A practical instrument for non-intrusive detection of light on singlemode optical fibres

It is noted that the widespread use of optical fibre within telecommunications networks creates the need for an instrument to identify whether a fibre is carrying traffic. This can be achieved by the controlled application of bending to the fibre. The instrument must be sensitive, wavelength-independent, and nonintrusive. The instrument that has been developed uses a combination of macro and microbending to achieve this. The design incorporates a motor-operated fibre handling system to ensure excellent repeatability of results. This also gives significant advantages in insertion loss minimization, self-testing, and transient insertion loss elimination. The instrument design is described, and the performance achieved is presented