DE2513861A1 - OPTICAL FIBER ARRANGEMENT - Google Patents

Description

BLUMBACH · WESER · BERGEN · KRAMER ZWIRNER · HIRSCH 25 I 386 I.

. PATENT LAWYERS IN MUNICH AND V / IESBADEN

Postal address Munich: Patentconsult 8 Munich 60 Radeckestrasse 43 Telephone (089) 88i633 / 883604 Telex 05-212513 Postal address Wiesbaden: Patentconsult 62 Wiesbaden Sonnenberger Straße 43 Telephone (06121) 562943/561998 Telex 04-186237

Western Electric Company, Incorporated

New York, N.Y., U.S.A. J.A. Arnaud 11

Optical fiber assembly

The invention relates to an optical fiber assembly for transmitting electromagnetic wave energy of the optical Spectral range, with a uniform structure, the elements of which are fused together and preferably from the same optically transparent material are formed.

There have been numerous paser waveguide arrangements in recent years as a transmission medium for electromagnetic wave energy in the infrared, visible and ultraviolet spectral range, the so-called. Optical spectral range, proposed

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been. The most common of these fiber arrangements consists of a central, low optical loss (low-attenuation) core, which is covered by an equally low-attenuation cladding with a lower refractive index than the of the core is surrounded. To the desired refractive index relationship To provide, the core material is different from the cladding material or has a different chemical Composition. Because of the non-ideal properties of the interface between the cladding and the core, as a rule optical perturbations in the optical wave energy modes transmitted from the core introduced. These disturbances give rise to numerous problems such as undesirable conversion of guided wave energy from one mode to another, which is accompanied by energy loss and distortion. The unwanted ones Limit effects at the core / clad interface generally the minimum losses that can be achieved with such fibers.

Another well-known fiber waveguide arrangement is characterized by an index of refraction that is radial does not decrease suddenly but continuously from the fiber axis outwards. The radial refractive index change has usually parabolic in shape. Such a fiber structure does not have an abrupt interface like the core-clad fiber and therefore avoids the undesirable interface effects on the guided Wave energy. However, it requires a continuous (e.g. parabolic) change in the chemical composition outward from the fiber axis to the desired radial

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To generate refractive index change. Complicated manufacturing processes are therefore regularly required for the production of such fibers necessary.

In the work of P. Kaiser, E.A. J. Marcatili, and S. E. Miller in Volume 52 of the Bell System Technical Journal, pages 265 bis (February 1973) an optical fiber assembly is described which can be made from a single material with uniform chemical composition. These fibers have an enlarged Central part, which is supported by one or more thin-layer support members with a hollow cylindrical outer tube is connected, wherein all components are preferably made of the same optical fiber material. Depending on the relative cross-sectional sizes of the central enlarged part and the thin support members in the fiber, can be optical wave energy effectively limited to and from the central enlarged part in either single mode or multimode form be transmitted. The advantages of single-material fibers are, among other things, that the need for sheathing is lower Refractive index is eliminated and consequently the optical losses normally occurring at the core / cladding interface can be avoided. Furthermore, the single-material fiber can easily be extracted from an enlarged preform Low-attenuation materials such as quartz glass can be produced by heating and drawing the fibers in the longitudinal direction. The so far proposed single-material fiber arrangements also have disadvantages « For example, the thin-film support members must be in the

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Fibers have a significantly smaller cross-section than the enlarged central part, so that the latter carries the wave energy can effectively limit yourself. The pasers are therefore more sensitive than the usual core-and-clad filaments or gradually decreasing refractive index, therefore, it persists in use an increased risk of breakage. In addition, these fibers are inherently single channel devices; H. it's just practical a single enlarged central part present, in which and lengthways to which optical wave energy is transmitted. It is therefore desirable for future optical communication systems, To have optical single-material fiber arrangements whose mechanical strength corresponds to the usual fiber arrangements and which at the same time are able to transmit optical wave energy in a plurality of independent optical channels.

The problem area outlined above is now in accordance with the invention solved for an optical fiber arrangement of the type described in the introduction that a central fiber element on its The outer surface is provided with a protruding bead which has the shape of a fiber element wrapping around and in the direction of the fiber axis has extending helix, and that the cross-sectional dimensions of the bead and the pitch of the helix for a through this transmission of optical wave energy occurring in at least one mode is dimensioned.

