Tolerance to optical feedback of 10-Gb/s quantum-dash-based lasers emitting at 1.51 μm

Tolerance to optical feedback is investigated on quantum-dash-based lasers emitting at 1.51 μm. The onset of coherence collapse regime is experimentally determined using three criteria: optical spectrum broadening, relative intensity noise increase, and bit-error-rate degradation. Measurements were first performed in static operation at different current values, using the first and second criteria. The onset of coherence collapse was found to increase from ∼ 41 to - 27 dB with the bias current. Then tolerance to optical feedback was assessed in dynamic operation at 10 Gb/s, using the third criterion. In spite of a relatively high linewidth enhancement factor (α H ∼ 4.5), a - 32-dB onset of coherence collapse corresponding to - 24-dB maximum optical return loss tolerance was achieved at 10-Gb/s rate.