CN1554960A - Wave guide type light adjustable attenuator and its compensating method for polarizing relative loss - Google Patents

Abstract

The present invention utilizes polarization related compensator to polarizing rotate the optical signal and make polarization direction of the light beam rotate by 75-105 deg in the efficiency of 45%-55%, so as to complete the compensation of polarization related loss. The light adjustable attenuator includes input signal, polarization related compensators, couplers, phase modulator, light guiding arms, protecting layer, base layer and output light signal. The present invention is superior to traditional mechanical light adjustable attenuator, and has small volume, capacity of being form array, fast operation speed, low cost and easy matching with other device and system. The present invention may be used for protecting detector or analysis instrument in various sensing system, optical communication system, etc.

Description

The compensation method of waveguide type adjustable optical attenuator and Polarization Dependent Loss thereof

Technical field:

The invention belongs to adjustable optical attenuator, particularly a kind ofly solve Polarization Dependent Loss in the waveguide adjustable optical attenuator and insert the technology of loss.

Background technology:

Adjustable optical attenuator is that a kind of intensity its optical signalling of process decays to protect optical signalling sensitive detection parts and the system under any condition by given requirement.Maximum fading depth is generally 20dB or greater than 20dB in the industrial products.Adjustable optical attenuator mainly is used in optical fiber telecommunications system, optical instrument test macro and the optical fiber sensing system.

The variable optical attenuation device produces in the North America the earliest, and is widely used, but nearly all is mechanical discrete device technically.In the peak time of North America optical communication, the adjustable optical attenuator of waveguide type has been subjected to great attention, and some new companies are as an important product development, and has developed product, and sale has been arranged on market.At first on performance, the structure of array brings great convenience to some users that are engaged in the research and development of novel optical network, fundamentally overcome the inconvenience that mechanical device is caused in network, because in these new networks, other used device such as Wavelength division multiplexer/demultiplexer spare AWG, optics get that to add device and matrix optical switch etc. also be waveguiding structure.In actual applications, the subject matter that the waveguide type adjustable optical attenuator is exposed is Polarization Dependent Loss, and works as this problem by some companies, and after solving with the electronics feedback technique, its higher cost has limited the promotion and application of waveguide type adjustable optical attenuator.

The mechanical type adjustable optical attenuator of institute's widespread use has volume big both at home and abroad at present, and operating speed is slow, and the cost height is difficult for and shortcomings such as other fiber optic telecommunications equipment and system are complementary.In addition, in recent years, the application of optical fiber sensing technology in military weaponry had new demand to adjustable optical attenuator, so can't satisfy the anti-vibration requirement of this new application based on the adjustable optical attenuator of mechanical technique.

Big for fundamentally solving in the mechanical technique volume, operating speed is slow, and the cost height is difficult for and shortcomings such as other fiber optic telecommunications equipment and system are complementary, and is an inevitable choice based on the technology or the method for the small-sized or miniature no moving-member of physical process.Utilize most passive devices in the guide technology research and development optical communication system is the important starting point of information capacity, efficient and the ratio of performance to price of attempting to increase substantially optical fiber telecommunications system always.Especially at the same time it is big to overcome in the mechanical type adjustable optical attenuator volume, and operating speed is slow, the cost height, be difficult for being complementary with other device or shortcomings such as integrated and freedom from vibration difference in have unique advantages.Thereby, obtained sufficient research and development based on the various optical communication passive devices of guide technology in the more than ten years in the past.Such as, Wavelength division multiplexer/demultiplexer spare, matrix optical switch, the research and development of devices such as wave filter have all obtained substantial progress.Yet Polarization Dependent Loss and optical insertion loss but are the major limitation of waveguide type adjustable optical attenuator widespread use in system always in the guide technology.

Content of the present invention: big for fundamentally solving in the mechanical technique volume, operating speed is slow, and the cost height is difficult for and shortcomings such as other fiber optic telecommunications equipment and system are complementary; The problem of Polarization Dependent Loss and optical insertion loss in the guide technology, but the objective of the invention is to provide the little and array of a kind of volume, operating speed is fast, cost is low, easily and the waveguide type adjustable optical attenuator that is complementary of other fiber optic telecommunications equipment and system and the compensation method of Polarization Dependent Loss thereof.

