Fast Response Microstructured Optical Fiber Methane Sensor With Multiple Side-Openings

We have demonstrated a fast response optical fiber methane sensor by use of a hollow-core photonic bandgap fiber with periodic microchannels fabricated by a femtosecond Ti:sapphire laser. A diffusion limited response time of ~3 s and a sensitivity of ~647 ppm have been achieved for a 7-cm sensing fiber with seven side-holes separated by 1 cm along the fiber. The side holes introduce very little loss and hence it would be practically possible to construct fiber gas sensors with long sensing length (up to a few tens of meters) to achieve highly sensitive distributed sensing without compromising the response time.