Liquid-crystal-based tunable filter for WDM (lambda=1550 nm)

Abstract

We report a new configuration of tunable optical filter for DWDM applications. In this design, first-order diffracted signal light by a grating is directed to a lens and focused on to a transmission-type liquid crystal spatial light modulator (LC-SLM). Wavelength channels are selected by opening the appropriate pixels of the LC-SLM for transmission. Filtering into 15 channels of the 1550 nm band is demonstrated in the initial experiment. The channels are designed according to the International Telecommunication Union (ITU) grid with channel spacing of 100 GHz. Channel crosstalk is less than -30dB. The average I dB, 3 dB, and 30 dB passbands of the filter are 0.07 nm, 0.13 nm, and 0.91 nm, respectively. The extinction ratio can be as high as 24.7 dB.