According to the invention, an optical fiber assembly in uniform, integral structure and advantageously made from a single material of uniform chemical composition.

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and has one or more waveguide channels in which and along which optical wave energy is transmitted can be. The central part of the fiber arrangement is a longitudinal fiber element with a comparatively large cross section. On its outer surface, the central fiber element has at least one helically extending bead, the cross-sectional dimensions of which are smaller than those of the central fiber element and which has the shape of a helix that wraps around the fiber element and runs in the direction of the fiber axis. If the cross-sectional dimensions of the bead and the pitch of its helical Properly chosen along the length of the fiber element, optical wave energy in and along the bead can be either in single mode form or transmitted in multimode form, although the bead is made of the same material as the central fiber element. A plurality of such beads can be provided in the fiber arrangement, which are on the outer surface of the fiber element are arranged at a mutual distance. If the distance between successive beads is sufficiently large, can optical wave energy can be transmitted in each of these beads independently of a seam, and the optical channels can are effectively separated from one another in the fiber array. With sufficiently large central fiber elements, optical

optical fiber assemblies with up to 100 separate / channels will.

According to an embodiment of the invention, a two-channel optical single-material fiber arrangement with an in the v / esent-

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Lichen cylindrical central paser element made of quartz glass. A pair of quartz glass rods, the cross-sectional dimensions of which are smaller than those of the paser element, are attached to its outer surface mounted diametrically opposite one another and oriented in such a way that two continuous looping around the paser element and spirals are created that run in the direction of the fiber axis. A pair of quartz glass support members are also attached to the outer surface of the fiber element attached at diametrically opposite points between the two coils and run in a similar manner Way helically along the paser axis. The support members protrude from the paser element radially outward by a greater amount than each bead and have a thickness that is sufficiently large to provide the necessary mechanical strength to hold the ensure central fiber element within the fiber array. The height and width of each bead, as well as the pitch its helical path along the fiber element are selected so that an optical signal wave in each of the two beads can be effectively limited due to the waveguiding properties of the arrangement. The outer edges of the support members are advantageous with the inner surface of a hollow quartz glass outer cylinder connected, which in turn is covered with a layer of an optically absorbing material. The Tragglieäer serve both to ensure the desired mechanical retention of the central Paser element in the fiber arrangement, as well as for damping of higher order modes by diverting the vibrational energy carried in these modes to the outer absorbent layer will.

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The "helical fiber" structures according to the invention can be produced from quartz glass starting preforms, their cross-sections geometrically similar but much larger than the fiber structures ultimately desired. The starting preform is cleaned, heated and drawn in the longitudinal direction to bring the dimensions of the initial cross-section to the desired to reduce relatively small end cross-section. While the paser is being pulled and before it has completely cooled, it will rotated or "twisted" about its longitudinal axis to obtain the desired helical configuration.

The invention is illustrated below with reference to the drawing Embodiments described in detail; 1 shows a view of a two-channel optical fiber arrangement according to the invention,

FIG. 2 is a sectional view of the arrangement according to FIG. 1, FIG. 3 is a view of a multichannel optical fiber arrangement

according to the invention,
FIG. 4 shows a sectional view of the fiber arrangement according to FIG. 5, FIG. 5 shows a sectional view of an optical according to the invention

away
Fiber arrangement with / rounded surface beads,

6 is a sectional view of a device designed according to the invention two-channel optical fiber assembly with an outer protective tube and

7-10 sectional views of the fiber arrangements according to FIGS. 2, 4, 5 and 6 in the initial stage of manufacture.

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1 and 2 show a simple, two-channel, optical V / end eleven fiber arrangement 10. The fiber arrangement 10 has a circular cylindrical, transparent central fiber element 11 and a pair of beads 12 and 14 running helically on the surface of the fiber element. The latter are on diametrically opposite points are melted onto the outer surface of the fiber element 11 and wrap around this each in the form of a helix running in the direction of the fiber axis 15. Advantageously, the fiber element 11 and the surface enlargements 12 and lh from the same optically transparent material are made. As will be explained in detail below, the cross-sectional dimensions a and d of each bead and the pitch or pitch ρ of the helical course of each bead along the fiber axis 15 is selected so that each bead carries an optical signal wave in a helical wave transmission path along and around Axis 15 is able to lead. (In this context it should be noted that the term bead as used herein is generally intended to encompass any possible cross-sectional shape, in particular square, rectangular and semicircular.) The illustrated fiber arrangement 10 thus has two separate optical channels passing through the surface beads 12 and 14 and in which wave energy is guided, although they are made of the same optical material as the central fiber element 11. With the correct choice of the parameters a, d and ρ for each surface bead, the transmission here can either take place in single-mode or in multimode form. For example, the one channel (bead 12) of the fiber arrangement 10 for the transmission of optical signal energy from in the

