Modulation dynamics of amplified spontaneous emission in saturated GaInAsP/InP semiconductor optical amplifiers

We investigate modulation dynamics of amplified spontaneous emission (ASE) of saturated semiconductor optical amplifiers (SOAs) with various device lengths. We measured the optical intensity modulation of ASE of GaInAsP/InP SOAs. In a long SOA, a large input-signal-wavelength dependence of the ASE response was observed, which was relaxed in a large-signal measurement in comparison with a small-signal measurement. Faster responses in ASE were obtained under higher bias current density and in longer SOAs even with the same injection current density. We demonstrated a high speed response beyond 20 GHz with an long SOA. In addition, we demonstrated 10 Gbit/s operation of the optical preamplifier using inverted ASE signal of a saturated SOA with a receiver sensitivity of -22.7 dBm.