Programmable holographic elements for WDM

We describe the results of a new wavelength-division-muitiplexing (WDM) technology for use in optical telecommunications. A polarisation-insensitive ferroelectric liquid crystal (FLC) spatial light modulator (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 WDM signals spaced by 4 nm, and dynamic equalisation to within 0.75 dB of eight channels spaced by 3.85 nm with an input signal range of 9.5 dB. An erbium-doped fibre laser (EDFL) has been tuned over 38 nm using the holographic filter, with controlled single and multiple lasing frequencies. Apodisation of the filter passband has also been demonstrated