ANALYSIS OF THE EFFECT OF VIBRATION-INDUCED NOISE IN DIFFERENT FIBER LEADS USED IN AN OPTICAL CURRENT-MEASUREMENT SYSTEM

The noise induced by environmental perturbations, such as vibration in fibre leads, degrades the performance of an optical current-measureme nt system, and should be suppressed. Vibration-induced noise in three types of fibre leads, single-mode, highly birefringent, and multimode fibre, has been measured when used in such an optical current-measurem ent system, and the effect quantified and discussed. The results have shown that vibration-induced noise may be suppressed in highly birefri ngent fibre by choosing carefully the input angle of a linearly polari zed beam or by using a low-coherence source in the sensor. The noise o bserved can be effectively eliminated by employing a long length of mu ltimode fibre and a low-coherence source, combined with appropriate co upling conditions. (C) 1997 Elsevier Science S.A.