The spontaneous Raman capture fraction-in a single-mode fiber is inversely related to the effective area of the fiber. This relation ties together classical and quantum approaches to stimulated Raman scattering in fibers and has implications for calculations of gain and noise in fiber Raman amplifiers. The relation between capture fraction and effective area is derived, first, by comparison of the classical and quantum treatments of spontaneous Raman scattering in a fiber and, second, by treatment of the source of the Raman scattered light as oscillating dipoles and calculation of the capture fraction of the dipole radiated power. (C) 2002 Optical Society of America. [References: 13]
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