Abstract

Photonic crystal fibres are in many ways a success story¹. Solid core versions have achieved losses that closely approach the best seen in conventional single-mode telecommunications fibre, and have been used in long-haul systems demonstrations in Japan. The lowest loss reported in hollow core PCF, which guides by the photonic band gap effect, is 1.1 dB/km at 1550 nm (as reported by BlazePhotonics Ltd in 2004), and there are good reasons to believe that with further development this could ultimately drop to 0.2 dB/km. The advantages of optical fiber made from just one material – usually pure silica glass - are seen in the ~100× better stability of optical properties such as birefringence against changes in temperature; this is important for example in optical strain sensing and for in-fiber components made by thermal post-processing. The endlessly single-mode (ESM) PCF design permits one to operate at wavelengths shorter than the LP₁₁ cut-off, where conventional single-mode fiber turns multimode; this allows access to unique flattened dispersion landscapes while offering a new way to design ultra-large mode area single-mode fibres with improved bend losses. The ability to control higher order dispersion in ESM-PCF has led to a new generation of entangled photon pair sources using four-wave mixing – by moving the modulational-instability sidebands far away from the pump frequency, Raman-induced noise is averted.

© 2007 IEEE