| 摘要 |
PURPOSE:To increase the net gain by providing an optical directional coupler having at least three pieces of terminals where a first terminal and a second terminal, and the first terminal and a third terminal are optically conducting and specifying an optical coupling rate eta between the first terminal and the second terminal. CONSTITUTION:The title device contains an optical directional coupler 4 having at least three pieces of terminals where a terminal A 41 and a terminals B 42, and the terminal A 41 and a terminal C 43 are conductive optically, respectively, and an optical coupling rate eta between the terminal A 41 and the terminal B 42 is set to a value conforming to an expression I. In the expression I, gB : A : alpha : l : eta0 :PP : DELTAupsilonP : ad DELTAupsilonS denote a Brillouin gain coefficient of an optical fiber, a core effective cross-sectional area of the optical fiber, a transmission loss of the optical fiber, length of the optical fiber, light transmittivity of the optical directional coupler, excitation light power inputted to the second terminal of the optical directional coupler, spectral width of an excitation light, and Brillouin gain band width of the optical fiber, respectively. In such a way, a signal light of large optical power can be fetched. |
