Optical fibre technologies for future communication networks

New transmission technologies need to be developed to satisfy the ever increasing demand for communication traffic. This paper reviews some recent research on optical fibre technology that aims at addressing this challenge

Façonnage d'impulsions optiques par filtrage intra-cavité dans un laser à fibre

National audienceNous démontrons numériquement la possibilité de façonner des impulsions optiques au sein d'une cavité laser fibrée à modes bloqués en insérant un filtre spectral programmable en intensité et phase. Différents profils temporels d'intensité sont obtenus, dont des impulsions paraboliques, triangulaires ou en dents de scie

Optical predistortion enabling phase preservation in optical signal processing demonstrated in FWM-based amplitude limiter

We propose and demonstrate a technique to obtain phase preservation in optical processing which is suitable for many four-wave mixing (FWM) based processing devices, provided they may be modified to incorporate two conjugating FWM stages. It functions by using a first conjugating nonlinear stage to predistort the signal using self-phase modulation (SPM) such that when the signal undergoes further SPM in a second conjugating FWM stage, the two SPM contributions negate each other, resulting in phase preserving output. In this work, we use the second stage to perform amplitude squeezing through parametric gain saturation and characterise the scheme by regenerating a QPSK signal contaminated with broadband amplitude noise. Experimental analysis of the system with and without predistortion is provided and phase preserving operation using the proposed scheme is confirmed

Pulse shaping-assisted nonlinear spectral broadening

Recent developments in optical fibre technology have allowed significant advances in the nonlinear generation and tailoring of broadband spectra. Much work in this direction has focused on the optimisation of the properties of the optical fibres used for the nonlinear pulse propagation. In this work, we combine the nonlinear element (a highly nonlinear fibre - HNLF) with a programmable phase and amplitude filter, which we use as a pulse shaper. This architecture allows power-efficient and flexible sculpturing of the output spectrum, which is no longer tied directly to the characteristics of the pulse source used at the input. The pulse shaping function is obtained by application of the inverse split-step Fourier method (ISSFM) [1], which uses the desired output spectrum and the HNLF characteristics as its input parameters [2]. As an example of the application of this technique, we study the generation of broadband flat (third-order super-Gaussian) spectra starting from a 10GHz mode-locked pulsed laser (MLL). Here we present our design procedure and a first experimental validation of the technique

Methodes simples et sensibles pour optimiser le taux d'extinction d'un modulateur optique

Nous exploitons l’auto-modulation de phase dans une fibre hautement non-linéaire pour optimiser les réglages d’un modulateur optique et ainsi obtenir le meilleur taux d’extinction. Cette méthode simple mais extrêmement sensible ne nécessite alors qu’un analyseur de spectre optique ou bien un oscilloscope

Regles de conception pour les regenerateurs optiques 2-R exploitant l'auto-modulation de phase

Nous présentons des règles de conception générales concernant l’optimisation de régénérateurs 2R exploitant l’auto-modulation de phase. Nous étudions les performances des dispositifs optimisés en termes d’amélioration du taux d’extinction et de réduction de la gigue d’amplitude

Exploitation de l'autoglissement frequentiel soliton limite par des radiations de cherenkov pour generer deux impulsions au decalage frequentiel ou temporel continument ajustable

Nous exploitons l’apparition de radiations de Cherenkov qui limitent l’autoglissement fréquentiel d’une impulsion soliton pour proposer une source de deux impulsions ultrabrèves dont, suivant l’énergie initiale, il est possible de contrôler de manière continue soit l’écart fréquentiel, soit l’écart temporel

Fast and broadband fiber dispersion measurement with dense wavelength sampling

We report on a method to obtain dispersion measurements from spectral-domain low-coherence interferograms which enables high accuracy (~ps/(nm·km)), broadband measurements and the determination of very dense (up to 20 points/nm over 500 nm) data sets for both dispersion and dispersion slope. The method exploits a novel phase extraction algorithm which allows the phase associated with each sampling point of the interferogram to be calculated and provides for very accurate results as well as a fast measurement capability, enabling close to real time measurements. The important issue of mitigating the measurement errors due to any residual dispersion of optical elements and to environmental fluctuations was also addressed. We performed systematic measurements on standard fibers which illustrate the accuracy and precision of the technique, and we demonstrated its general applicability to challenging problems by measuring a carefully selected set of microstructured fibers: a lead silicate W-type fiber with a flat, near-zero dispersion profile; a hollow core photonic bandgap fiber with strongly wavelength dependent dispersion and dispersion slope; a small core, highly birefringent index guiding microstructured fiber, for which polarization resolved measurements over an exceptionally wide (~1000 nm) wavelength interval were obtained

Homodyne operation of a phase-only optical amplifier

We utilise cascaded four wave mixing to multiply the modulation depth of a phase-only optical signal and generate a comb of phase locked local oscillators allowing homodyne retrieval of the phase information with enhanced fidelity

Dispersion-shifted all-solid high index-contrast microstructured optical fiber for nonlinear applications at 1.55µm

We report the fabrication of an all-solid highly nonlinear microstructured optical fiber. The structured preform was made by glass extrusion using two types of commercial lead silicate glasses that provide high index-contrast. Effectively single-moded guidance was observed in the fiber at 1.55µm. The effective nonlinearity and the propagation loss at this wavelength were measured to be 120W/km respectively at 1.55µm. These predictions are consistent with the experimentally determined dispersion of +12.5ps/nm/km at 1.55µm. Tunable and efficient four-wave-mixing based wavelength conversion was demonstrated at wavelengths around 1.55µm using a 1.5m length of the fiber