The Optotest bidirectional insertion back loss tester uses a combination of OP940 insertion back loss tester and OP720 optical switch, It can quickly and accurately measure the bidirectional insertion back loss of optical devices, and the back loss test is free of winding, which means there is no need for matching ointment or manual winding at the far end of the jumper The insertion loss test uses the continuous stable light source of the instrument combined with a built-in high-precision optical power meter for measurement, achieving measurement in both A-B and B-A directions. Adopting 2 × 2 optical switches for bidirectional measurement of single core jumpers, By using multi-channel optical switches, bidirectional measurement of MTP/MPO connectors can be achieved.