Analysis and Design of Transimpedance Amplifiers for Optical Receivers

Appendix A

Communication Signals

In this appendix, we review the non-return-to-zero (NRZ) signal, the return-to-zero (RZ) signal, the pulse amplitude-modulated (PAM) signal, the amplitude-modulated signal with vestigial sideband (AM-VSB) for analog television, and the quadrature amplitude-modulated (QAM) signal for digital television. For each signal we discuss the signal power, the power spectral density (PSD), the bandwidth, and the required signal-to-noise ratio (SNR). A partial summary of the results is given in Table A.1. Furthermore, we show how the notation and expressions typically found in the literature on optical communication relate to those found in the literature on communication systems such as [1–5].

Table A.1 Bandwidth and SNR requirement for some digital communication signals

Signal	Bandwidth (DC to null)	SNR requirement for
NRZ		16.9 dB
50%-RZ		15.7 dB
4-PAM		23.9 dB

A.1 Non-Return-to-Zero Signal

The NRZ signal is illustrated in Fig. A.1 with a voltage waveform. The signal is characterized by the swing , the mean value (or DC component) , and the ...