Optical part

Optical transmission lines in optical transmission systems or laser beam source-applied devices, which utilize optical fibers as optical transmission lines, are connected by optically coupling to an optical fiber terminal portion, which is configured by holding the vicinity of the optical fiber terminal portion with a capillary tube, a ferrule or the like at the connecting portions of the transmission lines. With this configuration, minimizing return loss at the optical fiber terminal portion is a key issue. As a solution thereof, a capillary tube made of glass is used; however, since insertion by driving in or press fitting to a metallic tube or the like is impossible, mass production is impossible, accurate processing is impossible, and it is costly due to the characteristics of the glass, there are many restrictions in the usage thereof. With the present invention, by utilizing as material for capillary tubes, translucent ceramics such as alumina ceramics that have not been conventionally considered in any way for using in this field, an optical fiber terminal portion, which can be processed with little return loss and high accuracy and is suitable for mass production, can be provided at low cost.