal with the ratio of TM mode amplitude,

That is: tg θ=Ap1 (TE)/Ap1 (TM)=Ap2 (TE)/Ap2 (TM),

Meanwhile, the TE mould of ideler frequency light is equal with TM mode amplitude,

That is: Ai (TE)=Ai (TM),

The analytic solutions formula of ideler frequency light is:

$A_i\≈{\mathrm{i\ω}}_i{\mathrm{\κ}}_{\mathrm{DFG}}{A}_s^{*}\frac{i}{2}{\mathrm{\ω}}_{\mathrm{SF}}{\mathrm{\κ}}_{\mathrm{SFG}}{A}_{P1}{A}_{p2}\underset{0}{\overset{L}{\∫}}\exp \left({\mathrm{i\Δk}}_{\mathrm{DFG}}z\right)\mathrm{zdz}=-0.5{\mathrm{\ω}}_i{\mathrm{\κ}}_{\mathrm{DFG}}{\mathrm{\ω}}_{\mathrm{SF}}{\mathrm{\κ}}_{\mathrm{SFG}}{A}_{P1}{A}_{p2}{A}_s^{*}$

$\×\{[\frac{L}{{\mathrm{\Δk}}_{\mathrm{DFG}}}\sin \left({\mathrm{\Δk}}_{\mathrm{DFG}}L\right)+\frac{\cos \left({\mathrm{\Δk}}_{\mathrm{DFG}}L\right)-1}{{{\mathrm{\Δk}}^2}_{\mathrm{DFG}}}]$

$+i[\frac{1}{{{\mathrm{\Δk}}^2}_{\mathrm{DFG}}}\sin \left({\mathrm{\Δk}}_{\mathrm{DFG}}L\right)+\frac{\cos \left({\mathrm{\Δk}}_{\mathrm{DFG}}L\right)L}{{\mathrm{\Δk}}_{\mathrm{DFG}}}]\},$

Above-mentioned condition is substituted into the analytic solutions formula of ideler frequency light, draws pump light TE mould and TM mode amplitude Than the graph of relation with ideler frequency polarization degree (polarized light intensity and the ratio of total light intensity).By on this curve Obtain the ratio of TE with TM amplitude corresponding when ideler frequency polarization degree is zero, the value of tg θ, i.e. try to achieve angle θ.

In this method fine adjustments line polarized light conversion equipment, the magnetic induction density B of faraday cell, the trickleest The polarization direction of the linear polarization pump light after the conversion of resonance line polarized light conversion device is become with vertical X-axis Angle, θ, making TM mould that linear polarization pump light decomposes in PPLN ridge waveguide and TE mode amplitude ratio is 1 to 1.

Compared with prior art, one of the present invention cascade and frequency and difference frequency AOWC and conversion side The advantage of method is: 1, PPLN ridge waveguide and the combination of faraday rotator mirror, solves well Conversion ideler frequency light and the polarization relevant issues of flashlight, flashlight polarization direction does not affect conversion ideler frequency light Intensity；2, by the magnetic induction density B of faraday cell in fine adjustments line polarized light conversion equipment, so that it may Change the polarization direction of pump light, using different PPLN ridge waveguide, having different various loss factors Time, if the pump light output wavelength of two tunable external cavity lasers of regulation, then regulate faraday cell Magnetic induction density B, fine tune θ, the wavelength convert unrelated with flashlight polarization state can be realized, relatively Wavelength conversion efficiency, favorable expandability is improved in wide wave-length coverage；3, the introducing of PPLN ridge waveguide, improves The conversion efficiency of conversion ideler frequency light；Reflectance spectrum centre wavelength is two optical fiber light of two pump wavelength Grid, can reflect the pump light having neither part nor lot in and frequently reacting with difference frequency, are allowed to return PPLN ridge waveguide recycling, Improve the utilization rate of pump light, improve conversion efficiency；4, polarize between flashlight and conversion ideler frequency light The group delay brought, by the rotational automatic compensation of polarization of 90 ° of rotating mirrors of faraday in transmitting procedure , so the most there is not polarization dependent loss.

