WDM channel management using programmable holographic elements

We describe results of a high-resolution (0.8 nm) holographic, digital multi-wavelength filter, based on a ferroelectric liquid crystal (FLC) spatial light modulator (SLM). The filter has applications as a wavelength-division-multiplexing (WDM) technology for use in optical telecommunications. The polarisation-insensitive FLC SLM acting as a programmable holographic element in conjunction with a highly wavelength-dispersive fixed diffractive element has been used to perform a number of important WDM functions: demultiplexing of single and multiple (up to 4), segmented passbands spaced by 0.8 nm, and dynamic erbium-doped fibre amplifier (EDFA) gain equalisation. Apodisation of the filter passband has been demonstrated, and optical add/drop multiplexing is also possible using the holographic technique. The filter offers potential low loss, excellent crosstalk characteristics, and a high resolution over a large tuning range