Fibre-optical strain gauge and method for the production of said strain gauge

Abstract

The fibre-optical strain gauge comprises a mechanical construction ( ) providing a strain-dependent relative movement of oppositely positioned, spaced apart first and second optical fibre ends in a direction substantially perpendicular to the axial direction of the optical fibres ( ) and uses the varying transmission of light between the two fibres ( ) as an indication of the strain. The mechanical construction comprises fibre-holding elements ( ) for securing the two fibres ( ) to the mechanical construction ( ) in an aligned relationship in the unstrained condition. The mechanical construction ( ) further comprises: a) anchorage means ( ) for providing two substantially pointy-formed connections between the mechanical construction ( ) and the object to be measured on, a line ( ) through said two connection points ( ) defining a strain-measuring direction; b) two connecting rods ( ), comprising articulated connections at both ends, to the respective anchorage means ( ) at one end and to respective further parts ( ) of the mechanical construction at the other end, respectively, said two rods ( ) extending substantially in the strain-measuring direction ( ); c) a transmission construction, connected articulated to the rod ( ) ends opposite the respective anchorage means ( ), for transferring the movement of said rods ( ) in said strain-measuring direction ( ) to the fibre-holding elements ( ) and for guiding the movement of said fibre-holding elements ( ) in a direction substantially perpendicular to said axial direction of said optical fibres ( ). By this construction it is possible to obtein strain gauge measurments which are substantially not influenced by movements of the measuring points in a plane perpendicular to the desired strain measuring direction.