Hybrid WDM and Optical CDMA Implemented with M-sequence Coded Waveguide Gratings over Fiber-to-the-Home Network

Abstract

In the last-mile access network, the hybrid wavelength-division multiplexing and optical code-division multiple-access (WDM/OCDMA) scheme for Ethernet passive optical network (the so-called WDM/OCDMA-EPON) is presented over fiber-to-the-home (FTTH) network. In this study, since the FTTH network is characterized by various distance between optical network unit (ONU) and optical line terminal (OLT), the ONU capacity is divided into several groups. Each ONU group is assigned the maximal-length sequence (M-sequence) code which is popularly used for spectral amplitude coding in OCDMA network. By employing the inherent cyclic and free spectral range (FSR) periodic properties of arrayed-waveguide grating (AWG) router, the AWG coder/decoder (codec) is shared by all the ONUs divided various groups with FSR interval range (Deltalambda <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</sub> ). Hence, the number of AWGs is significantly decreased. In addition, compared to the time division multiplexing and wavelength-division multiplexing EPON schemes, the proposed scheme is more flexible, scalable and confidential. The influence of degree of polarization (DOP) is investigated to evaluate the ratio of signal to phase-noise (SNR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PIIN</sub> ). By setting the depolarizer in front of balanced photo-detector, the system performance of simultaneous active ONUs is improved approximating 20% compared to the average DOP of 0.5