Patent ID: 7347631

Claim:
An optical power monitor comprising: a pig tail fiber composed of a columnar capillary having a light emission end surface at a certain angle to a plane perpendicular to a center axis of the capillary; a first optical fiber inserted and fixed in a through-hole of the capillary, wherein the first optical fiber is parallel to the center axis of the capillary, and has an end surface forming a plane with the light emission end surface; a second optical fiber inserted and fixed in a through hole of the capillary; a photo diode; and a lens disposed coaxially with the center axis of the capillary and with a space of a predetermined length between a tip of the lens and the first optical fiber end surface; wherein an optical axis of the first optical fiber is shifted from the center axis of the capillary in the direction that a distance from the first optical fiber end surface to the lens tip becomes greater, so that an optical signal emitted from the first optical fiber end surface irradiates the lens tip.