Accompanying drawing explanation

Fig. 1 is this cascade and frequency and difference frequency AOWC example structure schematic diagram；

Fig. 2 is the structural representation of the PPLN ridge waveguide in Fig. 1；

Fig. 3 is the line polarized light conversion device structure schematic diagram in Fig. 1；

Fig. 4 be this cascade and frequency with degree of polarization in the conversion method embodiment of difference frequency AOWC with The graph of relation of the TE mould that linear polarization pump light decomposes in the waveguide and the ratio of TM amplitude；

Fig. 5 is the conversion efficiency of this cascade and frequency with the conversion method embodiment of difference frequency AOWC Graph of relation with signal light wavelength；

Fig. 6 is the conversion efficiency of this cascade and frequency with the conversion method embodiment of difference frequency AOWC Graph of relation with flashlight polarization angle；

Figure is numbered:

1, the first laser instrument, 2, second laser, the 3, first Polarization Controller, the 4, second polarization control Device processed, 5, Polarization Controller, 6, line polarized light conversion equipment, the 61, first faraday cell, 62, Two faraday cells, the 7, first photo-coupler, the 8, second photo-coupler, 9, erbium-doped fiber amplifier, 10, optoisolator, 11, optical circulator, 12, PPLN ridge waveguide, 13,90 ° of rotary reflections of faraday Mirror, the 14, first fiber grating, the 15, second fiber grating.

Detailed description of the invention

Below in conjunction with embodiment and accompanying drawing, the present invention is further detailed explanation.

A kind of cascade and frequency and difference frequency AOWC embodiment

A kind of cascade and frequency with difference frequency AOWC embodiment as it is shown in figure 1, include the first laser instrument 1, second laser the 2, first Polarization Controller the 3, second Polarization Controller 4, Polarization Controller 5, line are inclined Shake light conversion device the 6, first photo-coupler the 7, second photo-coupler 8, erbium-doped fiber amplifier 9, light every From device 10, optical circulator 11, PPLN ridge waveguide 12,90 ° of rotating mirrors 13 of faraday, the first optical fiber light Grid 14 and the second fiber grating 15.

First laser instrument 1 and second laser 2 are tunable external cavity laser, the first pump light sent Wavelength is 1530nm, the second pump wavelength is 1570nm, is respectively connected to the first Polarization Controller 3 and second Polarization Controller 4, the output of the first Polarization Controller 3 and the second Polarization Controller 4 is each to be accessed through polarization maintaining optical fibre Line polarized light conversion equipment 6, line polarized light conversion equipment 6 changes the polarization of the pump light TM mould of X-direction polarization Direction, the polarization direction of the linear polarization pump light after conversion is parallel with the cross section of PPLN ridge waveguide, and with Vertical X-axis is at an angle of θ.Two bunch polarized pump soft exchange the first photo-couplers 7 after conversion couple, The second photo-coupler 8 is accessed again together with the flashlight of the random polarization state through Polarization Controller 5, second The output of photo-coupler 8 accesses erbium-doped fiber amplifier 9, and the output of erbium-doped fiber amplifier 9 is through optoisolator 10 the first ports accessing optical circulator 11, the light beam of the fl transmission of optical circulator 11 second port output After PPLN ridge waveguide 12, light beam is reflected by 90 ° of rotating mirrors 13 of faraday, the light beam of reverse transfers Entering again PPLN fiber waveguide 12, the conversion ideler frequency light of generation is output as through the 3rd port of optical circulator 11 The output of this wavelength shifter.

The PPLN ridge waveguide 12 of this example as in figure 2 it is shown, the substrate of this ridge waveguide is lithium niobate crystal chip, ducting layer Cut period polarized mix zinc niobate lithium wafer, substrate and ducting layer for Z and pass through Direct Bonding, the horizontal stroke of ridge waveguide Tangent plane is the XOY plane being perpendicular to Z axis, referred to as Z tangent plane.PPLN ridge waveguide both can transmit TM mould, can pass again Defeated TE mould.The waveguide length of this example PPLN ridge waveguide 12 is 5cm.This example line polarized light conversion equipment 6 is changed After the polarization direction of linear polarization pump light as shown in Fig. 2 double-head arrow line segment, parallel with XOY plane and with Vertical direction X-axis is at an angle of θ.

The line polarized light conversion equipment 6 of this example is as it is shown on figure 3, include the first faraday cell 61 and second farad The magnetic field of box 62, the angle, θ turned over by the line polarized light vibration plane of faraday cell and faraday cell Relational expression is:

θ=VBL

Magnetic induction in B is faraday cell in formula, L is the length of magnetic rotation material, and V is ratio Coefficient, Wei Erde constant.

