Abstract

Multi-wavelength monitoring is a well known technique which has been successfully applied to many types of optical sensors[l,2]. This technique makes use of two wavelengths or more, one wavelength being affected by the measurand, and the other being is used as a reference carrying information about the current state of the optical measurement system. The novelty of the reported system resides in the fact that the two wavelengths are time-multiplexed to reduce the need for expensive optical components, and was built from off-the-shelf equipment found in many research laboratories. The system described is computer driven, versatile and thus simplifies the investigation and optimisation of the parameters of the measurement system(e.g. signal processing, interrogation frequency). This monitoring system was used in conjunction with a novel optical fibre pH sensor previously reported[3] to show how it can de used to compensate for common mode perturbations such as temperature and misalignment of the launch optics.

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