Method of the present invention: the compensation method of Polarization Dependent Loss: utilize polarization correlative compensation device that optical signalling is carried out polarization rotation, make its have through light beam of polarization correlative compensation device with 50% ± 5% efficient half-twist ± 15 °, make Polarization Dependent Loss $\mathrm{PDL}=10\left|{\log }_{10}\left(\frac{{\mathrm{\η}}^{\mathrm{TE}}}{{\mathrm{\η}}^{\mathrm{TM}}}\right)\right|\≈0,$ Finish compensation at last to Polarization Dependent Loss.Adopt shaped form waveguide, stepped waveguide to design polarization correlative compensation device, shaped form or step-like periodicity depend on the light refractive index of waveguide material, the size of waveguide channels.

Adjustable optical attenuator all is to be used for protecting the optical signalling detector in the network of optical system test and optical communication.The present invention proposes a kind of low Polarization Dependent Loss; low optical is inserted the waveguide type adjustable optical attenuator of loss; it comprises polarization correlative compensation device 2; coupling mechanism 3; light-conducting arm 5a; light-conducting arm 5b; coupling mechanism 6; protective seam 8 around polarization correlative compensation device 7 and these parts; phase-modulator 4; the lower surface of protective seam 8 is fixedlyed connected with the upper surface of substrate 9; the output terminal of polarization correlative compensation device 2 is connected with the input end of coupling mechanism 3; two output terminals of coupling mechanism 3 are connected with the front end of light-conducting arm 5b with light-conducting arm 5a respectively; two input ends of coupling mechanism 6 are connected with the rear end of light-conducting arm 5b with light-conducting arm 5a respectively; the output terminal of coupling mechanism 6 is connected with the input end of polarization correlative compensation device 7, and phase-modulator 4 is fixedlyed connected with the upper surface of protective seam 8.Phase-modulator 4 of the present invention adopts hot optical modulation or electrooptical modulation.

When the present invention works: as shown in Figure 3, first coupling mechanism 3a makes light signal be divided into the light beam that two beam intensities all equate by 50% ratio, a branch of through by second coupling mechanism 3a two-beam being combined into again behind two light-conducting arm 5a and the 5b then, and the delivery outlet output that is intersecting with the light signal input port.Can regard a complete directional coupler as on the Joint effect principle of the coupling mechanism of these two 50% efficient.In fact, the coupling mechanism 3 and the coupling mechanism 6 that are used for adjustable optical attenuator can adopt two Y type forks, as shown in Figure 4: first Y type fork makes light signal be divided into the light beam that two bundle phase places and intensity all equate, then through forming a branch of by the method that optics superposes two-beam by second Y type fork again behind two light-conducting arms.If the not optical loss of taking into account system, and phase-modulator produces an optical phase difference Δ φ between two light-conducting arms, then have at the photosystem output terminal to be output as:

$P_{\mathrm{out}}=P_{\mathrm{in}}{\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="A20031010995400181.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2\frac{\mathrm{\&Delta;\&Phi;}}{2},$ Or ${\mathrm{\&eta;}}_{\mathrm{out}}=10{\log }_{10}\left(\frac{P_{\mathrm{out}}}{P_{\mathrm{in}}}\right)---\left(1\right)$

(1) the previous equation in the formula is that power is represented, a back equation is that dB represents.Wherein, P _InAnd P _OutRepresent optics input and output power respectively.Optical loss (is used η _LossExpression) comprises that the loss of optics (uses η _PrExpression) and the Y excess loss that structure causes that diverges (use η _ExExpression), η is obviously arranged _Loss=η _Pr+ 2 η _ExIf the present invention is without any phase modulation (PM), when promptly static, η ' _Out=η _Out-η _Loss, and this η _LossIt is exactly the optical loss on the device of the present invention.

As shown in Figure 1, input optical signal 1, enters coupling mechanism 3 then and is divided into two bundles and enters two light-conducting arms respectively by 50% ratio rotation 90 through its polarization direction, polarization correlative compensation device 2 back.Through behind these two isometric light-conducting arms, be combined into by coupling mechanism 6 a branch of, again through making its remaining polarization relevant difference obtain calibration behind the polarization correlative compensation device 7.At last by output terminal output becoming light signal 10.If it is 0 that phase-modulator 4 produces phase change, output light signal 10 is maximum.The increase of the phase change that produces along with phase-modulator 4, output light signal 10 can reduce gradually.The present invention utilizes polarization correlative compensation device 2 and polarization correlative compensation device 7 to make output light signal 10, and under any circumstance Polarization Dependent Loss all can be very little.

