A comparison of coherent digital PPM with PCM

Robert A. Cryan, Rodney T. Unwin, Alistair J. Massarella, Martin J.N. Sibley, Ian Garrett

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)


Digital pulse position modulation (PPM) is a preferred modulation format for the ideal photon counting channel and optical intersateilite links. Here we examine its potential for the coherent optical fibre communications channel. We present a thorough performance and optimisation analysis. Comparisons, at a wavelength of 1.5 μm, are made with shot‐noise limited coherent PCM (homodyne and heterodyne ASK, FSK and PSK) over a range of fibre band‐widths and varying PPM word size. We conclude that for moderate to high fibre bandwidths homodyne digital PPM should achieve an improvement in sensitivity of typically 5 dB over homo‐dyne PSK PCM.

Original languageEnglish
Pages (from-to)331-340
Number of pages10
JournalEuropean Transactions on Telecommunications
Issue number4
Publication statusPublished - 1 Jul 1992


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