A novel wideband radio frequency measurement based on photonic signal processing

Abstract

Photonic signal processing is a suitable alternative of electronics based processing for wideband frequency detection. We propose a novel technique for the detection of a wide range of frequencies based on photonic signal processing. The unknown frequency to be measured is used to modulate a tunable optical source by implementing single sideband suppressed carrier modulation. The modulated signal is combined with two fixed frequency optical carriers to perform heterodyne detection. The frequency of the tunable laser source is swept until significant power of the beat signal is observed after photodetection. A mathematical expression is presented that can be used to measure the frequency of the unknown electrical signal based on value of the center frequency of tunable laser source. The effect of increasing laser linewidth up to 100 MHz and instantaneous shift in laser center frequency up to 200 MHz has also been demonstrated. It has been shown that the proposed technique can measure almost any radio frequency by simply varying the frequency of the tunable laser source.

Features of the practical application of Mach-Zehnder modulators for the formation of probing radiation

“…Optical carrier modulation is a fundamental process not only in fiber optic transmission lines, but also in radio photonic systems. In the latter, with the help of modulation, both the transfer of a radiofrequency signal for its subsequent processing in the optical range, and for the formation of radiation with a special spectral structure, which are used to build radio-photonic measuring systems [1][2][3][4][5] , for example, vector analyzers [6][7][8][9][10][11][12] , are carried out. Despite the different purposes of generating radiation, similar requirements are imposed on the modulating stages in all cases, namely: providing the necessary dynamic range of the signal both at the input and at the output with a given level of intermodulation and nonlinear distortions, which makes it possible to determine the permissible values of the modulating voltages, which form an optical signal with the highest possible signal-to-noise ratio for given nonlinear distortions.…”