Multi-Section Semiconductor Optical Amplifiers for Data Centre Networks

Abstract

The ever-growing Internet based services and applications, involving a huge amount of computing and storage resources, have been powered by data centres (DC) [1]. The storage and movement of data within the DCs is driving the requirement for cost-effective, higher capacity inter- and intra- next generation DC networks [2]. Within the context of these next generation DC networks, the ability to transmit very high data rates (100 – 400 Gb/s) over both short and long distances (intra or inter DC fibre links) is one of the main challenges (within the optical sector. The modulation format that is currently touted as the most suitable for such high capacities is 4-level pulse amplitude modulation (PAM4), which carries 2 bits per symbol. Optical amplification is needed for reach extension for inter- and intra- DC communications, Semiconductor optical amplifiers (SOAs) are needed to realize a low cost amplification solution. SOAs possess many advantages, including low power consumption, small footprint, wide bandwidth, being integrateable, and the ability to accommodate wavelength ranges beyond the scope of Erbium doped fibre amplifiers. However, the use of SOAs for linear amplification of C-band optical signals is still relatively limited, mainly due to the relatively large noise figure (NF) associated with them compared to erbium doped fiber amplifiers and low saturation powers of about 10 mW. Multi-section SOAs are known to possess superior NFs and larger saturation powers than an equivalent single-section SOA [3], and hence may provide performance benefit for reach extension for DC networks. In this work, we examine the use of a multi-section semiconductor optical amplifier (MS-SOA) [3] to provide an improvement in its use as a linear amplifier compared to a single section SOA. The MS-SOAs have been shown to have superior noise and linearity performance compared with single section SOAs. We configure the MS-SOA to operate in the low-NF mode with high saturation power mode and the equivalent single-section SOA. We compare the input power dynamic range for the MS-SOA and equivalent single-section SOA. We expect an improvement in the input power dynamic range of at least 3 dB [4]. The combination of a lower NF and higher saturation power enables crosstalk-free amplification of simultaneous multi-wavelength channels using the same SOA device.