Using passive cyclic arrayed waveguide gratings (green trapezoid) will enable Super-PON to reach further than existing PON technologies


g meets transmission. Adequate energy per bit is required to overcome the system noise to

achieve this. ‘However, amplification is expensive,’ Lam

conceded. Perhaps surprisingly, combining two relatively expensive technologies can actually lower costs, he asserted. ‘Super-PON mitigates the cost of optical amplification, by applying it to all multiplexed wavelengths at once. In this way, the cost is distributed over a large number of customers and becomes bearable. In addition, amplification is performed inside the central office, to keep the optical distribution network fully passive.’ At the same time, the extended range

enabled by amplification reduces the number of central offices and equipment, including optical line terminals (OLTs), within. Tat’s desirable for operators, as the active OLT equipment requires power, cooling, administration and maintenance. ‘Reducing the number of OLT locations reduces the number of powered sites that may require manned operations,’ underlined DeSanti. ‘Significant operational and construction savings can be achieved when fewer of these structures are needed.’ ‘In addition, OLTs are active equipment that

can be subject to faults of various kinds,’ Lam observed. ‘By consolidating them in fewer and beter controlled places, it is possible to improve their reliability, potentially making the overall network more reliable.’ And because Super-PON reduces how many fibres are needed to support the same number of customers, the network operators can deploy smaller cables, which are easier to deploy and repair. Operators can use micro-trenching approaches, which only require thin cuts to be made in surface paving, to install them more simply and economically than using traditional trenching methods.

2020 vision In Super-PON individual wavelengths are spread between subscriber optical network terminals (ONTs) by passive wavelength

18 FiBRE SYSTEMS n Issue 23 n Spring 2019

spliters and optical power spliters. Unlike the Next-Generation Passive Optical Network 2 (NG-PON2) standard, tunability is not mandatory in ONT optical transceivers, although this would reduce inventory complexity. Te wavelength filtering inherent in the

Super-PON network would mean that ONT transceivers may only need tunable lasers, making them cheaper and simpler than NG- PON2 transceivers that also need tunable receivers. Overall, Super-PON is intended to complement existing PON technology, DeSanti explained. ‘Operators that already built their infrastructure for the current PON technology may continue to leverage it,’ he says. ‘When needed, new optical infrastructure could be more advantageously built with Super-PON.’ In DeSanti’s presentation to outline Super-

PON, he indicates the possibility of using a cyclic arrayed waveguide grating (CAWG) as passive wavelength router, to separate the 16 different wavelengths. Optical spliters then replicate each wavelength among up to 64 ONTs. Te AWG can be up to 40km from the central office, and the ONUs up to 20km from the AWG, as long as the sum of the two distances is less than 50km. Google Fiber has already deployed

one practical test of Super-PON, using general Gigabit PON (GPON) transmission specifications of 2.5Gb/s downstream and 1.25Gb/s upstream. Now, the IEEE effort is looking at 10Gb/s transmission. Google Fiber is also discussing whether the technology could serve as an extension of NG-PON2 with the International Telegraph Union (ITU) Telecommunication Standardization Sector (ITU-T). DeSanti’s outline presentation foresees a key opportunity for Super-PON beyond 2020, when 10Gb/s PON will become commercially significant.

An alternative view Key networking and communications equipment supplier ADTRAN, based in

Huntsville, Alabama, is involved in advancing the technology. ‘Super-PON is an example of how ADTRAN is enabling alternative network providers to innovate to meet growing demand for multi-gigabit services,’ revealed Ryan McCowan, their director of portolio management for fibre access. He stressed that reaching farther and

unlocking more capacity on each fibre are valuable to internet service providers without existing real estate. ‘Tis kind of innovation validates what we all

know – demand for multi-gigabit technologies like 10G PON is increasing around the world as more people, places and things need higher capacity, faster symmetrical broadband. As 10G PON optics’ cost continues to become more favourable compared to legacy technologies, both incumbent service providers and alternative network providers are deploying 10G technologies like XGS- PON and NG-PON2. Super-PON represents continuing innovation and evolution of these technologies,’ he said. And activities are now underway to drive

that evolution. Te IEEE P802.3cs project to develop the protocol was approved by the IEEE Standards Association’s standards board in December. It will be called IEEE P802.3cs Standard for Ethernet Amendment: Physical Layers and management parameters for increased-reach point-to-multipoint Ethernet optical subscriber access (Super-PON). ‘As a result of the approval, the first IEEE P802.3cs Task Force occurred on 15 January,’ said DeSanti. ‘At that meeting, the project started the selection of baseline proposals to address the project objectives to start development of the draſt. ‘Once there is a complete draſt, it will

proceed through two cycles of balloting, which, if conducted correctly and successful, will result in approval of an IEEE standard.’ n

Andy Extance is a freelance science writer based in Exeter, UK @fibresystemsmag

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