Optical waveguides – With optical coupler – Switch
Reexamination Certificate
1999-09-17
2002-02-05
Epps, Georgia (Department: 2873)
Optical waveguides
With optical coupler
Switch
C385S025000, C385S016000, C385S019000, C385S125000
Reexamination Certificate
active
06345132
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention concerns an optical switching element according to the preamble of claim
1
. Furthermore, the invention concerns a switching arrangement according to the preamble of claim
3
O. Such a switching arrangement is known from the IEEE Transactions on Components, Packaging, and Manufacturing Technology—Part B, Vol. 1B, No. 2, May 1995, pp. 241-244.
Matrix switches are familiar for connecting of fiber-optics lines by which N optical input channels can be switched to M optical output channels in any desired way. The number of the optical fibers being switched depends on the particular application. In the realm of telecommunications, matrix switches with a plurality of input and output channels find use.
There are known mechanical matrix switches in which mirrors or prisms are moved with high precision. Switches based on mirror or prism arrangements require a very stable and precise construction. The required precision generally entails high technical expense.
Besides the optical switching elements the microoptical components of which are moved with high precision, there are also known optical switching elements which work by a switching principle that does not require a movement of microoptical.
GB 1 494 150 describes an optical switching element in an optical waveguide wherein one boundary surface on which the incident light impinges is switched between a condition of total reflection and transmission. The known optical switch has a narrow slit in the core of the optical waveguide. The slit forms a regular boundary surface between an optically more dense medium, i.e., the material of the core of the optical waveguide, and an optically less dense medium, i.e., a gaseous substance in the slit, so that light impinging on the boundary surface at a slant and conducted along the optical waveguide is totally reflected at the boundary surface in the direction of an adjoining optical waveguide. In order to switch to the transmitting condition, in which the light impinging on the boundary surface maintains its direction of propagation, a fluid is introduced into the slit, the index of refraction of which corresponds to the index of refraction of the material from which the core of the optical waveguide is made. The device provided for optional introducing of the substance into its fluid or gaseous phase is a storage vessel with a heating device arranged on the optical waveguide. By thermal expansion, the fluid is forced into the slit protruding through the cladding layer into the core layer of the optical waveguide. In another configuration, the fluid substance located in the slit is brought into the gas phase by heating.
The costly production of the familiar switch is a disadvantage, since it is first necessary to make a slit in an optical waveguide, affix a device for filling to it, and seal off this construction against the outside. Because of slitting the optical waveguide, it is only possible to realize parallel surfaces, and moreover these reflecting surfaces do not have high optical quality. Furthermore, the known switch has a high optical damping, since the light beam emerging from the optical waveguide in the region of the slit is divergent and not guided. Therefore, in the transmitting condition of the switch, a portion can be coupled over to the adjoining optical waveguide, which leads to considerable cross-talk in the familiar switch.
SUMMARY OF THE INVENTION
The basic purpose of the invention is to create an optical switching element with low optical damping and low cross-talk, which has a compact construction and a long lifetime, yet which is economical to produce. Furthermore, the purpose of the invention is to provide a switching arrangement with N optical inputs and M optical outputs with the aforementioned properties.
The purposes of the invention are achieved by the features indicated in Patent claim
1
and
30
.
The optical switching element is characterized in that the recess contains a fluid and a body which can move in the recess, the fluid being of such nature and the movable body being of such configuration and able to move in the recess between a position in which the optical switching element is in the transmitting condition and a position in which the optical switching element is in a reflecting condition, that, in the transmitting condition of the switch, the region of the slit between the boundary surface and the surface of the movable body lying in the path of the incident light is filled completely with the fluid and, in the reflecting condition of the switch, at least the region of the boundary surface lying in the path of the incident light is free of the fluid, so that the incident light is essentially reflected at the boundary surface and at least one activating device is provided for switching the moveable body between the transmitting and the reflecting condition of the switch.
In the optical switching element according to the invention, the recess in the transparent base body is only partly filled with the fluid, which is extensively adapted to the index of refraction of the base body. For the switching between the transmitting and reflecting condition, a body which can move in the recess is provided. The movable body is configured such, and it can move in the recess between two positions, that in the transmitting condition of the switch at least the region of the slit lying in the path of the incident light between the boundary surface and the surface of the movable body is completely filled with the fluid. This ensures that the incident light is not totally reflected at the boundary surface, but rather passes through the boundary surface. In the reflecting condition, the body is situated in a position in which the boundary surface is free of fluid, so that the incident light is totally reflected at the boundary surface between the optically more dense medium, i.e., the material of the base body, and the optically less dense medium, i.e., a gas located in the cavity.
The decisive advantage of the switching element is that the boundary surface responsible for the switching process is not moved. Thanks to the preferential use of collimated light beams, no complicated waveguide structures are necessary for guiding the beam in the base body. Since the beam is not divergent, even in the recesses involved in the switching process, the optical multiple switch according to the invention has low optical damping and low cross-talk.
The use of the terms optical input and optical output in contrast with the term optical channel serves only to simplify the description of the optical switching element and its switching arrangements. Because the light paths are reversible, a use in both beam directions, i.e., bidirectional, is possible.
Preferably, the optical switching element according to the invention is operated with free beams, i.e., with light beams not traveling in waveguide structures. This can be achieved, for example, by collimating the light furnished by means of optical waveguides before it enters the switch proper. Basically, however, it is also conceivable to have optical structures for light guidance integrated in the optical switching element, e.g., by means of layer or groove waveguide structures, although this requires a more complex construction of the base body.
When the switching element is switched to the reflecting condition, the fluid must be completely retracted from the boundary surface in the shortest possible time. This effect can be supported in that the surfaces of the boundary involved in the switching condition are subjected to an additional treatment, such as chemical or plasma-chemical, or they are coated with one or more suitable materials. In this regard, a fine structuring of the relevant surfaces is also of advantage.
The base body and the body which can move in the recess consist at least in parts of materials which are transparent in the wavelength region used. If both bodies consist of the same material, this has the advantage that the bodies will have the same index of refraction. Th
Kamper Klaus-Peter
Neumeier Michel
Picard Antoni
Schmidt Martin
Schulze Jane
Epps Georgia
Hudak & Shunk Co. L.P.A.
Institut fur Mikrotechnik Mainz GmbH
Lucas Michael A.
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