OTDR - a practical tool for testing optical cabling
For error-free transmission over optical fibres, it is necessary to observe the limit of the optical path parameters. The most important parameters of optical paths are the Insertion Loss, Optical Return Loss and Reflectance of the individual components on the path.
For the measurement and evaluation of these parameters, the OTDR - Optical Reflectometer - is most useful in practice.
OTDR - (Optical Time Domain Reflectometry) optical pulse reflectometer method for measuring and analysing optical paths. It is important for the measurement and certification of optical cabling, for the installation and servicing of optical routes. It is based on Rayleigh scattering, in which a portion of the transmitted light pulse is returned to the transmitter as it passes through the optical fibre. This weak, backscattered signal is enough for the OTDR to evaluate distance, power loss and reflections along the route. It can thus measure the length, attenuation of fibers, cable sections, components, and reflections from these components, providing a variety of other practical information about the route.
Just be aware that OTDR does not measure the actual path attenuation, it only measures backscatter and reflections along the path. This is why the OTDR is sometimes referred to as a backscatter meter and we can only see the apparent path attenuation on the reflectogram curve. The apparent path attenuation is affected not only by the actual attenuation but also by other fiber parameters, which include, for example, the fiber core diameter. On the apparent attenuation curve, we can then see the gain instead of the loss in the optical connectors or couplers. In doing so, no energy is amplified in the connector, just the section of fiber behind the connector scatters the light more and on the reflectogram it looks like a gain in the connector. Similarly, multiple reflections of the optical pulse create ghosts and give the false impression of connectors where there are none.
Despite all this, the optical reflectometer is the most widely used cable tester. Especially in the automatic measurement mode, the iOLM intelligent Optical Link Mapper is becoming increasingly popular for both novice and experienced technicians.
iOLM (intelligent Optical Link Mapper)
Different variants of optical reflectometers are available for optical trace measurements using the OTDR (Optical Time Domain Reflectometry) method. These range from instruments for measuring short structured cabling routes to long distance routes of 150 km or more. In addition, for cabling systems, OTDR must be differentiated to measure either multi-mode MM fibers or single-mode SM fibers. The instrument should be selected with respect to the parameters and structure of the optical networks to be tested.
To help you choose, you can visit the OTDR configurator:
For more information: