Theoretical study of the erbium-doped fiber laser passively mode-locked by nonlinear polarization rotation

We investigate theoretically the mode-locking properties of an erbium-doped birefringent fiber laser in a unidirectional cavity containing an optical isolator. The mode-locking is achieved through nonlinear polarization rotation. The approach is based on a master equation which takes explicitly into account the angles between the eigen axis of the fiber at each side of the polarizer. The stability conditions of both the stationary and localized solutions are determined. This allows to establish a stability diagram versus the angles which gives the domains where the laser operates in continuous, mode-locked or unstable regime. The model also allows to calculate the pulse duration together with the pulse energy as a function of the orientation of the eigen axis of the fiber with respect to the polarizer

Modelling of figure-eight all-fiber laser

The figure-eight fiber laser is considered in two configurations, with either a unidirectional active ring cavity coupled with a nonlinear optical loop mirror (NOLM) or a unidirectional passive cavity and a nonlinear amplifying loop mirror (NALM). In each case, we derive a master equation of cubic complex Ginzburg Landau (CGL) type, in which the coefficients explicitly depend on the characteristics of the cavity. Single-pulse and continuous wave (cw) solutions in both normal and anomalous dispersion are discussed analytically

A comparative study of maximum power point tracking techniques for a photovoltaic grid-connected system

Purpose. In recent years, the photovoltaic systems (PV) become popular due to several advantages among the renewable energy. Tracking maximum power point in PV systems is an important task and represents a challenging issue to increase their efficiency. Many different maximum power point tracking (MPPT) control methods have been proposed to adjust the peak power output and improve the generating efficiency of the PV system connected to the grid. Methods. This paper presents a Beta technique based MPPT controller to effectively track maximum power under all weather conditions. The effectiveness of this algorithm based MPPT is supplemented by a comparative study with incremental conductance (INC), particle swarm optimization (PSO), and fuzzy logic control (FLC). Results Faster MPPT, lower computational burden, and higher efficiency are the key contributions of the Beta based MPPT technique than the other three techniques.Мета. В останні роки фотоелектричні системи набули популярності завдяки низці переваг серед відновлюваних джерел енергії. Відстеження точки максимальної потужності у фотоелектричних системах є важливим завданням і складною проблемою для підвищення їх ефективності. Було запропоновано безліч різних методів керування відстеженням точки максимальної потужності (ВТМП) для регулювання пікової вихідної потужності та підвищення ефективності генерації фотоелектричної системи, підключеної до мережі. Методи. У цій статті представлений контролер ВТМП, заснований на бета-методі, для ефективного відстеження максимальної потужності за будь-яких погодних умов. Ефективність ВТМП на основі цього алгоритму доповнюється порівняльним дослідженням з інкрементною провідністю, оптимізацією рою частинок та нечітким логічним управлінням. Результати. Швидше ВТМП, менші витрати на обчислення та більша ефективність є ключовими перевагами методу ВТМП на основі бета-методу порівняно з трьома іншими методами

Auto-organisation d’un grand nombre d’impulsions dans un laser à fibre dope Er:Yb

Nous proposons une étude inédite de l’interaction d’un grand nombre d’impulsions dans un laser à fibre double gaine dopée à l\u27Er :Yb fonctionnant par rotation non linéaire de la polarisation. A cause des phénomènes d\u27attractions et de répulsions entre solitons, des régimes auto-organisés peuvent être générés. Par analogie avec les états de la matière, nous nous sommes intéressés aux régimes "gaz de solitons", "jet supersonique de solitons", "polycristal de solitons", "liquide de solitons" et "cristal de solitons"

Algeria's Islamist Movement. Victims of Success

Following the 'bread riots' of October 1988, the Islamist movement was the biggest benefactor of the introduction of democracy in Algeria, quickly amassing huge political support and winning landslide victories in local and legislative elections. But instead of using its newly acquired power to install democratic principles throughout Algeria, the Islamist movement fell victim to its own aspirations. Today, as Algeria observes the tenth anniversary of the October riots, certain conclusions are self-evident. Overall, Algeria's Islamist leadership has proven ill equipped to handle its success or its own agenda

Comparative study of soliton complexes in different laser configurations

We investigate the formation of self-organized and disorganized soliton structures in passively mode-locked Er:Yb doped double-clad fiber laser. Two laser configurations are studied. The first one is based on mode-locking through nonlinear polarization rotation while the second geometry is a figure-eight cavity in which the mode-locking is obtained with a nonlinear optical loop mirror. Although the physical mechanisms of mode-locking are different, we demonstrate that collective behaviours and soliton complexes are similar in both configurations. That demonstrates the universality of the solitonic structures

Investigation of multiple pulsing and hysteresis phenomena in the erbium-doped double-clad fiber laser

We investigate both experimentally and theoretically the multiple pulsing behaviour of an erbium-doped double-clad fiber laser passively mode-locked through nonlinear polarization rotation. Hysteresis phenomena are found experimentally in both the normal and anomalous dispersion regime. Theoretical results are compared with experimental data allowing to fix the range of validity of the model

Soliton crystal fiber laser

We report on the observation of bound state of some hundreds of solitons in a passively mode-locked Er:Yb-doped fiber laser. A double-clad fiber is used in a unidirectional ring cavity where the mode-locking is obtained thanks to the nonlinear polarization rotation. The phenomenon is described theoretically using a multiscale approach to the gain dynamics

Coherent soliton pattern formation in a fiber laser

We report the observation of bound states of 350 pulses in a ring fiber laser mode locked by nonlinear rotation of the polarization. The phenomenon is described theoretically using a multiscale approach to the gain dynamics; the fast evolution of a small excess of gain is responsible for the stabilization of a periodic pattern, while the slow evolution of the mean value of gain explains the finite length of the quasiperiodic soliton train

Laser à fibre verrouillé en phase à haute cadence

We investigate different ways to considerably increase the repetition-rate of passively mode-locked fiber lasers. We first report the harmonic mode-locking of a double-clad fiber laser passively mode-locked through nonlinear polarization rotation. We then consider the theoretical possibility to generate a bound-state filling the optical cavity thus resulting in ultra-high repetition rate with a remarkable stability