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

In this 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(-2) is obtained experimentally, which is close to the theoretical value of 1.4×10(-2) at the wavelength of 1550 nm. To our knowledge, this is the highest birefringence reported to date for fabricated index-guiding PCF. Fiber Bragg gratings (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.