PLASTIC OPTICAL FIBER, OPTICAL CORD, AND ACTIVE OPTICAL CABLE

A plastic optical fiber of the present disclosure includes a core and a trench disposed on an outer circumference of the core. The core includes a first region and a second region, the first region having a refractive index n1 decreasing in a direction from a center of the core toward an outer edge of the core, the second region being positioned on an outer circumference of the first region, the second region including the outer edge of the core, the second region having a refractive index n2 being constant. The refractive index n2 of the second region is equal to or lower than the refractive index n1 of the first region, a thickness of the second region is 2 μm or more and less than 5 μm, and a refractive index n3 of the trench is lower than the refractive index n2 of the second region.