Increasing capacity of intra-datacenter communications using a novel combination of DQPSK and PAM-4 modulation formats

To cope with traffic bursts, unbalanced traffic and increase the capacity of already deployed data center networks, we have proposed a novel modulation/demodulation scheme. The proposed scheme combines pulse amplitude modulation and differential quadrature phase shift keying to transmit four different data streams over a single optical carrier. Each data stream has a rate of 40 Gbps, therefore, a total of 160 Gbps is transmitted over a single optical carrier. The proposed scheme is implemented for a typical data center employing free space optical communication to interconnect different racks. The connectivity between the top-of-rack switches of these racks is established via a mirror-based reflector mounted on the ceiling. The performance of the proposed scheme for varying symbol rates, ranging from one bit per symbol to four bits per symbol is evaluated in terms of bit error rate analysis.