COMPENSATION OF GAIN SATURATION IN SOA-GATES MACH-ZEHNDER WAVELENGTH CONVERTERS BY INTERFEROMETRIC

Compensation of signal degradation in SOA-gates for optical switch nodes using all-active integrated Mach-Zehnder interferometric wavelength converters is experimentally demonstrated at 2.5 and 10 Gb/s. More than 10 dB improvement of the dynamic range is obtained compared to a stand-alone SOA-gate. Introduction: Wavelength converters can be used in optical switching networks to reduce blocking probabilities of optical switches and thereby increase the throughput of the total network as well as to allow wavelength reuse and flexible management (1,2). Based on this, optical switch nodes that include interferometric all-optical wavelength converters (IWCs) (3) have been proposed (4). Additionally, fast (-1 nsec switching time) semiconductor optical amplifier (SOA) gates are attractive for space switching since they feature extremely high on-off ratios of 40 - 50 dB (4) needed to overcome the severe penalty induced by crosstalk in the optical switch block (5) and to simultaneously compensate for loss. However, the input power dynamic range of the SOA-gates is limited due to noise as well as gain saturation (6). This leads to a limited cascadability causing severe restrictions for the number of switch nodes that can be cascaded. Here, it is demonstrated that switch blocks using a combination of interferometric wavelength converters and SOA-gates as shown in Fig. 1 exhibit an improved power penalty performance compared to switch blocks