On waveform equalization and its economic advantage in an optical fiber PCM transmission system

This paper deals with the merits of waveform equalization in repeatered optical-fiber PCM communication systems and with the optimum equalized waveform which minimizes the power sum of shot noise, thermal noise and intersymbol interference. Although shot noise is the dominant disturbing factor, the optimum calculated equalized waveform does not differ much from that in a coaxial cable PCM system. An optical-fiber PCM system working at a bit rate of less than 100 Mb/s exhibits improvement in repeater spacing (about 2 km regardless of bit rate) due to waveform equalization. The multiplicative relation between shot noise and intersymbol interference is considered. Comparison of repeatered systems with and without waveform equalization is presented from the economic standpoint under the constraint that the total transmitted information and the transmission distance are fixed.