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.