Bending-imparting device for measuring bending loss, and bending test device

A bending applying device for measuring a bending loss including at least three mandrels and applying bending to a fed-out optical fiber by winding the optical fiber onto the mandrels,

• wherein the mandrels are alternately arranged at predetermined intervals such that outer circumferences of adjacent mandrels in a longitudinal direction of the optical fiber face each other in a non-contact manner,
• a diameter of the optical fiber is D,
• a radius of the mandrel is r,
• in a plane orthogonal to rotation axes of the mandrels, a direction connecting an upstream-side contact point and a downstream-side contact point is a first direction, the upstream-side contact point being a point where the optical fiber starts to come into contact with a mandrel located at the center among the three mandrels having the same diameter and continuously arranged along the longitudinal direction of the optical fiber, the downstream-side contact point being a point where the optical fiber wound around the mandrel at the center starts to move away from the mandrel located at the center,
• a distance between surfaces of the adjacent mandrels in the first direction is d,
• an interval between the adjacent mandrels in the first direction is 2r+d,
• a direction orthogonal to the first direction in the plane orthogonal to the rotation axes of the mandrels is a second direction,
• an interval between the adjacent mandrels in the second direction is s, and
• an angle θ between the second direction and a common internal tangent of the adjacent mandrels as viewed from a center position of the optical fiber is 0 degrees or more and 45 degrees or less, and
• the formed angle θ satisfies following formula
• (
• d
• +
• D
• +
• 4
• ⁢
• r
• )
• ⁢
• (
• d
• -
• D
• )
• +
• s
• 2
• =
• 2
• ⁢
• (
• r
• +
• D
• 2
• )
• ⁢
• tan
• ⁢
• θ
• +
• s
• cos
• ⁢
• θ
• .