High Gain, Low Noise and Broadband Raman and Brillouin Fiber Optic Amplifiers, Channel Selectors and Switches.

Abstract

Abstract : Wavelength independent Raman (sRs) and Brillouin (sBs) scattering processes in singlemode fibers have been exhaustively investigated for optical amplification - key to channel selection and switching in optical communication. The low gain and high pump threshold of sRs and the high gain, low pump threshold, but extremely narrowband sBs prevented further consideration of these processes for possible optical device fabrication for communication. Fiber rings have been employed to attempt to further lower the sBs threshold for optical switching with some success. However, such a device suffers from excessively long switching time of over 52 ns. Much work remains to improve the performance of fiber ring devices. Dependence of sBs gain and shift on the elastic properties of the fiber material and geometry, and its close correlation with the forward spontaneous but resonant Brillouin scattering, coined GAWBS, via numerous models and experimental verification, point to the possibility of employing both processes for sensing fiber and ambient parameters, such as fiber chemical composition, fiber core and diameter variations, fiber strain, fiber and ambient temperature, etc. The forward and backward sensing capability may render such a sensor fault tolerant. The noise level sensing of GAWBS using electronic heterodyne technique imparts robustness to such a device. Work is ongoing in the practical implementation of the device for structural health monitoring via bonding and embedding.