Threshold sensor using bifurcation as a function of the feedback level of a fibre-optic Brillouin oscillator

摘要

The invention relates to a fibre-optic sensor in which exceeding of a given threshold by the physical parameter to be measured causes flipping of a Brillouin oscillator from a steady-state regime of "mirror" type to a pulse regime, by modifying the feedback level in the oscillator. The critical feedback level is of the order of a few per cent in intensity, which allows the use of low-efficiency couplers, or use under conditions inducing severe losses in the oscillator. The sensor according to the invention is particularly suited to alarm devices when the constraints applied to the system - bending, temperature, pressure, etc. - exceed a precise critical threshold; it may be used on its own or in series, the duty ratio (repeat rate) of the pulses then being characteristic of each sensor. IMAGE