Intermodulation distortion analysis of feedforward linearised laser transmitter employing volterra series approach

This paper demonstrates intermodulation distortion (IMD) analysis of a feedforward linearisation technique in directly modulated semiconductor laser employing a Volterra series approach. Variations of IMD suppression with RF modulation frequency as well as modulation index are shown. The results show that the proposed system can reduce the third intermodulation distortion (IMD3) by more than 45 dB for the wide frequency range from 500 MHz to 10 GHz, 30 mA bias current and 0.1 modulation index. It is also shown that the IMD3 reductions remain constantly for variation of the index modulation from 0.1 to 0.9. Therefore the proposed system can reduce significantly IMD without influence of input power level.