RANGE-BY-RANGE GAIN-CONTROLLED LIGHT AMPLIFIER, METHOD FOR CONTROLLING GAIN OF LIGHT AMPLIFIER RANGE-BY-RANGE, LIGHT RECEIVER, AND LIGHT REPEATER

摘要

PURPOSE: To reduce noise over a wide range of input signals by controlling the output of an excitation light source so that the light amplification gains of light amplifier units can successively become corresponding gains from the unit of the preceding stage of cascade-connected light amplifier units while that of the light amplifier unit of the succeeding stage is suppressed as the light receiving level becomes lower from a high value. CONSTITUTION: First and second excitation light source drive circuits 22 and 23 are respectively made to generate drive currents so that the light outputs of first and second excitation light sources 11 and 12 can become proportional to an APC(automatic power control) reference current by means of current-voltage conversion circuits 20 and 21. When, for example, the light outputs of the light sources 11 and 12 become higher while the electric power of the signal light inputted to a first output signal level detector 15 is large, an excitation light source control circuit 19 controls the light output of the light source 11 until the output voltage of the detector 15 becomes about -0.75V. When the output voltage of the detector 15 becomes <=-0.75V, the light output of the light source 12 starts to increase.