Optical Communication Networks for the Next-Generation Internet

Computer and telecommunication networks are changing the world dramatically and will continue to do so in the foreseeable future. The Internet, primarily based on packet switches, provides very flexible data services such as e-mail and access to the World Wide Web. The Internet is a variable-delay, variable- bandwidth network that provides no guarantee on quality of service (QoS) in its initial phase. New services are being added to the pure data delivery framework of yesterday. Such high demands on capacity could lead to a “bandwidth crunch” at the core wide-area network, resulting in degradation of service quality. Fortunately, technological innovations have emerged which can provide relief to the end user to overcome the Internet’s well-known delay and bandwidth limitations. At the physical layer, a major overhaul of existing networks has been envisaged from electronic media (e.g., twisted pair and cable) to optical fibers - in wide-area, metropolitan-area, and even local-area settings. In order to exploit the immense bandwidth potential of optical fiber, interesting multiplexing techniques have been developed over the years.

Optical properties of boron carbide (B5C) thin films fabricated by plasma-enhanced chemical-vapor deposition

Variable angle of incidence spectroscopic ellipsometry was used to determine the optical constants near the band edge of boron carbide (B5C) thin films deposited on glass and n-type Si(111) via plasma-enhanced chemical-vapor deposition. The index of refraction n, the extinction coefficient k, and the absorption coefficient are reported in the photon energy spectrum between 1.24 and 4 eV. Ellipsometry analysis of B5C films on silicon indicates a graded material, while the optical constants of B5C on glass are homogeneous. Line shape analyses of absorption data for the films on glass indicate an indirect transition at approximately 0.75 eV and a direct transition at about 1.5 eV. ©1996 American Institute of Physics.