"Optical Gating by Ultrashort Pulse for High Quality Signal Detection and Demultiplexing"

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The next generation optical communication should support the demand of switching arbitrarily among optical channels as well as allocating broad bandwidth to individual users. Therefore high quality and simple optical device technology is required in access networks. We tried to implement a novel scheme of optical signal detection by combining such emerging technologies as ultrashort pulses, all optical switches, and micro-optics.Major achievements by this investigation are as follows :(a) Design and test fabrication were performed on a glass optical platform employing diffractive optical elements for all optical switch array. At the switch position the beam overlap between the trigger light and the signal light was excellent. (JJAP March 2000)(b) Multi-quantum well saturable absorber switches were mounted on the glass platform, and the switching experiment was performed using gain switched semiconductor laser pulses of 25 picosecond in pulse width. The switching sensitivity was comparable with the conventional free space illumination configuration. With the addition of the compactness and robustness of the present scheme, it is more promising for practical applications. (IEICE Trans. March 2001)(c) We proposed a new scheme of improving signal to noise ratio in detecting the pulse-position-modulated codes by optical gating technique, under the assumption that the signal is delivered by low duty ratio RZ signal stream. A simulation will be presented at CLEO2001 in May 2001.