Cancellation of third-order intermodulation distortion in a directly modulated DFB laser and optical discriminator

In this paper an improved model is used, based on the theory of Volterra kernels, that includes the effect of the laser's intrinsic distortion. Illustrative results are given that show that it is possible to achieve a significant reduction of a third-order intermodulation product (IMP). Moreover, the laser's intrinsic FM distortion is found to be essential for the accurate modelling of the system's IMD3 performance. As a result of this cancellation the intermodulation performance of the system can be better, than for a IM modulated laser without discriminator.