A comparative evaluation between internal and external polarization modulation of lasers

A comparison is made between internal polarization modulation (IPM) (or coupling modulation) and external polarization modulation (EPM). This is done for the case of maximum-available laser signal power output when both bias and drive voltages are optimized, as well as for the case of a small fixed drive voltage but optimized bias conditions. Signal-to-noise ratio and efficiency is also considered. Calculations were made without recourse to small-signal theory. Results reveal the conditions of laser gain and modulator loss under which IPM is advantageous.