Optical modulation depth improvement in SCM lightwave systems using a dissymmetrization scheme

A scheme is proposed that permits the increase of the rms optical modulation depth (OMD) in SCM lightwave systems, without correlative increase of clipping-induced nonlinear distortion. This scheme is based on the addition to the SCM signal of low-pass filtered pulses, produced in synchronism with the peaks of the SCM signal, in order to prevent the clipping occurring during these peaks. An experiment demonstrating the feasibility is described. An rms OMD improvement of 4 and 5 dB has been obtained for a SCM band of 200-800 and 200-600 MHz, respectively.<
>