Tiago Sutili

Laser Linewidth and Phase Noise Evaluation Using Heterodyne Offline Signal Processing

A simple heterodyne scheme with digital data acquisition and offline signal processing is introduced to obtain phase noise spectra and linewidths of monomode lasers. The data are analyzed using time-domain memorized signals, enabling the evaluation of parameters such as coherence time, phase noise, laser linewidth as a function of bias current, and the identification of points where loss of coherence occurs. Results are presented for lasers with linewidths from 20 kHz up to 2 MHz.

Optical Modulator Half-Wave Voltage Measurement Using Opposite-Phase Sine Waves

A simplified direct measurement of half-wave voltage (Vπ) based on the optical modulator third harmonic distortions to sinusoidal signals in opposite phase is proposed and performed for a quadrature Mach-Zehnder optical modulator. Experimental results are obtained from dc up to 11 GHz. The tested device Vπ value is 2.4 V for dc increasing to 3.8 Vat 10 GHz. A linear extrapolation predicts that Vπ will be close to 10.5 V at 40 GHz, which is equivalent to the first harmonic for a 80 GBd transmission rate based on QPSK modulation.

Guard time requirements for SOA-based electro-optical space switches and AM signals

The transient and steady state performances of optical space switches based on semiconductor optical amplifiers (SOAs) switching an optical carrier modulated in amplitude through several switching techniques and operating parameters were characterized. The analysis was focused on the switchs guard time, resulting from the sum of its rise time and ringing time, and the switching amplitude, related with the modulated bits vertical opening when the switch is at on or off operating states and the switching pulse optical amplitude. The results point to the SOA optimum operating region, in relation to the analyzed parameters, which is defined by low bias current (between 60 mA and 80 mA) and high step amplitude (above 2 V).

Time-resolved chirp of Pre-Impulse Step Injected Current modulated Semiconductor Optical Amplifier

Using Pre-Impulse Step Injected Current (PISIC) technique, it is possible to significantly improve the Semiconductor Optical Amplifier (SOA) rising time, although that will also affect chirp. Therefore, it is important to make a quantifying analysis of the event. The measurements are made using the intensity to frequency conversion provided by sharp optical filters. In this work two fixed filters are used instead of one alone, as available in the literature. The results evince chirp peaks during the SOA off-on gain rising time and at the on-off gain decay. The chirp values we found are coherent with published results.

Ultrafast Electro-Optical Switches Based on Semiconductor Optical Amplifiers

This chapter presents results from enhanced semiconductor optical amplifiers based switches to be employed on high-performance applications, which demand ultrafast transition times between operational states together with reduced guard times. A discussion on devices performance is accomplished through experimental characterizations of SOAs’ nonlinear properties and its oscillatory behavior. Switching techniques and mounting schemes are presented to improve switches’ dynamic operation, resulting in rise times below 200 ps and guard times of 650 ps. This performance, when combined with an improved energy efficiency, can offer a viable technical solution for switching in high-rates applications, such as Data Centers and supercomputers.