Patent ID: 7688502

Claim:
A three-terminal optical signal amplifying device comprising: a first semiconductor optical amplifying element including an active layer constituted by a p-n junction; a first input means and a second input means to respectively input a first input light of a first wavelength and a second input light of a second wavelength to the first semiconductor optical amplifying element from an end face side and another end face side thereof, respectfully; a third wavelength selecting element provided on the end face side of the first semiconductor optical amplifying element, which permits the first input light of the first wavelength input from the first input means to pass therethrough, and which reflects a light of the second wavelength in a light from the first semiconductor optical amplifying element to the first semiconductor optical amplifying element; and a fourth wavelength selecting element provided on the another end face side of the first semiconductor optical amplifying element, which permits the second input light of the second wavelength input from the second input means to pass through, and which reflects a light of the first wavelength in a light from the first semiconductor optical amplifying element to the first semiconductor optical amplifying element, the first input light of the first wavelength being an input light which is intensity-modulated; the second input light of the second wavelength being a control light; and an output light of the second wavelength being selectively output by the fourth wavelength selecting element, and having a signal waveform which is obtained by intensity-modulating the first input light during an input of the control light.