B. Neto

Efficient use of hybrid Genetic Algorithms in the gain optimization of distributed Raman amplifiers

In this paper, we propose an efficient and accurate method that combines the Genetic Algorithm (GA) with the Nelder-Mead method in order to obtain the gain optimization of distributed Raman amplifiers. By using these two methods together, the advantages of both are combined: the convergence of the GA and the high accuracy of the Nelder-Mead. To enhance the convergence of the GA, several features were examined and correlated with fitting errors. It is also shown that when the right moment to switch between methods is chosen, the computation time can be reduced by a factor of two.

All-optical XOR based on integrated MZI-SOA with co- and counter-propagation scheme

In this work we present a review of all-optical XOR gates based on Mach-Zehnder Interferometer with Semiconductor Optical Amplifiers (MZI-SOA), using NRZ modulated signals driven at 10 Gbit/s. The performance of two alternative schemes for logical XOR gates implementation is demonstrated through numerical simulations and experimentally. The extinction ratio shows high operation performance with low degradation.

Optical fiber bending limits for optical fiber infraestructures

In this work the high power propagation in tight bent fibers was studied. The signal losses and the temperature increase have been experimental measured for single mode optical fibers (SMF) as function of the bending diameter. These results were used to propose an approach to limit the bending diameter, as a function of the injected power, in order to maintain the operational condition bellow the safety limit.

Raman amplification in high 10 Gbit/s and 40 Gbit/s packet optical networks

Packet traffic will dominate the future optical networks. In this work we experimentally access the impact of Raman amplification on 10 Gbit/s and 40 Gbit/s packet traffic performances. For a 10 Gbit/s packet traffic it was observed a decreased of 21% on the Q factor value for the system with EDFA amplification and 9% for the same system with Raman amplification, as the burst off period decreases from 0.2 mus to 1.6 mus. For 40 Gbit/s systems it was not observed degradation, resulting from the bit sequence length.

Gain equalization technique for Raman amplification systems based on the hybrid optimization algorithm

We demonstrate, for the first time, the experimental implementation of a gain flattening technique based on the hybrid genetic algorithm. The results were confirmed in a 4 pump Raman system, with an experimental gain ripple of 0.24 dB.

Brillouin effects in distributed Raman amplifiers under saturated conditions

This paper analyzes experimentally the limitations observed in lightwave systems using distributed Raman amplifiers operating under large pump power input conditions. The Brillouin effect is observed as the pump power becomes equal to 1 watt centered in a specific pump wavelength. The presence of Brillouin peaks degrades the system performance. The Raman amplifier is set with singlemode and dispersion compensating fibers and evaluated in a high capacity WDM link at transmission rates up to 40 Gb/s per channel. The dispersion compensation was accomplished by adjusting the length of the dispersion compensating fiber. The system and amplifier characterization were developed in terms of the on-off gain, ripple, optical signal-to-noise ratio, eye diagram and extinction ratio.

Considerations on performance, cost and power consumption of candidate 100G EPON architectures

An overview of several candidate architectures for 100 Gb/s capable optical access networks is presented. Considerations for their system requirements are outlined in regards to performance, cost and energy efficiency, towards addressing the design issues for the next generation EPON.

Stability analysis of Raman propagation equations

Raman Fiber Amplifiers (RFA) are assuredly one of the most seriously renewed research subjects in the field of optical fiber communication systems. The amplification is based on stimulated Raman scattering (SRS), which occurs when there is enough pumping power within the fiber transferred to the signals. In the simplest situation, only the interaction between the pumping lasers and the probe signals needs to be accounted being the system power evolution along the distance given by a set of ordinary nonlinear ordinary differential equations (ODE). Although some consistent work has been done to provide numerical solutions for both forward and backward pumping configurations, the nonlinearity of the equations disable the computation of analytical solutions. However, efforts that lead to qualitative understanding of the solution rather than detailed quantitative information are quite valuable. This approach is geometrical and deals with the topic of stability. In this paper, we present a qualitative study of Raman equations valid for forward and backward pumping. The origin was proved to be an asymptotically stable node. The determination of the second equilibrium point is not straightforward for a generic number of equations, but some simplifications can be done.

Transience analysis of bursty traffic with erbium Doped Fiber Amplifiers

In this paper, we investigate experimentally the impact of optical amplifiers, namely Erbium Doped Fiber Amplifiers (EDFA) on Optical Burst Switching (OBS) networks, operating at 2.5 Gb/s (typical bit rate for current passive optical networks - PON). Bursts with 212 – 1 and 216 – 1 pseudo random binary sequence (PRBS) were studied, with different idle times (from 2µs to 80 µs). The use of traffic with variable idle time was assessed in order to evaluate the effect on the burst initial amplitude. We also analyzed the performance of the packet based system by measuring the Q factor at the receiver and concluded that the performance is not affected by the type of traffic (variable or fixed idle times).

Demonstration of improved OSNR in ring-based PONs with remotely pumped amplification

It is demonstrated an overall optical signal-to-noise ratio improvement of the ring-based passive optical networks with remotely pumped amplification resulting from the extra Raman amplification inherent to pump transmission.