Abstract

Optical fiber is usually modeled as a linear, attenuating, dispersive medium. In a real fiber thermally excited acoustic waves phase modulate the propagating light.¹ Thermal vibrations of atoms cause fiber-density fluctuations and consequent refractive-index fluctuations that induce phase noise in the transmitted light. Because of acoustic waveguiding provided by the optical fiber, the acoustic waves form a series of eigenmodes with discrete natural frequencies. Therefore optical fiber can be modeled as a phase modulator with modulating signals corresponding to discrete acoustic modes.

© 1993 Optical Society of America