Joaquim F. Martins-Filho

OSNR model to consider physical layer impairments in transparent optical networks

We propose a model that considers several physical impairments in all-optical networks based on optical signal-to-noise degradation. Our model considers the gain saturation effect and amplified spontaneous emission depletion in optical amplifiers, coherent crosstalk in optical switches, and four-wave mixing in transmission fibers. We apply our model to investigate the impact of different physical impairments on the performance of all-optical networks. The simulation results show the impact of each impairment on network performance in terms of blocking probability as a function of device parameters. We also apply the model as a metric for impairment-constraint routing in all-optical networks. We show that our proposed routing and wavelength assignment algorithm outperforms two common approaches.

Monolithic multiple colliding pulse mode-locked quantum-well lasers, experiment and theory

We report here on a monolithic multisectioned quantum-well laser that operates as multiple colliding pulse mode-locking source. With this type of operation several pulses are present within a laser simultaneously and it produces high-repetition rate pulse trains (up to 375 GHz) and pulse techniques of around 1-3 ps, as deduced from linear correlation technique measurements. By changing the configuration of the sections 1, 2, 3, or 4 pulse operation can be selected; frequency- and time-domain theories have been developed to explain this type of behavior. >

Novel sensor system for leakage current detection on insulator strings of overhead transmission lines

We report the development of a measurement system capable of monitoring and characterizing the main features of the leakage current flowing on a polluted insulator string of a high-voltage transmission line. The system comprises a fiber-optic sensor, directly connected to one insulator of the string, that emits a sample of the leakage current waveform to a processing module via an optical link. A capacitive sensor connected to the processing module allows recording the relative humidity of the outer environment. At the present stage, six measurement units have been deployed on CHESFs electrical transmission system in the Northeast of Brazil, and studies are underway to further correlate the degree of environmental pollution with humidity and leakage current activities on high-voltage insulator strings

Novel routing algorithm for transparent optical networks based on noise figure and amplifier saturation

We propose and demonstrate a novel dynamic routing algorithm for transparent optical networks based on physical layer impairments such as amplifier noise accumulation, amplifier gain saturation, wavelength dependent gain and losses along lightpaths. The metrics of our algorithm is based on the calculation of the noise figure using the well known formulation for cascade of elements in lightpaths. We assume no wavelength conversion capabilities in our network and we assign wavelengths using a first fit algorithm. For a given call, our algorithm assigns the first available wavelength and calculates the best route (minimum noise figure). Upon the calculation of the noise figure of the lightpath, we obtain the bit error rate (BER). Our algorithm blocks a call if there is no wavelength available or if the BER for the available wavelength is above a given level, which guarantees a pre-defined quality-of-service for the network operation. We present simulation results of dynamic traffic in a hypothetical meshed network in terms of blocking probabilities as a function of network load and amplifier characteristics. We show that our algorithm outperforms the traditional shortest path routing algorithm.

Characterization of efficient dual-wavelength (1050 + 800 nm) pumping scheme for thulium-doped fiber amplifiers

We report on the characterization of a recently introduced dual-wavelength pumping scheme for thulium-doped fiber amplifiers using 800 and 1050 nm. Using a counterpropagating pump configuration, 180 mW of total pump power yielded 27-dB small-signal gain and less than 5-dB noise figure. Furthermore, using optical frequency domain reflectometry, the distributed gain in this configuration was evaluated, allowing for optimization of the doped fiber length.

Wavelength Assignment for Physical-Layer-Impaired Optical Networks Using Evolutionary Computation

This paper presents a wavelength assignment algorithm suitable for optical networks mainly impaired by physical layer effects, named the Intelligent Wavelength Assignment algorithm (iWA). The main idea is to determine the wavelength activation order for a first-fit algorithm that balances the impact of the physical layer effects by using a training algorithm inspired by evolutionary concepts. The iWA presents some recently proposed concepts in intelligent optimization algorithms, such as an external archive to store the best solutions. Some different physical layer effects, such as four-wave mixing and residual dispersion, were considered in the tests of our proposal. We tested our proposal for transparent optical networks. However, we believe iWA can be used in other types of network, such as opaque networks and translucent networks. The proposed wavelength assignment algorithm was compared with five other wavelength assignment algorithms for two network topologies in three different scenarios. The iWA algorithm outperformed the other WA algorithms in most cases. The robustness of our proposed algorithm to the load distribution changes was also analyzed.

Blue light emission in thulium doped silica-on-silicon waveguides

Abstract We report the experimental observation of up-conversion in an integrated silica-on-silicon waveguide. Blue light at 455 nm and 475 nm was observed. In addition to the strong blue emission near infrared (∼ 800 nm), visible (648 nm) and UV (366 nm) lines were also detected. We investigated the excitation mechanisms by using different pumping wavelengths.

Multiple colliding pulse mode‐locked operation of a semiconductor laser

Multiple colliding pulse mode‐locked operation where 3 or 4 ultrashort pulses are present simultaneously within a semiconductor laser is described. Frequency and time domain measurements show that a multisectioned laser can be switched between two, three, and four pulse operation. In four pulse operation, pulse widths of approximately 1.3 ps at repetition rates of 240 GHz have been observed from a 600‐μm‐long laser.

A performance comparison of multi-objective optimization evolutionary algorithms for all-optical networks design

In this paper we investigate the performance of well known multi-objective optimization evolutionary algorithms (MOEA) applied to the design of all-optical networks. We focused on the simultaneous optimization of the network topology and the device specifications in order to both minimize the total cost to build the network, i.e. the capital expenditure, and to maximize the overall network performance. We used the network blocking probability to assess the quality of the network service. We have considered the following five different MOEA: NSGAII, SPEA2, PESAII, PAES and MODE. In order to suggest a suitable algorithm to solve the problem, we performed a set of simulations aiming to analyze the convergence ability and the diversity of the generated solutions. We used four well known metrics to compare the achieved Pareto Fronts: hypervolume, spacing, maximum spread and coverage. From our results, we believe that the NSGAII and the SPEA2 algorithms are more suitable to solve this specific problem.

Fast and adaptive impairment aware routing and wavelength assignment algorithm optimized by offline simulations

In all-optical networks, signals are transmitted through optical physical layer with no regeneration. Therefore, noise accumulation along lightpath can severely impair optical signal-to-noise ratio. Impairment aware routing and wavelength assignment algorithms (IA-RWA) can take into account these effects, improving the network performance. In this paper we describe a fast and high performance adaptive weight function to be used as the metric for the routing algorithm in optical networks constrained by physical impairments. The input information for this function are link availability, route length and two adjustable parameters. These two parameters provide information about the network impairments. An offline simulation must be run to adjust them prior to the online network operation. The main advantage of this approach is the use of simple network parameters during the routing process instead of a complex optical noise based formulation, which renders it a better performance in terms of both, time to find a route and blocking probability. In our simulations we considered three physical layer effects: ASE noise generation, Optical Amplifier gain and ASE saturation and OXC crosstalk. We performed a performance comparison between this new metric and other metrics previously described in the literature.