By L. Alberto Campos, Ph.D. & Zhensheng (Steve) Jia, Ph.D., CableLabs & Larry Wolcott, Comcast
Proactive network maintenance (PNM) in the HFC environment has taken advantage of the intelligence available in cable network elements such as the CMTS and CM, as well as plant information to determine type, severity, and location of the impairment. As fiber penetrates deeper in cable networks, the portion of transmission that takes places over coaxial cable is reduced and the resulting fiber networks become more elaborate. In these fiber networks, a fiber bundle branches into more paths to reach these deeper points.
Next generation optical systems will have to be deployed in this new optical transport environment. This new optical transport environment will have a greater number of short optical segments that will likely be subjected to more handling as numerous optical drops to customers are installed. This requires enhanced troubleshooting tools as well as very granular data from the optical distribution plant in order to extract the valuable information needed to perform PNM troubleshooting.
Luckily, as the cable industry prepares to introduce coherent optics into its access networks, we have a transport mechanism that enables rich intelligence through the numerous processes that take place within the transceivers. These processes, combined with information gathered with other instruments, plant topology, and device configuration knowledge, can lead to detailed information regarding location, nature, severity, and duration of the problem.
Drawing on similarities from the coaxial PNM predecessor, maintaining high-order optical modulation profiles will require more scrutiny and maintenance than traditional analog and digital optical systems.
When operating significantly higher data rates and service level agreements (SLA), many of the impairments that are commonplace within the optical domain will need to be maintained to a higher standard. This is especially important when considering some critical business services such as medical and mobile/cellular backhaul. These PNM capabilities will provide continuous reporting about the availability and quality of the optical links to support the SLA agreements of these services. Most importantly, operators can have a full awareness of problems before they impact the services, and provide an opportunity to proactively mitigate them.