Optical waveguides – With disengagable mechanical connector – Optical fiber to a nonfiber optical device connector
Reexamination Certificate
1999-08-06
2001-11-13
Bovernick, Rodney (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Optical fiber to a nonfiber optical device connector
C385S088000, C385S053000, C385S031000
Reexamination Certificate
active
06315464
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention is in the field of multi-channel electrooptical transmitting devices for the parallel optical transmission of information. The invention relates to an electro-optical coupling module having a plurality of optical transmitters with an optically active zone in each case and a corresponding plurality of optical fiber ends that are assigned to one of the transmitters. The optical fiber ends each have an end face that receives radiation emitted from a respective optically active zone and deflects the radiation entering the optical fiber end radially.
Within the scope of the invention, an optical fiber is to be understood as any element for relaying an optical signal in a fashion guided with restriction in space, in particular manufactured optical fibers that are combined in a so-called optical fiber ribbon. A light-emitting region of the transmitter is to be understood as the optically active zone of the transmitter; in the case of a vertically emitting laser transmitter (so-called VCSEL), the optically active zone is located on the top side of the transmitting element.
A coupling module of the type mentioned at the beginning is known from German Patent DE 196 47 685 C1. In this coupling module, the ends of a plurality of optical fibers running in parallel are fixed in a common holder. An oblique end face of the holder is ground and polished together with the ends at a prescribed angle so that the end faces of the optical fibers act as reflection surfaces for light which is incident perpendicular to the optical fiber axis (radially). Light emitted by the optically active zones of individually drivable transmitters penetrates into the respective optical fiber end through the cladding thereof, and is deflected by the end face in the direction of the optical fiber longitudinal axis. Under normal conditions, the end surface acts in a totally reflecting fashion; with regard to unfavorable environmental conditions, the end face can also be silvered. The individual transmitters can be a constituent of a transmitting array.
In the case of the use of a plurality of individual transmitters, in particular in the case of the use of surface-emitting laser arrays (VCSEL), there are practical problems because of the relatively strong scattering of the individual response thresholds of the lasers. Moreover, the transmitters, in particular laser transmitters, have a comparatively high steepness. This has a problematic effect with respect to existing laser safety regulations, in accordance with which it is impermissible to exceed a prescribed limiting value of the output power of the individual transmitter. Specifically, since a uniform operating point usually has to be selected for all transmitters, the selection of a suitable operating point is extremely difficult in practice because of the scattering previously described. Specifically, while transmitters with a relatively low response threshold already output comparatively high powers for low control currents, other transmitters may not yet have reached their response threshold for these drive currents.
These problems could be countered in principle by undertaking a specific maladjustment between the individual transmitters and the respective assigned optical fiber end. However, this would have to be undertaken for each coupling module individually, and signifies a substantial outlay on measurement and production engineering. Moreover, if the path of radiation between the transmitter and optical fiber end is to be protected after the adjusting operation by an optically transparent potting, this method of maladjustment shows itself to be entirely unsuitable. Since, after its curing, the potting has a higher refractive index than the air (still present during the maladjusting operation), the optical relationships change after the curing. Any setting of the desired coupling efficiency which could be determined in advance would therefore be impossible.
It is, furthermore, conceivable to reduce the steepness of the transmitters, for example by suitable coatings. However, this necessarily results in additional heating of the transmitters, which seems to be unacceptable with regard to their service life and operational reliability.
Finally, it is conceivable for additives that influence the light transmitted through to be admixed to a material to be introduced between an optically active zone and optical fiber end. However, it is to be considered in this case that the distance between an optically active zone and optical fiber end is subject to configuration-induced tolerances that cause different influences of the light.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide an electrooptical coupling module that overcomes the above-mentioned disadvantages of the prior art devices of this general type, which permits a selection of a uniform operating point with simple constructional changes and good reliability in the case of a coupling module having a plurality of optical transmitters with different steepness and response thresholds, and to prevent a prescribed output power limiting value from being exceeded.
With the foregoing and other objects in view there is provided, in accordance with the invention, an electooptical coupling module, including a plurality of optical transmitters each having an optically active zone for emitting radiation; and a plurality of optical fiber ends having end faces receiving the radiation emitted from a respective optically active zone and deflecting the radiation radially entering a respective optical fiber end of the plurality of optical fiber ends, the end faces having a coating effecting damping of the radiation, and each of the plurality of optical fiber ends associated with one of the plurality of optical transmitters.
According to the invention, the object is achieved in the case of an electrooptical coupling module of the type mentioned at the beginning by virtue of the fact that the end faces are provided with a coating which effects damping of the radiation. The coating of the end face with a layer that absorbs radiation at least partially and thus has a damping effect is provided according to the invention in a departure from the previously customary aim of the totally reflecting property of the end face. This renders it possible in a simple way to reduce the steepness of the individual transmitter output powers. A substantial advantage of the coupling module according to the invention thereby consists in that it is also possible to use optical transmitters or transmitter arrays with comparatively strongly varying individual response thresholds and steep power characteristics. This eliminates the previous stringent requirements for a relatively high uniformity of the response thresholds or power characteristics of the individual transmitters, with the result that it is possible to make recalls to transmitters or transmitter arrays that are more cost effective. A further substantial advantage of the coupling module according to the invention is to be seen in that the preparation of the end faces can be performed with only a slight additional outlay on production and simultaneously for all end faces. It is, furthermore, advantageous that the component of radiated energy converted into heat during the damping of the emitted radiation in the prepared end faces can be dissipated without a problem, and therefore that the operational performance and the service life of the transmitters is not negatively influenced.
A refinement of the invention particularly preferred in terms of production engineering provides that the coating contains an adhesive layer applied to the end face, and a metal layer applied thereon. In the case of this combination of layers, chromium or titanium is preferably used as the adhesive. In addition to reliable adhesion, this configuration of layers ensures a damping ratio that can be adapted particularly effectively to the respective requirements. In this connection, the metal layer (cover layer) is f
Melchior Lutz
Plickert Volker
Bovernick Rodney
Greenberg Laurence A.
Lerner Herbert L.
Pak Sung
Siemens Aktiengesellschaft
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