High-speed, low power optical modulator with adjustable chirp parameter

Abstract

Lithium niobate waveguide electrooptic modulators permit long fiber transmission spans with low dispersion penalty because of their capability for very low frequency chirp.¹ It has been proposed that waveguide Mach-Zehnder amplitude modulators may be operated in a perfectly chirpless mode and devices designed to operate chirp-free have been reported.²⁻⁴ However, the lowest fiber dispersion penalty is generally not obtained for a frequency chirp parameter identically equal to zero. Indeed, choosing a non-zero value for the chirp parameter, α, depending on the fiber dispersion coefficient and distance, so as to provide some amount of pulse compression can be advantageous. Here we propose and report a Ti:LiNbO₃ optical modulator that provides for complete adjustment of the modulation α-parameter. We demonstrate that this modulator can achieve virtually ideal amplitude or phase modulation, or any signed ratio thereof.