Optical waveguides – With optical coupler – Movable coupler
Reexamination Certificate
2000-03-13
2001-08-21
Schuberg, Darren (Department: 2872)
Optical waveguides
With optical coupler
Movable coupler
C385S037000, C385S088000, C359S199200
Reexamination Certificate
active
06278815
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a device for optical signal transmission between two dynamically decoupled systems, comprising at least on e emitter means including a first source of light, which is mounted on the first system, as well as a receiver means including at least one fibre optical wave guide, which is mounted on the second system and into which the light of said light source can be injected.
PRIOR ART
For the optical signal transmission between two spatially separate components, which are, as a rule, moreover moving relative to each other, light of a light emitter mounted on one component is injected into a wave guide which is mounted on the opposite component, and is then passed on inside the wave guide towards an appropriate light detector unit. An essential criterion of the quality of the signal transmission process is the introduction of the light into the wave guide because the process of coupling light into the wave guide with a subsequent transfer of the light inside the wave guide up to signal conversion in a detector array is linked up with high losses.
It is common that the wave guide, which is configured as a fibre optical wave guide, is irradiated in a direction orthogonal on the surface of the optical fibres so that the light fraction injected into the wave guide is equally oriented in a direction normal on the longitudinal axis of the fibre optical wave guide. With detector arrays being normally arranged at the fibre ends, only those fractions of the light injected into the optical fibre contribute to signal transmission which can propagate along the direction of the longitudinal axis of the optical fibre and which arrive at the detector array by way of total reflection relatively free of loss. With the aforedescribed lateral irradiation, this fraction is generally negligible. Therefore provisions must be made for deflecting the largest fraction possible of the light injected into the optical fibre in a direction towards the longitudinal axis o the fibre in such a way as if the light were injected at a face side of the optical fibre. For instance, the German Patent DE 28 46 526 C2 discloses an X-ray display unit providing for an annular optical wave guide having an out side contour al on g which a light source is moved as signal source. For deflecting the radiation orthogonally injected into the optical wave guide along the longitudinal direction of the optical wave guide steps are provided on the inside of the optical wave guide, which extend over the entire periphery of the optical wave guide and induce a light reflection so that the light of the light source, which is injected into the optical wave guide, will be uniformly distributed over the entire periphery of the optical wave guide. An appropriate receiver unit is provided on at least one end of the optical wave guide for detection of the light. Even though, on the one hand, the stepped configuration of the inside of the optical wave guide is suitable to deflect the light orthogonally injected into the optical wave guide into a direction along the longitudinal extension of the fibre, this structure impairs, on the other hand, the propagation characteristics of the light along the wave guide axis substantially so that the light guided within the wave guide is partly coupled out from the wave guide by refraction and reflection on the stepped contours and is hence subjected to substantial losses.
Moreover, solutions have become known which leave the guide guidance within the optical wave guide largely uninfluenced; to this end, for instance, the wave guide configured as fibre optical wave guide, contains fluorescent substances which emit fluorescent light in response to energetic excitation by irradiation. Those light fraction s of the fluorescent light which can propagate along the longitudinal extension of the fibre contribute to signal transmission within the optical wave guide. On e example of this type is apparent from the German Patent DE 44 21 616 A1 which describes a device for transmitting and receiving circulating light signals. Even though the light, which is guided by total reflection along t he longitudinal axis of the fibre, propagates in the optical fibre largely without any losses because this fibre presents a contour without any geometric impairment, the transmission of the optical signals is restricted with respect to high transmission rates on account of the delayed fluorescent effect, which is a disadvantage for an optimised use of data transmission channels.
In an approach to avoid the aforedescribed disadvantages of fluorescent light and yet any impairment of the wave-guiding characteristics of an optical fibre wave guide it is common to use a coupler prism for injecting the light, which is disposed on the surface of the optical fibre and through which the light orthogonally incident onto the surface of the optical wave guide is deflected by the coupler prism by means of refraction so that the light injected into the optical fibre will advance in a direction inclined relative to the longitudinal axis of the optical fibre and will be guided inside the optical fibre by means of total reflection. When, however, the light emitter moves relative to the optical fibre the coupler prism must be passed along, too, simultaneously with the light emitter, over the optical fibre, whilst attention must be paid to the fact that the spacing—which is in orders of magnitudes in the &mgr;m range—between the coupler prism and the optical fibre must be observed with extreme precision so that a high-precision mechanism is required which is not attractive for application in operation in terms of structure and particularly in financial terms.
The invention is now based on the problem of improving a device for optical signal transmission between two dynamically decoupled systems, preferably two systems moving relative to each other, comprising at least one emitter means including a first source of light, which is mounted on the first system, as well as a receiver means including at least one optical fibre, which is mounted on the second system, and having an extension along which the source of light is moved and into which the light of said light source can be injected in, in such a way that the optical coupling of the light originating from the emitter means into the optical fibre can be implemented without major losses if possible. In particular, the highest light fraction possible should be guided within the optical fibre along the longitudinal direction, whilst the light-guiding characteristics of the fibre should be left uninfluenced for an unimpaired propagation of the light inside the optical fibre by means of total reflection. The measures to be performed to this end should be moreover be suitable for production at low costs and not cause any problems in application so that the device may be used for operation at any site required.
The solution to the problem underlying the present invention is defined in the claims
1
,
4
and
6
. Features defining expedient improvements of the inventive idea are the subject matters of the dependent claims.
A device in accordance with the introductory clause of claim
1
is configured in correspondence with the invention in such a way that a photo refractive layer is applied on at least that surface of the optical fibre which is directly opposite to the first source of light, and that at least one source of coherent light is provided on the first system, which emits light which dynamically imprints an optical grating into the photo refractive layer due to beam superimposition at the site where the light is injected, which grating presents refractive properties for the light of the first source of light so that the light can be injected into the optical fibre.
The inventive idea makes use of the property of photo refractive materials having non-linear optical properties in a form that their refractive indices can be varied by irradiation with light. It is possible in particular to generate an interference pattern by selective interference of
Assaf Fayez
Schleifring und Apparatebau GmbH
Schuberg Darren
St. Onge Stewart Johnston & Reens LLC
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