OPTICAL FIBER

摘要

Provided is an optical fiber in which PMD is not greatly risen even when an external factor such as side pressure or bending is added thereto. A twist of an elastic strain with stress is given onto the optical fiber. A twist rate relevant to the number of rotations per unit length due to the twist is expressed by a function f(z) of a position (z) in the longitudinal direction of the optical fiber, which includes a predetermined twist period and in which a twist rotation angle in one direction and a twist rotation angle in the reverse direction during the predetermined twist period are defined to be equal to each other. When (g), (?) and (ße) designate a proportional coefficient that expresses a circular birefringence per twist rate, an angular frequency and a linear birefringence due to bending and side pressure, respectively, an average twist period (L)and an average twist rate (?av) in the optical fiber satisfy a predetermined relational formula.