Open AccessA simple delay-line 4-PPM demodulator with near-optimum performance
Author(s) -
Mark L. Stevens,
Don M. Boroson
Publication year - 2012
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.20.005270
Subject(s) - demodulation , comparator , computer science , sensitivity (control systems) , optics , modulation (music) , electronic engineering , bit error rate , signal processing , line (geometry) , signal (programming language) , digital signal processing , telecommunications , physics , computer hardware , mathematics , electrical engineering , decoding methods , acoustics , engineering , channel (broadcasting) , geometry , voltage , programming language
We describe a simple 4-PPM demodulator that uses analog delay lines and simple 1-bit comparators to determine the least-significant bit and most-significant bit of the 4-PPM encoded data without additional digital signal processing. We show that with good optical filtering the comparator-based demodulator can theoretically operate with sensitivity only 0.23 dB from the optimum 4-ary receiver. We describe as an example of this approach the demodulator built for the Lunar Laser Communication Demonstration and show measured performance within 1.1 dB of the expected sensitivity. The technique is extendable to higher-order, and higher-symbol-rate orthogonal modulation formats.