DYNAMIC-RANGE AND SWITCHING SPEED LIMITATIONS OF AN NXN OPTICAL PACKET SWITCH BASED ON LOW-GAIN SEMICONDUCTOR OPTICAL AMPLIFIERS

Two important system performance limitations-dynamic range and switchi ng speed-of an integrated packet switch fabric based on low-gain semic onductor optical amplifiers (SOA's) have been examined by using cascad ed blocks of an SOA model, which includes transient effect, nonlinear pulse distortion effect, and amplified spontaneous emission (ASE) nois e, Low-gain SOA's were used to minimize ASE noise considering that no optical filters can be integrated in an SOA-based switch fabric, The s ystem performance with and without a narrowband optical filter at the receiver were both studied, By assuming fixed wavelength transmitters and no optical filter can be used at the receiving end owing to the un predictability of arriving packet wavelengths, our simulation results indicate that the dynamic ranges of 4 x 4 and 8 x 8 SOA-based packet s witches at 2.5 Gb/s can only be about 3.2 and 0.8 dB, respectively, Ho wever, at 155 Mb/s, even without a receiving-end optical filter, the d ynamic range of each switch size can be increased by more than 17 dB a s compared to the cases of 2.5 Gb/s, Note that the dynamic ranges were estimated under the conditions of a bit error rate (BER) less than or equal to 10(-9) and a pulse distortion ratio less than or equal to 30 %. We have also shown that, when an optical filter with a 1 nm bandwid th was used at the receiving end to simulate 1) a circuit-switched con dition where the center wavelength of the filter can be adjusted accor ding to the established circuit, or 2) a packet-switched condition whe re each receiver has a wavelength demultiplexer and a detector array, the dynamic range of 4 x 4 and 8 x 8 switches can be increased to 16.3 and 14 dB, respectively, at 2.5 Gb/s.