DE1941923A1 - Optical coupling for transparent fiber-like light guides - Google Patents

Description

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Nippon SelfOC Company, Limited 7-15, Shiba Gochome, Minato-ku, Tokyo, Japan

Optical coupling for transparent fiber-like light guides

The invention relates to © in © optical © coupling for fa such transparent light guides, in particular convergent light guides, the refractive index of which is different from the Axis decreases radially to the surface, preferably © is it about such © komr © rg®nt © n light guides, whose refractive index is greatest along the Achs® and radial on the axis proportional to the surface to the square of the distance τοη the axis decreases.

In optical transmission systems in which Laserlioht is rerwendet as carrier waves, an accurate Llchtüb @ is rtragungsweg very important mostly nnä difficult to realize su, Sun 'lad b & v & ITSS been vorgasehlagen a number iron lenses and sin fasarartig & r Liehtleiter glass Suaatetoff and the like for Liofotübertragungswegs. The lenses are thereby by aeohanlBohe of X and very easily «κ * your precisely aligned *

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A careful control of the position or the like is therefore necessary! In order to be able to ensure that the lenses are in exactly the right position. On the other hand, the light guides withstand mechanical impacts, only the spatial arrangement of the two end faces of the light guides and the input and output light rays must remain unchanged. Since it is sometimes difficult "to get a long enough light guide for the camouflaged transmission path, a number of light guides have to be arranged in series one behind the other" to be able to realize an optical transmission path, In © in © 3? Iswei "wipe clutch each <- neighboring light guides 1st precise optical Kuppltragsanpassung much" Is this Kupplungaanpassung not ®rr # pulls in ₉ tends a laser light beam Bit © iner Saussian ~ Int © nsltätsvert © ilung iu repeated KonTsrgens and di ^ ergena after Tom © inen, SSUM other light guide sum incidence has been gebraoht "the temd is the periodic Imlerung of Dus? © hm © @ AaRa the laser light beam, DIs change of Dirröhraesaera makes ® @ 11 QH5 gaaauo Länganaiipasoujigan make" mm I "as © 3? liöhtsts? ahl ¥ on gevUnaohter flaekgrößs m tan, Ändörarßtita 1st dit exact Anpaieung la of the coupling with a lens of suitable clay Brenawvite?, wli & ®h®n dan £ £ nd 3.ä © h © n iwaiar light guide unerläB-Ii © 1% , / Uta da9 Itippluags part »su ^ arklelnsra, auö dl · 'de? Lenses as small as possible a @ isu D * r lines al t.

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Liclitleiter _t particularly with the aforementioned Bre "· - chungslnderverteilung indicate broadly enough that AEEN conditions for accurate optical coupling adjustment"

The invention solves the problem in the catfish that © in © Line «Gate seen Ibt which has the same Breohungeindex gradient en like dl · light guide «where the Line · at certain mutual distances from the adjacent end faces of two light guides Is arranged whose optical axis in the optical Axis of the lens lies "-

According to the invention, the refractive index η of the trans parent element »that as a lens for a coupling adaptation is used, essentially duroh di® relationship

b ^

determines, where r is the radial distance from the axis of the element _t n _{0 is} the refractive index along the axis and b is a constant «which denotes the degree of change in the broadeningBlzuUxes,

GMnäB investigations on a medium with the designated refractive index graduation Ton H, Kogelnlk in ^w Th · Bell Syitwa Teohnioal Journal ", Vol, 44, No. 3 (March 1965)" pages 455 to 494 is the focal length f Ton "Inem 1-om Medium given by the expression

2 n ₀ «la

009829/08 64 - ** ~

As can be seen from equation (2), the focal length of the medium, which has a breadth index graduation according to equation (1), is a function of length 1 of the medium and the constant b. In other words, a lens suitable for the invention for optically coupling aweier light guide is obtained by suitable selection of the sizes b and 1. There that loops. If both end faces for lenses are made of a transparent material which has the aforesaid expansion indentation, it is not necessary to obtain the desired curvature, manufacturing is easy and the aberration can be kept small. The refractive index of the light guides has a gradient given by equation (1). TJM having the Gaussian XntensitätS'- Ψ & Τ distribution a "beam of light", with constant Fleekgrößer © dureh in medium of this type transferred su _t of the light beam must be placed on the transmission path than simply © Vieile to accidents having the Fleakgröße _t which by the equation

^W 0 - VTtTST " ^} (3)

given is where Xq represents the wavelength of the light beam in free space. The fleok size Wq is taken as the characteristic pleek size in the following. The light beam that hits the medium with the characteristic electrical size penetrates the medium with the same size. "The exit beam, which emanates from the output end surface, diverges with the distance from the end surface. Therefore, a precise coupling connection is required for each coupling as well as light guides indispensable. Investigations showed that

00 98 29 / 088A

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_{the light beam with the shape W 2} emanating from the convex lens with the focal length f falls on the input end face of the light guide when this is arranged at a distance d2 from the lens. If the convex lens is in turn at a distance d 1 from the exit end face of a conductor, the shape of the light beam emerging from the conductor and incident on the lens is Wg for the distances d _{1 and d 2 the} following relationships then result

