Microwave fibre optic link design

The compromise between modulation depth and intermodulation distortion in the optical transmitter is shown to be a critical parameter in determining the performance of a microwave fibre optic link. At low modulation depths directly modulated lasers exhibit lower intermodulation distortion than externally modulated lasers, however when overmodulation is employed, the systems performance of both types of device are very similar. The strong correlation between two tone device measurements and multicarrier system measurements using Mach-Zehnder external modulators makes these devices particularly attractive when designing multicarrier optical links