Performance of optical receivers incorporating cascaded semiconductor laser preamplifiers

It has been shown that the gain spectrum obtained by cascading two or more semiconductor laser amplifiers (SLAs) can have a ripple amplitude that is significantly smaller than that currently attainable with a single stage of optical amplification. The paper examines the performance of optically preamplified receivers employing cascaded SLAs, emphasis being placed on the influence of signal frequency fluctuations. The authors results´ suggest that cascaded SLAs offer improved receiver sensitivity in the presence of laser chirp compared with a single-stage amplifier of the same net gain and facet reflectivity. They have used these techniques to investigate a new approach for cascading SLAs to realise optically preamplified receivers, which are less sensitive to optical signal polarisation. The approach uses a single optical receiver and no additional receiver electronics