High-Sensitivity All-Optical Phase Modulation Based on Fabry–Perot Interferometer Integrated With Er/Yb Co-Doped Fiber and Ultraviolet Glue

In this paper, we propose and demonstrate a fiber Fabry-Perot interferometer (FPI) with integrated Er/Yb co-doped fiber (EYDF) and ultraviolet (UV) glue for highly sensitive all-optical phase modulation, where the EYDF produces a strong temperature change under pump light excitation for regulating the refractive index and length of the UV glue cavity, inducing an effective phase shift. The integrated FPI is encapsulated in a hollow-core fiber (HCF) with outstanding all-optical controllability and environmental stability. Experimental results show that the proposed FPI has excellent phase modulation sensitivity (∼0.1922 π/mW) due to the high thermo-optic coefficient and high thermal expansion coefficient of the UV glue. In addition, the coherent characteristic of the FPI can convert phase shift into intensity change, realizing an all-optical tunable filter with a wavelength sensitivity of 0.6456 nm/mW. The proposed device has potential applications in the field of optical filters, fiber sensors and optical communications.