Anthony N Ho

US Patent:

6852966, Feb 8, 2005

Filed:

Oct 30, 2002

Appl. No.:

10/285264

Inventors:

Darin James Douma - Monrovia CA, US
James Walter Stewart - San Jose CA, US
Rudy Hofmeister - Sunnyvale CA, US
Anthony W. Ho - Sunnyvale CA, US
Lucy G. Hosking - Santa Cruz CA, US

Assignee:

Finisar Corporation - Sunnyvale CA

International Classification:

H01J040/14

US Classification:

250214AG, 250214 C, 327514

Abstract:

The method and apparatus for compensating a photo-detector allows both regulation and monitoring of the photo-detector to be performed with a common digital controller. The controller accepts input of monitored operational parameters including received signal strength and temperature. The controller provides as an output a bias control signal which regulates a positive the positive or negative side bias voltage power supply for the photo-detector. The controller maintains the bias voltage to the photo-detector at levels which optimize the gain and signal-to-noise ratios for the photo-detector thereby facilitating the decoding of the received signal over a broad range of signal strengths and temperatures. The controller includes a corresponding digital signal strength and temperature compensators the outputs of which summed with a summer to provide the bias control signal. The digital signal strength compensator also provides as an output a monitor signal a level of which corresponds to the actual signal strength received by the photo-detector after compensation for the variable gain of the photo-detector resulting from the bias voltage level.