OTDR: The Ultimate Troubleshooter for Fiber Optic

The copper wires used in the transmission of long-distance communication signals are replaced by the highly efficient fiber optic cables. As change is the only thing that doesn’t change, fiber optic cables have changed the use of copper wire in communication and network transmission. Fiber optics is the science of transmission of data, images, and voices as light signals through thin transparent fibers like glass or plastic. The fiber optics enables the transmission of larger data than that was transferred using copper cables. It also proves efficient to transfer larger data over a long distance much faster-compared to copper wires as the fiber optic cables have high bandwidth. Given the benefits of fiber optics, it has become a part of almost every workplace or home. After the installation of fiber optic cable, it has to be characterized, which needs an efficient fiber optic tools and test equipment.

Optical time domain reflectometer

The OTDR comes into play here. It is used to analyze and find a solution to any shortcoming in the fiber optic cable. The OTDR or the Optical time domain reflectometer is an instrument used for testing purposes that are used in the testing of building and certifying. It inputs a series of optical impulses into the test cable and extracts light reflected from the same end of the fiber optic. The light reflected is used to characterize the optical fiber. The data obtained is analyzed to get an insight into integrity and optical components like connectors, splices, splitters along the cable.

Reliability of OTDR

OTDR is the only efficient tool that can troubleshoot fiber optic cable faults. It identifies the root cause of the failure by locating the distance at which the fault has occurred. The common problems that occur in a fiber optic cable are micro bends, kinks, and breaks along the fiber cable path, contaminated connectors, faulty fusion splices, and various other field termination, cable management, or installation setbacks. It also identifies the loss of scattered light. The key parameters that an OTDR machine measures are;

  • Insertion loss (IL): The loss of signal power that occurs due to the presence of trouble in fiber links, such as a splice or a connector. The ratio of power that comes out of a link to the ratio of power that goes in, is represented by IL
  • Optical return loss (ORL): The loss of signal that occurs due to reflection caused at break bend or any other discontinuity along the fiber optic cable path.
  • Optical link length: The stretch between the first network connector and the end of a fiber link.
  • Fiber-based faultsAny mishaps on an optical fiber that doesn’t fulfill the required thresholds to get approved for a particular measurement.

The factors that are responsible for the reliability of the OTDR method of testing are accuracy, measurement of range, measurement of speed, and the ability to resolve the shortcomings.

Test Input wavelengths

OTDR usually uses a lower wavelength for transmission, but it’s best to test at both the 860 and 1350nm for multimode and 1300 and 1500 for single-mode while troubleshooting with OTDR. When a higher wavelength is used, the OTDR shows a lower loss making it tough to detect the problem but when the fiber is stressed, the higher wavelength will show notably higher loss which can be easily detected and solved. The scattered light’s strength is obtained as the function of time and plotted as the length of the fiber. The fiber optic test equipment manufacturers say that, given the advantages, OTDR is highly efficient in analyzing and resolving fiber optic mishaps at a lower cost.


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