Instructions of OTDR test modes and parameters

  OTDR handheld Optical Time Domain Reflectometry is a new generation of intelligent optical-fibre communication instrument. Which is widely used in the construction, maintenance, measurement, emergency repair of optical-fibre communication system works.

Test modes of OTDR

  OTDR has three test modes, i.e.: auto test, real-time test and average test.

Auto test:

  If OTDR has been set in auto test mode. When you click【START/STOP】 button, the system will immediately start auto test, and the instrument will automatically change testing conditions according to the conditions of the optical fibre to be tested.
  Click【AUTO】 button while in main menu, auto test will immediately become current mode, and the system will start testing.

Real-time test:

  If OTDR has been set in real-time test mode, the system will continuously refresh and test till you click【START/STOP】 button again, then OTDR stops testing.

Average test:

  If OTDR has been set in average test mode, OTDR will perform average test over the link circuit of the optical fibre to be tested based on the preset conditions. The testing curves appearing in main menu will be continuously equalized till the averaging times appearing in the screen reaches the preset averaging times, then OTDR stops testing.

Test parameters of OTDR

  Test parameters of OTDR include: wave length, measurement range, pulse width, attenuation, averaging times, refractive index, optical cable correction factor, event threshold.

Wave length:

  It is used to set the testing wave length of OTDR.

Measurement range:

  It is used to set the range for scanning curves, in general it is set as 4km, 8km, 16km, 32km, 64km, 128km, 256km. The range you set must be greater than the length of the optical fibre to be measured.

Pulse width:

  It is used to measure the laser pulse width to be used in the test. The wider the pulse is, the longer optical fibre the instrument can measure, but the lower the resolution will be. The thinner the pulse width is, the higher the resolution will be, but the shorter distance the instrument can test.


  It is used to measure the attenuation values of signals. The attenuation values can be set as 0dB, 5dB, 10dB. The smaller the attenuation value is, the longer optical fibre the instrument can measure, but the near end of optical fibre may appear saturated; The greater the attenuation value is, the shorter optical fibre the instrument can measure, the lower signal-to-noise ratio of testing curves is, but the smaller the test dead zone is.

Averaging times:

  It is used to maximum averaging times for average test. This value ranges within 1-10000.
  The bigger the number of averaging times is, the smoother the testing curve is (it means the higher the signal-to-noise ratio is, this is especially helpful for measuring the longer optical fibre).
  The increasing of signal-to-noise ratio of testing curve helps OTDR test smaller event points.
  While in auto test mod, the number of averaging time will influence the speed of auto test.

Refractive index:

  Refractive index of optical fibre or optical cable is available from manufacturers, it can be set within 1.00000~2.00000.

Optical cable correction factor:

  Optical cable correction factor is used to correct the bias between optical fibre and optical cable after optical fibre turns into optical cable. Such factor is available from manufacturers of optical cable, it can be set within 0.8000-1.0000.
  If the optical cable correction factor is improperly set, the length of optical cable you measured will be inaccurate.

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