Loss phenomena in perturbed single-mode optical fibers: investigation and applications

Abstract

Losses induced in a single-mode fiber due to periodic spatial deformations along the fiber axis have been investigated spectrally. Deformation losses in several single-mode fibers were found to be strongly wavelength dependent. This wavelength dependence was characterized by narrow attenuation bands in the transmission spectra of periodically deformed fibers. The attenuation bands were shown to shift as the spatial deformation period was varied. The amplitude and location of the attenuation bands were recorded as the number and amplitude of spatial deformations on the fiber were varied. The backreflected spectra of deformed fibers were also studied.

Applications of wavelength dependent losses in periodically perturbed single-mode fibers are proposed. In particular, a self-referenced, intensity-based, fiber sensor is suggested. A distributed sensor is proposed using several sets of deformations with different periods induced on the same fiber to measure the same physical measurand at multiple locations along the length of the fiber. Based on this scheme, a multiplexed fiber sensor is envisioned, capable of measuring different physical variables on the same fiber. Optical notch filters can be made by using the notch-like characteristic of each attenuation band.

Methods to induce permanent, periodic, axial deformations on an optical fiber are discussed. Spectral investigation of two-mode fibers with photo-induced refractive index changes is suggested. The proposed investigations would eliminate the need for external deformers to perturb the fiber and yield an intrinsic fiber sensor for sensing different physical variables.