Fiber optic sensor is proposed based on cladding modification method for detecting ammonia emissions. Nanocrystalline titanium dioxide is used as a sensing material and spectral characteristics of the
sensor are studied for different concentrations (50-500 ppm) of ammonia, methanol and ethanol. The sensor
shows a linear variation in the output light intensity with the concentration. The light intensity increases for
ammonia whereas it decreases for methanol and ethanol. Gas selectivity of the sensor is discussed.