Jose Ferreira da Rocha

Extraction of laser rate equation parameters

A technique for the extraction of laser rate equation parameters to be used in the simulation of high-speed optical telecommunication systems is described. The simulation using the extracted parameters exhibits good agreement with the experimental results, even for a large current modulation and soliton pulses. A model, which represents the parasite effect introduced by the mount fixture, was built. The model presented here is ready to use in the simulation of high-speed lightwave systems.

Pulse-shaping microstrip filters for 10- and 15-Gbit/s optical receivers

We report the implementation and characterization of microstrip broadband pulse shaping filters for multigigabit optical communications. These filters were specially designed for application where the dominant noise is signal dependent, such as optically preamplified receivers. They are easily fabricated, insensitive to manufacturing tolerances, have reasonable physical size, and are easily integrated with the other components of the optical receiver.

Bit synchronization in multigigabit receivers

In this paper we report the design and implementation of bit synchronizers for multigigabit transmission systems. We present the main features of dielectric resonators (DRs) and considerations to take into account when using them as filters for clock recovery circuits. We address the problem of using balanced and unbalanced nonlinear circuits (NLs) for which we perform a theoretical analysis of the full-wave and truncated squarer non-linearities. Finally we describe the design of a prototype for a 10 Gbit/s system and report measurements obtained with it.

Black Box Model of Erbium-Doped Fiber Amplifiers in C and L Bands

In this paper we analyze Gain and Noise Figure of a C and an L band EDFA verifying experimentally the behavior of the involved parameters as a function of the power and the wavelength.

All-optical routing limitations due to semiconductor optical amplifiers dynamics

In this work we describe a technique which associates the already matured code generation and detection technique of Optical Code Division Multiplexing with the all-optical routing needs and discuss its advantages and limitations due to one of the current optical gating techniques, based on the gain saturation of a Semiconductor Optical Amplifier.

Characterization of noise in semiconductor lasers and its influence in a practical FSK link

Quantum fluctuations in a semiconductor laser produce noise both in the amplitude and in the phase of the output field. These noise sources have a significant effect in optical coherent systems. Measurements of the field spectrum and RIN spectrum of a DFB laser, at three different optical power levels, are fitted to the corresponding analytical curves. The shapes of the measured curves are closely matched by the analytical expressions and the fitting produced very similar values for the common parameters in the field and RIN expressions, providing a good validation for the theory. These analytical/experimental results show a non-lorentzian shape for the field spectrum, as opposed to the commonly used lorentzian shape. Using the more accurate laser models derived from our work, we were able to predict successfully by simulation, the experimental values obtained for the BER in a practical FSK system.

Multicast Mobility in Heterogeneous Technologies: Experimental Validation

The convergence of services and technologies has been driven by service and network providers with the aim to develop a unified infrastructure. From the services side, we have multimedia through unicast, multicast and broadcast services. From the technologies side, we have wired and wireless technologies, including unidirectional technologies such as Digital Video Broadcasting (DVB). These trends allied to the increasing mobility and QoS demands, introduce strong requirements to future telecommunication networks. This paper presents an innovative approach to handle multicast services in a heterogeneous networks environment, including broadcast technologies. The presented architecture aims at guaranteeing end-to-end QoS in mobile scenarios, efficiently handling the underlying network resources and integrating the emerging broadcast technologies. This architecture was developed in a real environment with mobility of multicast sessions through heterogeneous technologies, Wi-Fi and DVB, using also Wi-Fi as a return channel. The results show that the architecture is able to support the seamless mobility of users receiving multicast sessions, with low degradation on the running communications.

Support of mobility and QOS in broadcast unidirectional networks

One main trend in 4th generation networks (4G) is to provide a common and scalable framework for seamless communication through a number of access technologies, wired and wireless, including unidirectional technologies such as DVB. In this paper we present an architecture for seamless mobility and QoS for the integration of unidirectional networks like DVB, featuring ubiquitous access and seamless mobility.

Chromatic dispersion allocable compensator for optical fibre communications systems

In this work we perform a study about the temperature implications on the optical fibers chromatic dispersion and the implications on the quality of transported information. To solve this constrain we suggest two approaches to dynamically compensate chromatic dispersion, one based on chirped fiber Bragg gratings and other based on dispersion compensation fibers. With the dispersion compensation fibers, we obtain a first and second order tuning coefficients of 3.472 ps nm-1 ºC-1 and -2.7 × 10 -3 ps nm-2 ºC-1, respectively. With the compensator based on chirped fiber Bragg gratings we obtain dispersion values between -113.2 ps nm-1 and 143.1 ps nm-1, for temperature gradients of 40ºC.

Optical Performance Monitoring in High Speed Transparent DWDM Networks through Asynchronous Sampling

In this paper we will show the application of asynchronous histograms for monitoring very high data rate systems. We will describe the method and its results for simulated and experimental data. From the results we show the possibility of obtaining an amplitude description of the eye diagram from one completely closed eye observed by asynchronous, under-sampled amplitude histograms. A theoretical model for the histograms has been obtained and tested with experimental and simulated signal at 10 Gbit/s and 40 Gbit/s.