SEPARATION OF TRANSVERSE SPACE MODE IN MICROSTRUCTURE OPTICAL FIBER

PROBLEM TO BE SOLVED: To provide an optical fiber with which transverse space modes are intrinsically separated from each other even when substantial perturbation exists. SOLUTION: According to an embodiment 1, an MOF is so designed as to simultaneously indicate relatively large abnormal dispersion and the intrinsically separated transverse space modes by forming the diameter of a core region below about 6 μm and making the difference between the effective refractive index of the core region and the effective refractive index of the cladding region greater than about 0.1 (10%). More preferably, the cladding region includes