All-fiber modulator derived from the large-transverse-offset Mach-Zehnder interferometer coated with ITO

In this paper, we first propose a fiber electrothermal modulator derived from the large-transverse-offset Mach- Zehnder interferometer (MZI) coated with transparent and conductive indium-tin-oxide (ITO). The fiber MZI was fabricated by welding single-mode fiber (SMF) with large-transverse-offset fusion. The fiber modulator is that the thermo-optic effect of the ITO film on the surface of the fiber leads to a change in the refractive index, which in turn causes the shift of the interference spectrum. Specifically, it is based on the thermo-optic effect of a large- transverse-offset MZI coated with ITO. Through the external electric potential, the ITO film generates Joule heat and then changes the effective refractive index of the cladding to realize fiber phase modulation. In the experiment, the spectrum is significantly shifted by 5.55 nm at the wavelength of 1650 nm and can obtain an optical modulator with a rise (fall) time of 0.65 (0.5) s. The proposed fiber modulator shows great performance in the optical switches and sensing.