W ₁

IT'S

O-- <W ₁ w ₂ / _A o->

Assuming that the characteristic field sizes of the first and second light transmission path are equal to W ^ and W ₂ ι then a lens with the focal length f, dl «offers on the one hand by the (criteria b and 1) to the equation (1 suffice) au, aniertrseits with distances dj and dg sound the end faces of the first or, sweiten Liohtleiter · migdordaet to genügtn 4) .tst ₃ to d # n Btsiehun * gene (and provided that the opti see Aohstn of the lens and d "r light guide aueinandör are disengaged, the possibility for an exact coupling »impa« - sung between sw # i light guides, Auoh is then m

009829 / 08S4

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on hand that the reduction in size of the coupling Bttile can be achieved by keeping the lengths ü <\ + dg small. If these conditions are met, the focal length βο would be as short as possible.

The invention is based on an exemplary embodiment a sohematicallyin drawing waiter explained » which is an axial section through an according to the invention Coupling arrangement shows.

The coupling arrangement according to the invention for two light conductors contains a lens 3 with the "Broöhungsindesnrertsllung" (the line is located between the light conductors .1 and 2, the same spacing as the lens © 3 on white © ». The optical axis of the line © 3 is aligned with the Aoh-Sβ 4-4 * of the light guides 1 and 2. The distances & -J and & 2 like the lens 3 and each of the end faces of the light guides 1 and 2 satisfy the relationship (4). Assume that the constants n ₀ and b in equation (1) for light guide 1 have the values u _o1 and b, | and for the Li oh ti alt sr 2 have the values · n _O 2 ' and b ₂ , the characteristic size W ,, and W ₂ ! in which botraffendan Konstantin has the values n _o j and b ^, so that equation (2) is tuned under the condition "that the right string of equation (4) assumes 0% n® & " aalen wisrt, or. " in other words, the Brennwsit® fd® «* lens 3 d # r condition

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enough.

Thus, d ^ and dg can be determined by adding the calculated sizes * such as di # Fleek sizes YL. and W2 "the focal length f and the equation (4) _r are used"

Because of the chance of scoring called calculations, the optical fibers 1 are _t, the lens 3 and the optical fibers 2 arranged in accordance with "A light beam 5> of the Graußßian intensity distribution having pflanat with the unchanged spot size W" j in the optical fiber 1, and emerges at the outlets face with the fleece size W / j as output light beam 5 from «The output light beam is brought to the lens © 3 £ to incidence. In this case, the light beam 5 is converged on a light beam 6 which has a fleece size Wg. which is caused by the lens 3. The light beam 6 is then brought to incidence on the light guide 2. Since the spot size is adapted to the characteristic spot size of the light guide, no divergence or convergence is brought about in the light guide 2.

As can be seen from the foregoing, "there will be a largely downsized optical coupling assembly for convergent light guides when the necessary adaption conditions are met according to the invention a single line which reaches the same Has Breohungeindex distribution like the light guide.

Claims

-6-009829 / 0864

Claims (1)

-β - ■■■■ - - Patiat am ρ r ti β h e (j) Optical coupling for transparent fiber-like light guides "in particular convergent light guides * whose refractive index varies on the axis radially to the surface" gek en aaei β has d VL τ 9 h a lens (3) "which has the same refraction index gradient as the light guide ( 1 «2), whereby the lens (3) is arranged at certain distances on both sides (d« j, d ^) opposite the adjacent end faces of a light guide whose optical axis (4-4 *) is in the optical axis ( 6) the lens cherishes. . S. Optical coupling according to claim 1, there being ο hge ke η η ae 1 eh η et, that the refraction - iadexgradlent of the lens (3) is given by the loan (1 - r is the radial distance τοη of the AChSe ₉ S ₀ which is a constant along the Acha · unA b. and that the distance (d ^) swisehen de »a light guide (1) and the lens (3) and the Ab ettjui Cd ₂ ) swiiohea the line Ό) and de »light guide (2) bestlamt 1st through the 009629/0864 - t bit f ₀ · ■ CW ₁ W ₂ / λ ο) wobtl di "" in "oba?" kteristiioh · Fl "sckgrö3 * Tone d * B Liciitleiter (1) fiUBS" h "adea Lichtftr * lil * s and W ₂ 'ia · ohaa ** kt" 3 "i" tiioii * FItcKgröB · de · «uf dtn UchUtiter (2) tinfalleiideii light · trahio 1 ·« and ₀ di · W »ll # iaäae * d ·· Lioht» trajats i «free * • η lam i> t and wok« lf dl Breast *! T dtr Lin (3) 3 · Opti * «h · lnppluag aaeb Aaiprueh 2, ί ι i a r β h I «kianitl9licit, d« £ di · e & asukt · " FleokgyöJ · through di · Glaieliuiig « _Λ . ( »Ae .1 / 2 let. KmtiltSBf αα # & jUipyueiuus 1 I »is |, da · d ii r · h iiki & uil th» it, isliii fd «v Uw (3)» Mtlmt ItI dttvtli di · f · _mi . ,,,
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