The performance of frequency-modulated (FM) subcarrier-multiplexed systems is assessed using Volterra series analysis to model laser nonlinear distortion accurately. The intermodulation-power spectral density and the carrier-to-intermodulation ratio are then determined. The performance of these systems is investigated by considering all noise contributions: intermodulation and relative intensity noise in the transmitter and receiver thermal and shot noise. Optimum performance is also identifed. A 62-channel FM video system occupying the bandwidth of 2.7–5.2 GHz provides an illustrative example.