All-optical decrementing of a packet’s time-to-live (TTL) field using logic XOR gates

A novel optical time-to-live (TTL) method based on the use of logic XOR gates is proposed. All-optical decrementing of a packetpsilas TTL field is shown employing a cascade of two SOA-based Mach-Zehnder interferometers. The principle of operation is validated by means of simulations, showing a good extinction ratio (higher than 10 dB) at the output of the 1-bit subtractor.