Optical modulator

Abstract

A method and apparatus for optical return-to-zero (RZ) modulation based on a single Mach-Zehnder modulator driven by non-return-to-zero (NRZ) electrical signals. The method and apparatus allow for continuously electrically tunable duty cycles and lead to chirped-RZ formats. A “push-pull” embodiment involves driving one control arm of the Mach-Zehnder with a differentially encoded version of an NRZ data stream and driving the other control arm with an inverted and time-delayed copy of the same differentially encoded data stream. A “push-push” embodiment involves driving one control arm of the Mach-Zehnder with a differentially encoded version of an NRZ data stream and driving the other control arm with a time-delayed but non-inverted copy of the same differentially encoded data stream. In one or more embodiments, the duty cycle of the RZ modulation is controlled via the selection of the time delay between the electrical signals that drive the two arms of the Mach-Zehnder.

Dependencies are inferred from the claim text.