| 摘要 |
PROBLEM TO BE SOLVED: To raise the signal light level causing gain saturation, while integrally enhancing noise characteristics by forming a two stage semiconductor optical amplifier, performing optical amplification with good noise characteristics at the first stage and performing optical amplification, while taking advantage of high saturation gain characteristics at the second stage. SOLUTION: A gain region 1, including means for induction emitting a signal lightλs by pumping carriers in the direction of signal lightλs incoming end to outgoing end of a semiconductor optical waveguide having the opposite ends applied with an endless reflective coat, i.e., a first semiconductor optical amplifier, a DBR region 11 including means resonant to a laser oscillation lightλo, i.e., a first Bragg reflector DBR, a gain region 2 including a means for induction emitting the signal lightλs by pumping carriers, i.e., a second semiconductor optical amplifier, and a DBR region 12 including means resonant to the laser oscillation lightλo, i.e., a second Bragg reflector DBR, are formed in this order. According to the structure, the signal light level causing gain saturation can be raised, while enhancing noise characteristics.
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