SU1340396A1 - Method of swirching optical radiation - Google Patents

Abstract

The invention relates to methods for switching an optical measurement propagating in two channels, in particular fiber optic, by acousto-optic interaction. The goal is to reduce nepeKpecTHbHt interference between channels. Switched beams are affected by two acoustic volume waves with different frequencies f, and fj, directed at angles corresponding to the angles of the Bragg synchro- nyeme at these frequencies. Moreover, the frequencies are chosen in accordance with the ratio 1.1 f ,, // fVv, & 1.8, where. V, and Vj are the propagation velocities of the first and second bulk acoustic waves with frequencies f, and f, respectively. The angle between the switched beams is determined by calculation from the values of the frequencies and parameters of the acousto-optic medium. - 1 sludge. § (L with NU oo with O5

Description

The invention relates to methods for switching optical radiation propagating in two channels, in particular fiber optic, by acousto-optic interaction of light with an acoustic wave, and can be used in fiber-optic switching systems, typelexers, information processing systems, and the like.

The aim of the invention is to reduce crosstalk between channels.

The drawing shows an acousto-optic interaction scheme on which the proposed method is based.

The method is carried out as follows.

Two beams 1 and 2 of optical radiation are directed through two channels into the acousto-optic medium at an angle b to each other. In region A, where they intersect, both beams are affected by a bulk acoustic wave with a frequency f, propagating in an acousto-optic medium along straight 3. This straight line lies in plane A, perpendicular to the bisector of 00 angle b, and forms with directions Beam Propagation 1 and 2 Angles Corresponding to Bragg Synchronism at Frequency f | . In this case, the angle between the forward 3 and the direction of propagation of the beam 1 is equal to / i | 90 - y, where y, is the Bragg angle for frequency f, and angle b, between straight 3 and beam propagation direction 2 is pt ~ 90 ° + y,.

As a result of the acousto-optic interaction, both beams 1 and 2 undergo diffraction. The diffracted radiation beams propagate at an angle of 0 to each other in the directions

acoustic full. Direct 9 is located in plane A and forms angles with the directions of propagation of beams 1 and 2 corresponding to Bragg synchronism at frequency f. In this case, the angle between the direct 9 and the direction of propagation of the beam 1 is equal to 90 ° | f,,, is the angle

10 Bragg for frequency f, and the angle p, between direct 9 and beam propagation direction 2, is 90 ° - jp. The frequency fj is chosen in accordance with the ratio / 1). In order to

15, when both beams 1 and 2 were exposed to an optical radiation from an acoustic wave with a frequency fJ, channel switching occurred, an angle b between the directions of the beam propagation is necessary

20 1 and 2 set depending on the selected ratio of the frequencies f and fj in accordance with condition (2), if ordinary beams 1, 2 are used, and in accordance with condition (3

25 if unusual beams 1 and 2 of optical radiation are used.

This method can be implemented using both isotropic and anisotropic diffraction. With

30 using isotropic diffraction, the angle 9 between the directions of propagation of the diffracted beams 5,6 of optical radiation is equal to the angle in between the propagation directions

From the original beams 1 and 2; When using anisotropic diffraction, the beams 1 and 2 are directed into the acousto-optic medium so that the bisector 00 of the angle b coincides with the optical

40 axis of this environment. With anisotropic diffraction, the plane of polarization of the diffracted radiation is rotated relative to the initial one by 90, and beams 5, 6 will propagate

5 and 6, lying in the plane 7, which is 45 ° D angle 0 to each other, the value

forms with the initial plane 8 of the propagation of the beams 1 and 2 an angle "6. In this case, the diffracted part of the beam 1 propagates in the direction 5, and the diffracted part of the beam 2 - in the direction 6. For mutual switching of the optical radiation from one channel to another to both beams 1 and 2 in the area of their intersection A, another volume acoustic wave acts fj, propagating in an acousto-optic medium along straight 9, and at the same time terminating the effect of the first volumetric

50

55

which corresponds to the condition (3), if the initial bundles 1 and 2 are ordinary, and the condition (2), if the initial bundles 1 and 2 are extraordinary. This method is completely reversible, i.e. bundles 5, 6 can be input, and bundles 1,2 - output.

We give specific examples of the implementation of the proposed method.