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The fiber end shown in the figure can be used with the other fiber end located at a great distance (for example! Km or more), while the other channel (bead 14) of the fiber arrangement 10 for the transmission of optical signal waves in the opposite Direction is used. There were then an optical receiver and an optical receiver at both ends of the fiber arrangement 10 Transmitter must be provided.

Generally speaking, it becomes the radius r of the central fiber element 11 of the fiber arrangement 10 is chosen so that it is a multiple of the optical wave energy to be transmitted through the beads 12 and 14 amounts to. Preferably, the fiber element radius r is at least ten times the wavelength of the guided optical Energy and is usually in the range between about fifty times and a thousand times the wavelength. So are the fiber arrangements constructed according to the invention are relatively large and therefore comparatively stable and easy to use.

The cross-sectional width a and the cross-sectional height d of the surface beads 12 and lh are selected to be smaller than the fiber element radius r, but they are still preferably considerably larger than the wavelength of the optical energy to be transmitted. In general, it should be noted that the values of the cross-sectional dimensions a and d determine the number of modes in which optical energy can be transmitted in each bead. The examples described below also show that individual node

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Transmission in the beads 12 and 14 can also then be achieved can if the cross-sectional dimensions of each bead are an order of magnitude higher than the optical wavelength.

If the surface beads 12 and \ K are made of the same optical material as the central fiber element, then they must have the helical configuration if they are to effectively guide the optical wave energy. Single-material beads which would run parallel to the fiber axis 15, ie which have an infinitely large pitch and a pitch angle er of 0 ° relative to the axis 15, will not be effective waveguides, since wave energy transmitted here tends to laterally into the larger central fiber element 11 to escape. Effective optical waveguide occurs, however, when the single-material beads run at a suitable angle of inclination (for example greater than about 1) to the fiber axis 15. Theoretically, the pitch ρ of the helical course of each bead can assume any value greater than zero (which corresponds to a pitch angle less than 90) up to about a thousand times the radius r of the central fiber element 11 for the optical waveguide. Comparatively small pitches can be useful for obtaining an optical delay for the wave energy transmitted below. For long-distance transmission, the pitch ρ is preferably in the range from one to a thousand times the fiber element radius r.

The transmission modes in the helical fibers according to the invention

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are analogous to the "PlUstergallerie" modes first observed for sound waves by Lord Raleigh (see Volume V of the Scientific Papers, page 6YJ, Dover, Cambridge, England In the case of optically transmitting fiber arrangements, plush gallery modes are characterized by propagation paths that are in the form of coaxially located coils in the fiber and are located just below the outer surface of the fiber. The essential properties of these modes have theoretically been investigated for optical waves by JB Keller and SE Rubinow in Volume 9 of the Annals of Physics, pages 24 to 75 (1960). For the detailed mathematical model of the propagation in whispering gallery modes, reference is made to this article The principle and structure of the fiber arrangements according to the invention should be mentioned below sufficient.

Let it be the fiber arrangement according to FIGS. 1 and. 2, where ρ is the pitch of each bead waveguide and r 'is the total radius of the fiber (r '= r + d) means. The local radius of curvature 9 of a given helical wave path in the fiber, measured by the central axis 15 is given by

l + (p / 277-r} ² ] (1)

= r '

If the pitch ρ is at least several times larger than the radius r 'then results

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ρ = P ² ATfV (2)

Using the von Keller a. a. O. given mathematical Model it can be shown that the distance t (in the radial direction) below the fiber outer surface, inside which the wave energy remains localized is given by

^{(2ra + 3/2)} * "*

where p is the radius of curvature of the wave path according to the definition according to equation (l), furthermore ra is an integer which is the order (in the radial direction) of the mode propagating in the fiber (m = 0,1,2 .. .); and. finally k means the port planting constant of the wave in the paser (k = ~~ with Λ equal to the optical wavelength in the fiber medium). If the fiber has an index of refraction η then the wavelength in the paser is Ao , where A _{n is} the optical wavelength in free space.

