Estimating loss of mechanical splices interconnecting optical fibers, and connector installation tool

REFMMREFINREFMFFirst and second optical fibers are spliced by a mechanical splice-based connecting device having a portion whereby light leaked from the splice can leave the connecting device. A reference power level (P) of light leaked while only the first fiber is inserted into the connecting device, and a measured power level (P) light leaked while both fibers are inserted are measured. Insertion loss of the splice is derived from the measured power level (P), the measured reference power level (P) and a calibration factor (C) previously obtained by using the same or substantially identical measuring apparatus and connecting device to measure a corresponding calibration input power level (P′) and calibration reference power level (P′) with only the first fiber inserted, and a calibration measured power level (P′) and output power level (P′) of light coupled into a second fiber after the second fiber has been inserted.