Microbend fiber optic strain gauge

Claim 1

A strain gauge operable in hostile environments comprising: a pair of plates made of a material having a temperature expansion coefficient dissimilar to that of a material to be tested for the purpose of increasing the range of the sensor and having facing and offsetting corrugated surfaces and wherein at least one plate is attached to the material to be tested; a buffer coated first optical signal fiber clamped between the corrugations of the plates for being bent to a greater or lessor extent depending on pressure exerted on the plates for moving the plates together; a buffer coated reference optical signal fiber located in the vicinity of the plates so as to be simultaneously exposed to the same thermal and other conditions along its length as the first optical fiber; optical signal applying means including a light source and light splitting means connected to one end of each optical fiber for simultaneously applying an optical signal to both optical fibers; and optical detector means connected to the opposite ends of both optical fibers for measuring the modulations in the optical signal transmitted through the first optical fiber which modulations correspond to pressures applied to the plates and for reading the modulations in the optical signal transmitted through the reference optical fiber.