The increasing transmission capacity of optical fiber has focused attention on high-speed optical processing of digital information. Complex optical processing requires a high-density, high-speed, low-power optical memory that can be integrated with planar semiconductor technology. There is no optical memory equivalent to the electronic RAM, therefore optical devices for buffering of decisions must be implemented. One of the most promising solutions to implement these storage systems is the optical flip-flop. This device has two stable states and thereby is capable of serving as one bit of memory. An optical flip-flop is controlled by pulsed optical control signals. The Mach-Zehnder interferometer based on semiconductor optical amplifiers (SOA-MZI) has received considerable attention in recent years for use in optical signal processing because of the fact that it is versatile and can be integrated. In this Thesis a novel architecture of an all-optical flip-flop is proposed. The architecture is comprised of a single SOA-MZI with a feedback loop. This device shows a bistable behaviour under proper operation conditions. Its main advantages are a complexity reduction (lower power consumption), high switching velocity and the integration ability. Additionally, a theoretical model based on the basic SOA equations was developed in order to study the SOA-MZI with feedback. Both static and dynamic system characteristics were investigated. Finally, two novel applications for the interferometer with feedback were proposed. The first one is an optically controlled 1x2 switch. This is the first time that this functionality is implemented with a single block. Secondly, a novel architecture for all-optical packet routing is studied. The solution used to process the label adds scalability and simplicity.