| 摘要 |
<p>PURPOSE:To obtain a constant gain regardless of the polarized state of signal light to be simplified by passing the light to be amplified through the same semiconductor optical amplifying element twice, and replacing the two orthogonal polarized components of the object light to be amplified in the 2nd passage and making the resulting light incident on a photosemiconductor amplifying element. CONSTITUTION:Signal light which is propagated in a 1st optical fiber 1 is made incident on the 1st terminal 21 of a 3dB branching element 2, outputted from the 2nd terminal 22 of the element 2, and made incident on the 1st terminal 41 of the semiconductor optical amplifying element 4. The signal light which is amplified by this element 4 is made incident on the 1st terminal 61 of a TE-TM mode separating element 6 through a 1st optical fiber for maintaining plane of polarization 5. Then signal light beams which are separated by the element 6 in TE and TM mode are outputted from the 2nd terminal 62 and 3rd terminal 63 respectively and supplied to the 1st terminal 71 and 2nd terminal 72 of a TE-TM mode converting element 7. Here, the signal light is made incident on the element 6 again and further mode incident on the element 4 while the TE/TM polarization plane is maintained. Consequently, the constant gain is obtained.</p> |
