Optimum Mode Field Diameter Region in Thermally-Diffused Expanded Core Fiber

We indicate the existence of optimum expanded mode field diameters in thermally-diffused expanded core (TEC) fiber. The optimum ranges under our experimental conditions were from 14 μm to 18 μm for both 1.3 μm-single-mode fiber and 1.55 μm-dispersion-shifted fiber. By applying the TEC fiber fabricated in our experimental conditions to a multifiber connector, the connection loss can be reduced to less than 0.2 dB without improving fiber and connector ferrule fabrication accuracy.