External optical feedback effects on intensity noise of vertical-cavity surface-emitting lasers

The authors have experimentally evaluated the effect of external optical feedback on the relative intensity noise (RIN) of a vertical-cavity surface-emitting laser (VCSEL) diode. In the absence of optical feedback, the smallest RIN is found to be -135 dB/Hz. For optical feedback levels approaching -25 dB, the RIN is degraded by about 20 dB. The authors have measured feedback-induced power penalties in a 500-Mb/s intensity-modulation/direct-detection (IM/DD) link and determined that the penalty exceeds 1 dB if the optical feedback ratio is larger than -30 dB.>