Fig. 2 has provided the structure of two kinds of phase-modulators commonly used, and phase-modulator is to phase change of a light signal generating, and Fig. 2 (a) is a kind of hot optical modulations, and its phase-modulator is a well heater; Fig. 2 (b) is the electrooptical modulation mode, and its phase-modulator is a pair of electrodes.

In the waveguide process, because waveguide channels processing back is different at the last stress of different directions, this has just caused birefringence effect, and promptly material light refractive index that TE light and TM light are reacted is different (is n ^TEAnd n ^TMDifferent).So the coupling efficiency of coupling mechanism can not be 50% simultaneously, generally uses k ^TEAnd k ^TMExpression.Simultaneously, because birefringence effect, device is in operating process, and its modulation effect also is different to the light wave of two polarization directions, i.e. Δ n ^TEWith Δ n ^TMDifferent), so corresponding phase modulation is also different, we use ΔΦ ^TEAnd ΔΦ ^TMExpression obviously has

ΔΦ ^TE=2 π L Δ n ^TE/ λ and ΔΦ ^TM=2 π L Δ n ^TM/ λ (2)

Wherein L is modulated waveguide geometrical length, and λ is the aerial wavelength of light wave.If phase modulation (PM) adopts hot optical modulations such as Fig. 2 (a), the temperature variation and the hot light of material (TO) the coefficient d n that cause by well heater of amount of phase modulation then ^TE/ dT and dn ^TM/ dT determines.So the light refractive index variable quantity on polarization direction on TE and the TM two is

${\mathrm{\&Delta;n}}^{\mathrm{TE}}=\frac{{\mathrm{dn}}^{\mathrm{TE}}}{\mathrm{dT}}\&CenterDot;\mathrm{\&Delta;T},\mathrm{\&Delta;}{n}^{\mathrm{TM}}=\frac{{\mathrm{dn}}^{\mathrm{TM}}}{\mathrm{dT}}\&CenterDot;\mathrm{\&Delta;T}---\left(3\right)$

If phase modulation (PM) adopts electro-optical method such as Fig. 2 (b), then amount of phase modulation is by electric light (EO) coefficient (r of electro-optical transducer material ^TEAnd r ^TM) and added electric field intensity (E) come to determine.So the light refractive index variable quantity on polarization direction on TE and the TM two is

$\mathrm{\&Delta;}{n}^{\mathrm{TE}}=-\frac{1}{2}{r}^{\mathrm{TE}}{\mathrm{<figure-callout\; id="3"\; label="n\; TE"\; filenames="A20031010995400161.png"\; state="\{\{state\}\}">n</figure-callout>}}_{\mathrm{TE}}^{}\&CenterDot;E,\mathrm{\&Delta;}{n}^{\mathrm{TM}}=-\frac{1}{2}{r}^{\mathrm{<figure-callout\; id="3"\; label="TM\; n\; TM"\; filenames="A20031010995400161.png"\; state="\{\{state\}\}">TM</figure-callout>}}{n}_{\mathrm{TM}}^{}{}_3^{}\&CenterDot;E---\left(4\right)$

Suppose P ^TEAnd P ^TMRepresent the normalization output efficiency of TE light and TM light respectively, then have

$P^{\mathrm{TE}}={4k}^{\mathrm{TE}}(1-k^{\mathrm{TE}}){\cos }^2\left(\frac{{\mathrm{\&Delta;\&Phi;}}^{\mathrm{TE}}}{2}\right)\mathrm{and}---\left(5\right)$

$P^{\mathrm{TM}}={4k}^{\mathrm{TM}}(1-k^{\mathrm{TM}}){\cos }^2\left(\frac{{\mathrm{\&Delta;\&Phi;}}^{\mathrm{TM}}}{2}\right)$

According to the definition of Polarization Dependent Loss (PDL), we have

$\mathrm{PDL}=10|{\log }_{10}\left(\frac{P^{\mathrm{TE}}}{P^{\mathrm{TM}}}\right)---\left(6\right)$

As seen, Polarization Dependent Loss (PDL) all exists at any state.According to formula (6), the removing method of Polarization Dependent Loss is as follows:

We add a polarization correlative compensation device respectively at the Mach-Zehnder interferometer two ends that are made of coupling mechanism 3a, light-conducting arm 5a, light-conducting arm 5b, coupling mechanism 6a, as shown in Figure 1.Wherein, polarization correlative compensation device 2 before being called of input end, and be called rear polarizer correlative compensation device 7 at output terminal.Polarization correlative compensation device can directly pass through waveguide design, it is had the light beam through it is rotated 90 with 50% efficient.Therefore, by means of this preceding polarization correlative compensation device, the new output of Mach-Zehnder interferometer can be write as following new form:

