Patent ID: 7214924
Filing Date: 2007-05-08
Classification: H01L

Abstract:
1. An optical apparatus for receiving signal light, comprising: an avalanche photodiode having a light-receiving surface including a first region and a second region, said avalanche photodiode outputting a photo current including a signal component generated in said first region and a monitor component generated in said second region; a bias control circuit for outputting a bias voltage to be provided to said avalanche photodiode, said bias control circuit comprising, a high-pass-filter for extracting said signal component from said photo current output from said avalanche photodiode, a variable gain amplifier having a preset gain, said variable gain amplifier extracting said monitor component from said photo current by comparing said photo current with said signal component output from said high-pass-filter, and amplifying said extracted monitor component by said preset gain; and a comparator for comparing said signal component and said amplified monitor component, wherein said bias voltage applied to said avalanche photodiode is controlled such that said signal component is substantially equal to said amplified monitor component.