Geometrical noise bandwidth of the optical spectrum analyzer

Abstract

Background. Coherent optical spectrum analyzers (COSA) are widely used in data processing systems. The efficiency of the spectrum analyzers is determined by their generalized characteristics such as the operating range of spatial frequencies, spatial bandwidth, the spatial spectral resolution and the energy resolution. One of such characteristics is geometric noise bandwidth GNBW that determines the spatial spectral resolution of spectrum analyzer. Objective. The purpose of this article is to provide a physical and mathematical model of COSA for calculating its geometric noise bandwidth, which determines the spatial spectral resolution of the spectrum analyzer. Methods. Based on the analysis of physical-mathematical model of COSA invited to determine the field amplitude at the output of the spectrum analyzer using the geometric noise bandwidth. Results. It was found that the spectrum analyzer can be considered as a coherent optical invariant linear system characterized by the impulse response and a transfer function. The geometric noise bandwidth of COSA is equal the square of the input transparency, amplitude transmittance of which is determined by the amplitude of the investigated signal. Conclusions. Analysis of the developed physical and mathematical model of the COSA showed that the geometric noise bandwidth is one of the important characteristics of the spectrum analyzer as it allows us to calculate the spatial spectral resolution. It was found that the coherent transfer function of the optical spectrum analyzer is equal to the square of the input transparency, amplitude transmittance of which is determined by the amplitude of the investigated signal.