| 摘要 |
PROBLEM TO BE SOLVED: To provide a linear repeater that is easily adopted in various systems independently of multiplexity and used for the wavelength division multiplex transmission system with high reliability. SOLUTION: A bias current used to control the gain of an optical direct amplifier 2 amplifying a plurality of received optical signals is controlled for each of a plurality of optical signals at an automatic gain control section 7. The automatic gain control section 7 is provided with a variable wavelength optical filter 5 controlling a transmission wavelength variably, a light quantity detection circuit 6 detecting a timewise mean light quantity of an optical signal transmitted through the variable wavelength optical filter 5 to provide a voltage corresponding thereto, and a bias current/transmission wavelength control circuit 4 controlling the transmission wavelength at the variable wavelength optical filter 5 and controlling the bias current of the optical direct amplifier 2 so that the light quality of one optical signal detected by the light quantity detection circuit 6 is constant; and the bias current/transmission wavelength control circuit 4 changes sequentially the transmission wavelength in the variable wavelength optical filter 5. |
