CableLabs' many hands make light work – at four terabits per second

New optical standards give cable operators lots of headroom as they fibre up

Boffins at CableLabs, the cable TV network operators' pet research house, have turned out two fresh photonic standards: the P2P Coherent Optics Architecture Specification; and the P2P Coherent Optics Physical Layer v1.0 Specification.

Principal Architect Matt Schmitt blogged that the new efforts are all about bandwidth – in particular, bandwidth for cable operators moving to fibre access networks.


CableLabs backhaul spec gets speed boost


At the moment, Schmitt wrote, those operators are deploying wavelength division multiplexed (WDM) 10 Gbps upstream links, but they're running out of fibres and wavelengths.

As we explained in March, the organisation's coherent optics project pushes new modulation schemes into the network, increasing capacity by replacing on-off keying with a 16-symbol quadrature amplitude modulation (16QAM) scheme.

  • The P2P Coherent Optics Architecture Specification defines overall architecture, and provides deployment scenario guidance. It sets down the minimum feature set for an access network;
  • The P2P Coherent Optics Physical Layer v1.0 Specification is where the photon meets the fibre. It defines transceiver interop at 100 Gbps per wavelength.

CableLabs hopes that standardising these aspects of the network will increase vendors' ability to scale their products, reducing the cost for network operators.

One of the good things about all this, Schmitt notes, is that coherent optics isn't a brand-new technology – it's been around in long-distance networks for years.

“What is new is applying it to the access network and realising that by optimising this technology for these shorter distances, we could dramatically reduce the cost of the technology”, he continued.

The technology should also simplify networks, as shown in the “before” and “after” images below.

CableLabs diagram - current optical architecture

Things are getting complex for cable operators who need more bandwidth to serve fibre customers. Image: CableLabs

CableLabs coherent optics

Coherent optics offers a simpler architecture. Image: CableLabs

The result, Schmitt writes, is that “before, a 40 channel fibre network could have a capacity of 400 Gbps, now it’ll be 4 Terabits per second, a full order of magnitude increase.” ®

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