| 摘要 |
PROBLEM TO BE SOLVED: To provide a preamplifier which can decrease the influence of interference light, even if the interference light is overlapped in an optical input to extract an electrical signal at a high signal to noises ratio, and a light-receiving device which comprises the preamplifier and demodulates the optical input under superior code error characteristics. SOLUTION: A preamplifier comprises a transimpedance amplifier for amplifying a signal obtained by current-converting an optical input by a photodiode; a first amplitude detection means for detecting amplitude, in correspondence with the entire optical input obtained by overlapping an interference light on a signal light; a second amplitude detection means for detecting an amplitude, in correspondence with the signal light of an output amplitude of the transimpedance type amplifier, even if the interference light is overlapped on the signal light; and a current source, which is driven according to a difference between an output of the first amplitude detection means and an output of the second amplitude detection means, and the current of the current source is supplied to the photodiode. |
