Optical fibre ultrasonic sensor
First Claim
1. An ultrasonic sensor comprising a polarization maintaining fibre having two orthogonal linear principal axes, an input end and an output end, input means for launching into said fibre light beams respectively aligned with each of said two orthogonal linear principal axes, and output means for determining a phase difference induced between said light beams by ultrasonic waves incident upon a substantially straight intermediate portion of the polarization maintaining fibre, the ultrasonic waves having a propagation direction aligned with a principal axis of said polarization maintaining fibre.
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Abstract
An ultrasonic sensor utilizing a polarization maintaining optical fibre. The invention includes a polarization maintaining fibre, a light source for launching light beams into the fibre so that the light beams are respectively aligned with each of the principal axes of the fibre, and an output detection system for determining a phase difference induced between the light beams by ultrasonic waves incident upon the fibre. A bias control may be provided to compensate for environmentally induced phase differences. The invention also include a polarization maintaining fibre divided into a sensor portion and a lead portion optically joined together by a 45 degree joint. A light source launches a linear polarized beam into the lead portion in alignment with one of the principal axes and a detection system determines phase difference induced by incident ultrasonic waves between the two components passing through the sensor portion.
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17 Claims
- 1. An ultrasonic sensor comprising a polarization maintaining fibre having two orthogonal linear principal axes, an input end and an output end, input means for launching into said fibre light beams respectively aligned with each of said two orthogonal linear principal axes, and output means for determining a phase difference induced between said light beams by ultrasonic waves incident upon a substantially straight intermediate portion of the polarization maintaining fibre, the ultrasonic waves having a propagation direction aligned with a principal axis of said polarization maintaining fibre.
Specification