Cisco Technology, Inc.

Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.v.

Jan Sundermeyer

Juergen Hauenschild

Sachidanandam Sundarraju

Norbert Weber

Daniel Micusik

An interface circuit that interfaces a digital-to-analog converter (DAC) to a vertical-cavity surface emitting laser. The apparatus includes a first cascode amplifier that receives as input positive and negative differential outputs of the DAC and provides a positive amplified output and a negative amplified output, and a second cascode amplifier having a positive input and a negative input. The positive input of the second cascode amplifier being coupled to the positive amplified output of the first cascode amplifier. The second cascode amplifier is configured to generate a positive amplified current and a negative amplified current at a negative amplified output. The positive amplified current and the negative amplified current are combined and a resulting output current is provided as input to an anode of the laser. A transformer is coupled between the negative amplified output of the first cascode amplifier and the negative input of the second cascode amplifier.

Power efficient transformer-based interface circuit to interface a differential current sinking DAC to laser anode

A method and apparatus that cancels or reduces DC offset in a fully-differential optical receiver. The method includes receiving differential optical signals, converting, with photodetectors, the differential optical signals to differential current signals representative of the differential optical signals, converting, using a transimpedance amplifier, the differential current signals to differential intermediate voltage signals, amplifying, using a main amplifier, the differential intermediate voltage signals to generate differential output voltage signals, and cancelling a DC component of the differential output voltage signals using a fully differential DC cancellation circuit. Output offset may also be cancelled or reduced using digital control.

DC and offset cancellation for fully differential optical receiver

Embodiments of the present invention provide a level converter circuit with a resistor and a current adjustment circuit. The resistor is connected between an input and an output of the level converter circuit. The current adjustment circuit is configured to influence a current through the resistor such that an output voltage of the level converter circuit does not exceed a maximum allowable value.

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Nuremberg, Germany

Jan Sundermeyer