BIDIRECTIONAL CLADDING POWER MONITOR FOR FIBEROPTIC BEAM DELIVERY SYSTEMS

A technique is described for the measurement ot the power propagating in either the forward or the reverse direction in the cladding of an optical-fibre beam delivery system. The technique is based on the use of a novel fibre component which is analogous to a directional coupler, except that it transfers power from the cladding of the system fibre (rather than its core) to the monitor fibre. Applications are described for the use of the bi-directional cladding power monitor for determining the efficiency with which light is coupled into the beam delivery system, for monitoring its integrity, and when used in material processing applications, for monitoring the power back-coupled into the fibre from the workpiece.