• Title : Highly Spectral-Efficient Optical Code-Division Multiplexing Transmission System
• Authors : Hideyuki Sotobayashi, Wataru Chujo, and K.en-ichi Kitayama
• Journal : IEEE Journal of Selected Topics in Quantum Electronics., vol.10, No.2, pp.250-258, 2004.
• Abstract : A highly spectral-efficient transmission system based on optical code-division multiplexing (OCDM) technique is investigated. To meet the rapid increase in the demand of data bandwidth, spectral efficiency is becoming a key factor in optical transport systems. Several modulation formats along with the optical receiver design have been proposed to upgrade the spectral efficiency.OCDM is one of the promising techniques for this purpose. OCDM is the other class of multiplexing technique than optical time-division multiplexing and wavelength-division multiplexing (WDM). OCDM provides unique features such as asynchronous transmission, secure communication, soft capacity on demand, and high degree of scalability. In this paper, we apply OCDM technique to the highly spectral-efficient transmission system by quartenary phase-shift keying optical encodeing/decoding along with ultrafast optical time-gating and optical hard thresholding. As a result, a transmission of 6.4 Tbit/s OCDM/WDM (4 OCDM x 40 WDM x 40 Gbit/s) using only C-band wavelength region is experimentally demonstrated with 1.6-bit/s/Hz spectral efficiency.
• Key words : Optical code-division multiplexing (OCDM), photonic network, photonic processing, spectral efficiency, wavelength-division multiplexing (WDM)

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