Olga V. Shtyrina

Numerical modeling of fiber lasers with long and ultra-long ring cavity.

We highlight two important aspects related to a mathematical modeling of pulsed fiber lasers with long and ultra-long ring cavity -impact of an initial noise and a cavity length on generation of single optical pulses. Using as an example a simple scalar model of a ring fiber laser that describes the radiation build-up from noise and the following intra-cavity pulse dynamics during a round trip we study dependence of generated pulse characteristics on the resonator length in the range from 30 m up to 2 km.

Highly chirped dissipative solitons as a one-parameter family of stable solutions of the cubic–quintic Ginzburg–Landau equation

In this paper, the stability of the analytical solutions of the cubic–quintic Ginzburg–Landau equation (CQGLE) in the high-chirp approximation has been studied numerically. The existence domain for the stable solution in the CQGLE parameter set has been found. A temporal and spectral shape of the stable solution as dependent of the cavity parameters has been analyzed. Direct comparison of the spectra with numerical calculations has been performed, demonstrating 10−2–10−4 accuracy of the analytical solution for chirp parameter f>10. The stable solutions represent the dissipative soliton family with only one composite parameter. Inside this family, the pulse shape in the time domain evolves from the conventional soliton shape, sech−2, to a rectangular one in the opposite limit with a parabolic shape as an intermediate one. The obtained theoretical results make it possible to classify experimentally observed highly chirped pulses and to optimize experimental schemes with an all-normal-dispersion cavity.

Modulation instability at propagation of narrowband 100-ns pulses in optical fibers of various types

The instability of the propagation of narrowband 100-ns laser pulses in the transparency window of a single-mode fiber in the presence of continuous broadband noise is demonstrated. The modulation instability developed due to the nonlinearity and anomalous dispersion leads to a rapid decay of the narrowband component after passing through the fiber. The modulation-instability threshold is shown to be sensitive to the noise level in a spectral interval of about 100 GHz near a central wavelength of about 1.55 μm and is inversely proportional to the fiber length (varied from 1.6 to 21.0 km in the experiments). The effect is completely eliminated owing to the application of a dispersion-shifted fiber with normal dispersion.

Optical black hole: Design and performance

We discuss the design of a realistic optical black hole (OBH) using the exact frequency domain solutions for TM and TE waves. The design includes thin separating layers between the absorbing core and the metamaterial shell. The overall objective is to develop an on-line simulation tool, which could help to design experimentally realizable OBH with a continuous radius-dependent index. Example structures working at 1.5 μm are presented and analyzed.

Patterning of Errors in 40 Gbit/s WDM RZ-DBPSK SMF/DCF Optical Transmission System

Through extensive direct modelling we quantify patterning effects in a WDM RZ-DBPSK fibre link at 40 Gbit/s channel rate. We demonstrate BER improvement through skewed channel pre-encoding reducing the occurrence of the most dangerous triplets.

Experimental measurement and analytical estimation of the signal gain in an Er-doped fiber

We propose a theoretical method to estimate the saturation power and the small signal gain of an active Er-doped fiber as functions of the fiber length and the pump power. The results make it possible to carry out the numerical simulation of a given Er-doped fiber. The results allow us to carry out the optimization of fiber laser systems by means of a numerical simulation using the nonlinear Schrodinger equation.

Analytical Solutions for Power Evolution in the Effective Two-level Medium Laser Models

We present analytical solution describing power evolution in the general two-level active medium and the generated output power in the Fabry-Perot and ring fiber laser configurations.

Theoretical analysis of the energy evolution in dissipative soliton fiber lasers

Theoretical results on the energy evolution in ring and linear cavities of dissipative soliton fiber lasers are analyzed. The correctness of the theoretical results is confirmed by mathematical modeling.

Suppression of Patterning Effects in Digital Communications by an Adaptive Constrained Coding

We quantify the error statistics and patterning effects in a 5x 40 Gbit/s WDM RZ-DBPSK SMF/DCF fibre link using hybrid Raman/EDFA amplification. We propose an adaptive constrained coding for the suppression of errors due to patterning effects. It is established, that this coding technique can greatly reduce the bit error rate (BER) value even for large BER (BER > 101). The proposed approach can be used in the combination with the forward error correction schemes (FEC) to correct the errors even when real channel BER is outside the FEC workspace.

Evolution and stability of pulse regimes in SESAM-mode-locked femtosecond fiber lasers

One of the key technologies exploited in femtosecond lasers is the application of semiconductor saturable absorber mirrors (SESAMs) [1, 2]. The SESAM technology is based on bandgap engineering and epitaxial growth and has many advantages compared to other methods. From the laser design view point it is important to know how SESAM parameters affect properties of steady-state pulses and overall laser system performance. We have performed here a massive optimization of the laser system including total gain, cavity dispersion, saturable absorber recovery time and saturation energy.