Fibre coupled optical sensors for chemical and biologial species are important for process control, environmental control and pollution detection. An integrated optic ammonia sensor is described here; this is based on evanescent field absorption. The sensitive element of this sensor is a strip waveguide, fabricated by field assisted ion exchange, coated with a immobilized indicator dye. The sensor has a short response time and a long lifetime. An experimental arrangement is shown which has been built up for the characterization of different integrated optic sensor elements. Spectral response characteristics, response times and the generation of reference signals are reported in detail. The simple temperature dependence, the humidity independence and the very low cross sensitivity of this ammonia sensor is illustrated.
