Patent ID: 9459329
Filing Date: 2016-10-04
CPC Classification: G01R,G02B

Claim Text:
1. An apparatus for magnetic field detection, comprising: a first length of optical fibre; a second length of optical fibre deployed alongside the first length of optical fibre; a fibre optic interrogator configured to interrogate said first length of optical fibre with interrogating radiation, detect radiation backscattered from said first length of optical fibre and analyse said detected radiation to provide a first distributed sensing signal indicative of mechanical disturbances of said first length of optical fibre and to interrogate said second length of optical fibre with interrogating radiation, detect radiation backscattered from said second length of optical fibre and analyse said detected radiation to provide a second distributed sensing signal indicative of mechanical disturbances of said second length of optical fibre; wherein the said first length of optical fibre is mechanically coupled to a magnetically responsive material whose dimensions vary dependent on the applied magnetic field; and wherein said second length of optical fibre is configured to be substantially insensitive to any changes in applied magnetic field.