| 摘要 |
PROBLEM TO BE SOLVED: To solve such problem that the limit of S/N is about 40 to 50 dB and does not comply sufficiently with the request of an optical communication system. SOLUTION: A 2nd optical fiber 6 is arranged between an optical waveguide 1 and a PD 5 for reception and directivity is given between the optical propagation path from a reception PD-side end 14b of a 3rd core part 14 to the reception PD 5 and the extension direction on the side of a WDM filter 4 of a 1st core part 12. |