Example 1. Switched optical radiation wavelength And 0.488,. As acousto-optic medium, two consecutive crystals are used.

acoustic full. The straight line 9 is located in the plane A and forms with the directions of propagation of the beams 1 and 2 angles corresponding to Bragg synchronism at the frequency f. In this case, the angle between the direct 9 and the direction of propagation of the beam 1 is equal to 90 ° | f,,, is the angle

Bragg for frequency f, and the angle p between direct 9 and the direction of propagation of beam 2 is 90 ° - jp. The frequency fj is chosen in accordance with the ratio / 1). In order to

impact of both beams 1 and 2 of optical radiation by an acoustic wave with a frequency fJ, switching of channels occurred, an angle b between the directions of the beam propagation is necessary

1 and 2, set depending on the selected frequency ratio f and fj in accordance with condition (2), if ordinary beams 1, 2 are used, and in accordance with condition (3),

if unusual beams 1 and 2 of optical radiation are used.

This method can be implemented using both isotropic and anisotropic diffraction. With

using isotropic diffraction, the angle 9 between the directions of propagation of the diffracted beams 5,6 of optical radiation is equal to the angle in between the propagation directions

of the original beams 1 and 2. When using anisotropic diffraction, beams 1 and 2 are directed into the acousto-optic medium so that the bisector 00 of angle b coincides with the optical

the axis of this medium. With anisotropic diffraction, the plane of polarization of the diffracted radiation is rotated relative to the initial one by 90, and beams 5, 6 will propagate

° D angle 0 to each other, size

which corresponds to the condition (3), if the initial bundles 1 and 2 are ordinary, and the condition (2), if the initial bundles 1 and 2 are extraordinary. This method is completely reversible, i.e. bundles 5, 6 can be input, and bundles 1,2 - output.

We give specific examples of the implementation of the proposed method.

Example 1. Switched optical radiation wavelength And 0.488,. As acousto-optic medium, two consecutive crystals are used.

Bi.npOig, KOTf) pbie are optically isotropic. The value of the refractive index of this material for the specified wavelength Pd Pr 2.65, Select the directions of propagation and frequency values of acoustic waves in acousto-optic crystals: a longitudinal wave in one crystal, the direction of its propagation SO, velocity V, 3.65-10 cm / s, frequency f, 1 GHz; in another crystal, a longitudinal wave, the direction of its propagation is Dlol, the velocity is v 3.4 x 10 cm / s, the frequency f ,, 0.85 GHz. In accordance with the expression (1)

wearing ---- 1.1. Using known dependencies, the Bragg angles are calculated for each wave: 1, D4, 1.31, and the angle 0 4.21 is calculated using formula (2). Two beams 1 and 2 of optical radiation at an angle of 9 4.21 to each other are directed into said crystals 1 1. The crystals are oriented so that the direction 1OOj of a single crystal and the direction 110 of the other crystal are located in the plane 4, which is perpendicular to the bisector of angle 0, and intersects with it. At the same time, the direction of the F and the lOOJ of the first crystal was with the direction of propagation of the beam 1 angle p, 90 - y, 88.56 °, and the direction 1 of the second crystal was with the direction of propagation of the beam 1 angle 90 ° + Ug 91, SG . In the first crystal, a longitudinal acoustic wave with a frequency of ft 1 GHz, propagating in the direction lOn, is excited. In this case, both beams undergo diffraction, and the diffracted beams 5 and 6 propagate in plane 7 at an angle b 0 4.21 to each other. The angle oc, between planes 7 and 8, is determined for isotropic diffraction from the formulas

about 2arctp (). ,

In this example, the angle is od 5.4. To switch the radiation from one channel to another, in the second crystal, an extension of the 1 st acoustic wave with a frequency f of 0.85 GHz is propagated in the direction of

110.-

Example 2. Switched optical radiation wavelength p 1 10, cm. As an acousto-optic medium, TcOj dpl crystals are used, which are statically anisotropic. The magnitudes of the refractive indices of the material for this duration are full, p 2.2, Pd 2-, 35. Choose propagation directions, polarization and frequency of acoustic waves p both crystals shear waves with propagation direction along 110 and direction of oscillation of displacement 110. Speed their distribution in this direction is v, g 0.610 cm / s. The frequency of an acoustic wave excited in one crystal, f 100 MHz, the frequency of an acoustic BOJUibi excited in another crystal, f 66.7 M1 c. In accordance with the expression (1) ratio

-- 15 . Calculate the Bragg angles: g J v

y, 2.05, y, 1.28, and using the formula (2) calculate the angle b 3. Two beams of 1.2 polarized optical radiation direct the r-, said crystals at an angle to each other so that the 1; 1 plane of the IK polarization is orthogonal to /, and the bisector of angle 9 and the latter coincided with the optical axis of the crystals. The crystals are oriented so that the direction of the software of each of them is located in a plane perpendicular to the bisector of angle 9 and intersects with it. In this case, the direction 1TOJ of a single crystal should be 1 with the direction of propagation of the beam.

