Power scheme boosts optical interconnect performance in data centres
The lower power with performance over 100Gb/s can signficantly reduce the energy consumption in data centres.
The team in the EU-funded ADDAPT project have designed four channel CMOS transceiver that can wake-up and achieve phase-lock in 8ns, the shortest switching time in record.
This rapid power-on/off feature dramatically reduces energy consumption has the transceiver can be switched off between data packets even at the 160Gb/s speeds. The transceiver is packaged with an 850nm photodiode array and is aimed at low-cost VCSEL-based optical links for datacentre interconnects.
“This is the first optical an receiver that combines high-speed data transmission rate and rapid power-on and off functionality while being extremely low lower [at] about 88mW,” said Alessandro Cevreroat the IBM Research Lab in Switzerland. “Our design, for the first time, allows for the on/off switching of and optical link on a per-packet basis. There were previous scientific attempts to turn off the links when there is no data, however the timescale to switch on and off the link was orders of magnitude longer than that of an individual data packet. To achieve shorter power-on, time at a very high data transmission speed is the key challenge.”
The transceiver uses four identical channels with analogue circuits that can rapidly align the receiver’s clock with the arrival of the incoming data, detecting the optical signal sequences to rapidly turn the link system on and off. The researchers tested the receiver at 40 Gb/s second with a reference transmitter consisting of an 850nm Mach-Zehnder modulator followed by a variable optical attenuator. They also performed power on/off experiments by generating an optical signal implementing the proposed link protocol. They observed correct power cycling and that the receiver operates error free at 40 Gb/s second yielding 160 Gb/s aggregated bandwidth over multi-mode fibres. The experimental data also showed an 85 percent power saving in the overall operation by shutting down between packets.
This power saving would also allow a higher bandwidth in the same thermal budget of the package. The next step is to validate a complete optical interconnect system by measuring the optical transmitter, as well as to increase the data transmission speed on the receiver side to 56 Gb/s per channel, or over 200Gb/s.
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