The Optical Time Domain Reflectometer, briefly OTDR (The optical time domain reflectometer), is a device used for evaluating the length of fiber optic cables, measuring transmission attenuation, and connections. This device, which can be used to identify the location of faults in fiber connections, characterizes the optical cable and provides an analysis report.
Due to these functions, OTDR is widely preferred for the maintenance and application of fiber optic cables. Additionally, OTDRs represent the most effective method for assessing the quality of cable splicing and termination locations.
How is the analysis of OTDR testing devices performed?
OTDR uses Rayleigh scattering and Fresnel reflections to detect the characteristics of the fiber optic cable. A portion of the light sent from the OTDR device’s output returns to the system. Since light scatters in all directions, some of it returns to the light source along the fiber. By analyzing the reflected light, the OTDR device can determine the condition of the fiber optic cable.
To analyze the fiber optic cable, the testing equipment must measure and determine the following key parameters.
Information about the OTDR test
Dynamic Range: It is the maximum optical loss that an OTDR can analyze, from the reflected dispersion level at the OTDR port to a certain noise level. Based on this loss, the distance that the OTDR testing device can cover is determined.
Event Dead Zone: It is the shortest distance after a Fresnel reflection at which the OTDR can detect another state. In other words, it is the minimum fiber length required between two reflective events.
Pulse Width: It is defined as the duration during which the laser is active. Since time is converted into distance, the pulse width has a specific length. If the pulse width is increased, the attenuation dead zone increases proportionally. This situation limits the ability to detect other events.
OTDR testing devices react differently to the parameters mentioned above. Since field personnel do not work under laboratory conditions, they do not want to waste time determining the optimal OTDR configuration. The OTDR must automatically optimize all necessary parameters to meet user needs. The signal-to-noise ratio will not improve by itself in terms of the quality of event detection and measurement. Therefore, it must be ensured that OTDR parameters are automatically optimized to always obtain good results.
