The Differential 4-Quadrature Coding Scheme for Applications in Optical Communications

Kuen-Suey HOU  Jingshown WU  

IEICE TRANSACTIONS on Communications   Vol.E83-B    No.7    pp.1379-1388
Publication Date: 2000/07/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Transmission Systems and Transmission Equipment
communication system performance,  modulation/demodulation,  optical communication,  polarization,  polarization shift keying,  

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The differential 4-quadrature (D4Q) coherent optical system which does not need absolute phase information is proposed. The input information is encoded in the relative position of the present symbol with respect to the reference frame constructed by the previous 3 symbols. The general theory of the system operation including encoding and decoding is presented. This system does not need to track the fluctuation of the states of polarizations which is essential for most other polarization modulation systems. As an example, the 4-symbol D4Q system is described. And the saddle point approximation is applied to estimate the bit error rate performance. The analytic approximation agrees with the simulation results very well.