Optical Processing of High Dimensionality Signals

Optical parametric amplifiers (OPAs) combine high-gain broadband ampli- fication at nearly arbitrary wavelengths with the prospect for achieving an ideally 0-dB noise figure when used in phase-sensitive configuration. Furthermore, several recent demonstrations confirm their potential for alloptical signal processing, including wavelength conversion, optical phase conjugation (OPC), and signal regeneration.
This project focuses precisely on the applications of OPAs for all-optical signal processing with a two-fold focus: on the one hand, processing the advanced modulation formats required to increase the capacity of future communication systems; on the other hand, the different nonlinear material suitable for providing parametric amplification. Therefore, three different materials, namely silica highly nonlinear fibers (HNLFs), silicon waveguides, and periodically poled lithium niobate (PPLN) waveguides, are investigated. The limits of parametric amplification for 16-quadrature amplitude modulation (QAM) signals are first characterized. The acquired knowledge is then applied to the design of a black-box OPC-device used to provide Kerr nonlinearity compensation for a 5-channel polarization-division multiplexing (PDM) 16-QAM signal at 1.12 Tbps with significant improvements in received signal quality.
Furthermore, the first demonstration of phase regeneration for binary phase-shift keying (BPSK) signals using the silicon platform is presented. The silicon-based OPA relies on a novel design where a reverse-biased p-i-n junction fabricated along the waveguide allows decreasing the nonlinear absorption, thus achieving phase-sensitive extinction ratios in excess of 20 dB. Finally, a recently proposed quadrature phase-shift keying (QPSK)-to- 2×BPSK wavelength and format converter is characterized experimentally by implementing it using fiber-, silicon, and PPLN-based platforms. Similar results have been measured for all three media under continuous-wave operation and for fiber- and PPLN-based implementations under modulated signal operations with little penalty introduced by the conversion.
Altogether this work demonstrates the potential of phase-insensitive and phase-sensitive parametric processing applied to high-dimensionality modulation formats.