Low-loss optical connector between dissimilar single-mode fibers using local core expansion technique by thermal diffusion

The insertion loss in optical connectors for coupling small-core fibers or dissimilar fibers can be reduced by using thermally diffused expanded core fibers. The mode-field diameters of small-core fibers were locally expanded from 3.8 to 11.1 mu m by applying heat directly to the fibers. The average insertion loss between small-core fibers with expanded cores was 0.42 dB, which is less than half the value of 0.92 dB without thermal treatment. The improvement in the average loss between small-core and standard single-mode fibers was even greater. A value of 0.49 dB was achieved, which is less than one fifth that of 2.56 dB without treatment.<>