Differential differencing transimpedance amplifier for coherent applications

A device comprising:

• a 90 degree optical hybrid configured to receive a coherent optical signal and output a first optical signal and a second optical signal, wherein the first optical signal and the second optical signal comprise one pair of sum and difference signals output by the 90 degree optical hybrid;
• a first photo diode configured to generate, from the first optical signal, a first differential signal;
• a second photo diode configured to generate, from the second optical signal, a second differential signal;
• and
• a differential-differencing programmable gain amplifier configured to:
• receive the first differential signal and the second differential signal;
• transconduct the first differential signal and the second differential signal, to produce a first differential transconducted signal and a second differential transconducted signal;
• perform a differencing operation on the first differential transconducted signal and the second differential transconducted signal to produce a combined differential-differencing transconducted signal that is representative of the first optical signal and the second optical signal;
• and
• output the combined differential-differencing transconducted signal as a differential output.

A device comprising:

• a 90 degree optical hybrid configured to receive a coherent optical signal and output a first pair of sum and difference optical signals and a second pair of sum and difference optical signals;
• a first pair of photo diodes configured to generate, from the first pair of sum and difference optical signals, a first differential signal and a second differential signal;
• a second pair of photo diodes configured to generate, from the second pair of sum and difference signals, a third differential signal and a fourth differential signal;
• a first asymmetric differential differencing transimpedance amplifier configured to receive the first differential signal and the second differential signal and to output a first transconducted differential signal;
• a second asymmetric differential differencing transimpedance amplifier configured to receive the third differential signal and the fourth differential signal and to output a second transconducted differential signal;
• and
• a load configured to receive a combined differential-differencing transconducted signal, based on the first transconducted differential signal and the second transconducted differential signal, and to output the combined differential-differencing transconducted signal as a differential output.