Abstract: The present invention relates to protecting optical devices, such as an optical fibre sensor connected in series with a cable, from a hostile environment, such as encountered when making measurements in oil and gas wells. A liquid can protect the optical device. Packaging an optical fibre sensor inside a capillary containing the liquid can provide this protection. The liquid can be liquid metal, gel, inks, grease or oil. The liquid metal can be gallium or indium, or an alloy that includes indium and/or gallium. The grease can contain lithium, molybdenum, or synthetics, or be synthetic grease. The liquid can contain other components such as a scavenger or getter for molecules and/or ions.

Abstract: A non-mechanical modulating device for use in infrared detection. The device is of particular use in the 8-14 &mgr;m range and has application in thermal imaging cameras and gas sensing systems. The modulator comprises a germanium element and a means of varying the carrier concentration. In particular, the variation of the hole concentration gives rise to the absorption of infrared radiation due to interband transitions between the light and heavy hole bands in the split valence band in germanium. The variation in hole concentration may be initiated in any convenient way, for example, by the irradiation of the germanium with visible or near infrared light, by the electrical injection of free carriers across a germanium diode structure or by electron impact on the germanium surface following acceleration under vacuum. In the case where the variation in carrier concentration is initiated by optical means, the surface of the germanium is treated so as to produce a low surface recombination velocity.