Abstract: A detection assembly comprising: a body portion having a slot formed along at least a portion of a length thereof, the slot having a slot opening formed in an outer surface of the body portion, the slot opening being arranged to receive a sensor optical fibre through the slot opening; a sensor optical fibre constrained to lie in said slot and in juxtaposition with a plurality of protrusions; and at least one swell member, the swell member being configured to increase in volume in response to exposure to a target measurand, the detection assembly being arranged whereby an increase in a volume of said swell member causes said sensor optical fibre to be urged against at least one of said plurality of protrusions thereby to cause bending of said sensor optical fibre.

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: A system for detecting the presence of a target measurand, such as water or specified chemicals which are carried in an aqueous solution, and which includes a fibre-optic probe assembly which incorporates an optical fibre, a thin film of a water swellable hydrogel, and a rigid containment structure. The hydrogel is in contact with the optical fibre such that a volumetric change in the hydrogel causes a microbend of the optical fiber. The microbend is detected by a sensor assembly which is coupled to the probe assembly.

Abstract: A sensor is provided which is sensitive to a particular property of a medium and which is thermally activated when in contact with the property containing medium. The sensor is externally mounted on the undersurface of a silicon wafer, the upper surface of which contains a well in which a vibratile bridge element is located. The top of the well is closed off so that the vibratile bridge element is within a chamber. Excitation energy from a source is delivered to the vibratile bridge element to establish vibratory motion which is monitored and detected by a circuit. Presence of the particular property in the medium causes a thermal change in the wafer resulting in a change in the resonance frequency of the vibratory motion of the vibratile bridge element. The frequency shift is a measure of the particular property.

Abstract: An optical signal processor (1) used with a method of processing optical data has at least one optical coupling unit (12). Each coupling unit (12) has two optical couplers (12A, 12B) which are connected so that principal channels (14) are connected in series with a time delay of a predetermined value between adjacent couplers (12A, 12B). The optical coupling units (12) are formed into stages. The number of optical coupling units (12) or stages determines further coding of each bit of the input optical signal or code sequence. Stages can be coupled together to process a sequence of optical pulses corresponding in number to the number of optical coupling stages in the system. The outputs of each stage are coupled via optical switches (18) to an optical summing device (24) to simultaneously process the coded data and determine whether the processing has resulted in matching or mismatching of data.

Abstract: An optically-excited vibratile transducer (10) of microstructural form has a plurality of vibratile elements (11, 12) in stacked formation. End (10A) of the transducer (10) is connected via an optical fibre (13) to an optical device (14) for exciting and interrogating the stack. The other end (10B) of the stack is exposed to the influence of a plurality of variables, such as pressure and temperature, in a gaseous atmosphere. The elements (11, 12) are free to vibrate without mutual physical interference and are respectively decoupled from the influence of the variable. For example, element (11) is subjected to the influence of both pressure and temperature but vent (15) is provided adjacent element (12) to decouple the effect of pressure from element (12) leaving it subject only to the influence of temperature.

Abstract: A fiber optic interferometer provides Kerr effect compensation by intensity modulating counterpropagating waves of unequal intensity such that the average value of the square of the intensity is equal to a constant times the average value of the intensity squared, the constant preferably being equal to about two. The intensity modulation may be achieved by using a modulator in combination with a light source or by using a source in which plural frequencies combine to provide the modulation.

Abstract: A zener diode comprises a reverse biased pn junction having a p-type layer on one side of the junction and two successive n-type depletion layers on the opposite side of the junction with the n-type layer adjacent the junction being more heavily doped than the other n-type layer. The more heavily doped n-type layer determines the temperature co-efficient of the breakdown voltage and the other n-type layer contributes to the total value of the breakdown voltage.