Baseline-wander effects on systems employing digital pulse-interval modulation

Fluorescent lamps introduce a periodic interference signal in optical wirel ess receivers, which has the potential to degrade link performance severely . Usually, electrical high-pass filtering is employed to mitigate the effec ts of this interference, but this results in baseline wander or intersymbol interference. Digital pulse-interval modulation (DPIM) is a modulation tec hnique which has been shown to be suitable for deployment in optical-wirele ss-communication systems. The effect of baseline wander on systems employin g DPIM is examined. A new expression is given for the slot autocorrelation function of DPIM and, from this, the power spectral density is calculated. The error performance of DPIM, as a function of high-pass filter (HPF) cut- on frequency, is compared with the more established techniques of on-off ke ying using nonreturn-to-zero signalling (OOK) and pulse-position modulation (PPM), using both numerical analysis and computer simulation.