<p>An optical sensor includes an optical fibre (1), a polychromatic light source (2) and a detector (3). The optical fibre is disposed such that a change in the parameter to be measured causes a movement of the fibre to vary the amount of microbending such that the portion of the polychromatic light which is no longer constrained within the fibre is varied. The detector (3) detects the intensity of the polychromatic light transmitted by the optical fibre (1) at a plurality of different wavelengths, and a microprocessor (6) interprets the output of the detector (3) in terms of the parameter to be measured.</p>
