Ultra-High-Capacity Optical Communications and Networking: Advanced Raman Gain for Next Generation Networks

0123484

Stegeman

This proposal was submitted in response to the solicitation NSF 01-65 on 'Ultra-High Capacity Optical Communications and Networking.' The continuously growing demand for communications channels in short and long distance networks necessitates an expansion of the available spectral region near the loss minimum of silica-based fibers. Dramatic reduction of the 'water' absorption peak at 1400 nm opened up the available communications window from 1270 to 1650 nm, corresponding to about 50 THz. Such a large bandwidth rules out existing erbium doped fibers and semiconductor lasers leaving Raman gain as the prime amplification mechanism. However, the Raman bandwidth in silica fibers is only 10 THz, and gain coefficients in silica glass are small. As a solution the PIs propose to investigate new materials for signal amplification by Raman gain for local networks, intermediate distance networks and long-haul fiber transmission. New Raman gain media will be considered in both bulk and fiber form, the first for local area networks and specialized applications, and the second for longer distance transmission.

New glass, molecular and polymeric materials will be fabricated, and characterized by spontaneous Raman scattering, Raman gain measurements. and the evaluation of the Raman gain materials in a fiber network environment. A selection of those will be fabricated into fibers and the Raman gain evaluated in network scenarios.

The PIs propose to explore new classes of oxide and non-oxide glasses to optimize the structure-property relations that give the best properties for Raman gain. These will include chalcogenide glasses with varying As, S, and Se content, and heavy metal halides such as the 'TeX' glasses. Oxide glasses of interest are phosphates, heavy metal oxides, and borophosphates which exhibit spectrally broad Raman bands. A variety of organic species will be examined, mostly in polymer form. The diversity of functional groups in organic media can cover the fully desired 50 THz bandwidth, and more, for Raman gain. Polymer blends and composites will be prepared that contain specifically designed molecules that cover this spectral range and their Raman signal strength measured. Families of interest will include polythiophenes and related polymers that have previously shown strong Raman scattering. Also investigated will be the fluorenyl family of chromophores which possess high thermal and photochemical stability. Inorganic and organic components can be combined in virtually any ratio to obtain hybrid sol-gel nano-composites extremely versatile in their composition, processing characteristics, and properties. Thus through judicious selection of the organic component, particular optical properties can be realized such as extended Raman bandwidth and gain coefficient.