Double-sideband heterogeneous pulse modulation method for distributed acoustic sensing

In this paper, a double-sideband heterogeneous with suppressed carrier (DSBH-SC) pulse modulation method for fiber-optic distributed acoustic sensing is proposed. An electro-optic in-phase/quadrature (I/Q) modulator is used to realize carrier-suppressed double-sideband heterogeneous pulse modulation in which the positive and the negative optical sidebands can carry independent modulation signals. Due to the modulation curve of the electro-optic I/Q modulator irregularly, the factors that influence the performance of the DSBH-SC are analyzed from modulation amplitude and frequency. The analysis shows that the constant frequency modulation on the lower optical sideband while a stable wide band linear frequency chirping on the upper optical sideband can be obtain in appropriate modulation conditions. It presents a method of digital subcarrier modulation for distributed optical sensing.