Abstract: A PAM4 signal processor calibrates slicing thresholds to reduce bit error rate in a PAM4 clock data recovery circuit by determining a first target value of a first slicing level. The PAM4 signal processor is configured to retrieve the first target value of the first slicing level and sweeps a first reference voltage down from the upper voltage threshold. The PAM4 signal processor is further configured to detect a first filtered output associated with the first reference voltage and determines whether the first filtered output is higher than a target value. Responsive to determining that the first filtered output is higher than the target value, the PAM4 signal processor stores the first reference voltage value.

Abstract: In a system for calibrating PAM4 signals, an equalizer determines a first signal amplitude measurement of the PAM4 signal. The equalizer determines a first signal boost measurement of the PAM4 signal. The equalizer determines whether the first signal boost measurement and the signal amplitude measurement are substantially consistent with each other. Responsive to determining that the signal boost and the signal amplitude are not substantially consistent with each other, the equalizer determines a reference amplification modification and calibrates a PAM4 signal according to the determined reference amplification modification.

Abstract: A system to program parameters of one or more stages of a transimpedance amplifier (TIA) in an optical sub-assembly (e.g. TO-can package) is disclosed. With this invention, users have the option/flexibility to discretely program any of the stages of the TIA after production of the sub-assembly, i.e. they can still change the TIA settings once the TIA has been installed in a system and the system is in use.

Abstract: A laser diode driving method that reliably maintains average optical power and extinction ratio is disclosed. The present invention for laser driving uses a preloaded laser diode characteristic curve/table and/or mathematical equations to create a programmable bias and modulation current range. This ensures stable closed-loop operation and prevents system failure if the feedback signal is impaired by confining the operation of the laser diode to a normal operating range.