| 摘要 |
PURPOSE:To eliminate the use for a Faraday rotator by forming branch paths so as to satisfy specific conditions and connecting optical fibers to a main path and the branch paths of small propagation constants. CONSTITUTION:The branch paths 4, 5 are formed in such a manner that the value (betai-betaj)/(thetaXgamma) determined by the constant gamma expressed by equation I and a branch angle theta (radian) attains >=2 where the refractive index of the core of waveguides is designated as n, the wavelength (nm) of the guided light as lambda, and the propagation constants of waveguides as betai, betaj (betai>betaj). The optical fibers 6, 9 are photoconnected to the main path 3 and the branch path 5 of the small propagation constant. Since the incident light signal to the main path 3 from the optical fiber 6 is, therefore, made incident to the branch path 4 of the large propagation constant and absorbed in this metallic films 7, 8, the signal is not emitted to the optical fiber 9. On the other hand, the incident light signal from the optical fiber 9 to the branch path 5 is guided to the main path 3 and is emitted to the optical fiber 6. Thus the need for the Faraday rotator is eliminated and the inexpensive and small-sized optical isolator is obtd. |
