Speed Enhancement of a Single-Mode FP-LD-Based Switch Using the Weak-Lock Technique

A technique called weak-lock (WL) has been proposed and applied to a simple optical on/off switch to increase its working speed from 1 to 12 Gb/s with clear output waveforms, whereas the required injection power is decreased. The switch is based on the injection-locking property of a single-mode Fabry-Pérot laser diode (SMFP-LD). Unlike the case of full-lock (FL) in which self-locked mode and all side modes of the SMFP-LD are fully suppressed due to high injected input power, in the WL case, the injection power is gradually decreased as if the SMFP-LD's self-locked mode is still maintained. It was observed that the output waveform's rising edge, taken at the self-locked mode's wavelength after the filter, in the WL case is clean at speed of 12 Gb/s compared to the blur and noisy rising edge in the FL case even at much lower speed (1 Gb/s). In summary, the WL technique shows advantages compared to the conventional FL technique in terms of lower injection power and higher on/off switching speed.