Spectrally Efficient Frequency-Domain Optical CDM Employing QAM Based on Electrical Spatial Code Spreading

Shin KANEKO  Sang-Yuep KIM  Noriki MIKI  Hideaki KIMURA  Hisaya HADAMA  Koichi TAKIGUCHI  Hiroshi YAMAZAKI  Takashi YAMADA  Yoshiyuki DOI  

IEICE TRANSACTIONS on Communications   Vol.E94-B   No.10   pp.2877-2880
Publication Date: 2011/10/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E94.B.2877
Print ISSN: 0916-8516
Type of Manuscript: LETTER
Category: Fiber-Optic Transmission for Communications
optical access network,  optical CDM,  spatial code spreading,  multi-level modulation,  self-homodyne detection,  

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We propose frequency-domain optical code-division-multiplexing (CDM) employing quadrature-amplitude-modulation (QAM) using two of multi-level (M-ary) data generated based on electrical-domain spatial code spreading. Its spectral efficiency is enhanced compared to the conventional scheme with amplitude-shift-keying (ASK) using only one of M-ary data. Although it demands the recovery of amplitude and optical phase information, the practicality of the receiver is retained with self-homodyne detection using a phase-shift-keying (PSK) pilot light. Performance is theoretically evaluated and the optimal parameters are derived. Finally, the feasibility of the proposed technique is experimentally confirmed.