Tunable bandwidth optical filter based on MEMS Gires-Tournois interferometer

This paper demonstrates an optical filter, in which the center wavelength and 3-dB bandwidth can be tuned using MEMS technology. The proposed device has a periodic characteristic in the spectral domain with a free spectral range (FSR) matching the channel spacing of DWDM system. This spectral periodicity makes this type of device suitable for colorless narrow bandpass filters. When combined with wavelength multiplexers/demultiplexers with the channel spacing equal to the FSR of the device, for example, this optical filter can be used in any ports to tune the center wavelength and the bandwidth of individual WDM channel. Continuous tuning of the center wavelength and the FSR for these devices have been demonstrated in earlier studies. In this paper, the focus is mainly on variable optical bandwidth. Compared to filters implemented in planar lightwave circuit, the reported device offer improved insertion loss, FSR, and speed of tuning.