| 摘要 |
PURPOSE:To prevent the self-oscillation of a semiconductor optical amplifying element by respectively defining an input coupling space and an output coupling space as optical long-range coupling due to parallel rays and arranging the respective types of optical devices in these coupling spaces. CONSTITUTION:An inputted optical signal and an amplifying signal, which is outgoing from a semiconductor optical amplifying element 106, are caused to be the parallel rays respectively in the input coupling space and output coupling space. Thus, the optical coupling between an input fiber 102 and the semiconductor optical amplifying element 106 and between the output coupling space, namely, the semiconductor optical amplifying element 106 and a photo- detecting element 111 can be defined as the long-range coupling and the various optical devices, etc., can be arranged in these coupling spaces. Here, isolators 104 and 108, which are arranged in the respective input coupling space and output coupling space, transmit only a light to be emitted from an optical fiber 101 to the photo-detecting element 111. Thus, the self-oscillation of the semiconductor optical amplifying element 106 can be prevented. |
