Evandro Conforti

Reduction of semiconductor optical amplifier switching times by preimpulse step-injected current technique

A practical way to implement a technique for the reduction of the semiconductor optical amplifier electrooptic switching time is presented. The technique, called PISIC (preimpulse step-injected current), was tested and achieved a reduction of the SOA switching times from almost 2 ns (simple-step current response) to little more than 200 ps (step with prepulse response). Forecasts obtained through simulations, using optimized values of current step and prepulse, showed even a faster optical switch response, with switching time reduction to values around 10 ps.

Carrier reuse with gain compression and feed-forward semiconductor optical amplifiers

The results of two techniques for optical carrier regeneration and wavelength reuse using semiconductor optical amplifiers (SOAs) are presented in this paper. The main objective is to recover an optical carrier by erasing its amplitude modulation. The first technique employs gain compression of deeply saturated SOAs. The second technique uses a feed-forward approach, where a delayed current signal is injected into the SOA with the same shape of the incoming optical pulse. The second technique could be capable to recover the optical carrier with less than 3-dB noise. However, it was observed that the SOA gain recovery time limits the maximum usable bit rate. Theoretical simulation showed good agreement with experimental results.

Hundred-Picoseconds Electro-Optical Switching With Semiconductor Optical Amplifiers Using Multi-Impulse Step Injection Current

An ultrafast electro-optical amplified switch based on chip-on-carrier semiconductor optical amplifier with high optical contrast (33 dB) is presented. Switching times up to 115 ps with small overshoot were achieved by using the multi-impulse step injected current technique. These results are compared with previous preimpulse step injected current technique, and achieve a reduction of the inherent, post switching gain fluctuations without worsening the switching times. In addition, pulse formats for controlling such a kind of electro-optical switches are numerically analyzed and compared with experiments.

Rise Time and Gain Fluctuations of an Electrooptical Amplified Switch Based on Multipulse Injection in Semiconductor Optical Amplifiers

Subnanosecond electrooptical switching times with 26-dB extinction ratio were obtained by using semiconductor optical amplifiers driven by a multipulse injection current. The multipulse switching current was generated by superimposing fast electronic pulse signals in a microwave resistive combiner. Although very fast switching is achievable, nonlinear behavior and circuits parasitic induce gain fluctuations and overshooting during the off-on process. Theoretical and experimental results show that the reduction of parasitics is an important parameter for improving the switching performance. The multipulse injection technique can improve the switching speed for a chosen degree of overshoot.

An EDFA theoretical analysis considering different configurations and pumping wavelengths

The propagation behavior of an erbium-doped fiber amplifier parameters is theoretically analyzed in this work for different amplifier configurations and pumping wavelengths. These configurations were devised from the basic amplifier arrangement and developed to improve specific amplifier operational characteristics. By using the amplifier basic theory for pumping at 980 nm and 1480 nm, the configurations were modeled and simulated for given input boundary conditions. As a result, the longitudinal characteristics of signal, pumping, spontaneous emission, and noise figure were observed for all configurations and compared to those of the conventional amplifier. All simulations were carried out using parameters from a commercial erbium-doped fiber.

SDN-enabled EDFA gain adjustment cognitive methodology for dynamic optical networks

We propose and experimentally validate an SDN-enabled cognitive methodology for EDFA gain adjustment that relies on case-based reasoning. Results show OSNR improvements over time demonstrating the cognition process regardless the deployed amplifier type.

Optical amplitude modulation extinction by a deep saturated ultra-long semiconductor optical amplifier

The recovery of an optical carrier with the deletion of its amplitude modulation is introduced using a deeply saturated ultra-long semiconductor optical amplifier (UL-SOA). The experimental results were achieved for input signal bit rates up to 12.5 Gbps with high extinction ratio (up to 13.9 dB). The influence of parameters such as UL-SOA bias current, optical bandwidth, signal input power, modulation depth and bit rate are analyzed including the carrier spectral broadening effects due to the self-phase modulation effect.

Cognitive Methodology for Optical Amplifier Gain Adjustment in Dynamic DWDM Networks

Our recently proposed cognitive methodology for optical amplifier gain adjustment, that relies on case-based reasoning, showed optical signal-to-noise ratio improvements over time demonstrating the cognition process regardless the deployed amplifier type. In this paper, we extend our preliminary analysis exploring the cognitive methodology benefits for different and larger network topologies. The obtained results show agreement between networks, demonstrating the methodology suitability regardless the network scenario.

Data rewriting after carrier erasing by ultra-long SOA

Optical carrier erasing is demonstrated with evaluation of further remodulation up to 12.5Gbps. Small impairments achieved for all but the 7G–7G and 12.5G–12.5G cases, when spurious-pattern noise force higher penalties (respectively 2.3dB and 0.7dB).

Low-cost, simplified systems for photon-counting measurements in biological samples

Two simplified prototype systems for photon-counting measurements in biological experiments, in in-vivo and in-vitro, are presented. Low cost solutions are adopted for the dark-chamber design and for specification of devices, equipments and system control. Further practical applications are presented, being at first with focus on online eco-toxicology and seed viability assays.