J. Ferreira da Rocha

Effect of soliton interaction on timing jitter in communication systems

Timing jitter in soliton communication systems is studied, taking into account both soliton interaction and amplifier noise. Deviations from Gordon-Haus jitter for closely spaced solitons are observed. A new analytical model for the timing jitter is proposed. The model presented considers interaction in a random sequence of solitons and the effect of the amplified spontaneous emission noise added in each amplification stage. We obtain a good agreement between the new analytical model and simulation results for practical communication systems.

Influence of the laser detuning on optical WDM network performance

The laser wavelength dependence on the temperature, polarization current, aging can represent a problem in networks where multiple multiplexing and demultiplexing operations occur. In this contribution we evaluate the system performance dependence on the laser frequency alignment, considering demultiplexing performed by some of the commonly used filters.

Computationally efficient methods for bit-error rate evaluation in weakly coherent optical systems

A semianalytical method to estimate the bit-error rate performance of nonsynchronous ASK and FSK optical heterodyne systems is presented. This approach takes into account numerous system details with an accuracy similar to Monte-Carlo simulation, but with a computation time reduced by several orders of magnitude. An analytical approximation, based on a closed-form expression for the decision variable moment generating function, is also presented. The results obtained with the semianalytical method and the analytical approximation are compared to Monte-Carlo simulation results and to measurements obtained on a practical FSK system. >

Intra-channel nonlinear effects in dispersion compensated DWDM optical networks

We consider a generic single channel of a DWDM optical network, where losses and dispersion are fully compensated. In this scenario the only limitations to the transmission capacity of our optical channel are the noise, the channel bandwidth and the fiber nonlinear effects.

Study of 16/spl times/20 Gsymb/s WDM dispersion supported transmission systems using different line-codes

In this contribution we assess and compare the performance of 16/spl times/20 Gsymb/s WDM dispersion supported transmission systems, considering three different line-codes: binary NRZ, duobinary and 4-level. The demultiplexing operation is performed using uniform fiber Bragg gratings. The capability of 320 Gbit/s (16/spl times/20 Gbit/s) WDM dispersion supported transmission systems over 65 km and 100 km, using respectively binary and duobinary coding, is demonstrated. It is also verified the feasibility of such a system using 4-level coding at 640 Gbit/s (16/spl times/40 Gbit/s), for a fiber length of 45 km. High density WDM signal with approximately 1 bit/s/Hz spectrum efficiency is produced by optical 4-level coding.

An electrically adjustable equalizer for very high bit rate transmission systems based on dispersion supported transmission

This paper presents an electrical equalizer suitable for optical communications systems using the standard single mode fibre (SMF) and based on dispersion supported transmission (DST). It is shown that using the electrical equalizer and the DST technique it is possible to transmit at very high bit rates (20 Gbit/s) and long distances (40 km), well beyond the dispersion limit. The equalizer was designed using a GaAs monolithic technology and has the main advantages of being electrically adjustable, a good input and output impedance match and also a small size.

Design of clock-recovery GaAs ICs for high-speed communication systems

This paper deals with clock recovery circuits for multigigabit communications. For these bit rates, the integration of the timing recovery circuit represents many advantages from the viewpoint of cost, size, reliability and performance. Motivated by this, we developed in the same GaAs monolithic microwave integrated circuit, a nonlinearity and a tuned amplifier for a 20 Gbit/s open-loop clock recovery circuit. The theoretical analysis and design are presented, and also the experimental results that confirm the feasibility of both circuits.

Comparison of the Crosstalk Characteristics of Optical Add/Drop Multiplexers Based on Mach-Zehnder Interferometers with FBGs

In this contribution we report an investigation of the homodyne/heterodyne crosstalk of optical add/drop multiplexers, based on Mach-Zehnder interferometers with fiber Bragg gratings, in wavelength division multiplexing optical networks. Two different types of gratings are studied, with different average refractive index perturbations, one constant and equal to zero and another nonuniform and negative. Two alternative structures of the referred type are proposed to minimize the homodyne or heterodyne crosstalk.

Fiber Bragg gratings for telecommunications

Fiber Bragg gratings (FBGs) are nowadays widely used in various fields, including telecommunications. Since its emergence, this component has found many applications due to its properties, versatility and variety of controllable parameters that can shape in various manners its spectral properties. These devices have the advantage of being built of fiber and they are widely used in mono and multichannel networks.

WITHDRAWNNonlinear intrachannel effects in dispersionmanaged data transmission systems

It is shown that nonlinear intra-channel effects imposed a limit to the transmission capacity of pulse-overlapped dispersion-managed systems. However, using pre and postcompensation techniques, thousand of kilometers at 40 Gbit/s under standard step-index fibers with 100 km amplifiers span are achievable.