Connection structure for lens-attached optical fibers and method for setting radius of curvature of end surface of lens-attached optical fiber

A connection structure for lensed optical fibers, which is configured to establish PC connection of lensed optical fibers each including an optical fiber and a GRIN lens that has a rod-like shape and is coaxially fused to a tip of the optical fiber,

• wherein each of the lensed optical fibers includes an end surface subjected to spherical polishing, and
• wherein the end surface has a curvature radius (R) satisfying conditions expressed by the following relations (1) and (2):
• (W/2a)≤1 (1);
• and
• a=(R·F·(¾)·(1−v2/E))1/3 (2),
• where “a” represents a radius of a contact surface obtained when the lensed optical fibers are brought into press contact with and establish PC connection to each other,
• W represents a beam diameter in a plane containing the contact surface,
• F represents a pressing force at the time of PC connection per pair of lensed optical fibers,
• “v” represents a Poisson's ratio of the GRIN lens, and
• E represents a Young's modulus of the GRIN lens.