We compare by numerical simulation several options to increase up to 112 Gbit/s the bit rate used for intra-data center interconnections relying on the recently proposed Passive Optical Pod Interconnect (POPI) architecture, itself derived from the TWIN (Time-Wavelength Interleaved Network) concept. The motivation for such bit rate is the need to migrate full server content in a small energy-source-aware data center. The analysis focuses on Pulse Amplitude Modulation (4 or 8 PAM), due to its performance/cost ratio. Three types of receivers are considered including a PIN photodiode with integrated semiconductor optical pre-amplifier (SOA-PIN), associated with pre-distortion mechanism. Depending on modulation format and receiver type, the maximum number of connected entities, N, (servers or racks) is limited either by the insertion losses or by the number of channels that can be packed into the band of the fast tunable POPI emitters. The highest N value, 48, is obtained using 8-PAM and SOA-PIN in conjunction with a 62.5 GHz grid.