A simple scheme for an all-optical AND logic gate is proposed based on a sagnac interferometric structure. The operations of this scheme with a 40-Gbit/s return-to-zero (RZ) pseudorandom bit stream (PRBS) are simulated correctly with an output extinction ratio (ER) of about 14.7 dB. Through numerical analyses and discussions, it can be seen that the output ER of the AND operation is improved more than 6 dB, and the output pattern effect is decreased by about 0.4, compared to terahertz optical asymmetric demultiplexer schemes under the same condition. Furthermore, the carrier recovery time of a semiconductor optical amplifier (SOA) is no longer a crucial parameter to restrict the operation speed of this scheme. This scheme is potentially capable of AND operation rates to 100 Gbit/s.
Taking into account ultrafast carrier dynamics, we model 640 Gbit/s wavelength conversion based on nonlinear polarization rotation (NPR) assisted with sideband filtering in a single semiconductor optical amplifier (SOA) and investigate the performance of two types of wavelength conversion schemes: one based only on NPR and the other based on NPR assisted by red-shifted filtering. Simulated results show that the two types of wavelength conversion schemes are achieved with clear open-eye diagrams and have signal regeneration capability at 640 Gbits/s. Simulated analyses also show that the wavelength conversion based on NPR assisted by red-shifted filtering scheme exhibits better performance in terms of wavelength conversion and signal regeneration.
Two types of all-optical non-return-to-zero to return-to-zero (NRZ-to-RZ) format conversion schemes are presented by exploiting semiconductor optical amplifier (SOA) nonlinearities, including nonlinear polarization rotation (NPR) assisted with blue-shifted filtering (NPR-BF) and cross-phase modulation (XPM) assisted with blue-shifted filtering (XPM-BF). Experimental results show that the power penalties of the NPR-BF and XPM-BF schemes are about −0.5 dB and 1 dB, respectively. Furthermore, experimental results also show that the converted output extinction ratio (ER) of the NPR-BF scheme is higher than that of the XPM-BF scheme under the same conditions.
A novel all-optical logic NOR gate is presented that is composed of a semiconductor optical amplifier (SOA) and an optical bandpass filter. The NOR gate is successfully experimentally demonstrated at 40 Gbit/s. The experiment result shows good extinction ratio of larger than 12.0 dB with clear and open eye. The NOR gate has a simple configuration and allows photonic integration.
In coherent optical systems or sensors, polarization matching between the two superposed waves must be achieved by some means. One of the methods used in practice is the feedback control of the input polarization. In this paper, a new theoretical analysis of the feedback control principle of the input polarization is given, by which polarization matching between the superposed waves can be obtained. Numerical simulation indicates it agrees with the experimental results.