Effective guidance for the mode of the m-th order (and all modes of the lower order) in the surface beads 12 and I ² J of the fiber arrangement 10 is obtained when the cross-sectional height d of each bead is chosen so that it is in terms of value Size t for that mode is the same as determined by equation (3) and when the cross-sectional width a of each bead is approximately equal to the value of d. The dimension a does not have to be exactly the same as the dimension d, but it is sufficient for optical waveguide that a is of the same order of magnitude as d.

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The value for a is preferably between two and about simple and about three times d.

A single mode operation in the surface ridges of the fiber array 10 is obtained if only the fundamental mode (m = O) is transmitted. If one assumes that a is approximately equal to d and if one sets m = O in equation (3), then the Condition for single-mode waveguide should be written with

^{2 2 22/5} , (4a)

The assumption a ~ d «^ t is essentially based on qualitative ones Considerations. A more detailed calculation shows that the exact expression for the single mode condition is given by

ad a * 0.043 A ² (kp) ^2/5 (4b)

Provided that the value of a is not significantly different from that of the quantity d, then one sees that.3 only the cross-sectional area given by ad and not the separate quantities a and d are important. In the single mode case, the modes of a higher order than the fundamental testicle extend over the bulges both azimuthally and radially, so they are not confined by the beads and are attenuated in the fiber. The fundamental mode field, on the other hand, drops rapidly outside the bead and is not attenuated.

The following is an explanation of the above principles

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Consider a specific example in which single-mode operation is provided in the two-channel single-material fiber arrangement 10 according to FIGS. 1 and 2. Quartz glass (refractive index η = 1.46) is provided for the material of the central fiber element 11 and the surface beads 12 and 14, and the wave energy to be conducted in the beads should have an optical wavelength of approximately one micrometer. The central fiber element 11 is provided with a radius r of 50 micrometers, and the surface beads 12 and 14 each have a pitch ρ of about 7 mm. From equation (2) it follows that the radius of curvature ρ of the helical wave path in each bead is about 25 mm. To achieve single mode operation in each bead 12 and 14, their cross-sectional dimensions a and d are selected according to equation (4b). Accordingly, in the example assumed, a single mode transmission is achieved in each of the two waveguide channels of the fiber arrangement 10 when a ^ d ^ 8.5 micrometers.

To obtain multimode transmission in the surface ridges 12 and 14, the sizes a and d are typically dimensioned so that their values are at least several times greater than the calculated values for single mode transmission. For example surface beads 12 and 14, the dimensions a and d of which are each approximately equal to 50 micrometers, would be several modes of one optical wave with a wavelength of one micrometer. Using equation (.3) can be reasonably accurate Calculations can be made for bead dimensions that are suitable for multimode transmission.

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The optical fiber assembly 10 of Figures 1 and 2 is preferably made in substantially the same manner as the single material optical fiber assemblies described in the above-referenced paper by P. Kaiser et al in Volume 52 of Bell System Technical Journal, page 265 ( February 1973). It is expedient to start from optically polished fiber segments 5I, 52 and 5 ² J- in the preform structure 50, the cross-sectional view of which is shown in FIG. Typically, all of these segments are made from the same optical material, e.g. B. made of quartz glass. The preform segment 5I is a substantially straight cylindrical rod, and the preform segments 52 and 5 ^ are similarly substantially straight rods with smaller and rectangular cross-sections, all segments being oriented perpendicular to the plane of the drawing. In order to have clean optical surfaces, the exposed surfaces of these segments are first cleaned one after the other with a suitable cleaning solution, for example in a solution of trichlorethylene, acetone and nitric acid (diluted 1: 1 with deionized water) and deionized water. The overall cross-section of the segments in the preform arrangement 50 (FIG. 7) advantageously forms a geometrically similar, but greatly enlarged, cross-section of the ultimately desired cross-section, which is shown in FIG. 2. After they have been cleaned, the preform segments 5I »52 and 5 ^ are heated to a sufficiently high temperature to fuse them together. During the heating, the

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Preform arrangement in the direction of the longitudinal axis to reduce cross-section to that of the optical fiber arrangement desired value drawn. During the drawing process and before the Paser has completely cooled down, it will move along its longitudinal axis rotated or twisted at the appropriate speed to achieve the desired helical surface configuration. For example, if a pitch of about 7 mm is desired for each bead waveguide, the fiber arrangement will be uniform by a full 3βΟ around its longitudinal axis per 7 mm drawn fiber length rotated, d. H. the fiber is rotated about 51 ° per mm of drawn fiber. It should be noted that this final twisting step does not occur in the manufacture of the single-fabric fibers according to P. Kaiser et al, but only for the fiber arrangements according to the invention because of the helical configuration provided here. It should also be noted that FIG. 7 is not to scale Is enlargement of Fig. 2, but that normally the preform assembly 50 has a much larger cross-section than the resulting final fiber assembly 10.

