| 摘要 |
PURPOSE:To offer the light receiving equipment which can suppress deterioration of receiving sensitivity caused by a noise increase of an optical fiber amplifier and the influence of a reflection, when a rare earth added optical fiber amplifier of back excitation. CONSTITUTION:A signal light is made incident on an Er added optical fiber 1. A stimulating ray emitted from an excitation light source 3 is multiplexed with the signal light by an optical multiplexer/demultiplexer 2 of an optical fiber type so that it is propagated through the inside of the optical fiber in the direction opposite to the signal light amplified by the Er added optical fiber, and made incident on the ER added optical fiber 1. The signal amplified in the Er added optical fiber 1 passes through the optical multiplexer/ demultiplexer, and also, passes through a narrow band passing optical filter 4 using an interference film filter whose center wavelength coincides with wavelength of the signal light, and thereafter, is received by an avalanche photodiode 5. |