$P_{\mathrm{New}}^{\mathrm{TE}}=2[k^{\mathrm{TE}}(1-k^{\mathrm{TE}}){\cos }^2\left(\frac{{\mathrm{\&Delta;\&phi;}}^{\mathrm{TE}}}{2}\right)+k^{\mathrm{TE}}(1-k^{\mathrm{TE}}){\cos }^2\left(\frac{{\mathrm{\&Delta;\&phi;}}^{\mathrm{TE}}}{2}\right)]---\left(7\right)$

$P_{\mathrm{New}}^{\mathrm{TM}}=2[k^{\mathrm{TE}}(1-k^{\mathrm{TE}}){\cos }^2\left(\frac{{\mathrm{\&Delta;\&phi;}}^{\mathrm{TE}}}{2}\right)+k^{\mathrm{TE}}(1-k^{\mathrm{TE}}){\cos }^2\left(\frac{{\mathrm{\&Delta;\&phi;}}^{\mathrm{TE}}}{2}\right)]$

Obvious P ^TEAnd P ^TMEquate, so there is new Polarization Dependent Loss expression formula to be:

${\mathrm{PDL}}_{\mathrm{New}}=10\left|{\log }_{10}\left(\frac{P_{\mathrm{New}}^{\mathrm{TE}}}{P_{\mathrm{New}}^{\mathrm{TM}}}\right)\right|=0---\left(8\right)$

Then the present invention has eliminated Polarization Dependent Loss.

In fact, rear polarizer correlative compensation device is that not have the effect in other words of practical function be unessential.If the input port of device and output port are given, only the input end that needs a polarization correlative compensation device to be placed on the Mach-Zehnder interferometer gets final product, and post-compensators can be saved.If both's usefulness, input and output side can be general.

Advantage of the present invention:

In the waveguide device of background technology, the beam splitting effect of coupling mechanism still depends on the birefringent phenomenon of material, makes splitting ratio can depart from 50%, and finally causes Polarization Dependent Loss than bigger based on the Mach-Zehnder interferometer structure of Y fork.So usually the Mach-Zehnder interferometer is generally with the Y structure that diverges.But all there is the problem of Polarization Dependent Loss in they.The present invention utilizes the polarization correlative compensation device of polarization correlative compensation method design to solve the Polarization Dependent Loss problem of variable optical attenuation device.

Traditional adjustable optical attenuator overwhelming majority is mechanical, regardless of its performance, variable optical attenuation device itself all is discrete at present, bring inconvenience to use, and adopt the present invention and utilize guide technology to solve the problem in the conventional art, can realize the array of variable optical attenuation device, make the volume of variable optical attenuation device little, easily and other fiber optic telecommunications equipment and system be complementary.

As previously mentioned, guide technology is further innovation and the inexorable trend that develops of optic communication device.And for the device of widespread usage in the such optical communication of adjustable optical attenuator, Polarization Dependent Loss is a significant obstacle moving towards guide technology.Though this problem can be resolved by the feedback technique of electronics, this method makes device cost improve several times, to such an extent as to can't widespread use.Therefore, the adjustable optical attenuator that act as of the present invention moves towards waveguide arrayization technique guarantee is provided, and has reduced cost simultaneously significantly.

Main application of the present invention: the receiver that can be used for each information channel in the optical communication system is protected receiver before, especially can obtain widely applying in the multi-channel information transmission of broadband connections.Secondly, in the development of optical communication and other optical instrument be used for online in producing in batches or sampling Detection is protected detector or analytical instrument.In addition, along with the high-technicalization development of military weaponry, multichannel optical fiber sensing system can have bigger demand to product of the present invention.Along with the increase of quantity of information, the miniaturization of system and the high speed of device operation are an inevitable trend, and superiority of the present invention and competitiveness can be more obvious.

Along with optical communication technique the developing rapidly of China, the hyperchannel transmission can be satisfied the requirement of increasing quantity of information.Therefore, integrated passive devices being had bigger demand, then is the array device of quicker response for the requirement of adjustable optical attenuator naturally.As previously mentioned, along with the high-technicalization of military weapon, multichannel optical fiber sensing system development is rapid, and therefore the application that resembles matrix optical switch and adjustable optical attenuator that matches with it is absolutely necessary.