Figs. 3 and 4 show a longitudinal view and a sectional view, respectively an optical multi-channel single-material fiber arrangement 20 in accordance with the invention Education. In detail, the fiber arrangement 8 separate beads 22.1 to 22.8 are provided on the Outer surface of a central fiber element 11 are arranged distributed to eight spaced apart helical to form optical channels. As with the simple two-channel fiber array 10 of Figs. 1 and 2, each of the surface

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Bulges of the fiber arrangement 20 so dimensioned with respect to its pitch ρ and with respect to its cross-sectional dimensions a and d be that it has wave energy in either single mode or hultimode operation transmits. In addition, the transfer in each of the surface ridges can be independent of the transfer in adjacent beads take place (i.e. the fields emerging from neighboring channels in a decaying manner can be made negligible) if they are sufficient large distance c on the surface of the fiber element 21 from each other are separated. To ensure independent transmission in each channel of the fiber array 20, the distance c between adjacent beads must be at least twice as large as the cross-sectional width a of each bead (d. λ * c> 2a). This condition can easily be met with the fiber arrangements according to the invention, since they have a relatively large overall cross section.

For example, if the central fiber element 21 has a radius r of about 1 mm, then its circumference (2vv) is about 63ΟΟ micrometers. Assuming that the eight greatest 22.1 to 22.8 are evenly distributed on the fiber element 21 and that each bead has a cross-sectional width of about 100 micrometers (multimode V / ulste), then the distance between any two adjacent beads would be greater than 600 micrometers . It will therefore be seen that fiber array optical fiber assemblies 20 can be made with many independent optical channels; they are therefore analogous to the coaxial cable assemblies of

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usual lower frequency transmission systems. With a A radius of one millimeter for the central fiber element 21 could, for example, have 100 separate surface beads Cross-sectional dimensions a and d of about 20 micrometers each are accommodated in the fiber array, with the distance then c between adjacent beads would still be larger than 2a, i.e. larger than 40 micrometers. Central fiber elements with even larger radii would be the use of a correspondingly larger number of bead waveguides and / or bead waveguides with larger cross-sections.

To produce the fiber arrangement 20 according to FIGS. 3 and 4, one would, for example, start with the preform arrangement 60 according to FIG. The preform assembly is βθ oraktisch identical to the preform assembly 50 of FIG. Y, except that the assembly 60 has a central segment Gl and eight spaced-apart segments 62.1 to 62.8. Manufacture would be in the same manner as discussed above in connection with preform assembly 50. Again, it should be noted that the cross section of the preform assembly 60 is geometrically similar, but many times larger than the cross section of the desired fiber assembly 20 of FIG. The cross-section of the bead waveguides in the various embodiments of the invention need not be rectangular; other contours can be used which are equally acceptable from an optical point of view. Fig. 5 shows in section

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views an embodiment with rounded waveguide beads. The Pig optical fiber assembly 30. 5 has a central fiber element 31 and two separate surface beads 32 and 34 which are fused opposite one another on the outer surface of the fiber element 31 and which run helically in the axial direction of the fiber element 31. The beads 32 and 3 ^ have a substantially semicircular shape, in which the cross-sectional width a is approximately equal to twice the cross-sectional height d. The desired number of modes to be transmitted in the beads and Ja is determined by making the cross-sectional height d of each bead approximately equal to t in accordance with equation (3) above. The fiber arrangement 30 is otherwise identical to the fiber arrangement 10 of FIGS. 1 and 2, except that the cross-sectional shape of the beads 32 and 34 is different.

9 shows a preform arrangement 70 in cross-sectional view. which are used in the manufacture of the fiber array $ 3 can. Instead of rectangular bead segments, the preform has an arrangement 70 two cylindrically shaped bead segments 72 and 74, which are to be melted to the larger cylindrical segment 71. The manufacture of the fiber array 30 on the preform array 70 can be done in the manner described above.

