| 摘要 |
<P>PROBLEM TO BE SOLVED: To set intensity of light to be received within dynamic ranges in confirmation of presence. <P>SOLUTION: A subscriber terminal includes a variable optical attenuation part 370, a light-electricity conversion part 320, a clock extraction part 390, a clock extraction determination means 362, a reception level adjustment means 364, and an attenuation change means 366. The variable optical attenuation part attenuates a light signal to be received. The light-electricity conversion part converts the light signal received through the variable optical attenuation part to an electric signal. The clock extraction part extracts clocks from the electric signal, and generates a clock extraction information signal indicating whether a clock is stably extracted. The clock extraction determination means determines whether the clock extraction part stably extracts the clock based on the clock extraction information signal. The reception level adjustment means sets the attenuation of the variable optical attenuation part to a value not less than the minimum and not more than the maximum. The attenuation change means changes the attenuation of the variable optical attenuation part to the attenuation value set by the reception level adjustment means. <P>COPYRIGHT: (C)2011,JPO&INPIT |
