| 摘要 |
The efficiency and freedom from cross-talk achieved by transmissive multiplexer/demultiplexer devices is achieved in a reflective multiplexer/demultiplexer device. The reflective geometry avoids the large size devices necessitated by transmissive geometries handling a large number of optical channels. The reflective geometry also avoids long bends in waveguides used in optical gratings in high efficiency transmissive geometries. Integrated optical multiplexers/demultiplexers in accordance with this invention comprise a plurality of waveguides for carrying unmultiplexed optical signals interleaved with a plurality of waveguides for carrying multiplexed optical signals. The two pluralities of waveguides are connected to the boundary of a free space region. The pluralities of waveguides communicate through the free space region with an optical grating comprising a plurality of waveguides each terminated in a reflective element. The length of each waveguide in the grating differs from the lengths of adjacent waveguides in the grating by a predetermined amount to introduce predetermined path length differences for the optical signals traveling in the waveguides of the grating. Unmultiplexed optical signals, introduced into one or more of the input waveguides for carrying unmultiplexed optical signals, travel through those waveguides into the optical grating and are reflected towards one or more of the output waveguides for carrying multiplexed optical signals. When the device is used as a multiplexer in this fashion, it causes the optical signals introduced into the device to be multiplexed together and appear in a predetermined one or more of the waveguides for carrying multiplexed signals. Multiplexed optical signals introduced into one or more of the waveguides for carrying multiplexed signals are directed through the free space region to the optical grating and are reflected toward one or more of the output waveguides for carrying unmultiplexed optical signals. When the device is used as a demultiplexer in this manner, input signals which comprise a mixture of optical frequencies are demultiplexed so that the individual optical frequencies are separated from one another and appear at one or more predetermined waveguides for carrying unmultiplexed optical signals.
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