Patent ID: 7621673

Claim:
A capillary tube for holding an optical fiber, the capillary tube comprising: an insertion hole in which an optical fiber is to be held; a first flat portion located on an exterior surface of the capillary tube; a second flat portion located on the exterior surface opposite to the first flat portion and parallel to the first flat portion; a third flat portion located on the exterior surface and perpendicular to the first and second flat portions; a fourth flat portion located on the exterior surface opposite to the third flat portion, perpendicular to the first and second flat portions, and parallel to the third flat portion; and a plurality of cylindrical portions located on the exterior surface of the capillary tube, a first of the cylindrical portions being between and adjacent to the first and third flat portions, a second of the cylindrical portions being between and adjacent to the third and second flat portions, a third of the cylindrical portions being between and adjacent to the second and fourth flat portions, and a fourth of the cylindrical portions being between and adjacent to the fourth and first flat portions, wherein the cylindrical portions have a same radius from a single central axis of the capillary tube, the insertion hole is located at a position deviated from the single central axis of the capillary tube in a direction perpendicular to the first flat portion, and the capillary tube is made of a drawn glass material.