2.b Suppose a semiconductor laser is designed to produce primarily a single frequency output. Discuss what we mean by the "side mode suppression ratio" and describe one very important example where this parameter is important in optical communications.
Side Mode Suppression Ratio (SMSR) defined as the power ratio of the main lasing longitudinal mode to the next strongest mode.
SMSR plays vital role in optical communication, to transmit signal with least noise or distortion. In an optical signal SMSR value should be more than 25dB (>25dB) because less than 25dB builds up noise due to mode partition effect (i.e due to nearest intensity peak as shown in figure). Preferred SMSR vales in optical communication is around 60dB.
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