Alcatel

Hewlett-packard Development Company, L.p.

Alcatel Lucent

John K Sikora

Gary Williams

Paul Anthony Wirtzberger

A system may comprise a control system that controls a state of a switch network, the control system having first and second thresholds that determine the state of the switch network based on the relative voltages at an input and an output of the switch network. A scaling network is coupled across the input and the output of the switch network and providing a gain scaling signal to a first input of the control system. An offset network is coupled to the output of the switch network and providing an offset signal to a second input of the control system, the first threshold being set independently of the second threshold based on the gain scaling signal and the offset signal.

Independent thresholds for power supply control circuitry

A system and method for generating return-to-zero (RZ) optical data in a digital lightwave communications system using a two-stage modulator arrangement. RF electrical data is provided to a first stage modulator for modulating a light input into an intermediary optical data output having a non-return-to-zero (NRZ) format. Phase differences between the data and a clock signal associated therewith are controlled via a phase feedback control loop that is operable responsive to a phase dither reference signal. The clock signal is adjusted based on a phase control signal provided by the phase feedback control loop so as to generate a phase-adjusted clock. The phase-adjusted clock is supplied to a second stage modulator operable to blank out a suitable portion of each NRZ data bit interval and thereby create optical data having the RZ format.

System and method for generating return-to-zero (RZ) optical data in a digital lightwave communications system

A method and system are disclosed for robustly (using first order effects) controlling the bias point and radio frequency (RF) amplitude level of a modulator for an optical transmitter. The method comprises the steps of extracting an output dither signal component of a digital optical output signal from the optical transmitter to drive a feedback loop; measuring the output dither signal component in the feedback loop for comparison to an input dither signal to the modulator; comparing the output dither signal to the input dither signal to determine their difference; and, based on the difference between them, maintaining the bias point and the RF amplitude level at an optimum value by varying an input voltage to the modulator via the feedback loop. One embodiment of the system of this invention comprises a laser for providing an input light, a modulator to modulate the input light and generate a digital optical output signal, a radio frequency (RF) feedback loop to control an RF input voltage to the modulator, a bias feedback loop to control a bias input voltage to the modulator, an RF amplitude dither circuit to provide an RF input dither signal to the RF voltage input, and a bias dither circuit to provide a bias input dither signal to the bias voltage input. The modulator can be a Mach-Zehnder modulator.

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Allen, TX, United States of America

John K Sikora