Ultrahigh birefringence index-guiding photonic crystal fiber and its application for pressure and temperature discrimination

Inthis Letter, we reported on an ultrahigh birefringence photonic crystal fiber (PCF) with a germanium-doped elliptical core, which is fabricated in our lab using the stack-and-draw method. An ultrahigh birefringence of 1.1 × 10-2is obtained experimentally, which isclosetothe theoretical value of1.4 × 10-2at the wavelength of1550 nm. Toour knowledge, this is the highest birefringence reportedto date for fabricated index-guiding PCF. Fiber Bragggratings(FBG) were written in the fiber to confirm its ultrahigh birefringence, and we demonstrated the capability to simultaneously measure the FBG's pressure and temperature experimentally. Because of the large separation of the two FBG peaks (>12 nm), such fiber is a promising candidate for a single polarization device.