Abstract: A strain transducer strand (10) is provided comprising an elongatable central core (12) around which are helically wound one or more plastic tubes (14) each of which contains an optical fibre (16). Each tube (14) is overfilled with the optical fibre (16), such that the fibre (16) is longer than the tube (14). As the transducer strand (10) experiences strain, the core (12), plastic tubes (14), and optical fibres (16) elongate, with the helical winding acting as gearing to produce a reduced elongation in the fibres (16) proportional to the elongation of the transducer strand (10). The degree of elongation may be detected by monitoring the optical properties of light transmitted along the fibres (16). The transducer strand is particulary intended for incorporation into elongate load bearing members, such as ropes.

Abstract: Sensing the presence of furfuraldehyde (FFA) in oil is effected by a porous solid sensor (10) comprising aniline acetate entrapped in an inert matrix. The matrix may be a sol-gel preferably based on methyltrimethoxysilane. The solid sensor (10) reacts with FFA to form a pink colored complex which has a characteristic which correlates with the concentration of FFA in the oil and which can be measured photo-optically. Photo-optical measurement may be by absorption or fluorescence when the sensor is irradiated with an interrogating beam. The absorption maximum wavelength is about 525 nm and irradiation at that wavelength produces a maximum fluorescent output at about 570 nm.