IEEE Study Group tackles Google Fiber Super-PON

At its meeting this past July, the IEEE 802.3 Working Group launched a Study Group to investigate EPON specifications based on Google Fiber’s Super-PON technology. Google Fiber Architect Claudio DeSanti, chair of the new IEEE 802.3 Physical Layers for increased-reach Ethernet optical subscriber access (Super-PON) Study Group, told attendees of this month’s ADTRAN Connect media and analyst event that the technology enables a single central office to serve 1024 customer sites with a reach of approximately 50 km. Both specifications are greater than current EPON and GPON implementations, most of which support reaches of 20 km and subscriber counts of up to 64.

At its meeting this past July, the IEEE 802.3 Working Group launched a Study Group to investigate EPON specifications based on Google Fiber’s Super-PON technology. Google Fiber Architect Claudio DeSanti, chair of the new IEEE 802.3 Physical Layers for increased-reach Ethernet optical subscriber access (Super-PON) Study Group, told attendees of this month’s ADTRAN Connect media and analyst event that the technology enables a single central office to serve 1024 customer sites with a reach of approximately 50 km. Both specifications are greater than current EPON and GPON implementations, most of which support reaches of 20 km and subscriber counts of up to 64.

The key underlying technologies for Super-PON are DWDM and downstream and upstream amplification, DeSanti said. The powered mux/demux and amplification elements reside in the central office, which means the outside plant retains the passive nature of conventional PONs. Passive wavelength splitters and optical power splitters in the field deliver individual wavelengths to each subscriber optical network terminal (ONT). Unlike NG-PON2, the ONT optical transceivers don’t need tunability – although DeSanti said that Google Fiber likes the idea of tunability to reduce inventory complexity. Because of the filtering inherent in the network, the transceivers only need tunable lasers, making them less expensive and complex than NG-PON2 transceivers that also require tunable receivers.

DeSanti said Super-PON offers a variety of potential benefits. These include central office (CO) consolidation opportunities, a requirement for lower-count cables, lower opex, and potentially lower network latency. Besides the CO consolidation use case, DeSanti said Super-PON could prove useful when looking to extend existing network footprints into new service areas. And, despite its name, Super-PON also supports point-to-point architectures for business customers that require more capacity than their residential counterparts or for such applications as cellular fronthaul and backhaul.

Google Fiber has deployed Super-PON in one of its markets, DeSanti said. That implementation uses general GPON transmission specifications – 2.5 Gbps downstream and 1.25 Gbps upstream. The IEEE effort is looking at 10-Gbps transmission, he added. DeSanti expects the Study Group to complete its work in time for the November meeting, at which point the effort could move to the standards creation stage with the naming of a Task Force. Meanwhile, Google Fiber is attempting to get the ITU-T interested in the technology as an extension of NG-PON2 as well.

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