Optical time domain reflectometry

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The optical time domain reflectometry , also known under the English name Optical-Time-domain reflectometry OTDR is a method for the identification and analysis of run lengths and reflection characteristics of electromagnetic waves and signals in the wavelength range of the light .

In practice, the area of ​​optical time domain reflectometry is playing an increasingly important role , especially in network technology and telecommunications . The OTDR is a direct further development of the time domain reflectometry , which has its roots in the beginning of radar technology in the 1930s.

The procedure

In optical time domain reflectometry, a laser pulse with a duration of 3 ns to 20 µs is coupled into an optical fiber and the backscattered light is measured over time.

The logarithmically plotted backscatter intensity can then be used to determine the losses from splices on the route and reflections from connectors as well as the attenuation of the glass fiber (in dB / km). The measured signal has a time dependency which can be converted into a location dependency using the group speed v g . A spatially resolved attenuation measurement can thus be implemented. With varying capture factors S and changing scattering coefficients α, the measured signal can be misinterpreted. This can be compensated by a second measurement at the other end of the fiber and by averaging the two measured results.

A detailed description of the (electrical) method can be found under time domain reflectometry .

literature

  • Dieter Guicking: Vibrations. Theory and applications in mechanics - acoustics - electrics and optics, Springer Fachmedien, Wiesbaden 2016, ISBN 978-3-658-14135-6 , p. 298 f.
  • Peter Fetzer, Bettina Schneider: Lexicon for IT professions. Technical and commercial terms for training, Friedrich Vieweg & Sohn Verlag, Wiesbaden 2005, ISBN 978-3-528-05867-8 , p. 207.

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