Fiber optic cable has unexpectedly turned out to be sensitive to moisture and must be monitored. The transmission quality over the entire cable is measured using attenuation values in a reference fibre.
Top-quality OTDRs (Optical Time Domain Reflectometers) are used to quickly and precisely locate faults. OTDRs tailored to the relevant transmission wavelength are employed as the particular task dictates.
The LANCIER Monitoring system for PON is compact and modular. The RTU (Remote Testing Unit) is installed in the central office (exchange). The built-in high-end OTDR comes with three measurement wavelengths (1310 nm, 1550 nm and 1625 nm) to be prepared for any measurement task and state-of-the-art deadzones, which makes PON monitoring possible in the first place. An optical switch with the necessary amount of fiber connectors sequentially attaches the fibers to be measured to the OTDR.
If the transmission equipment installed in the central office is not already equipped with monitoring channels, additional wave division multiplexers (WDM) are used to couple the monitoring signal into the active fibers.
The OTDR then measures the fiber even past the passive splitter all the way down to the ONUs (subscriber site). During the measurement the end reflection is evaluated to determine whether the connection between splitter and ONU is still fully functional. Additionally an exact fault localization between the OLT and the splitter is possible, which saves even more time for the diagnostics.