First, second linear polarization pump light after conversion is respectively connected to the first faraday cell 61 and second farad Box 62.

A kind of cascade and frequency and the conversion method embodiment of difference frequency AOWC

This example uses above-mentioned cascade and frequency and difference frequency AOWC embodiment, and conversion method is as follows:

First, second pump light that first laser instrument 1 and second laser 2 send is respectively connected to the first polarization Controller 3 and the second Polarization Controller 4, adjusting first, second pump light polarization direction is TM mould, through protecting Polarisation fibre tie-in line polarized light conversion device 6, the TM mould pumping of 6 X-direction polarizations of line polarized light conversion equipment It is parallel with the cross section of PPLN ridge waveguide and be at an angle of θ's with vertical direction X-axis that light is changed into polarization direction Line polarized light.The linear polarization pump light of 2 kinds of wavelength after conversion is after the first photo-coupler 7 and through partially The flashlight of random polarization state of controller 5 of shaking is coupled by the second photo-coupler 8 together, then through er-doped After fiber amplifier 9 amplifies, the first port of optical circulator 11 enter, by the second of optical circulator 11 Port output, first time are coupled into PPLN ridge waveguide 12 simultaneously.In PPLN ridge waveguide 12 after conversion Linear polarization pump light is decomposed into TE mould and TM mould, and the amplitude ratio of TE mould and TM mould is equal to tg θ.PPLN ridge ripple Leading 12 and transmit TM mould and TE mould simultaneously, now there is cascade and frequency in the TM mould of flashlight and the TM mould of pump light Reacting with difference frequency, produce conversion ideler frequency light TM mould, the TE mould of flashlight is not involved in during fl transmission Cascade and frequency react with difference frequency.Ideler frequency light TM mould, flashlight TE mould and the pump that PPLN ridge waveguide 12 produces Pu light TE mould continues onwards transmission, arrive 90 ° of rotating mirrors 13 of faraday reflected, come back for backward Transmission, now, the reflection of 90 ° of rotating mirrors 13 of faraday makes the ideler frequency light TM mould produced during fl transmission Be changed into TE mould, flashlight TE mould is changed into TM mould, the TE mould of linear polarization pump light is changed into TM mould, after To being transferred into PPLN ridge waveguide 12, the TM mould of flashlight new transition occurs with the TM mould of pump light new transition Cascade and frequency react with difference frequency, produce new conversion ideler frequency light TM mould, and the TE mould that ideler frequency light is newly changed is not joined React with difference frequency, by PPLN ridge waveguide 12 with cascade and frequency.After changing ideler frequency light TM and TE mould, reaction Remaining pump light continues reverse transfer and enters the second port of optical circulator 11, changes ideler frequency light TM and TE Mould is exported by optical circulator 11 the 3rd port.After reaction, remaining pump light is through optical circulator 11 first end Mouthful continue to be stopped by optoisolator 10, reflect during reverse transfer, the defeated of pump light and flashlight will not be returned Enter end, but again return to PPLN ridge waveguide 12 further through optical circulator 11 second port.When with frequency and difference After frequency reaction, remaining pump light exports, by first from the 3rd port of optical circulator 11 with conversion ideler frequency light Fiber grating 14 and the second fiber grating 15 reflect, return optical circulator 11, again entrance PPLN ridge waveguide 12 Recycling.

In fine adjustments line polarized light conversion equipment 6, the magnetic induction of first, second faraday cell 61,62 is strong Degree B, can fine tune line polarized light conversion equipment 6 conversion after linear polarization pump light polarization direction with Vertical X-axis angulation θ, makes TM mould and TE mould that linear polarization pump light decomposes in PPLN ridge waveguide 12 Amplitude scale is 1 to 1.

Fig. 4 show the TE mode amplitude that in the present embodiment, degree of polarization and linear polarization pump light decompose in the waveguide The relation curve of the ratio of Ap (TE) and TM mode amplitude Ap (TM), from curve in figure, degree of polarization is 0dB Time, TE mould is 1.096 with amplitude ratio Ap (the TE)/Ap (TM) of TM, i.e. tg θ=1.096, by trigonometric function Obtain the θ value of this example.

