Narrow Bandwidth Grating-Assisted Acousto-Optic Tunable Filter

摘要

Dense wavelength division multiplexing (D-WDM) is promising in future informationnetworks to increase the communication bathwidth. One of the most crucial components in D-WDM is the fast tunable optical filter. The optical tunable filter should be able to filter out desired wavelengths quickly, finely (narrow spectral bandwidth) and over a broad tuning range to cover the erbium-doped fiber amplifier (EDFA) passband (1530nm-1570nm). The acousto-optic tunable filter (AOTF) is most commonly used for the current D-WDM. However, the spectral bandwidth of current AOTFs is broad (several nm for the interaction length of 1 cm) and so it causes serious crosstalk problems due to sidelobes. This limits the number of wavelength channels in D-WDM. The authors describe a new acousto-optic tunable filter that can increase the number of channels significantly by combining a diffraction grating with an acousto-optic spectrum analyzer. The novel grating-assisted acousto-optic tunable filter (GA-AOTF) allows a very narrow spectral bandwidth (only 5% of those of conventional AOTFs) permitting approximately 20 times more channels.