Abstract

Distributed fiber sensors based on Brillouin scattering are of great interest, e.g. for the temperature monitoring over long distances at installed current cables, pipelines, tunnels, mines or buildings [1]. Recently realized Brillouin temperature sensors achieve the promising results of 51 km sensing length, 5 m spatial resolution and 1° temperature resolution [2]. However, the application area of this sensor is limited, since it operates on both fiber ends and exhibits high technical efforts. In order to enhance the application potential of Brillouin sensors, one-end measuring techniques were realized, but these systems involve complicated optoelectronic elements (EOM [3], AOM [4]), allowing a laser frequency shift of the Brillouin frequency shift. In this contribution we present novel concepts on Brillouin fiber temperature sensing, which enable one-end measurement without having to use an external frequency shift element. The general sensing mechanism of the presented temperature sensors is the excitation of stimulated Brillouin scattering and the measurement of the temperature dependent Brillouin frequency shift. In principle, the spatial resolution can be achieved by the (i) OTDR (optical time domain reflectometry) or the (ii) OFDR (optical frequency domain reflectometry) technique.

© 1996 IEEE