Optical fiber ribbon, and optical-fiber-ribbon production method

A method of producing an optical fiber ribbon including a plurality of optical fibers arranged in parallel, wherein:

• a form of a cross section of each of the optical fibers taken in a perpendicular direction to a longitudinal direction thereof has an orientation in a rotational direction with the longitudinal direction of the optical fiber as an axis, the method including:
• a light introducing step which introduces light into a core of each of the optical fibers;
• a light leaking step which leaks the light introduced into the core to the outside of each of the optical fibers;
• a light detecting step which detects the light of each of the optical fibers leaked in the light leaking step;
• an optical-fiber rotating step which rotates each of the optical fibers in a circumferential direction thereof so as to maintain the leaked light detected in the light detecting step to be substantially constant among the plurality of optical fibers;
• and
• a coating step which coats the optical fibers together to make the optical fiber ribbon.