A novel optical fibre sensor has been developed for on-line monitoring of oil quality within industrial equipment. The monitoring is based on chromatic modulation because of the inherent self-referencing demonstrated by this technique. The sensor is shown to exhibit long-term stability and is capable of operating up to a temperature of 120 degrees C. Several industrial oils have been examined using the sensor, and typical modulation depths of 20% were obtained with resolution in the range of 0.1%. This is sufficient to record some interesting physical and chemical changes related to the reaction kinetics of oil degradation. The sensor is also capable of detecting oil leaks within a system since it can distinguish between the chromaticities of oil and air.

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A thin film measuring system for the online monitoring of semiconductor films during processing with a radio frequency plasma is described. The method is based upon the use of chromatic processing of polychromatic interference signals produced by the thin semiconductor film when illuminated with white light. A description is given of the interpretation of the polychromatic signals produced by interference effects and some typical experimental results are presented to illustrate the capabilities of the technique. The approach utilizes cost effective instrumentation with acceptable time response for real time process control via optical fibre transmission. It is currently being incorporated as part of an intelligent knowledge based system for such process control.