comcast cable tech

Comcast said today that it received the first prototype full duplex DOCSIS (FDX) amplifiers for system testing. The amplifiers, supplied by CommScope, are one of several elements necessary to suppport Comcast’s plans to offer symmetrical multi-gigabit services.

A Comcast spokesperson declined to specify how soon the amplifiers would be installed but did confirm that they are not part of the company’s plans to complete upgrades to 10 million locations this month.

“FDX amplifiers are not required for the 10 million upgrades to be complete by the end of February,” the spokesperson wrote in an email in response to questions from Telecompetitor. “The upgrades planned for these locations are compatible with our current amplifiers which support our new multi-gig speeds launched as part of our network upgrade.”

Note that the spokesperson didn’t say symmetrical multi-gigabit speeds. Those speeds will have to wait until later this year.

As for the FDX amplifiers, the spokesperson said, “We’ll be installing on an ongoing basis when we complete the qualifications and have successfully tested them in scaled production.”

Comcast previously tested FDX amplifiers in September 2022. At that time, the company said the amplifiers could support speeds of 6 Gbps downstream and 4 Gbps upstream throughout most of the company’s network, in combination with certain other upgrades, without having to take fiber deeper into the network.

The company plans to launch symmetrical multi-gigabit speeds later this year but has not said the specific speeds it plans to offer.

Comcast Symmetrical Multi-Gigabit Requirements

Replacing existing amplifiers and/or installing diplex filters are key initiatives for cable companies today because doing so enables the companies to expand the amount of spectrum within the coaxial portion of the cable companies’ hybrid fiber coax (HFC) infrastructure.

This enables the cable companies to boost the speeds they can offer, particularly when deployed in combination with other network upgrades that can boost speeds, including distributed access architecture (DAA) and DOCSIS 4.0. The latter is the next-generation version of cable industry DOCSIS cable modem standards.

The cable industry uses the term 10G to encompass this family of network upgrades, which the industry expects to eventually support speeds up to 10 Gbps downstream and 6 Gbps upstream.

Equipment supporting the DOCSIS 4.0 standard will not be available until later this year, but cable companies have been expanding spectrum within the coaxial portion of the connection and deploying DAA in anticipation of the arrival of DOCSIS 4.0 and because doing so boosts speeds, even with DOCSIS 3.1, the current generation of DOCSIS.

Comcast’s amplifier choice is different from the one that some other cable companies, including Charter, are making. Charter and some other companies plan to use a high-split approach, which boosts overall and upstream speeds, but potentially doesn’t boost upstream speeds to the same extent that a full-duplex (FDX) approach does.

The reason is that FDX amplifiers enable a substantial portion of the spectrum within the coax to be used for upstream or downstream communications.

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