Effective Mode Field Diameter for LP11 Mode and Its Measurement Technique

The effective mode field diameter (MFD) for the second-order (LP
₁₁
) mode in two-mode fibers is determined to allow estimation of the coupling efficiencies at a splice with axial misalignment. Simulations are performed to verify its validity. In addition, we propose a novel technique for measuring the effective MFD distribution for the LP
₁₁
mode along two-mode fibers. The technique is based on optical time-domain reflectometry; it conducts measurements in the two-mode region of test fibers and individually observes the LP
₀₁
and LP
₁₁
modes of the backscattered light. Its feasibility is demonstrated experimentally.