CableLabs announced it has adapted coherent optics technology, used in long-haul fiber networks for many years, for use in short-haul access networks by simplifying it to reduce costs considerably. The update could essentially provide up to 1,000 times more capacity than the analog optics that are used in many HFC networks currently, according to CableLabs.
Alberto Campos, distinguished technologist at CableLabs reviews the potential application of the technology in a blog posted this week. He points out that the most constrained part of the network, and the most costly to upgrade, is the fiber infrastructure between the headend and the fiber node, to the wireless cell radio or to large business customers. “Avoiding costly fiber re-trenching requires a fundamentally new approach to this part of the network,” he says. “This is where coherent technology provides an opportunity.”
Campos further reviews the fact that the access network environment is very different from long haul since optical links in access networks are typically no longer than 30 km, and long haul can sometimes span distances up to 3,000 km. CableLabs has reportedly re-engineered the coherent link to meet the special conditions of the access network, and developed technology that is higher performance and much lower cost when compared to long haul or metro environments.
“The complex and expensive system implementation that long haul is known for no longer applies to access implementation. The shorter fiber lengths result in minimal dispersion of the optical signal,” Campos writes. “Furthermore, since no in-line amplification is needed, non-linear distortion and noise are significantly reduced. This increases the link margin and enables much lower implementation costs. It is NOT your father’s coherent implementation!”
“In the laboratory, we have achieved 256 Gbps over 80 km on a single wavelength with minimal dispersion compensation. That is ~26 times the capacity of what can be achieved over an analog optical carrier fully loaded with 1.2 GHz worth of DOCSIS 3.1 signals,” Campos reports.
Campos’ blog takes a deeper technology dive into the topic, and is available at the CableLabs site here.