Bi-directional dense wavelength division multiplexed systems for broadband access networks

Dense wavelength division multiplexing (DWDM) is becoming the technology of choice for meeting the increasing bandwidth demands in optical networks. DWDM has been used to increase the capacity of long-haul optical transport systems. Efforts are being made to move DWDM into the broadband access network serving residential and business subscribers. The use of DWDM in the passive optical network (PON) presents a viable future solution for transmitting multiple services, including video, voice, and data on a single network. In addition, privacy and bandwidth are enhanced in DWDM PON since each subscriber could receive a single unique wavelength or each wavelength could be shared among several subscribers using time division multiplexing (TDM). The objective of the research presented in this thesis is to develop novel, efficient, bi-directional broadband optical networks using dense wavelength division multiplexing (DWDM) technology.; First, a new centralized DWDM PON scheme is demonstrated for bi-directional upstream and downstream transmissions. The proposed DWDM PON scheme is implemented using optical carrier suppression and separation (OCSS) technology to generate a wavelength pair from a single laser source at the central office. This method enables the co-location of both upstream and downstream DWDM transmitters in the central office. In addition, the complexity, cost, and maintenance of the optical network unit are reduced by enabling wavelength independent operation. The feasibility of symmetric, bi-directional, single fiber transmission over the proposed DWDM PON architecture has been studied for both eight and 16 generated OCSS wavelength pairs.; Second, a new multistage architecture is proposed for the delivery of information to groups of subscribers located at different distances from the central office. A 25 GHz DWDM comb is generated using OCSS technology, and error-free transmission of four 10 Gbps channels is demonstrated.; Finally, a new wide area access network with bi-directional DWDM amplification using semiconductor optical amplifiers (SOAs) is demonstrated. The detrimental effect of SOA crosstalk resulting from cross gain modulation can be suppressed using a constant intensity modulation format such as differential phase shift keying (DPSK). The feasibility of bi-directional DPSK transmission of 16 interleaved DWDM channels using an in-line SOA has been studied experimentally. In addition, the reduction of bi-directional SOA reflections has been realized by optimizing the SOA bias current and facet reflectivities.