On the Wavelength-Selective Nature of Rayleigh Backscattering in Single-Mode Fibers

Spectral measurements of the Rayleigh backscattered light in a single-mode fiber are performed for a white input source with coherence length 100 times shorter than the fiber length. The experimentally measured spectrum of the backscattered light from a 45 cm-long fiber exhibits a jagged intensity profile that is highly wavelength-dependent. Measurement data were compared with model predictions based on small fluctuations of the fiber refractive index on a centimeter scale, generating interference fluctuations on the spectrum of the backscattered light. The agreement between measured data and model simulations supports that optical interference is behind the wavelength-selective nature of Rayleigh backscattering in single mode fibers and that white light becomes colored when backscattered in a single mode fiber.