Optical waveguides – With optical coupler – Input/output coupler
Reexamination Certificate
2001-06-28
2004-06-29
Healy, Brian (Department: 2874)
Optical waveguides
With optical coupler
Input/output coupler
C385S033000, C385S050000, C385S059000, C385S060000, C398S079000, C398S085000
Reexamination Certificate
active
06757460
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to an electro-optical module for transmitting and/or receiving optical signals on at least two optical data channels.
Modules for bidirectional optical data traffic operate, for example, in a star structure in such a manner that data streams are transmitted in opposite directions—in the direction of a central feed point (upstream) and in the direction of further receivers (downstream)—in an optical fiber, in which case identical or different wavelengths can be used for the individual data channels. In particular, wavelength-division multiplexing methods are used in which light signals at a number of wavelengths are transmitted simultaneously on one optical fiber. There is thus a need for electro-optical modules having transmitting and receiving components which inject into an optical fiber, and output from it, signals for a number of optical data channels.
A module of this generic type is known from European Publication EP-A-238 977. This transmitting and receiving module for a bidirectional communications network uses free-beam optics in which spherical lenses are arranged at a distance from one another between a laser diode and the end of an optical fiber, and focus the laser light onto the end of the fiber. A wavelength-selective beam splitter is arranged between the spherical lenses, for wavelength separation, and separates light which is emitted from the end of the fiber and is at a wavelength different to the wavelength of the laser light from the beam path and passes it to a detector or receiving component.
A disadvantage of this known module is that the light is passed through free-beam areas. The lenses that are used thus act refractively, that is to say the refraction power acts only on the boundary surface between the lens and air. The presence of free-beam areas demands hermetic encapsulation of the module, in order to prevent condensation in the free-beam area. Furthermore, the known module must be mechanically very robust and insensitive to temperature fluctuations in order to ensure that the laser light is reliably injected into the optical fiber (the diameter of a single-mode optical fiber is generally only 9.3 mm). A final disadvantage of the known module is that an electrical connecting contact must be made on two different sides of the module. This involves increased installation complexity for the user.
International publication WO-A-96/00915 discloses a module for multiplexing/demultiplexing of optical signals, which forms a phased array grating on a substrate and is used both for separation and for combination of a number of optical channels. The waveguides are in the form of integrated optical waveguides. A disadvantage of this arrangement is that the transmitting and receiving components must be mounted on or attached to the substrate without being capped. The substrates are also relatively large, since the waveguides must be routed with large radii, and are correspondingly expensive. A further problem is that special structures are required in order to couple external optical waveguides to the substrate.
Furthermore, fully integrated bidirectional modules for transmitting and receiving optical signals are known, in which the waveguides, transmitting component and receiving component are integrated on a common semiconductor substrate mount. However, these modules are very expensive.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide an optical module which overcomes the above-mentioned disadvantageous of the prior art apparatus and methods of this general type. In particular, it is an object of the invention to provide an optical module based on a new module concept for transmitting and/or receiving optical signals, and which has a simple, compact and modular design and can be produced cost-effectively.
With the foregoing and other objects in view there is provided, in accordance with the invention an electro-optical module for transmitting and/or receiving light of a plurality of optical channels. The electro-optical module includes an optical waveguide with at least two optical waveguide sections each section having at least one inclined end surface. The inclined end surfaces of the optical waveguide sections are positioned axially one behind the other. Light is injected into or light is output from the optical waveguide for a specific optical data channel by light for the optical data channel being passed to an inclined end surface, or emerging from it, at an angle relative to the optical axis of the optical waveguide.
The solution according to the invention provides a physical concept which is based on using a type of optical “T-piece” in which the horizontal arm of the T is provided by mutually adjacent optical waveguide sections. Light is output/injected at right angles or transversely from/into the optical waveguides by inclined end surfaces of optical waveguide sections at which the light is emitted or injected transversely. Such an end surface in this case always has an associated transmitting or receiving component arranged essentially at right angles to the optical axis of the optical waveguide. Optical coupling is provided in such a way that the light which is deflected on an inclined end surface passes through the sheath of the optical waveguide section (and adjacent materials) and is then coupled essentially by a free beam to the optically active area of the transmitting or receiving component, or vice versa.
The invention provides closed wave guidance in a transparent medium which essentially requires no free-beam optics for injecting light into and outputting light from the optical waveguide. The stability with regard to thermal and mechanical loads is in this case very high because of the closed wave guidance and because of the lack of optics which increase errors. A further advantage is that no wavelength-selective elements, which need to be installed separately, are required since the inclined end surfaces of the optical waveguide segments are used as mounts for these waveguide-selective elements.
Another advantage is that the solution according to the invention allows the optical waveguide to be routed close to the transmitting or receiving component, which can be connected directly to a holder for the optical waveguide, and that the electrical connections of the module are located on one side of the module. The latter facilitates simple installation.
In accordance with an added feature of the invention, at least one end surface of the optical waveguide sections is coated with a wavelength-selective filter. This allows use for wavelength division multiplexing, in which light signals at different wavelengths are transmitted on the optical waveguide. One wavelength is output via each wavelength-selective filter applied to the end surface, while that end surface is transparent to any other wavelength or wavelengths.
In accordance with an additional feature of the invention, the end surfaces of two adjacent optical waveguide sections are coplanar. This means that the two end surfaces of adjacent optical waveguide sections are immediately adjacent to one another with as little gap as possible in the joint so that scarcely any losses arise due to reflections between the two end surfaces. The angle of the end surfaces to the optical axis of the optical waveguide is essentially 45°. The term “essentially” in this case means that there may also be deviations from this value (of up to 20°) in order to avoid feedback, for example. The only essential feature is that the injected or output light is deflected sufficiently by the inclined end surface.
In accordance with another feature of the invention, the optical waveguide sections are each arranged in a glass ferrule which is transparent for light at the wavelengths used and which has an end surface inclined in a corresponding manner to the optical waveguide sections at its ends. The deflective light in this case first of all passes through the sheath of the optical waveguide section, and then
Melchior Lutz
Plickert Volker
Greenberg Laurence A.
Healy Brian
Infineon - Technologies AG
Locher Ralph E.
Stemer Werner H.
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