Patent ID: 7421161

Claim:
An optical power monitor comprising: a pig-tail fiber having two optical fibers aligned parallel to and at a small distance from each other and an end face having ends of the two optical fibers on the end face, the end face being an angled face having a perpendicular line at a certain angle with a pig-tail fiber axis; a columnar GRIN lens having two opposite end faces, one of which faces the angled face of the pig-tail fiber at a predetermined spacing with the angled face of the pig-tail fiber, and the other of which has a tap film formed on it, the one of the two opposite end faces being an angled face having a perpendicular line at a certain angle with a columnar GRIN lens axis; a first sleeve having a through-hole, in which the columnar GRIN lens is fixed, and an end face, which is disposed on a side of the angled face of the columnar GRIN lens and has a perpendicular line in an axial direction of the first sleeve; a second sleeve having a through-hole, in which the pig-tail fiber is fixed, and an end face, which is disposed on a side of the angled face of the pig-tail fiber, has a perpendicular line in an axial direction of the second sleeve, and is in contact with the end face of the first sleeve; and a photo-diode disposed to face the tap film of the columnar GRIN lens; wherein at least one element of the pig-tail fiber and the columnar GRIN lens has an arc-segmental end face with a perpendicular line in an axial direction of the element having the arc-segmental end face, and the arc-segmental end face is formed by removing a portion of an axial tip of the angled face of the element and positioned in a same plane as an end face of a sleeve in which the element is fixed.