Abstract: Operation of a power-by-light valve (15) by a source (11) along an optical fibre (13) is monitored by means of optical sensors (14) from which light passes back along fibre (13) to monitoring and processing units (16, 17). The sensors (14) include fibre bragg gratings (41, 43) for detecting differential pressure across diaphragms (42) and for detecting temperature. At the input end, an optical coupler (12) supplies sensor signals to units (16, 17) which can control source (11) via a signal (32).

Abstract: Operation of a power-by-light valve (15) by a source (11) along an optical fibre (13) is monitored by means of optical sensors (14) from which light passes back along fibre (13) to monitoring and processing units (16, 17). The sensors (14) include fibre bragg gratings (41, 43) for detecting differential pressure across diaphragms (42) and for detecting temperature. At the input end, an optical coupler (12) supplies sensor signals to units (16, 17) which can control source (11) via a signal (32).

Abstract: A bimorph piezoelectric flapper element is mounted at one end in a valve casing so that it extends into a valve chamber as a cantilever. The flapper element tapers to the unsupported end on which a fluorosilicone blocking plate is mounted. An outlet port is formed by a tubular boss which projects into the valve chamber and which tapers to a fine annular rim formed around a mouth of a bore at the tip of the boss. The blocking plate is normally held by the flapper element seated on the tip of the tubular boss to close the outlet port, the tip making an indentation in the fluorosilicone whereby to form a `bite` seal. The blocking plate is unseated by the application of a low voltage to the bimorph piezoelectric element. The valve is suitable for hydraulic fluids and may be operated by optical power.