Patent ID: 8752434

Claim:
A fibre optical system for pressure measurement comprising a pressure sensor element ( 4 ) having at least two parallel partially reflecting surfaces ( 5 , 7 ), one of which is arranged on a diaphragm ( 6 ) movable with respect to another fixed said surface as a consequence of pressure differences across said diaphragm, said surfaces are arranged to cause interference phenomena of light inciding substantially perpendicularly onto and reflected by the two surfaces ( 5 , 7 ) depending upon the actual distance between these surfaces, a light source ( 1 ) configured to emit light, an optical fibre ( 3 ) configured to receive and transmit light from said light source to said pressure sensor element in one direction and a measurement signal in the form of light reflected by said surfaces in the opposite direction, and an arrangement ( 12 ) configured to receive said measurement signal and evaluate this signal to determine a value of a pressure at said diaphragm, wherein said pressure sensor element ( 4 ) is made of material being stable at a continuous temperature up to at least 800° C., at least said diaphragm ( 6 ) of said sensor is made of SiC, and at least the part ( 23 ) of said optical fibre ( 3 ) connecting to said sensor element is made of a material able to withstand a continuous temperature of at least 800° C., and a fluorescent member ( 8 ′, 8 ″) is arranged in the path of said light transmitted from said light source ( 1 ) up-stream said reflecting surfaces ( 5 , 7 ) of the pressure sensor element ( 4 ) and configured to absorb a portion of said light from the light source for resending secondary light resulting from optical excitation in the opposite direction in said optical fibre for being provided for evaluation.