Designing Semiconductor Optical Amplifiers For Low Multi-Channel Gain Crosstalk

Gain crosstalk in semiconductor optical amplifiers (SOAs) developed for WDM networks has in the past been a limiting factor in SOA deployment. One recently-proposed solution is the gain-clamped SOA, where the amplifier gain is stabilised in a complex cross-cavity configuration. In this paper, we describe the design of conventional SOAs for low multi-channel gain crosstalk (GXT). Specifically, we compare alternatives for reducing crosstalk, including reductions in SOA length, current density, and the number of quantum wells. Numerical modeling shows the reduction in well number to have the largest impact; experimental results for a 4-well device show 2-channel GXT of -20 dB at a modulation frequency of 10 GHz, a fiber-coupled output power of +5 dBm (+2 dBm per channel), and a module gain of 15 dB.