| 摘要 |
<p>A time-multiplexed pulsed heterodyne optical fibre sensing system has two optical fibre arms along which modulated light signals are fed. The first arm has a balancing coil 24 which provides it with a greater optical path than the second arm. The two light pulses which are spaced in time are recombined and fed to a sensor array which can be an optical fibre hydrophone, or it might detect changes in pressure, temperature, stress and/or strain along a fibre. Acoustic and vibrational noise can cause the optical path length of the balancing coil to change, thus introducing noise into the system and reducing its sensitivity. By providing a compensating coil 32 in the second arm, such that the compensating coil is sensitive to the same environmental noise as affects the balancing coil and its optical path length is changed by an equivalent amount, there is no net change in the desired optical path length difference between the arms and so sensitivity is not affected by environmental noise.</p> |
