Abstract: The optical device includes a first capillary tube assembly including a capillary tube into which an optical fiber is inserted and fixed, and a retaining sleeve for retaining the capillary tube; a second capillary tube assembly including a capillary tube into which optical fibers are inserted and fixed, and a retaining sleeve for retaining the capillary tube; and a lens assembly including a first lens that faces a forward end face of a first optical fiber with a gap therebetween, a second lens facing end faces of optical fibers with a gap therebetween, a band pass filter interposed between the first lens and the second lens, and an accommodation member for receiving the first and second lenses and the band pass filter. The retaining sleeve of the first capillary tube assembly is secured to one end surface of the accommodation member, and the retaining member of the second capillary tube assembly is secured to another end surface of the accommodation member.

Abstract: The optical device includes a first capillary tube assembly including a capillary tube into which an optical fiber is inserted and fixed, and a retaining sleeve for retaining the capillary tube; a second capillary tube assembly including a capillary tube into which optical fibers are inserted and fixed, and a retaining sleeve for retaining the capillary tube; and a lens assembly including a first lens that faces a forward end face of the optical fiber with a gap therebetween, a second lens facing the end faces of the optical fibers with a gap therebetween, a band pass filter interposed between the first lens and the second lens, and an accommodation member for receiving the first and second lenses and the band pass filter. The retaining sleeve of the first capillary tube assembly is secured to one end surface of the accommodation member, and the retaining member of the second capillary tube assembly is secured to another end surface of the accommodation member.

Abstract: A resin coated optical fiber 1 comprising a bare optical fiber 2 and sequentially provided on its circumference with a primary coating layer 3a and a secondary coating layer 3b both made of an ultaviolet-curing urethane resin. The primary coating layer 3a and the secondary coating layer 3b have respective thicknesses of 60 to 200 ?m and 20 to 300 ?m. The pulling force for simultaneously removing the primary and secondary coating layers 3a and 3b is 100 gf or less. The primary coating layer 3a has a tensile strength of 0.5 to 1 MPa. The primary coating layer 3a after immersed in a solvent has a swelling ratio of 5 to 150%. The secondary coating layer 3b has a Young's modulus of 100 to 1,500 MPa. This resin coated optical fiber allows its coatings to be removed without deteriorating the strength or other properties of the bare optical fiber and without leaving any coating waste on the surface of the bare optical fiber after the coatings were removed.