Random mode coupling assists kerr beam self-cleaning in a graded-index multimode optical fiber

Spatiotemporal light beam dynamics in multimode fibers (MMF) recently has attracted renewed interest in both fundamental physics and various fields of practical application . Recent experiments have shown that, owing to the Kerr effect, a process of beam self-cleaning can be observed in graded-index (GRIN) MMFs. As a result, one observes a robust nonlinear beam, which has a size that is close to the fundamental mode at the fiber output, in contrast to a speckled output beam, which is obtained in the case of the linear regime

Mitigation of nonlinear transmission effects for OFDM 16-QAM optical signal using adaptive modulation

The impact of the fiber Kerr effect on error statistics in the nonlinear (high power) transmission of the OFDM 16-QAM signal over a 2000 km EDFA-based link is examined. We observed and quantified the difference in the error statistics for constellation points located at three power-defined rings. Theoretical analysis of a trade-off between redundancy and error rate reduction using probabilistic coding of three constellation power rings decreasing the symbol-error rate of OFDM 16-QAM signal is presented. Based on this analysis, we propose to mitigate the nonlinear impairments using the adaptive modulation technique applied to the OFDM 16-QAM signal. We demonstrate through numerical modelling the system performance improvement by the adaptive modulation for the large number of OFDM subcarriers (more than 100). We also show that a similar technique can be applied to single carrier transmission

Development and Research of Technology Manufacturing of Semi-Finished Products from Solder Alloys Based on Silver

Proposed new compositions of solder alloys based on silver. Developed technological schemes of production of wire diameter 1,2 mm. Developed scheme of production of wire diameter 1,2 mm from alloy SAg-40I with operation combined casting, rolling and extruding. Modeling of temperature-rate parameters of the process of combined casting, rolling and extruding has been made. Designed and constructed the installation CCRE-80. The analysis of the structure and properties of semi-finished solder alloys based on silver has been done.Предложены новые составы припойных сплавов на основе серебра. Разработаны технологические схемы производства проволоки диаметром 1,2 мм. Разработана схема производства проволоки диаметром 1,2 мм из сплава ПСр-40И с применением операции совмещенного литья, прокатки и прессования. Проведено моделирование температурно- скоростных параметров процесса совмещенного литья, прокатки и прессования. Спроектирована и изготовлена установка СЛИПП-80. Проведен анализ структуры и свойств полуфабрикатов из припойных сплавов на основе серебра

Mechanism of brightness enhancement in multimode LD-pumped graded-index fiber Raman lasers: numerical modeling

We develop a comprehensive theory for describing the experimental beam profiles from multimode fiber Raman lasers. We take into account the presence of random linear mode coupling, Kerr beam self-cleaning and intra-cavity spatial filtering. All of these factors play a decisive role in shaping the Stokes beam, which has a predominant fundamental mode content. Although the highly multimode pump beam is strongly depleted, it remains almost insensitive to the different physical effects. As a result, the intensity of the output Stokes beam is an order of magnitude higher than the pump intensity at its maximum, in quantitative agreement with the experimental results and in contrast with the simplified balance model

Mechanism of brightness enhancement in multimode LD-pumped graded-index fiber Raman lasers

A theory describing experimental beam profiles of multimode fiber Raman lasers is developed: random mode coupling, Kerr self-cleaning and spatial filtering play a decisive role in shaping Stokes beams, whereas depleted pump beams remain insensitive

Development and Research of Technology Manufacturing of Semi-Finished Products from Solder Alloys Based on Silver

Proposed new compositions of solder alloys based on silver. Developed technological schemes of production of wire diameter 1,2 mm. Developed scheme of production of wire diameter 1,2 mm from alloy SAg-40I with operation combined casting, rolling and extruding. Modeling of temperature-rate parameters of the process of combined casting, rolling and extruding has been made. Designed and constructed the installation CCRE-80. The analysis of the structure and properties of semi-finished solder alloys based on silver has been done.Предложены новые составы припойных сплавов на основе серебра. Разработаны технологические схемы производства проволоки диаметром 1,2 мм. Разработана схема производства проволоки диаметром 1,2 мм из сплава ПСр-40И с применением операции совмещенного литья, прокатки и прессования. Проведено моделирование температурно- скоростных параметров процесса совмещенного литья, прокатки и прессования. Спроектирована и изготовлена установка СЛИПП-80. Проведен анализ структуры и свойств полуфабрикатов из припойных сплавов на основе серебра

Spatio-spectral beam control in multimode diode-pumped Raman fibre lasers via intracavity filtering and Kerr cleaning

Multimode fibres provide a promising platform for boosting the capacity of fibre links and the output power of fibre lasers. The complex spatiotemporal dynamics of multimode beams may be controlled in spatial and temporal domains via the interplay of nonlinear, dispersive and dissipative effects. Raman nonlinearity induces beam cleanup in long graded-index fibres within a laser cavity, even for CW Stokes beams pumped by highly-multimode laser diodes (LDs). This leads to a breakthrough approach for wavelength-agile high-power lasers. However, current understanding of Raman beam cleanup is restricted to a small-signal gain regime, being not applicable to describing realistic laser operation. We solved this challenge by experimentally and theoretically studying pump-to-Stokes beam conversion in a graded-index fibre cavity. We show that random mode coupling, intracavity filtering and Kerr self-cleaning all play a decisive role for the spatio-spectral control of CW Stokes beams. Whereas the depleted LD pump radiation remains insensitive to them

Thermalization of orbital angular momentum beams in optical fibers

We experimentally and theoretically study the thermalization of orbital angular momentum beams in nonlinear multimode graded-index optical fibers. Our results shed new light on the physical mechanism of the beam self-cleaning effect