Tunable fiber attenuators for channel power equalization in WDM systems

A tunable fiber attenuator is proposed for channel power equalization in wavelength-division-multiplexed (WDM) optical communication systems. This fiber attenuator consists of two identical fiber Bragg gratings, which are subject to bending in opposite directions by an electrically controlled mechanical driver. The attenuation level at the desired wavelength depends on the amount of bending applied to the gratings. A device with a continuous adjustment of attenuation over a range of 32 dB and a driving voltage of less than 2 V has been demonstrated. The performance of these tunable attenuators for channel power equalization in a two-channel WDM system has been measured. Excellent spectral flattening (+/-0.1 dB) has been achieved for static channel power equalization.