For instrumentation purposes there are six main types of signal which can be used to modulate sensors.These are mechanical, thermal, electrical, galaxy harmony nc magnetic, chemical and radiant.Fibre optic sensors depend mainly for their operation on the modulating effect of the first five on visible or infrared radiation carried by optical fibres and components.Many modulating 6-0 igora vibrance techniques have been described in the literature over the past five years and an attempt is made to review the breadth rather than the depth of this new and interesting branch of sensor development.