Optical Wave guide Transmission

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PROCEEDINGS OF THE IEEE, VOL. 58, NO. 10, OCTOBER 1970

Optical WaveDETLEF

Abstract-As optical commu nication systems an, being smore detail, the need for many different types of optical wabecomes apparent. The applications range from.miniaturecircuit connections to long-distance high-capacity tranlinks. The requirements wi th respect to co st attenuation, dior flexibil ity are vastly diff erent. As different as the specifica


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a divergence angle of 1" one has8=0.5" and t=0.25 nThe corresponding bandwidth limitation restricts pithis kind to systems of fairly modest capacity.111. SURFACE AVEGUIDES

Rather thanusing the reflection at a metallic wallonguide electromagnetic wavesby total internal refleThis is accomplished when the waves propagate in a drical core made of a material of higher refractivethan the surrounding dielectric. Fig. l(b) illustratepropagation mechanism. The critical angle for total inreflection is givenby Snell's law


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Work on long-distance fibers sjust beginning. Ftional fiber applications, attenuations of 1000 dBmore were acceptable.A reduction by almost two omagnitude seems necessary before experiments otancesof the order of kilometerswill become feasi[l l1. This is primarily a material problem. Oxideseem to be the most promising with respect to atteand fiber formation. Hopefully, reducing the ilevels in these glasses (particularly transition metal levels below one part n a million will bring the abloss to something like 10 dB/km [lo]. Avoiding thetion of crystallites during the cooling process should


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Fig. 4. Laser beams pr opagating n a guide withparabolic index profile [24].

over a certain distance the energy is maintained in a Gsian beam. At longer distances this beam breaks up


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GLOGE: OPTICAL WAVEGUIDE TRANSMSSI ON

the same way as the film channel after the mask removed. A detailed description of film guides ancomponents can be found in [44].

VI . IRISGUIDESShort electromagnetic waves propagate in freespso little divergence that, even in he millimeter-wavoccasional interactions with the waves are suffguide them along a straight pipe of practical dim[45]. The interaction may be in the form of irisesat intervals of lengthD, as shown in Fig. 6(a). absorbs the light outside its circular aperture of a


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changes or bends require the insertionof special deflecdevices such as prisms or the mirror arrangements shoin Fig. 6(c).Every mirror is polished and coated for abetion-free reflection and focusing at 45" incidence, andrectional changes are accomplished by rotating the mirrors of a pair with respect to each other. The lens locomprise absorption, reflection, and scattering in the terial and on the surfaces. For currently available antflection coatings, the surface losses prevail and are of order of 1/2 percent or 0.02 dB per lens. The same canachievedwith good dielectric mirror coatings so thamirror pair has abouthe same loss as a lens [55].The sp


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GLOGE: OPTICAL WAVEGUIDE TRANSMISSION

URETHANE FOAM) , - EXHAUSTA P

\ GA

Fig. 8. Section of a gas ens guide showing one counterflow


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ported, but there is no infermation on the resoluachieved [28]. he apertures of presently available gas leprohibit multibeam transmission through this type of gTypical lensguides made of conventional lensemirrors havenegligible aberration even or distancehundreds of kilometers. Mirrors can be made20to 30in diameter without unreasonable effort. The sourccrosstalk which imits the capacity and the transmisdistance of these guides iscattering from the lens or msurfaces.This scattering seems to be somewhat smallemirrors than for lenses. In bothcases itpeaks sharply inforward direction and decreases roughly with the h


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[9] C. G. B. GarrettandD. E. McCumber, ThepropagaGaussian light pulse through an anomalous dispersion Phys. Ret.., vol . 1, pp. 305-313, February 1970.[lo] K . C. K ao and G.A . Hockham, Dielectric-f iber surface for optical frequencies, Proc. EE (L ondon), vol. 1131158, July 1966.[I I ] A. Werts, Propagation de la lumiere coherente danoptiques, Onde Elec.,vol. 4 6 , pp. 957-980, September 1[I21 K . C. K ao and T. W . Davies, Spectrophotometric studlow loss optical glasses-I : single beam method, J . Scvol . 1, ser. 2, pp. 1063-1088, November 1968.[13] R. D. Maurer, L ight scattering by glasses, J . Chem. Phpp. 12061209, December 1956.[I41 A . R . Tynes, A . D. Pearson, and D. L . Bisbee, L oss mand measurements in clad glass fibers and bulk glass (lished).


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[64] D. Gloge and W. H . Steier, Pulse shuttling in a half-mile oplens guide, Bell Syst. Tech. ., vol.47, pp.767-782, May-June 1[65] S . Saito, Y . Friji, and S . Shiraishi, Low-loss laser beam transmisthrough lenses at the Brewster angle, Proc. IE EE Letters), volpp. 78-79, J anuary 1969.[66] G. G oubau and J .R. Christian, Some aspects of beam wavegufor long-distance transmission at optical frequencies, ZEEE TrMicrowave Theory Tech.,vol. M TT -12, pp. 212-220, March 196[67] J . R. Christian, . W. M ink, G.Goubau,andF. K . SchweDi ffractional distortions in beam waveguides with off-axis beamProc. IE EE , vol. 57, pp. 829-831, May 1969.[68] D . Gloge, Regellbse Stiirungen in L insenleitungen, Arch.ElUbertragung,vol. 20,pp. 82-90, February 1966.[69] J . H irano and . Fakutsu, Stabil ity of a light beam in a beam wguide, Proc. IE EE , vol. 52, pp. 1284-1292, November 1964.[70] D. Marcuse, Statistical treatment of light-ray propagation in b


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Optical Wave guide Transmission