Showing papers by "Francesca Parmigiani published in 2016"

Inter-modal four-wave mixing study in a two-mode fiber

Abstract: We demonstrate efficient four-wave mixing among different spatial modes in a 1-km long two-mode fiber at telecommunication wavelengths. Two pumps excite the LP01 and LP11 modes, respectively, while the probe signal excites the LP01 mode, and the phase conjugation (PC) and Bragg scattering (BS) idlers are generated in the LP11 mode. For these processes we experimentally characterize their phase matching efficiency and bandwidth and find that they depend critically on the wavelength separation of the two pumps, in good agreement with the numerical study we carried out. We also confirm experimentally that BS has a larger bandwidth than PC for the optimum choice of the pump wavelength separation.

Multi-Channel Phase Regenerator Based on Polarization-Assisted Phase-Sensitive Amplification

Abstract: We propose and demonstrate simultaneous phase regeneration of six nonreturn-to-zero binary phase shift keying signals in a single nonlinear medium. The regenerating system, which exhibits binary steplike phase transfer functions, uses four-wave mixing in degenerate dual-pump vector parametric amplifiers implemented in the same nonlinear optical fiber, followed by polarization filtering. Bit-error-ratio measurements confirm optical-signal-to-ratio improvement and negligible crosstalk across all the regenerated channels, which were impaired at the regenerator input by broadband phase noise.

All-optical Phase Regeneration with Record PSA Extinction Ratio in a Low-birefringence Silicon Germanium Waveguide

Abstract: We report a low-power continuous wave-pumped phase sensitive amplifier (PSA)-based phase regenerator implemented in a passive silicon-based waveguide. A polarization assisted-PSA, consisting of two orthogonally-polarized pumps and a phase-locked signal copolarized to one of them, was implemented in a low-birefringence silicon germanium (SiGe) waveguide. The strong TE/TM modal symmetry of the waveguide and its large nonlinear coefficient enabled the achievement of an extremely large phase sensitive extinction ratio of approximately 29 dB for a total input power of only 21.3 dBm. This SiGe-based PSA was used to demonstrate phase regeneration on a 20 Gb/s differential phase-shift keying signal, thereby reducing its error vector magnitude and phase error by three and six times respectively and enabling a bit-error ratio improvement of up to 2 dB.

Optimisation of amplitude limiters for phase preservation based on the exact solution to degenerate four-wave mixing

Abstract: Adopting an exact solution to four-wave mixing (FWM), wherein harmonic evolution is described by the sum of two Bessel functions, we identify two causes of amplitude to phase noise conversion which impair FWM saturation based amplitude regenerators: self-phase modulation (SPM) and Bessel-order mixing (BOM). By increasing the pump to signal power ratio, we may arbitrarily reduce their impact, realising a phase preserving amplitude regenerator. We demonstrate the technique by applying it to the regeneration of a 10 GBaud QPSK signal, achieving a high level of amplitude squeezing with minimal amplitude to phase noise conversion.

Phase Regeneration of QPSK Signal in SOA Using Single-Stage, Wavelength Converting PSA

Abstract: We demonstrate, for the first time, all-optical phase regeneration of a quaternary phase shift keying signal through phase sensitive amplification in nonlinear semiconductor optical amplifiers (SOAs), using a scheme only previously demonstrated in highly nonlinear fibre. We make use of a highly tunable phase quantizing scheme to circumvent some of the limitations imposed by the use of SOAs and show that it may function in either a conjugating or nonconjugating manner.

Study of inter-modal four wave mixing in two few-mode fibres with different phase matching properties

Abstract: We experimentally study inter-modal four-wave mixing (FWM) in few-mode fibres with different phase matching properties. The possibility of transmitting two spatial modes without intermodal FWM cross-talk in the C-band is presented.

Polarization Insensitive Wavelength Conversion in a Low-Birefringence SiGe Waveguide

Abstract: We report the first demonstration of a single-pass dual-orthogonal-pump four-wave mixing-based wavelength conversion scheme in a silicon-based waveguide. The silicon germanium waveguide used was designed to exhibit strong TE/TM mode similarity across a broad wavelength range as well as a large nonlinear coefficient. A polarization-dependent loss of just 0.42 dB was measured, and the conversion of 40-Gb/s differential phase-shift keying signals was demonstrated with 1.5-dB power penalty at a bit error ratio of $10^{-9}$ .

Nonlinearity mitigation for multi-channel 64-QAM signals in a deployed fiber link through optical phase conjugation

Abstract: We report nonlinearity mitigation of two 64-QAM signals, tested in a WDM environment, through mid-link optical phase conjugation. Efficient reuse of signal bandwidth and a Q-factor improvement of more than 1.7 dB is demonstrated in a 400 km installed fiber link.

Detailed phase matching characterization of inter-modal four-wave mixing in a two-mode fiber

Abstract: We experimentally characterize the phase matching properties of two inter-modal four-wave mixing processes in a graded index fiber guiding the LP01 and LP11 mode-groups.

FWM-based amplitude limiter realizing phase preservation through cancellation of SPM distortions

Abstract: We present a FWM-based amplitude regenerator that includes an optical phase pre-distortion stage to compensate for the effects of Kerr-induced amplitude-to-phase noise conversion of the signal. Successful operation of the scheme is demonstrated on a QPSK signal.

Multi-channel all-optical signal processing based on parametric effects

Abstract: Two different experiments that use parametric effects for the processing of multiple signals in a single fiber are reviewed. The first experiment uses optical phase conjugation to mitigate the effects of nonlinearity in transmission, whereas the second uses multiple phase-sensitive amplifiers to regenerate six different channels.

Applications of nonlinear parametric effects for advanced processing of optical signals

Abstract: Phase-sensitive amplifiers constitute powerful tools for the regeneration of phase-encoded optical signals. However, they are often accompanied by a detrimental phase-to-amplitude noise conversion. We present techniques to overcome this effect and discuss their potential.