For many practical applications it is desired that the fiber array used for the transmission of optical signal waves is housed in an outer protective sheath, which, among other things

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protects the light-guiding zones of the fiber arrangement from disturbances due to touching or other environmental influences. One such type of protective sheathed or encapsulated fiber array is shown in cross-sectional view in FIG. Like the fiber arrangement 30 according to FIG. 5, the fiber arrangement 40 in FIG. 6 has an enlarged central fiber element 4l and. two separate surface ridges 42 and 44 which are diametrically opposed to each other are fused to the outer surface of the fiber element 41 and extend helically along the fiber axis. Everyone who Ridges 42 and 44 are designed in accordance with the above considerations in order to be able to transmit optical signal waves. A couple Support members 43 and. 45 are also attached to the outer surface of the Fiber element 41 melted at diametrically opposite points between the surface beads 42 and 44 and. get lost similarly helical along the fiber axis. The support members 43 and 45 extend from the fiber element 41 to outside by a greater amount than either of the beads 42 and 44, and they are of a thickness sufficient to provide that required ensure mechanical strength for holding the fiber element 4l in the fiber array. The outer edges the support members 43 and 45 are attached to the inner surface of a fused hollow outer cylinder 46, which in turn is coated with a layer of optically absorbing material 48. Fiber element 41, beads 42 and 44, support members 43 and 45 and outer cylinder 46, all of the same optical structure, are advantageous Material, for example made of quartz glass.

The thickness b of the support members 43 and 45 in Fig. 6 is typically chosen so that it is significantly larger than the transmitted

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gene optical wavelength to provide the desired mechanical support for the fiber element 41. It should be noted that, in contrast to the thin-layer support members which are provided in the single-material pasers according to P. Kaiser et al. ie to have the beads 42 and 44). In addition, the support members 4; 5 and 45 extend radially outward from the outer surface of the fiber element 41 by an amount which is at least one order of magnitude greater than the wavelength, by a sufficient distance in that through the fiber element 41 and the inner surface of the outer cylinder 46 to have defined cavity. Such a cavity would typically be occupied by air (refractive index approximately equal to one). For example, if the cross-sectional height d of the beads 42 and 44 is about 20 micrometers and if the optical wavelength to be transmitted is about one micrometer, then the Trar members ^ 5 and 45 would have a thickness b of at least J> 0 micrometers and away from the fiber element 41 extend radially outward by at least 60 micrometers. Of course, if beads with larger cross-sections are used, the support members 43 and 45 would have correspondingly larger cross-sectional dimensions.

In addition to their mechanical support of the central fiber element 41 in the fiber arrangement 40, the support members serve 43 and 45 have another useful purpose. As mentioned above, tend to be higher order modes than those for whose transmission the

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Beads 42 and 44 are designed to be in both azimuth as well as extending radially above and above the beads in the fiber array, d. H. these fashions will not limited by the bulges. The support members 4j and 45 are therefore a useful means of dissipating energy oscillating in these undesirable higher order modes out to the outer cylinder 46, where this energy is rapidly absorbed by the optically Layer 48 is absorbed so that the transmission of energy in the selected modes is not significantly impaired.

Figure 10 shows a cross-sectional view of a preform assembly 80, which is suitable for producing fiber arrangements similar to the fiber arrangement 40 according to FIG. 6. The elements of the fiber assembly 40 of FIG. 6 corresponding segments of the preform arrangement 80 have been provided with reference numbers 40 higher in FIG. After the fiber assembly 40 from the Preform assembly 80 has been produced in the manner described above, the whole is made by conventional methods a layer of optically absorbing material, for example with methyl methacrylate, coated.

Numerous modifications are possible. So can, although the ones shown Embodiments all have two or more helical surface ridges, and only one fiber arrangement possess only helical surface bulges, in and lengthways of the optical wave energy to be transmitted is *. Such a one Single-channel fiber array can specifically be called optical

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line for the transmitted wave energy. In addition to quartz glass, numerous other optically transparent materials can be used can be used for the individual elements of the fiber arrangements. Although these elements are preferably composed of the same optical material, they do not need it for as long they can be fused together in the manner described. The special ones for the production of the fiber arrangements The method described is not the only one; other methods can also be used. Furthermore, they are for the individual elements of the above fiber arrangements are to be understood only in an illustrative but not in a restrictive sense. The optimal choice of parameters for every special application can best be determined experimentally without difficulty.

