Abstract
This work uses Volterra kernels to model the distortion of complex optical systems using both frequency and intensity modulation of a DFB laser and an optical discriminator. The laser's IM and FM complex responses and also the laser's intrinsic FM distortion are shown to be crucial to model accurately the system's third-order intermodulation product (IMP3) performance. The results show that it is possible to achieve a large reduction of the third-order IMP3 in some frequency ranges by off-setting the bias of the discriminator from the point of maximum slope. Furthermore, at high frequencies the system's IMP3 performance can be better than in the case of a purely intensity modulated laser without a discriminator.

Abstract
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 identified. A 62-channel FM video system occupying the bandwidth of 2.7-5.2 GHz provides an illustrative example.

Abstract
The paper describes the results to date of the RACE project R2005. The project addresses the optical generation and fibre delivery of mm-wave signals for future mobile radio and remote customer access connections. The authors identify potential application areas and appropriate performance targets for such fibre/mm-wave systems. The major issue identified is the need to achieve low-cost antenna units due to the large number of such units that would be required; this arises from the limited propagation distances achieveable at mm-wave frequencies. A brief review of current optical methods for the generation of mm-waves allows the identification of the inadequacies of these techniques and leads to a description of a new method, developed for the project, that overcomes most of the disadvantages outlined earlier.

Abstract
A frequency domain analytic study of laser nonlinear distortion is presented, based on the Volterra nonlinear functional series. This analysis is shown to predict all the intermodulation products up to third order, of particular relevance to the design of subcarrier multiplexed systems, when the laser is modulated by an arbitrary number of channels. Illustrative analytic and simulation results are presented for two and three input subcarriers and are shown to match very closely.

Abstract
The theory of nonlinear systems based on frequency domain analysis using Volterra series is shown to provide an appropriate means of assessing laser distortion which includes the effects of laser resonance. Hence, it is an appropriate and tractable means of assessing the performance of optical subcarrier multiplexed (SCM) systems. Based on this analysis the performance of SCM systems is examined, with calculation of the carrier-to-intermodulation ratio for an eight-channel SCM system providing an illustrative example.

Abstract
Analytic techniques proposed for distortion analysis are shown not to predict adequately the higher order terms generated by a semiconductor laser diode of relevance to the design and dimensioning of subcarrier multiplexed optical communications systems. A modified analysis which avoids this deficiency is outlined and illustrative results are presented.