Method for manufacturing fan-in fan-out device and fan-in fan-out device

A fan-in fan-out device comprising:

• a plurality of optical fibers;
• and
• a holding portion holding the plurality of optical fibers in a bundled state,
• wherein the holding portion comprises:
• a large-diameter portion;
• a reduced-diameter portion extending from the large-diameter portion while reducing in diameter;
• and
• a small-diameter portion extending from the reduced-diameter portion,
• wherein the large-diameter portion comprises:
• a first holding member;
• and
• a second holding member having a hole larger than an outer diameter of the first holding member, the first holding member and the second holding member being of quartz glass,
• wherein an outer periphery of the first holding member or an inner periphery of the hole of the second holding member has a plurality of grooves,
• wherein the plurality of optical fibers are held between the first holding member and the second holding member respectively along the plurality of grooves in the large-diameter portion, and
• wherein the first holding member and the second holding member are melted and integrated with each other in the small-diameter portion.