| 摘要 |
PURPOSE:To minimumize the changing width of an optical receiving level in an another light receiver by controlling the attenuating quantity of a variable optical attenuating element inserted to an optical wavelength multiplex transmission path before an optical demultiplexing based on the size of the light receiving level of one light receiver. CONSTITUTION:From an optical transmitter 1-1, an optical signal is wavelength- multiplexed with a multiplexer/demultiplexer 2 and sent to an optical fiber transmission path 10. In a receiving side, the optical signal is passed through a variable optical attenuating element 3, wavelength-separated by a multiplexer/ demultiplexer 4 and inputted to a light receiver 5-1. The receiver 5-1 has a light receiving level detecting means, controls optical attenuating quantity based on the size of the light receiving level and keeps the light receiving level to the receiver 5-1 constant. Then, even to an optical signal to a light receiving device 5-2 and an optical signal from optical transmitters 5-3-5-n, a level limit is loaded and the light receiving level to light receivers 1-3-1-n is kept almost constant. |
