| Transparency of the optical channel to transmission rate, format, and protocol is a well-known concept that has been explored in various Wavelength Division Multiplexing (WDM) all-optical networks, having subnetworks geographically separated and homogeneously designed (i.e., using same rate, protocol, and format).; However, geographic boundaries of current subnetworks are becoming fuzzy, e.g., due to the introduction of virtual private networks. Moreover, the degradation of the quality of the optical signals, due to physical impairments, can affect the optical transparency even inside a subnetwork, e.g., by constraining the channel bandwidth-distance product. Also, part of the huge available bandwidth on each channel could remain unused if channels are transmitted all-optically, without the possibility of traffic aggregation at some intermediate nodes.; This dissertation investigates the impact and advantages of channel transparency, in hybrid network architecture (also referred to as multi-hop architecture). The key features of hybrid networks considered in this dissertation are: multi-rate, i.e., the possibility to choose the most appropriate transmission rate on a given optical channel; and multi-span, i.e., the possibility to choose how many fibers and optical nodes the optical channel may span across transparently, before conversion of the signal from optics to electronics is required. The optimal rate and span of each optical channel is determined by a number of factors including resource availability, technology, user's application requirements, amount of multiplexed traffic, and cost effectiveness.; The potential advantages provided by the Multi-Hop and Multi-Rate (M& M) network when compared to first generation optical networks, to single- and multi-hop (constant single rate) optical networks, are discussed in general and demonstrated numerically for ring and mesh topologies. Also, the impact of transmission impairments—such as chromatic dispersion combined with self-phase modulation, and polarization mode dispersion—on the design and on the cost reduction in M&M networks is evaluated. Results show that the network cost reduction achieved by the M&M design, in the presence or absence of transmission impairments, is a function of the cost ratio between the optical bandwidth (wavelengths) and the optical terminals. The study contradicts the commonly believed fact that optical transparency is advantageous only when bandwidth is inexpensive compared to electronic processing. |
