Fiber networks all over the world has been increasing with the explosive growth in the data market. Globally, there are more than 5 billion kilometers of optical fibers installed, underground, aerially or under the sea. This corresponds to almost 138 million cable kilometers. It is also estimated roughly by some experts that on an average there are around 1566 fiber cuts every day. In other words, there are more than 1 fiber cut at every minute at some part of the world.
Faults in the network could be due to many reasons, which can be broadly classified as Naturally occurring, Natural disasters, Human-made and Equipment faults. Optical fibers made of glass used in telecommunication networks are cylindrical threads of silica doped with chemicals. They have inherent flaws that leads to cracks over a period of time. Such cracks pick up growth acceleration by the natural factors such as shrinkage due to cold temperature and expansion at high temperature. Micro-cracks may develop due to the mechanical stresses during installation. Some of these micro-cracks eventually leads to breakage of the glass thread and causes network interruption.
The nature and the animal kingdom has its share on network failure. Rodents sharpen their teeth by biting the cables. Termites degrade the cables sheaths and finally expose the fibers to water and other animals to destroy. Fire destroys the cables directly, while excessive snow accumulated on the cables will lead to mechanical weakness and finally fiber breaks.
Human-made mistakes outscore other causes. Digging for infrastructure construction work is one of the major causes. Equipment faults come from faulty connectors, splitters, terminal equipment etc.
There are numerous causes to make the network down. Some of them are avoidable and preventable, but most of them are not. Installation crew must be on vigil to attend repair work at any time round the clock, delaying of which will lead to customer outrage and business loss for the service providers. The loss does not limit to monetary, but may threaten human lives by affecting the medical emergency service and economy of a country by affecting banking and stock exchange services.
Maintenance of this nervous system is the key to the healthy day-to-day life of network owner. Negligence is hazardous and no chance should be taken to preserve and monitor the network. This is where the importance of monitoring systems come to the fore-front.
Fiber optic network monitoring can be continuous or periodic. Continuous monitoring requires dedicated optical time domain reflectometer (OTDR) for a single fiber. If monitoring of multiple fibers is required, it is recommended to use an optical fiber switch, which will test one fiber and then move to the other periodically by following settings in the system. Switching takes approximately 3 seconds and depending on the length and resolution settings, the averaging time will vary. Typically it may be around 30 seconds. So, a total of 33 seconds are required for a single fiber. Periodic monitoring is cheaper and practically viable compared to the continuous monitoring.
Periodic monitoring has its drawbacks especially when the OTDR is shared among many fibers such as 100 fibers. For a monitoring system shared for 100 fibers, it takes approximately 55 minutes for the switch to return back to the first fiber.
Currently available Network Management Systems (NMS) are capable of integrating with the fiber monitoring systems. This integration enables the NMS to send information to the monitoring system as soon as a fault is identified in any of the fiber under monitoring and instructs the monitoring system to test that particular fiber in priority. Optical fiber selector switch returns back to that particular fiber irrespective of its current test position. This allows shorter detection and Alarm reporting time. Integration with NMS makes monitoring systems more competitive by reducing the fault detection time, multiple fiber monitoring and reduced cost compared to the continuous monitoring methods. Imagine the space required for 100 OTDR test units in the case of continuous monitoring compared to the 2U space occupied by a 100 fiber selector switch unit.
It would not be exaggerated if we say that fiber optic networks are like nervous system of a country. Fiber optic networks are of utmost importance in our life and therefore monitoring of these networks are not different from monitoring our health. Monitoring of network needs some cost but selecting high quality equipment and reliable supplier is the key to the success of installation of reliable monitoring system.