Patent ID: 7884951

Claim:
A tool adapted to be positioned inside a well-bore wherein the tool comprises an apparatus for measuring an internal dimension of the well-bore, the apparatus comprising: an optical caliper comprising an optical sensor providing a response correlated to the internal dimension of the well-bore, the optical sensor being coupled to an optical fiber and coupled to a caliper arm in contact with a wall of the well-bore; wherein the optical sensor comprises a Bragg grating inscribed in a portion of the optical fiber, the caliper arm being coupled to the portion of the optical fiber by a first coupling point so that a movement of the caliper arm elongates/compresses the portion of the optical fiber; and wherein the response of the optical sensor is a measurement of a refractive index modulation modification of the portion of the optical fiber comprising the Bragg grating due to an elongation/compression of said portion of the optical fiber.