A liquid crystal-based Fourier optical spectrum analyzer

We propose a liquid crystal (LC)-based cost-effective Fourier optical spectrum analyzer (FOSA) without moving parts. Unlike normal spectrometers, the LC FOSA retrieves the spectrum´s Fourier coefficients instead of the direct spectrum measurement by changing different LC states in a number of stages. Besides the common applications, the LC FOSA can precisely read and recover the envelope of a dense wavelength-division-multiplexing spectrum to act as a spectral monitor and then work with a gain-flattening device to control the optical network instantly and dynamically.