fj; 90 y, 87.95, and the direction D 1 of the other crystal should be with the beam propagation direction 1 angle / ij 90 4-y – j 91.28. A transverse acoustic wave with a frequency of f, 100 MHz, propagating in the direction 110, is excited in the first crystal. The diffracted beams 5 and 6 propagate in plane 7 at an angle of 0 5.35 to each other. In this case, the orientation of the polarization plane of optical radiation in Hvrx is rotated by 90 relative to the polarization plane of radiation in beams 1 and 2. The angle ab between planes 7 and 8 is determined for anisotropic diffraction from the formula

arccos

(L) 2 (fl) 2

one . J

: ,,

(Il) 2+ (V,

X +

Dt) n

In this example, an angle of about 112.3. In order to switch the radiation from one channel to another, a transverse acoustic wave with a frequency fi of 66.7 MHz, propagating in the direction plOJ, is excited in the second crystal.

Example 3. Switched optical radiation wavelength

l

 0.63-10 cm. As an acousto-optic medium, two successively located PbM pO crystals are used, which have a structure similar to that of TeOj. The values of the main refractive indices for the specified wavelength n are 2.39, n is 2.26.

The directions of propagation, polarization, and frequency values of the acoustic waves are chosen: shear waves in both crystals. The direction of oscillation of the GOY bias. The speed of their spread is this direction v, v 2, cm / s. The frequency f, 200 MHz, the frequency fj "111 MHz. In accordance with the expression WITH the ratio

liYL 8. Ras-,

read for each acoustic wave Legger angle: 0.71; y, 0, D2 and, using formula (2), calculate the angle Q 1.6 °. Two beams 1 and 2 of polarized optical radiation are directed into these crystals at an angle of 1.6 ° to each other so that their plane of polarization is orthogonal to the bisector of angle 0, and the latter coincides with the optical axis of the crystals. The crystals are oriented so that the direction of each of them is located in a plane perpendicular to the bisector of angle 0, and intersects with it. In this case, the direction of the SO of one crystal should be with the direction of propagation of the beam 1 angle / J, 90 + + Y 90 - J, 89.29, and the direction ClOOj of the other crystal should be with the direction padnpocTpa of the beam 1 angle / 3 90 ° - 90.45. A transverse acoustic wave with a frequency of f, 200 MHz, propagating in the direction, is excited in the first crystal.

The diffracted beams 5 and 6 propagate in plane 7 at an angle

d

1.52 to each other. Wherein

about

The orientation of the polarization plane of the optical radiation in them is rotated by 90 relative to the polarization plane of the radiation in beams 1 and 2. The angle 6 6 between planes 7 and 8 is determined by the formula () and is equal in this example to ot ≈ 122.2 °.

To switch the radiation from one channel to another, a transverse acoustic wave with a frequency of f < -1 > 111 MHz, propagating in the direction 100, is excited in the second crystal 10.

Claims (1)

f5 claims The method of switching optical radiation, including the direction of the beams of this radiation into the acousto-optic medium through two channels at an angle B to each other, their deviation by acting on both beams in the region of their intersection by the first acoustic wave with a frequency f, perpendicular to the bisector of angle b, at angles to the direction of propagation of each beam, corresponding to Bragg synchronism at a frequency f " thirty the first acoustic wave, and the switching of optical radiation from one channel to another by acting on both Luchka in the area of their intersection by the second volume acoustic wave 35, propagating in the same plane, which is different in that between the channels, the frequency fj of the second surround acoustic 40 45 50 55 the waves are set different from the frequency f, and directed at angles corresponding to the Brzgg synchro-i bottom at the frequency f to the direction of propagation of each beam of optical radiation, whereby the frequency of the volume of the volume acoustic waves is chosen according to the ratio 1.1 i 6 1.8, (t) livt . a angle 9 between the directions of distribution of the original optical radiation beams is established from the conditions 21  rjfe :) PT (2) for ordinary beams and sin b 2 | (f;). (i). i k ite - Hir -t j ( extraordinary beams, V ,, v are the propagation speeds of the first and second volume acoustic waves with frequencies f, and fi, respectively (3) L, - optical wavelength radiation in a vacuum, Pd, n, are the values of the main refractive indices of the acousto-optical medium. ABOUT Editor I.Ivanova Order 499 Tehred M. Khodanich Proofreader L Circulation 463 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, st. GTroektna, 4 Compiled by L. Arkhontov Tehred M. Khodanich Proofreader L. Patay