Description of drawings:

Fig. 1 a is the structural plan figure that the present invention adds polarization correlative compensation device,

Fig. 1 b is the cut-open view of Fig. 1 a in the A-A position

Fig. 2 a is the structural drawing of hot optical phase modulator among the present invention

Fig. 2 b is the structural drawing of electro-optic phase modulator among the present invention

Fig. 3 is the structural drawing that the present invention utilizes coupling mechanism

Fig. 4 is the structural drawing that the present invention utilizes the Y fork

Fig. 5 and Fig. 6 are the performance simulation curves that adopts the adjustable optical attenuator of coupling mechanism

Embodiment: it comprises polarization correlative compensation device 2, coupling mechanism 3, phase-modulator 4, light-conducting arm 5a, light-conducting arm 5b, coupling mechanism 6, polarization correlative compensation device 7, protective seam 8, substrate 9 the present invention.Fig. 2 has provided the structure of two kinds of phase-modulators commonly used, and phase-modulator is a kind of hot optical modulations to phase change of a light signal generating, and its phase-modulator is a heating plate; Be the electrooptical modulation mode, its phase-modulator is a pair of electrodes.

(1) shown in Fig. 2 (a): when the present invention adopts hot optical modulations; polarization correlative compensation device 2, coupling mechanism 3, light-conducting arm 5a, light-conducting arm 5b, coupling mechanism 6, polarization correlative compensation device 7 and protective seam 8 used materials can be silicon dioxide, also can be polymkeric substance.The present invention at first adopts the latter half of doing protective seam 8 in substrate 9; then with template and photoetching technique make waveguide channels constitute polarization correlative compensation device 2, at coupling mechanism 3, light-conducting arm 5a, light-conducting arm 5b, coupling mechanism 6, polarization correlative compensation device 7; afterwards, the first half with protective seam 8 is made on them.At last, make phase-modulator 4, i.e. well heater with the method for photoetching.

(2) shown in Fig. 2 (b): when the present invention adopts the electrooptical modulation mode; substrate 9 can be adopted block electrooptical material; utilize template and metal deposition technology (or ion exchange technique) to make waveguide channels and constitute polarization correlative compensation device 2, coupling mechanism 3, light-conducting arm 5a, light-conducting arm 5b, coupling mechanism 6, polarization correlative compensation device 7; then, above-mentioned parts are coated with protective seam 8 or be not coated with.At last, make phase-modulator 4, i.e. electrode with the method for photoetching.Electrooptical material as waveguide also can adopt film to be produced on the optical substrate 9; utilize template and photoetching technique to make waveguide channels and constitute polarization correlative compensation device 2, coupling mechanism 3, light-conducting arm 5a, light-conducting arm 5b, coupling mechanism 6, polarization correlative compensation device 7; then, above-mentioned parts are coated with protective seam 8 or be not coated with.

(3) adopt shaped form waveguide, stepped waveguide to design polarization correlative compensation device, shaped form or step-like periodicity depend on the size of waveguide optical refractive index, waveguide channels.When the present invention adopted earth silicon material in the hot optical modulations, light refractive index was approximately 1.5, and the size of waveguide channels is approximately 5 * 5 μ m, and curved radius is approximately 1 0-20 μ m, and curved periodicity is approximately 2-4; Step-like ladder height is approximately 0.5-1.5 μ m, and width is approximately 5-20 μ m, and step-like periodicity is approximately 2-4.

The optical insertion loss instance analysis:

When polarization correlative compensation device 2, coupling mechanism 3, light-conducting arm 5a, light-conducting arm 5b, coupling mechanism 6, polarization correlative compensation device 7, protective seam 8 adopt SiO 2 waveguide material and phase-modulator 4 to adopt hot photomodulator; the loss of this SiO 2 waveguide material is minimum, generally can reach 0.1-0.15dB/cm.

When selecting the Y fork for use, the Y fork excess loss of utilizing the SiO 2 waveguide material to be produced can reach 0.25～0.30dB.The total length of device of the present invention is generally 2cm, so the loss on device of the present invention is generally η _Loss=0.7-0.9dB.And minimumly in each optical fiber one waveguide-coupled to produce the 2-3dB loss, to insert loss less than the 1dB device be very difficult so seek out with this structure.

