C. Reis

Single Mach-Zehnder interferometer based optical Boolean logic gates.

In this paper, we demonstrate different optical logic gates using a single Mach-Zehnder interferometer with controlled phase modulators in each arm. The operational conditions to obtain 16 optical logic circuits, using the same design, are investigated and are a result of a constructive or destructive interference process. The proposed configuration presents significant low complexity and high scalability, and its feasibility is evaluated through numerical simulations.

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.

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.

Experimental study of a phase modulator using an active interferometric device

A novel architecture for an optical phase modulator is presented and experimentally demonstrated. This approach relies on a commercially available integrated Mach-Zehnder interferometer structure with Semiconductor Optical Amplifiers (MZI-SOA) and it is based in cross-phase modulation effect (XPM). The feasibility of the proposed optical phase modulator is experimentally investigated using different scenarios of input power and bit rates.

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.

All-optical clocked D flip-flop using a single SOA-MZI

All-optical flip-flops are key elements in photonics switching techniques, which justify the continuous interest to develop new solutions for high-speed and low-power one-bit memories. In this paper, a novel scheme for all-optical clocked D flip-flop based on a single Mach-Zehnder interferometer, with semiconductor optical amplifiers in both arms (SOA-MZI), is numerically demonstrated. The proposed flip-flop will allow the synchronization of different optical devices and since its input presents the same value as the variables at the next state, are suitable for being used in finite state machines. Simulations results show that the proposed flip-flop can operate with switching energies below 20 fJ and presents high photonic integration capability

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).

EDFA transient assessment for bursty traffic

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 the typical bit rate for current passive optical networks (PON), 2.5 Gb/s. A packet with 216-1 pseudo random binary sequence (PRBS) with an idle length equal to 50000 was studied under different pumping powers of the EDFA. To assess the impact of transients on the system performance, the gain excursion and signal to noise ratio (SNR) were measure and eye diagrams were analyzed. It was observed that as the pump power increases (driving current from 0.80 A to 1.50 A, the SNR and the extinction ratio decrease 3.59 dB and 2.33 dB respectively, while the gain excursion increases 8.4 dB.

All-optical flip flop using two gain-clamped RSOAs

In optical packet switching is necessary to temporary storage information, in particular during the time the packet passes through the node. Therefore, it is so important to find a high-speed and low-power optical flip-flop that can be integrated with planar semiconductor technology. In this paper, a numerically assessment of a novel optical flip-flop scheme, based on two gain-clamped semiconductor optical amplifiers, is presented.

Inherent fabrication yields and asymmetries impacts on MZI-SOA static modelling

The characteristics of MZI-SOA are affected by its internal design yields and asymmetries, leading to an unbalanced power distribution at the output arms and difficult or non optimum biasing. Therefore, we propose an experimental methodology and model for MZI-SOA structures taking into account internal asymmetries as well as the internal SOA behaviour under different current both as what regards amplitude and phase.