Enhancing Photosensitivity in Optical Fibers

Abstract

Photosensitivity in optical fiber enables fabrication of gratings and grating-based devices that are critical components in optical communications networks. The intrinsic photosensitivity in standard singlemode (SSM) telecommunication fiber is typically low. As a result, several methods of enhancing the fiber photosensitivity have been actively researched in the past. One of the major areas of research has been to develop intrinsically photosensitive fiber by increasing the germanium (Ge) content in the fiber core and also by co-doping with materials such as boron, phosphorous, erbium, and tin. Using these specialty fibers results in large splice losses with the SSM fiber due to mode-field diameter mismatch, an increase in ultraviolet (UV)-induced impairments such as absorption loss and birefringence due to grating fabrication, and a reduction in thermal stability of the gratings due to dopant migration. The chapter also discuses that developing new methods to increase the intrinsic photosensitivity in the SSM fiber is still attractive because of their wide use, excellent optical characteristics, low polarization mode dispersion, low cost, and minimal insertion loss. It also discusses the results using two methods-UV sensitization and dilute hydrogen sensitization-of enhancing photosensitivity in SSM optical fibers for manufacturing fiber Bragg grating (FBG)-based devices. © 2006 Elsevier Inc. All rights reserved.