Modern communications systems are shifting from electronic methods of transmitting data to high bandwidth optical communications systems. In order to improve efficiencies, such systems ideally utilize an optical switching system. An example of such a switching systems that switches an output of a fiber into one of several different fibers is described in U.S. Pat. No. 4,365,863 entitled xe2x80x9cOptical Switch for a Very Large Number of Channelsxe2x80x9d issued to Broussaud et al. in December 1982 and hereby incorporated by reference.
One difficulty with optical systems is that alignment between optical components is critical. Minor deviations can cause signal loss, or improper,transmission of information. The problem is particularly acute in switching systems that propagate an optical signal over significant distances in free space before coupling the optical signal back into an optical fiber.
In order to improve alignment, various alignment techniques have been proposed. In one technique, a diverting device such as a mirror or beam splitter diverts a portion of the original optical beam or signal to a sensor. The system determines the expected position of the original optical beam or signal based on the relative orientation and position of the diverting device and the position of the diverted beam. A feedback loop transfers information from the sensor to mirrors or other apparatus to assure that the original optical beam remains properly aligned.
The described systems of using beam splitter has several disadvantages. A first disadvantage is increased system complexity. In particular, the described system requires diverting devices and careful positioning of components and sensors in relation to the diverting device. A second disadvantage is that the diverting devices typically divert a large percentage of the incident light reducing the signal strength of the original optical beam. The reduced optical signal strength decreases the signal to noise ratio and may increase the need for amplifiers to amplify the transmitted optical signal.
Thus an improved system for aligning optical components is needed.
A highly transmissive sensor ideally suited for use in systems that require accurate alignment is described. The sensor includes a highly transmissive detector layer such as an amorphous silicon layer to detect incident optical signals. The amorphous silicon layer is deposited on a substrate that is highly transmissive to the optical signals being detected. Examples of such substrates include glass. In one embodiment, a substantially highly transmissive conducting plate serves as an electrode. Such conducting plates may be made from material such as Indium Tin Oxide (ITO).