Optical fiber device and method of making the same

摘要

The present invention relates to an optical fiber device having a structure for effectively restraining the splice loss from increasing between two kinds of optical fibers having respective mode field diameters different from each other. The optical fiber device comprises first and second optical fibers fusion-spliced to each other, which are partly heat-treated such that both of their respective ratios of change in mode field diameter in the longitudinal direction become a predetermined value or less after fusion-splicing. When the ratios of change in mode field diameter in the vicinity of the fused point are appropriately controlled as such, the increase in splice loss at the fused point between the first and second optical fibers is effectively suppressed.