The frequency multiplication in electrooptical modulator of the Mach–Zehnder

Abstract

The analysis of parameters of work of the electrooptical modulator of the Mach–Zehnder circuits for frequency multiplication of the radio signal. The possibilities of frequency multiplication are revealed and the optimal parameters of signals are determined. It is determined that for a given geometry of the modulator electrodes for longer laser waves, the half-wave voltage is higher than for shorter wavelengths. The maximum permissible modulation index is higher in Mach–Zehnder electrooptical modulators with a shorter wavelength of laser radiation. The number and amplitude of the spectral components at the output of the modulator depends on the amplitude of the modulating microwave signal, as well as on the location of the working point on the transfer function of the modulator. Without shifting the operating point, the Mach–Zehnder electrooptical modulator multiplies the signal frequency by 2, 4 and 6 times (to obtain even harmonics). If the modulator allows for a larger modulation index, even harmonics of a larger order can be obtained. The shift of the working point of the Mach–Zehnder modulator to the linear region of the transfer function (by half the half-wave voltage) allows to obtain odd harmonics. When the displacement voltage of the working point is equal to a quarter of the half-wave voltage, the Mach–Zehnder electrooptical modulator allows to obtain both even and odd harmonics. The maximum frequency of harmonics is limited by the allowable voltage amplitude for RF electrodes (the permissible amplitude of the modulating voltage). A further significant increase in the frequency multiplication factor is possible in circuits with two or more Mach- Zehnder modulators. Diagram with two modulators of the Mach–Zehnder allows you to get a grid of frequencies. The Mach–Zehnder modulator in the mode of odd harmonic generation can be used as a converter of sinusoidal voltage to a periodic voltage close to the pulse voltage. Radio-photon frequency multipliers have a wide band of operating frequencies. It is determined by the frequency properties of the modulator and photodetector. Frequency multipliers signal current in radiophonic systems to transfer sinusoidal frequencies in the microwave range, to synthesize a grid of frequencies.