Furthermore, although not preferred, all of the exposed Surface of the fiber assemblies 10, 20 and JO with a Layer of a material of lower refractive index must be coated in order to have suitable protection for the fiber arrangement. Furthermore, a suitable optically non-linear material can be used to obtain an optical interaction between the transmitted modes in contact with the wave energy carrying zones along selected lengths of the fiber. For example In the fiber arrangement 40 according to FIG. 6, a selected part of the cavity between fiber element 41 and. Outer cylinder 46 be filled with an optical nonlinear material,

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for example with rhodamine 6G in water or methanol, ethyl alcohol, Chlorobenzene or carbon disulfide. Optical amplification, optical frequency mixing and other optical interactions would therefore be convenient to incorporate into the fibers.

Finally, there could also be an optical cable that many similar contains fiber assemblies according to the invention are produced by having these fibers in a single peripheral assembly suitable size and suitable cross-section. The cable would then be a suitable means of immovable retention of the individual fibers within the cable.

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Claims (3)

BLUMBACH WESER BERGEN KRAMER ZWIRNER HIRSCH PATENTANWÄLTE IN MUNICH AND WIESBADEN XS Postal address Munich: Patentconsult 8 Munich 60 RadeckestraSe 43 Telephone (089) 883603/883604 Telex 05-212 313 Postal address Wiesbaden: Patentconsult 62 Wiesbaden Sonnenberger Strasse 43) Telephone (06121) 562943/561998 Telex 04-186237 patent response 1./Optical fiber arrangement for the transmission of electromagnetic Wave energy of the optical spectral range with a uniform structure, the elements of which are fused together and are preferably formed from the same optically transparent material, characterized in that a central fiber element (11) is provided with a protruding bead (12) which has the shape of a fiber element wrapping around it and has helix extending in the direction of the fiber axis, and that the cross-sectional dimensions (a, d) of the Bead and the pitch of the helix (p) for a transmission of optical wave energy occurring through this are sized in at least one fashion. 2. Optical fiber arrangement according to claim 1, characterized in that that the fiber element has a substantially circular cross-section of a radius r which is at least one Is order of magnitude greater than the wavelength of the optical energy to be transmitted through the bead, and that the The pitch ρ of the helical bead (12) is one to a thousand times the fiber radius. 509840/0841 j>. Optical fiber arrangement according to Claim 1, characterized in that the bead (12) has an essentially rectangular cross-section, the height d of which, measured from the fiber outer surface, is vertically greater than the wavelength to be transmitted through the bead optical wave energy, and its width a is one to three times the height d. 4. Optical fiber arrangement according to claim 1, characterized in that that the cross-sectional width a of the bead (12) is approximately equal to the cross-sectional height d and that a and d are chosen so are that relationship ad = 0.043A ² (kp) ^{2 /; 3} is approximately fulfilled, where A is the optical wavelength of wave energy to be transmitted through the bead, further k is equal to 27r / A, and ρ is given by ρ = r [l + (p / 27rr) ² J, where r is the radius of the fiber element (11), whereby Wave energy is only transmitted in a single mode in the bead. 5. Optical fiber arrangement according to claim 1, characterized in that that several beads (12, 14) run helically at a mutual distance on the outer surface of the fiber arrangement, wherein the distance c between two adjacent beads is at least twice as large as the cross-sectional width a of one every bead. 509840/0841 6. Optical fiber arrangement according to claim 5, characterized in that that at least two helical support members (4j, 45) on between the helical beads (12, 14) are fused to the outer surface of the fiber element that the support members from the outer surface of the fiber element protrude radially outward by a distance which is greater than the height of each bead that the outer edges the support members are fused to the inner surface of a hollow outer casing (46), the outer casing consists of a material that is transparent to the optical wave energy to be transmitted in the beads, thereby creating a void in the fiber array between the outer surface of the central fiber element and the inner surface the hollow outer jacket is formed. 7 «Optical fiber according to claim 6, characterized in that that the fiber element (11), the helical beads (12, 14), the support members (4 ^, 45) and the hollow outer casing (46) are all made of the same optically transparent material. 509840/0841 3.2 Blank page