All-Optical Variable Buffer Based on Semiconductor Optical Amplifier

An all-optical solution for packet buffering in optical packet switching (OPS) nodes is here proposed. Discrete variable delays are obtained by exploiting an optically controlled fiber loop. Semiconductor optical amplifiers (SOAs) are used as switching gates in order to store or route the packet to the buffer output. Cross gain modulation effect is responsible for SOA-based switching, thus allowing for polarization and wavelength independent operation in the whole C-band. A maximum storage time of 50 μs is demonstrated without significant signal degradation. Performances are evaluated in terms of bit error rate measurements for 10 Gb/s non-return-to-zero data payload, providing an optical signal-to-noise ratio penalty lower than 3 dB after 10 rounds. Cross talk measurements confirm the scheme suitability for OPS applications. The proposed solution is particularly attractive in slotted OPS nodes architectures where packet contention would be managed entirely in the optical domain.