MPPM: a method for improving the band-utilization efficiency in optical PPM

Multiple pulse position modulation (MPPM) is proposed as a modulation method to improve the band-utilization efficiency in optical pulse position modulation (PPM). Optical PPM gives higher transmission efficiency (bit/photon) in optical communications but degrades band-utilization efficiency. The proposed method reduces the required transmission bandwidth in optical PPM to about half with the same transmission efficiency, thus increasing band-utilization efficiency. While in conventional optical PPM, only one optical pulse is transmitted in every signal block, multiple pulses are transmitted using this method. Information is represented by different combinations of the positions of these pulses. The principle of bandwidth reduction applied, the transmission characteristics of the proposed method, and examples of improvement in band-utilization efficiency are also shown.<
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