Development of dispersion reduced FBG for DWDM system

摘要

In response to the rapid increase in demands for larger communication capacity, technical innovation of the Dense Wavelength Division Multiplexing (DWDM) system for optical communications is progressing at remarkable speed. The channel spacing is becoming narrower from 100 GHz to 50 GHz, and the bit rate is getting faster from 2.5 Gb/s to 10 Gb/s. In order to carry out dropping and adding of signals of specific wavelength with a dense DWDM system, an optical filter must have response time uniformity as well as steep spectrum characteristics within the band. Although the Fiber Bragg Gratings (FBG) have steep spectrum characteristics, they have large wavelength dependency of reflection response time within the band, thus may result in the problem of deteriorated transmission quality during high-speed transmission. To solve this problem, a dispersion reduced FBG has been developed, aiming toward application in the DWDM systems of channel spacing 50 GHz and bit rate 10 Gb/s. Due to introduction of phase inversion to refractive index modulation amplitude, this new FBG has greatly improved wavelength dependency of response time within the band (group delay characteristics). The transmission experiment has verified that this FBG is effective in a 10 Gb/s DWDM system.