When selecting coupling mechanism for use, if coupling efficiency is 50%, also still input light there is 50% five equilibrium effect, the excess loss of the waveguide coupler of earth silicon material is 0.10-0.15dB.So as shown in Figure 3, the Mach-Zehnder interferometer that is made of coupling mechanism 3a, light-conducting arm 5a, light-conducting arm 5b, coupling mechanism 6a is such as shown in Figure 4: the Mach-Zehnder interferometer that is made of Y fork 3b, light-conducting arm 5a, light-conducting arm 5b, coupling mechanism 6b has the optical loss on the less device.If device length of the present invention also is 2cm, then the optical loss on device of the present invention is generally η _Loss=0.4-0.6dB.Thereby when adopting the coupling mechanism of same material, the insertion loss of device of the present invention just can be less than 1dB.As a Mach-Zehnder interferometer, no matter be Y fork type, type still is coupled.Its output relation all is equation (1).

The Polarization Dependent Loss instance analysis:

We are example with hot light modulating method still.The coupling effect of supposing coupling mechanism is desirable, i.e. k ^TE=k ^TM=0.5, get heater length L=2mm, wavelength X=1550nm, the thermo-optical coeffecient of SiO 2 waveguide material TE and TM light is respectively

With Utilize formula (2)-(4) and formula (6), the optics output (η that we obtain ^TEAnd η ^TM) with the relation of the relation of refining temperature and Polarization Dependent Loss (PDL) and fading depth respectively as Fig. 5 curve and Fig. 6 curve.Therefrom as can be seen, Polarization Dependent Loss increases gradually with the fading depth of device.Behind the polarization correlative compensation device of introducing as shown in Figure 12, the polarization direction of input optical signal 1 can be by with 50% ratio half-twist, the situation of 10 coincidence formulas of optical output signal of the present invention then (8).Along with the generation of polarization correlative compensation device 2 operating errors, Polarization Dependent Loss can occur.Studies show that, when ratio 50 ± 5%, corner is in the time of 90 ± 15 °, Polarization Dependent Loss is generally less than 0.1dB.

Following curve is the performance simulation curve that adopts the adjustable optical attenuator of coupling mechanism: the relation curve of the output of Fig. 5 optics and institute's applied power, the relation curve of Fig. 6 optical polarization dependent loss and fading depth.

Claims (5)

1, the compensation method of the Polarization Dependent Loss of waveguide type adjustable optical attenuator, it is characterized in that: utilize polarization correlative compensation device that optical signalling is carried out the polarization rotation, make its have through the polarization direction of the light beam of polarization correlative compensation device with 50% ± 5% efficient half-twist ± 15 °, then finish compensation to Polarization Dependent Loss.

2, the compensation method of Polarization Dependent Loss according to claim 1, it is characterized in that: adopt shaped form waveguide, stepped waveguide to design polarization correlative compensation device, shaped form or step-like periodicity depend on the size of waveguide optical refractive index, waveguide channels.

3; the waveguide type adjustable optical attenuator; it comprises coupling mechanism 3; phase-modulator 4; light-conducting arm 5a; light-conducting arm 5b; coupling mechanism 6; protective seam 8; substrate 9; two output terminals of coupling mechanism 3 are connected with the front end of light-conducting arm 5b with light-conducting arm 5a respectively; two input ends of coupling mechanism 6 are connected with the rear end of light-conducting arm 5b with light-conducting arm 5a respectively; phase-modulator 4 is connected with protective seam 8; it is characterized in that also including: polarization correlative compensation device 2; polarization correlative compensation device 7; the output terminal of polarization correlative compensation device 2 is connected with the input end of coupling mechanism 3; the output terminal of coupling mechanism 6 is connected with the input end of polarization correlative compensation device 7, and polarization correlative compensation device 7 is made output terminal output light signal 10.

4, waveguide type adjustable optical attenuator; it comprises Y fork 3, phase-modulator 4, light-conducting arm 5a, light-conducting arm 5b, Y fork 6, protective seam 8, substrate 9; two output terminals of Y fork 3 are connected with the front end of light-conducting arm 5b with light-conducting arm 5a respectively; two input ends of coupling mechanism 6 are connected with the rear end of light-conducting arm 5b with light-conducting arm 5a respectively; phase-modulator 4 is connected with protective seam 8; it is characterized in that also including: polarization correlative compensation device 2; the output terminal of polarization correlative compensation device 2 is connected with the input end of Y fork 3, and the output terminal of doing of Y fork 6 is exported light signal 10.

5, according to claim 2 and 3 described waveguide type adjustable optical attenuators, it is characterized in that: phase-modulator 4 adopts hot optical modulation or electrooptical modulation.

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