optical decision circuit based on feedback between a laser diode and an SOA
Research Area: III-V Semiconductor Photonic ICs
Main Researcher: Wouter D'Oosterlinck
With the current trend towards all-optical networks all the funcions need to be performed in the optical domain. Among these functions are optical decision functions and as a part of that all-optical regenerators. Several solutions have been proposed to come to an optical decision circuit or regenerator, also in this research group (see above). Most of them are based on the non-linear effects of a SOA in or near saturation. To take advantage of those non-linear effects usually interferometric schemes are used. Since the rely on the phase difference between two different paths of the interferometer they are quite dependent on environmental changes but still offer the big advantage of the possibility to integrate them on a single chip.
for a low input signal the laser can still inject a lot of power into the SOA resulting in a situation where the injected laser power determines the carrier distribution in the SOA. When the input power rises the power coming from the SOA and injected into the laser also rises, resulting in a (initially) slightly lower output power of the laser. When the feedback between the rising output power of the SOA and the consequently decreasing laser output power reaches a threshold value the output power of the SOA drops significantly causing a flip in the carrier distribution in the SOA. This causes a steep step in the output power of the decision circuit.
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