| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical circuit in which the loss of transmitted light and reflected light generated in branching and demultiplexing is reduced, and to provide an optical fiber amplifier and an add/drop module device. SOLUTION: The optical circuit 1 is provided with first to fourth optical waveguides 8, 10, 12 and 14, and an optical filter 4. The optical waveguides 8 and 12 are provided on a first 16 axis, and have a first and second ends 8a, 8b, 12a and 12b. The optical waveguides 10 and 14 are provided on the first 16 axis, and have a first and second ends 10a, 10b, 14a and 14b. The optical filter 4 is disposed so as to optically be coupled to the first ends 8a, 10a, 12a and 14a of the first to fourth optical waveguides 8, 10, 12 and 14. In the optical circuit 1, at least any of the first to fourth optical waveguides 8, 10, 12 and 14 have a mode field diameter(MFD) which increases from the second end toward the first end. At least any of the first to fourth optical waveguides may have a portion in which an optical waveguide width decreases from the second end toward the first end. |
