Fiber Digitalization

Date of publication: 26.01.2018

Fiber Digitalization

At present, MSO mainly uses an analog fiber to feed the HFC Nodes. In most cases, the broadcast video signal is delivered by a separate optical wavelength and DATA/VoD services are on the separate narrowcast optical wavelength. Also, some operators use Broadband Digital Return (BDR) for the upstream signal.  This makes MSO’s network access very uncompetitive as each service needs a separate management.

Distributed Access Architecture (DAA) goal is to move PHY to the HFC node, and use a digital Converged Interconnect Network (CIN) as a transport layer between PHY and CCAP Core.  It resolves the aforementioned problems.

The MSO needs to define a new network access architecture in order to support digital connections between headend and fiber node. It will bring some new challenges to MSO among which are:

Capacity Planning – delivery of a high bandwidth service using DOCSIS 3.1,  Remote PHY CIN requires a nonblocking network architecture. That is why the operator needs to plan and build a CIN network that will support the total capacity which is required by all Remote PHY nodes. The CIN network at the HE should be designed to allow full expected capacity of the CCAP Core.

Out-Of-Band support:  with the digitalization of the fiber between HE/HUB and the fiber node, MSO loses a classic analog transport layer that is used by many systems like SWEEP, and at the same time, is required for operation of the network beyond the RPD. This challenge is adressed in our OOB section. Using a digital fiber for Remote PHY is far more beneficial than challenging.

MSO optical fiber ring capacity with AM DWDM

 

Optics cost reduction  –  10GE optics in opposition to the AM Optics is a commodity hardware. The SFP+ modules are used in the HE/HUB and also in DataCenters or elco backhaul networks.  This makes the 10GE optics more competitive due to lower prices and a bigger variety of the vendors.

DOCSIS 3.1 performance increase –  by eliminating the analog laser, the optical noise contribution to SNR is eliminated too. This allows for higher modulation profiles and use of the full potential of the DOCSIS 3.1 in the MSO network. Elimination of the AM optics improves SNR around 4 dB. This allows using a very high modulation like 4k QAM, and in the future, with the elimination of amplifier cascades, even up to 16k QAM in a coaxial plant.

Operational improvements – AM optics is much more complicated to set up and maintain than the Ethernet optical link. For MSO operation teams, it will be much easier to set up and maintain the optical link.

Higher capacity digital optical links, such as 10GbE, are designed to operate over much longer distances than AM Optics.  Extending the distance between the CCAP and HFC node allows MSO to move CCAP equipment from HUB to the main HE. Moreover, digital interfaces allows more capacity on the fiber with up to 40 DWDM 10GbE channels for the single pair of fiber. The same fiber can be used for different access technologies even for the radio access backhaul.

MSO optical fiber ring capacity with Remote PHY

The simplicity of the transport platform – Rather than managing and maintaining separate networks and operations for linear TV, VoD, Internet, and OOB in AM Optics network. MSO will have the single all-IP infrastructure to deliver all services in the same way. Also, services like VIDEO or VOD can be delivered from the main HE or even DataCenter of the MSO. The scenario of aggregation of the services is adressed in the Multicore architecture section.

Want to read more about challenges and opportunities for MSO with Remote PHY implementation?