Dynamic range of a coherent optical spectrum analyzer with a liquid-crystal matrix signal-input device

Abstract

Subject of study. This study investigates the dynamic range of a coherent optical spectrum analyzer with a liquid-crystal signal-input device. Aim of study. The goal is the theoretical and experimental assessment of the false signal levels at the spectrum analyzer output and experimental determination of the dynamic range. Method. A theoretical analysis of the spectral components in the output signal is performed based on the representation of the transmission dependence of a liquid-crystal input device in terms of light amplitude on the input control signal in the form of an expansion into a series of power functions in the proximity of the operating point. The output signals of the spectrum analyzer were experimentally registered, and the values of the dynamic range were determined for the cases of one-, two- and three-frequency input signals. Main results. A calculating technique for the false signal levels at the output of an optical spectrum analyzer with a liquid-crystal matrix signal-input device is proposed, and its dynamic range is measured. Practical significance. A dynamic range higher than 40 dB is achieved for a three-frequency input signal.