Implementation Of Optical Logic Unit Based On Nonlinear Properties Of Semiconductor Optical Amplifiers

Abstract

Optical communication systems operating at gigabits per second are commercially available and the data rates are achieved above 10 Tb/s in research laboratories. In order to achieve such data rates, all-optical computing should be realized using digital optical devices. These days, ultra-fast and all-optical processes are required in the high-capacity photonic networks to avoid optoelectronics conversions. The key components for these all-optical networks amongst others are all-optical regenerators, wavelength converters, packet switches and all optical memory. All optical gates, optical arithmetic and logic circuits and flip-flops form important subsystems of these components. An all-optical arithmetic and logic unit is the integral part of optical computing and data processing. So, there is a need of all optical digital devices which provide better performance (in terms of simple structure, operation at multi Gbs-1 speeds, photonic integration etc.) for future all optical networks. With the advances in the optical semiconductor device design and fabrication techniques, the semiconductor optical amplifiers (SOAs) have become a preferred choice for use in future optical communication networks for in line amplification and optical switching. This thesis mainly designs, characterizes and investigates all optical arithmetic and logical devices using on nonlinear properties of semiconductor optical amplifiers. The all optical digital devices are implemented considering various important design aspects such as data rate; simple structure potential for integration etc. Semiconductor optical amplifiers (SOAs) are very attractive nonlinear elements for the realization of different logic functions, since they can exhibit a strong change of the refractive index together with high gain. In this report, a principle of operation, simulation step and experimental result of different all‐optical logic gates (AND Gate, OR Gate, XOR Gate) are well presented. These gates are based on the nonlinearities on SOAs. The experimental results were exactly matched with standard results and increasing the speed of optical logic gates. All‐optical logic gates became key elements in the realization of node functionalities, as add drop multiplexing, packet synchronization, clock recovery, address recognition, and signal processing. Semiconductor optical amplifiers (SOAs) are very attractive nonlinear elements for the realization of different logic functions, since they can exhibit a strong change of the refractive index together with high gain. Moreover, different form of fiber devices SOAs allow photonic integration. The nonlinear behaviour that is a drawback for the SOAs as a linear amplifier makes it a good choice for an optically controlled optical gate. In this an optical gate architecture is proposed to perform AND, OR and NOT logic gates using a single SOA. All optical logic operations are simple and reconfigurable and are implemented using RZ modulated signals at 40 Gb/s operational speed. Contrast ratio and extinction ratio values have also been analyzed for the above mentioned logic gates. Maximum extinction ratio and contrast ratio achieved are 19dB and 17.2 dB respectively.Simple structure and potential for integration makes the proposed architecture an interesting approach in photonic computing and optical signal processing. Therefore, this study establishes the designs and investigations of all optical arithmetic and logical devices, which are very essential in the high capacity core networks in order to avoid optoelectronics conversions and deal with the revolutionary growth of internet traffic for the future photonics networks.