Numerical Analysis of Suppression Effects on Optical Feedback Noise by Superposition of High Frequency Current in Semiconductor Lasers

Semiconductor lasers tend to suffer from the optical feedback (OFB) noise caused by the reflection of the output light at the surface of the optical disc or the optical fiber. Superposition of high frequency (HF) current is used as a technique to suppress the OFB noise. However, this is not effective when the frequency of the HF current coincides with a rational number of the round trip time for the OFB. This paper shows numerical simulations on the phenomena of the OFB noise, its suppression by the superposition of HF current and conditions at which the HF current is unable to suppress the noise. The model used here is based on multimode rate equations that include nonlinear gain, Langevin noise sources, the OFB, and the HF superposition. Generating mechanism of the OFB noise and its suppression are explained with approximated but analytical equations. Excellent correspondence between experimental data and simulation is also demonstrated.