The each analog parameter of the present embodiment is: first, second pump wavelength is respectively 1530nm and 1570nm, 774.871nm a length of with frequency light wave, flashlight centre wavelength 1545nm, change ideler frequency optical wavelength 1554.5nm. Polarization cycle is the waveguide loss that waveguide loss is 0.2dB/cm, 775nm of 16.754um, 1550nm wavelength Waveguide length for 0.4dB/cm, PPLN ridge waveguide is 5cm.

It it is the conversion efficiency graph of relation with signal light wavelength of this conversion method embodiment shown in Fig. 5；Figure Middle block curve is the conversion efficiency of TE mould flashlight, and dashed curve is the conversion efficiency of TM mould flashlight. When the polarization direction of first, second pump light is parallel with the cross section of PPLN ridge waveguide 12 and and Vertical Square When X-axis becomes above-mentioned angle, θ (tg θ=1.096), signal light wavelength in the range of 1520nm to 1580nm, The flashlight tuning curve of this example TE mould and TM mould almost overlaps, polarization correlated the least.

It it is the conversion efficiency relation curve with flashlight polarization angle of this conversion method embodiment shown in Fig. 6 Figure, in figure, block curve is the conversion efficiency of TE mould flashlight, and dashed curve is the conversion of TM mould flashlight Efficiency, two the most substantially horizontal lines of curve, it is seen that the polarization angle of the flashlight of this example TE mould and TM mould Unrelated with conversion efficiency.

Above-described embodiment, is only to the purpose of the present invention, technical scheme and beneficial effect the most specifically Bright specific case, the present invention is not limited to this.All done within the scope of disclosure of the invention Any modification, equivalent substitution and improvement etc., within being all contained in protection scope of the present invention.

Claims (6)

1. cascade and frequency and a difference frequency AOWC, including laser instrument, Polarization Controller, photo-coupler, erbium-doped fiber amplifier, optoisolator, optical circulator, PPLN fiber waveguide, 90 ° of rotating mirrors of faraday, it is characterised in that:

nullFirst laser instrument (1) and second laser (2) are tunable external cavity laser，The first pump light sent and the second pump light are respectively connected to the first Polarization Controller (3) and the second Polarization Controller (4)，After the output of the first Polarization Controller (3) and the second Polarization Controller (4) accesses the first photo-coupler (7) coupling、The second photo-coupler (8) is accessed together with the flashlight of the random polarization state through Polarization Controller (5)，The output of the second photo-coupler (8) accesses erbium-doped fiber amplifier (9)，The output of erbium-doped fiber amplifier (9) accesses optical circulator (11) first port through optoisolator (10)，The light beam of the fl transmission of optical circulator (11) second port output is after PPLN fiber waveguide (12)，Light beam is by 90 ° of rotating mirror (13) reflections of faraday，The light beam of reverse transfers enters again PPLN fiber waveguide (12)，The conversion ideler frequency light produced is output as the output of this wavelength shifter from the 3rd port of optical circulator (11)；

Described first pump light, the second pump light and flashlight are C-band；

Described PPLN fiber waveguide (12) is PPLN ridge waveguide, the substrate of this PPLN ridge waveguide is lithium niobate crystal chip, ducting layer is that Z cuts and period polarized mixes zinc niobate lithium wafer, substrate and ducting layer Direct Bonding, and the cross section of ridge waveguide is the XOY plane being perpendicular to Z axis；

Respectively through the first Polarization Controller (3) and first, second pump light tie-in line polarized light conversion device (6) of the second Polarization Controller (4), then access the first photo-coupler (7)；It is parallel with the cross section of PPLN ridge waveguide that the pump light of the TM pattern that line polarized light conversion equipment (8) polarizes X-direction is converted to polarization direction, and is at an angle of the line polarized light of θ with vertical X-axis.

Cascade the most according to claim 1 and frequency and difference frequency AOWC, it is characterised in that:

Described line polarized light conversion equipment (6) includes the first faraday cell (61) and the second faraday cell (62), and the angle, θ turned over by the line polarized light vibration plane of faraday cell with the relational expression in the magnetic field of faraday cell is:

θ=VBL

Magnetic induction in B is faraday cell in formula, L is the length of magnetic rotation material, and V is proportionality coefficient Wei Erde constant,

Described first, second pump light respectively enters the first faraday cell (61) and second faraday cell (62) of line polarized light conversion equipment.

