Semiconductor laser precision gain switching experiment for Gbaud ternary optical signaling

An experiment performed to gain switch a 1.3 μm semiconductor laser at Gb/s rates and with sufficient electrical-drive precision to validate a previous theoretical study is discussed. The method takes advantage of the relaxation oscillation phenomenon to produce shortened, single optical pulses by careful control of the electrical bias, drive excursion and pulse duration. It was demonstrated that two-level and three-level (i.e ternary) optical data stream generation could be reliably achieved with only two electrical drive levels. The latter was performed by control of the drive pulse duration and is the first demonstration of a three-level PCM system based on two-level gain switching. Furthermore, the pulse shortening which results recommends this technique for optical TDM (time-division multiplexing) of multiple laser transmitters. It is suggested that this combination of formats may ultimately allow the 100-Gb/s target to be achieved