Patent ID: 6859582

Claim:
A device, comprising: a first fiber having a first untapered fiber section which is a single-mode fiber for light at a first wavelength and a first tapered fiber section which has one end conforming to and connected to said first untapered fiber section and has a fiber diameter gradually reducing from said one end to another opposing end; and a second fiber having a second untapered fiber section and a second tapered fiber section which has one end being spliced to said another opposing end of said first tapered fiber section and another end conforming to and connected to said second untapered fiber section, wherein a fiber diameter of said second tapered fiber section gradually decreases from said one end to said another end, and wherein said second untapered fiber section is a single-mode fiber for light at a second wavelength and has a core diameter greater than a diameter of a fiber core of said first untapered fiber section.