Abstract
As the bit-rate per wavelength channel and the number of channels steadily keep increasing in telecommunication networks due to the development of optical transmission technologies, switching still is experiencing the limitations of electronics. It is expected that the great mismatch between the transmission bandwidth and the switching capacity may be overcome by the development of photonic technologies. All-optical signal processing in photonic devices, including wavelength conversion, logic gates, signal regeneration, optical memories, etc., are key issues that have to be address in order to realize all optical switching in photonic devices.
Semiconductor micro-ring lasers are very promising devices for all-optical signal processing as they are very compact, relatively easy to fabricate, show power efficiency and have high wavelength selectivity. It is therefore very important to evaluate the performance of these devices, by means of numerical models for the micro-ring lasers in order to understand their behavior in several all-optical signal processing configurations, especially when the interacting pulse duration becomes very short as expected for very high operation bit-rates.
To investigate the performance of micro-ring based all-optical signal processing systems, a comprehensive model as close to the physical world as possible, has been developed for this thesis, which includes both inter- and intra-band ultra-fast carrier dynamics, broadband noise and gain dispersion effects. In the proposed model the lasing modes directly arise from the ring-laser boundary conditions applied, and their power is controlled by the gain dispersion.
After the model has been completed, two main targets have been evaluated along this thesis: evaluate if the recovery time of the micro-ring laser is fast enough for high-speed signal processing and therefore if it can beat the performance of alternative SOA-based devices.
To carry out these objectives, firstly a 300 and 30 μm ring lasers are characterized and the results qualitatively compared with experimental data gathered from a 2 mm ring-laser. Secondly, the response of a single 30 μm ring-laser operating as a wavelength converter is studied for input signals of 2.5, 10 and 40 Gb/s and its performance is tested.
Relaxation oscillation phenomena has been found to be the most limiting factor in the performance of these devices for signal processing applications at high bit-rates. This performance can be improved only to a certain limit by increasing the bias current. Also, pulse energy must be carefully selected to avoid recovery delays due to gain saturation or even laser shut-off.
