It consists of continuous evaluation of fiber quality through the use of software tools and devices that form an integrated fiber optic monitoring and management system. These elements facilitate the detection of failures, degradation, and security intrusions, and alert the system administrator in real time when threats to the integrity of the fiber optic network occur.
Monitoring systems can also be used to establish trends, analyze attenuation, and other fiber optic performance metrics.
The Need to Monitor Optical Fiber
Optical cabling supports the communications infrastructure of our connected planet. This same optical cabling, fragile by nature, can be affected by water ingress, poorly located excavations, rodent infestations, security intrusions, and many other possible hazards. Keeping optical fiber in good condition with optimal performance requires advanced fiber monitoring practices to identify problems and take action quickly.
New technologies and network expansion continue to push the boundaries of optical fiber monitoring capability. Submarine cables form extremely long fiber optic cable runs laid in trenches on the ocean floor, installed by specialized vessels at a rate of 200 kilometers or more per day. While the value provided by these cable runs is extremely important, it entails considerable installation and maintenance expenses.
Robust optical fiber monitoring can provide earlier detection and highly precise localization, which would reduce reaction and repair times.
Fiber to the Home (FTTH) is becoming increasingly relevant in everyday use, with fiber optic runs direct to each home, allowing greater bandwidth and superior data integrity for users.
Active Fiber Monitoring
While fiber optic cabling is generally considered safer than conventional cabling, incidents of fiber optic intervention continue to challenge authorities and the capability of optical fiber monitoring systems.
Intervention techniques, including the introduction of optical splitters or fiber bends to induce leakage, have continued to evolve in an attempt to evade detection. Data encryption is an obvious first line of defense against such intrusions, but fiber monitoring technology can also be employed to identify changes in optical feedback that perpetrators intend to conceal.
An innovative approach to optical fiber monitoring that can improve security with minimal additional hardware infrastructure is active fiber monitoring (AFM). By detecting small changes in light transmission on active fiber lines, alarms can be triggered so appropriate security measures can be taken.
Remote Fiber Monitoring
A remote optical fiber monitoring system enables supervision of the entire fiber optic network, including dark fiber, from a central location. With a comprehensive method, network performance can be continuously evaluated, while also minimizing mean time to repair (MTTR).
MTTR is the measure that best encompasses the overall effectiveness of an optical fiber monitoring and management system. It is the average amount of time required to resolve a failure and return the system to its correct operating state. The repair and troubleshooting process consists of the search process, that is, the process of locating and repairing failures. When a major break or bend event occurs, typically four or five technicians are sent for about four or five hours to search for the problem before it can be resolved. Automated remote monitoring reduces by 10% the localization portion that makes up the repair process to less than five minutes.
Alert messages generated by remote fiber optic monitoring systems can be notified by email, SMS message, or via SNMP protocols. SMS messages are simple out-of-band text messages that are automatically sent to relevant users when alarms are triggered. This can minimize the need for constant monitoring of monitoring interfaces. Simple Network Management Protocol (SNMP) is another communication tool commonly used to remotely monitor devices and transmit alerts to a central host or location.
Limitations of Optical Fiber Monitoring
The first limitation refers to dead zones, which can occur in an OTDR instrument if there is a high reflectance event on the fiber optic line. These can be due to air gaps, splices, or connectors that produce sufficient reflectance to temporarily saturate the OTDR detector.
During this “blackout” period while the detector recovers from saturation, the OTDR will not be able to accurately distinguish other nearby events on the fiber optic line. This becomes important when a failure occurs close enough to an existing splice or connection where a new problem is hidden by a pre-existing reflectance source.
Another limitation is the prevalence of dark fiber. Although the term may sound sinister, it simply refers to the presence of unused or “unlit” fiber optic in the network. Sometimes this term is also used to describe fiber optic cables that are leased from the original carrier to another party.
This fiber optic still requires testing and monitoring to ensure its integrity, especially if the fiber has been designated for possible future expansion. The presence of unused terminated fibers can sometimes have advantages for monitoring purposes. Failures typically affect all fibers in a cable, so monitoring certain dark fibers is an effective way to continuously check cable integrity without disrupting service on active fibers.
The Future of Optical Fiber Monitoring
As the reach and bandwidth of fiber optic cabling continue to advance, the need for complete and accurate fiber optic monitoring systems will also increase. Innovative P2MP network architectures, including Passive Optical Networks (PON), will enable greater FTTH network infrastructure with lower power consumption and fewer chances of electrical interference. The expected increase in fiber optic network complexity will make fiber monitoring more important than ever.
Advances that continue to improve OTDR accuracy and performance on short cable runs will benefit optical fiber monitoring systems and reduce the impact of dead zones and other elements that could be exploited to interfere with optical fiber.
Safeguarding the security of fiber optic networks is paramount, so future fiber monitoring technology must continuously evolve to stay one step ahead of these challenges.