Laurent Provino

Supercontinuum generation in air–silica microstructured fibers with nanosecond and femtosecond pulse pumping

We study the generation of supercontinua in air–silica microstructured fibers by both nanosecond and femtosecond pulse excitation. In the nanosecond experiments, a 300-nm broadband visible continuum was generated in a 1.8-m length of fiber pumped at 532 nm by 0.8-ns pulses from a frequency-doubled passively Q-switched Nd:YAG microchip laser. At this wavelength, the dominant mode excited under the conditions of continuum generation is the LP11 mode, and, with nanosecond pumping, self-phase modulation is negligible and the continuum generation is dominated by the interplay of Raman and parametric effects. The spectral extent of the continuum is well explained by calculations of the parametric gain curves for four-wave mixing about the zero-dispersion wavelength of the LP11 mode. In the femtosecond experiments, an 800-nm broadband visible and near-infrared continuum has been generated in a 1-m length of fiber pumped at 780 nm by 100-fs pulses from a Kerr-lens model-locked Ti:sapphire laser. At this wavelength, excitation and continuum generation occur in the LP01 mode, and the spectral width of the observed continuum is shown to be consistent with the phase-matching bandwidth for parametric processes calculated for this fiber mode. In addition, numerical simulations based on an extended nonlinear Schrodinger equation were used to model supercontinuum generation in the femtosecond regime, with the simulation results reproducing the major features of the experimentally observed spectrum.

Generation of a broadband single-mode supercontinuum in a conventional dispersion-shifted fiber by use of a subnanosecond microchip laser

We report the experimental generation, simply by use of a subnanosecond microchip laser at 532 nm and a conventional dispersion-shifted fiber, of a supercontinuum that spans more than 1100 nm. We show by detailed spectral analysis that this supercontinuum originates from a preliminary four-wave mixing process with multimode phase matching and subsequent double-cascade stimulated Raman scattering and is transversely single mode as a result of Raman-induced mode competition. This technique is believed to be the simplest configuration that allows one to generate a stable supercontinuum.

Broadband and flat parametric amplifiers with a multisection dispersion-tailored nonlinear fiber arrangement

We describe a simple scheme to allow for the achievement of flat gain over ultrabroad bands with a single-pump fiber-optic parametric amplifier operating in the zero-dispersion wavelength region. The proposed method, based on a multisection dispersion-tailored in-line nonlinear fiber arrangement, is demonstrated by both modulational instability theory and numerical simulations of the nonlinear Schrodinger equation. The results show that the design can be adjusted to generate gain bands that exceed either 100 nm with a ripple of less than 0.2 dB and for a pump power of only 500 mW, or even 200 nm when a pump power of 5 W is used. In addition, the robustness of this gain-flattening technique has been numerically checked against random fluctuations of the zero-dispersion wavelength in each of the fiber sections.

Polarization mode dispersion and vectorial modulational instability in air-silica microstructure fiber.

The birefringence of an air-silica microstructure fiber has been studied by measurement of the fiber polarization mode dispersion (PMD) over the wavelength range 545-640 nm. The experimental results are shown to be in good agreement with vectorial numerical calculations, assuming an elliptical core with an eccentricity of 7%. We also report controlled experiments studying nonlinear vectorial modulation instability in the fiber, yielding 3.9-THz modulational instability sideband shifts that are in good agreement with theoretical predictions based on the calculated fiber dispersion and PMD characteristics.

Broadband and nearly flat parametric gain in single-mode fibers

Summary form only given. In optical WDM communication systems, the 35 nm gain bandwidth available with conventional EDFAs sets a limit to the increase of transmission rates. It is important to develop new optical amplifiers in several spectral ranges between 1.3 /spl mu/m and 1.6 /spl mu/m, with broad bandwidths and flat spectral gain profiles, another restrictive factor in long-haul systems involving repeated steps of amplification. Multi-pumped fiber Raman amplifiers and dual-band doped-host EDFAs are some of the presently developed devices. We study another approach based on parametric amplification which is spectrally flexible and can additionally provide low noise features and the possibility to achieve phase-conjugate wavelength conversion. We present broad and nearly flat parametric gain profiles around the zero-dispersion wavelength of single-mode fibers, obtained from modulational instability (MI) calculations and simulations of the nonlinear Schrodinger equation.

A large mode area elliptical hollow photonic crystal fiber

We report on the design, fabrication and characterization of an elliptical hollow photonic crystal fiber (EH-PCF), a PCF with an elliptical hole in its solid core, for applications requiring large mode area and high birefringence

Broadband and flat parametric gain with a single low-power pump in a multi-section fiber arrangement

We have theoretically investigated a new fibre optical parametric amplifier (OPA) architecture that provides a nearly flat gain over a 100 nm bandwidth without any gain-equalization filter. It consists in a multi-section in-line dispersion-tailored NLF arrangement and a single low-power pump which meets the current telecommunications requirements. Recent experiments haw shown that this kind of OPAs would be potentially useful for telecommunications applications and the results presented here predict interesting enhanced performances.

System Performances of Fiber Optical Parametric Amplifiers

Abstract The research field of fiber optical parametric amplifiers has steadily expanded over the last two decades as a host of all-optical signal processing techniques have been demonstrated in nonlinear optical fibers such as wavelength conversion, optical regeneration, optical switching, limiting, buffering, and sampling. This article reviews the system performances of theses parametric devices such as gain bandwidth, focuses on the main limitations and demonstrates efficient techniques for suppressing them. * Arnaud Mussot is now with the Laboratoire de Physique des Lasers Atomes et Molécules, Université des Sciences et Technologies de Lille, 59655 Villeneuve dAsq cedex, France. † Armand Vedadi is now with the Institute of Advanced Telecommunications, Swansea University, Singleton Park Swansea SA2 8PP Wales, United Kingdom. ‡ Laurent Provino is now with PERFOS, 11 rue de Broglie, 22300 Lannion, France.

Compact visible continuum source based on a microchip laser pumped microstructured fiber

A broadband visible continuum is generated in a 1.8 m length of microstructured fiber pumped in the normal dispersion regime by a frequency-doubled passively Q-switched Nd:YAG microchip laser.

Broadband and flat parametric gain with a single pump in a multi-section nonlinear fiber arrangement

Summary from only given. Parametric amplification appears now as a promising solution for fiber WDM systems and opens up a new means to cover actual and future telecommunications windows. Optical parametric amplifiers (OPA) can directly generate a broad and flat gain region by using two pump lasers or multiple fibers with different group-velocity dispersions. In this work, we propose and theoretically study multi-section OPA configurations based on four NLFs with different zero-dispersion wavelengths to achieve broadband and flat parametric gain.