Effect of external optical feedback on the spectral properties of cleaved-coupled-cavity semiconductor lasers

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Abstract
The effects of external optical feedback on the spectral properties of cleaved‐coupled‐cavity (C3) single mode lasers have been investigated. cw mode rejection ratios and intensity dropout rates have been measured at different optical feedback strengths. The study shows some individual variations in sensitivity to optical feedback between lasers of the same structure. Optical feedback as small as −22 dB can cause a significant number of intensity dropouts from the main lasing mode in some units whereas other units can tolerate a −15 dB optical feedback without causing dropouts or degradation in the mode rejection ratio. By taking some simple steps in preventing reflections in fiber optic systems, it is shown that even the most sensitive C3 laser can be operated without penalty due to optical feedback. cleaved‐coupled‐cavity semiconductor lasers