Effect of macro-bending on resonant wavelength and intensity of long-period gratings in photonic crystal fiber

We report the spectral characteristics of CO2-laser inscribed long-period gratings ( LPGs) in endlessly single mode photonic crystal fiber ( PCF) subject to macro-bending. The coupling modes as a result of bending were studied by examining the shifts of resonant wavelengths, the splits of attenuation bands, and the variation in coupling strength of the transmission spectra. A bending coefficient of similar to 27.9 nm.m was determined in the PCF at 1800 rotational orientation relative to the point of laser inscription in the curvature range from 2.6 m(-1) to 3.5 m(-1). Compared with conventional fiber LPGs fabricated using the same method, the PCF-based LPGs possess higher sensitivity both to bending and orientation, making them promising for sensor applications. (c) 2007 Optical Society of America.