US Patent 7532825 Optical receiver

An optical signal emitted from an optical transmitter is received and converted into electrical signals by a plurality of photodetectors individually. A plurality of amplifiers individually amplify the electrical signals converted by the respective corresponding photodetectors. A plurality of identification sections individually identify multivalued digital data of the optical signal based on the amplified electrical signals output by the respective corresponding amplifiers. A determination section examines all of a plurality of pieces of digital data output by the plurality of identification sections to determine digital data which is to be output from the optical receiver.