Design and performance of a tunable optical demultiplexer using an acousto-optic light deflector

A design and the test results of a tunable optical demultiplexer is described. This demultiplexer is made tunable by addition of an acousto-optic light deflector to a grating optical demultiplexer. In the design of a wavelength division multiplex (WDM) transmission system, one must consider: (1) variation of the optical source wavelength at the time of fabrication and due to temperature variation; and (2) fluctuation of demultiplexing characteristics due to characteristic deviations and orientation accuracy of the components in the demultiplexer. Therefore, in the conventional optical demultiplexer with a fixed demultiplexing characteristic, the passband width of each channel and the wavelength spacing between channels must be wide. Therefore, the number of wavelength multiplexing has been limited. In the present demultiplexer, the demultiplexing characteristics can be adapted to the optical source wavelength at the time of operation. Hence, the number of multiplexing can be increased. In the tunable demultiplexer fabricated for trial, the wavelength spacing between channels is 5 nm, the number of channels is 8, the channel passband width is 2.3 nm, the crosstalk attenuation between adjacent channels is 21 dB, the insertion loss is 9.4 dB, and the tuning width is 3.3 nm.