Detection of gases with porous-clad tapered fibers.

The detection of gases by the attenuation of the transmitted power in a multimode step-index tapered fiber with porous cladding is described. The results have been compared with those obtained for a uniform fiber. It has been shown that, for given fiber parameters, the absorptivity of the gas and its diffusion coefficient in the porous cladding, the sensor response time, and the minimum detectable concentration of the gas depend on the taper ratio. The higher the taper ratio, the smaller the response time and the minimum detectable concentration.