Optical Multicast Overlay and Survivable Architectures in High Speed Multi-Wavelength Optical Access Networks

Nowadays, broadband applications, such as interactive video and multimedia services, have further increased the demand of bandwidth, and thus make high speed multi-wavelength optical access network highly desirable. Wavelength division multiplexing passive optical network (WDM-PON) is a promising candidate to realize the next generation optical access networks due to its dedicated bandwidth for each subscriber and more flexible bandwidth management. As the network traffic is becoming more data-centric, more networking capabilities are required to provide the data service in a more flexible and reliable way. In this thesis, we have proposed and investigated several interesting optical multicast overlay schemes and network protection architectures for WDM-PONs. Optical multicast overlay technique can support the additional multicast transmission on the existing point-to-point data services, while network protection architectures can assure network availability with short traffic restoration time. We will briefly discuss our work in the following sub-topics.;Optical multicast overlay in WDM-PON: Traditional WDM-PONs support only two-way point-to-point data transmission between the optical line terminal (OLT) and the individual subscribers, via the respective designated set of wavelengths. To enhance the network flexibility, it is more desirable to support various different modes of data or video delivery such as broadcast and multicast, in addition to point-to-point transmissions. In this thesis, we systematically investigate the problems and propose our several feasible schemes to overlay multicast transmission onto the existing point-to-point traffic in a WDM-PON. In the first approach, the control of the multicast transmission is achieved by a simple polarization-assisted scheme at the OLT. By the cross-use of wavelengths, a separate path is provided for the multicast differential phase shift keying (DPSK) data from downstream point-to-point amplitude shift keying (ASK) data without additional light sources, which guarantees the transmission performances in both directions, since the upstream ASK signal is imposed on the multicast DPSK signal. We have also demonstrated its variant, in which an optical switch replaces the polarization-assisted control for multicast transmission. The second approach is based on the optical carrier suppression (OCS) technique at the OLT so as to generate the optical subcarriers or sidebands for multicast ASK data modulation. The downstream unicast data is modulated in DPSK format, which will be re-modulated with the upstream ASK data at the respective optical network unit (ONU). As the downstream unicast signal and the upstream signal are calTied on different fiber feeders, while the upstream signal and the multicast signal are carried on different subcarriers, though on the same fiber feeder, the possible Rayleigh backscattering effect is much alleviated. In the third scheme, by using subcarrier modulation technique, we have first successfully overlaid two independent multicast data streams simultaneously onto a WDM-PON, which is believed to further enhance the network capability for multiple destination traffic and improve the cost effectiveness for the future network. Finally, we will provide a comprehensive comparison on all the proposed schemes in this topic.;Survivable network architectures for WDM-PONs: A survivable WDM-PON architecture which can provide self-protection is attractive to avoid enormous loss in data and business due to fiber cuts. To facilitate the network management, the protection switching is realized at the OLT. In this thesis, a simple centrally controlled survivable WDM-PON architecture employing OCS technique is proposed. Protection switching at the OLT employs electrical switches to control the clock signal for the protection sub-carrier generation, via optical carrier suppression. Both distribution and feeder fibers are protected simultaneously. By employing inverse-RZ (IRZ) format for the downstream transmission and non-retum-to-zero (NRZ) for the upstream re-modulated signal, the optical network units are kept colorless and simple. On the other hand, wavelength division multiplexing/time division multiplexing (WDM/TDM) hybrid network, which combines TDM technology and WDM technology, can further increase the network reach, transmission capacity, and reduces the cost per subscriber. Although the bandwidth per subscriber in a WDM/TDM PON is less than that in a WDM-PON, it is still considered as a smooth migration from TDM-PON to WDM-PON. In this thesis, we have proposed a novel WDM/TDM PON architecture which can provide self-protection using a ring topology to connect the subscribers. Finally, we will provide a comprehensive comparison on all the proposed schemes in this topic.