Cascade the most according to claim 2 and frequency and difference frequency AOWC, it is characterised in that:

The output of described first Polarization Controller (3) and the second Polarization Controller (4) is each accesses the first photo-coupler (7) through polarization maintaining optical fibre.

Cascade the most according to claim 3 and frequency and difference frequency AOWC, it is characterised in that:

Being connected to the first fiber grating (14) and the second fiber grating (15) on the optical fiber that described optical circulator (11) the 3rd port is connect, the reflectance spectrum centre wavelength of the first fiber grating (14) and the second fiber grating (15) is respectively the first pump light and the wavelength of the second pump light.

5. the conversion method of a cascade according to claim 4 and frequency and difference frequency AOWC, it is characterised in that:

The first pump light and the second pump light that first tunable laser (1) and the second tunable laser (2) send are respectively connected to the first Polarization Controller (3) and the second Polarization Controller (4), adjust its polarization direction, making the first pump light and the second pump light is TM mould, the output of the first Polarization Controller (3) and the second Polarization Controller (4) is each through polarization maintaining optical fibre tie-in line polarized light conversion device (6), it is parallel with the cross section of PPLN fiber waveguide (12) that the TM mould pump light that line polarized light conversion equipment (6) polarizes X-direction is changed into polarization direction, and it is at an angle of the line polarized light of θ with vertical direction X-axis；Described PPLN fiber waveguide (12) is PPLN ridge waveguide；The linear polarization pump light of 2 kinds of wavelength after conversion is after the first photo-coupler (7), coupled by the second photo-coupler (8) together with the flashlight of the random polarization state through Polarization Controller (5), again after erbium-doped fiber amplifier (9) amplifies, entered by the first port of optical circulator (11), from the second port output of optical circulator (11), it is coupled into PPLN fiber waveguide (12) for the first time simultaneously, in PPLN fiber waveguide (12), the linear polarization pump light after conversion is decomposed into TE mould and TM mould, the amplitude ratio of TE mould and TM mould is equal to tg θ；PPLN fiber waveguide (12) transmits TM mould and TE mould simultaneously, now the TM mould of flashlight and the TM mould of pump light occur cascade and frequency to react with difference frequency, produce conversion ideler frequency light TM mould, and the TE mould of flashlight is not involved in cascade during fl transmission and frequency reacts with difference frequency；Ideler frequency light TM mould, flashlight TE mould and pump light TE mould that PPLN fiber waveguide (12) produces continue onwards transmission, arrive 90 ° of rotating mirrors (13) of faraday；The ideler frequency light TM mould produced when the rotary reflection of 90 ° of rotating mirrors (13) of faraday makes fl transmission is changed into TE mould, flashlight TE mould is changed into TM mould, the TE mould of linear polarization pump light is changed into TM mould, and transfer reverse transfers entrance PPLN fiber waveguide (12) to, the TM mould of flashlight new transition occurs cascade and frequency to react with difference frequency with the TM mould of pump light new transition, producing new conversion ideler frequency light TM mould, the TE mould that ideler frequency light is newly changed is not involved in cascade and frequency reacts with difference frequency, by PPLN fiber waveguide (12)；After changing ideler frequency light TM and TE mould, reaction, remaining pump light continues reverse transfer entrance optical circulator (11) second port, conversion ideler frequency light TM and TE mould are exported by optical circulator (11) the 3rd port, after reaction, remaining pump light was stopped by optoisolator (10), reflects when optical circulator (11) first port continues reverse transfer, again returned to PPLN fiber waveguide (12) further through optical circulator (11) second port；After reacting with difference frequency with frequency, remaining pump light is with conversion ideler frequency light from the 3rd port output of optical circulator (11), is reflected by the first fiber grating (14) and the second fiber grating (15), returns PPLN fiber waveguide (12) recycling.

Cascade the most according to claim 5 and frequency and the conversion method of difference frequency AOWC, it is characterised in that:

The magnetic induction density B of 2 faraday cells in fine adjustments line polarized light conversion equipment (6), the polarization direction of the linear polarization pump light after i.e. fine tune line polarized light conversion equipment (6) is changed and vertical X-axis angulation θ, the TM mould and the TE mode amplitude ratio that make linear polarization pump light decompose in PPLN fiber waveguide (12) are 1 to 1.