Tag Archives: CPON

The Future of the Last Mile

The last two blogs in this series looked at the broadband demand for speed and usage. The first blog predicted that demand in 25 years for broadband speeds could be as much as 100 times more than today’s definition of broadband of 100 Mbps download. The second blog predicted that demand for broadband usage in 25-years could conservatively be 12 to 15 times more than today, and could be a lot more.

Today’s blog looks at what that kind of future demand means for last mile technologies. The fastest broadband technology today is fiber, and the most common fiber technology is passive optical network (PON). This technology brings broadband to local clusters of customers. The original PON technology deployed in the early 2000s was BPON, which had the capability to deliver 622 megabits of speed to share in a cluster of 32 homes.

The next PON technology, introduced widely around 2010, was GPON. This technology uses faster lasers that deliver 2.4 gigabits of speed to share in a cluster of 32 homes. The industry has pivoted in the last few years to XGS-PON, which can deliver 10 gigabits of bandwidth to a neighborhood cluster of homes. Vendors are already working on a PON technology that will deliver 40 gigabytes to a cluster of homes. Cable Labs is working on a PON technology they have labeled as CPON that will deliver 100 gigabits of speed to a cluster of homes.

Consider the following table that shows the increase in last-mile fiber bandwidth that comes with PON technologies:

 

 

 

XGS-PON is a great upgrade, but has only 4 times the capacity of GPON. XGS-PON is not going to satisfy broadband needs in 25 years when demand is at least 12 to 15 times greater than today. By then, fiber ISPs will likely have upgraded to 40G PON, which has over 16 times the capacity of GPON. There will be a lot of talk in 25 years of upgrading to something like CPON, with a capacity of over 40 times that of GPON.

Something that cable executives all know but don’t want to say out loud is that cable networks will not be able to keep up with expected future demand over 25 years. The planned upgrade to DOCSIS 4.0 brings cable company technology close to the capability of XGS-PON. DOCSIS 4.0 will allow for multi-gigabit speeds over coax, but there is no planned or likely upgrade for coax to match the capabilities of 40G PON.

Any discussions about boosting the future capacity of cable networks is moot anyway. Most coaxial networks were built between the 1970s and 1990s, and in 25 years the copper will be between 60 and 80 years old. There is no question that the coaxial copper will be past its useful life by then.

A few cable companies have already acknowledged this reality. Altice announced a transition to fiber years ago but doesn’t seem to have the financial strength to complete the upgrades. Cox has quietly started to upgrade its largest markets to fiber. All big cable companies are using fiber for expansion. By 25 years from now, all cable companies will have made the transition to fiber. Executives at the other big cable companies all know this, but in a world that concentrates on quarterly earnings, they are in no rush to tell their shareholders about the eventual costly need for an expensive infrastructure upgrade.

There is no possibility for wireless technology to keep up with the increased demand that will be expected in 25 years. The only way to increase wireless speeds and capacity would be to greatly increase the size of wireless channels – which the FCC is unlikely to do – or use much higher frequencies. We’ve already learned that millimeter-wave and higher frequencies can deliver much faster speed, but don’t play well in an outdoor environment in an end-to-end wireless network. This doesn’t mean that wireless ISPs won’t be delivering broadband for decades to come – but over time, wireless last-mile technologies will fall behind fiber in the same way that DSL slowly fell behind cable modems.

Unless satellite technology finds a way to get a lot faster, it won’t be a technology of choice except for folks in remote areas.

Mobile data is always going to be vital, but there will be major pressure on wireless companies to finally deliver on the promises of 5G to keep up with future demand for speed and bandwidth.

The Next Big Fiber Upgrade

CableLabs recently wrote a blog announcing the release of the specifications for CPON (Coherent Passive Optical Networks), a new fiber technology that can deliver 100 gigabits of bandwidth to home and business nodes. The CPON specification working group that developed the new specification includes seventeen optical electronics vendors, fourteen fiber network operators, CableLabs, and SCTE (Society for Cable Telecommunications Engineers). For those interested, a link to the new specifications can be downloaded here.

The blog notes the evolution of PON from the first BPON technology that delivered 622 Mbps to today’s PON that can deliver 10 gigabits. The blog notes that current PON technology relies on Intensity-Modulation Direct-Detect (IM-DD) technology that will reach its speed limitations at about 25 gigabits.

The CPON specification instead relies on coherent optical technology, which is the basis for today’s backbone fiber networks that are delivering speeds up to 400 Gbps. The specification calls for delivering the higher bandwidth using a single wavelength of light, which is far more efficient and less complicated than a last-mile technology like NG-PON2 that balances multiple wavelengths on the customer path. This specification is the first step towards adapting our long-haul technology to serve multiple locations in a last-mile network.

There are a few aspects of the specification that ISPs are going to like.

  • The goal is to create CPON as an overlay that will coexist with existing PON technology. That will allow a CPON network to reside alongside an existing PON network and not require a flash cut to the new technology.
  • CPON will increase the effective reach of a PON network from 12 miles today to 50 miles. This would allow an ONT placed in a hut in a city to reach customers well into the surrounding rural areas.
  • CPON will allow up to 512 customers to share a neighborhood node. That means more densely packed OLT cards that will need less power and cooling. On the downside, that also means that a lot of customers can be knocked out of service with a card failure.

The blog touts the many benefits of having-100 gigabit broadband speeds in the last-mile. CPON will be able to support applications like high-resolution interactive video, augmented reality, virtual reality, mixed reality, the metaverse, smart cities, and pervasive communications.

One of the things not mentioned by the blog is that last-mile fiber technology is advancing far faster than the technology of the devices used in the last mile. There aren’t a lot of devices in our homes and businesses today that can fully digest a 10-gigabit data pipe, and stretching to faster speeds means developing a new generation of chips for user devices. Releasing specifications like this one puts chipmakers on alert to begin contemplating those faster chips and devices.

There will be skeptics who will say that we don’t need technology at these faster speeds. But in only twenty years, we’ve gone from broadband delivered by dial-up to bandwidth delivered by 10-gigabit technology. None of these skeptics can envision the uses for broadband that can be enabled over the next twenty years by newer technologies like CPON. If there is any lesson we’ve learned from the computer age, it’s that we always find a way to use faster technology within a short time after it’s developed.