Understanding OTDRs (Optical Time Domain Reflectometers) What You Will Learn In This Basic Self-Study Program: What is an OTDR – optical time domain. 17 Apr Optical time-domain reflectometer (OTDR) is an optoelectronic instrument used to characterize an optical fiber. It can help you understand the. 24 Jan OTDR is a popular fiber optic testing tool which can be used to test the fiber loss, and locate the faults in fiber optic links. However, the OTDR.

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You cannot see two events closer than otdr tutorial allowed by the pulse width. It will simply take longer to acquire each trace. Look closely and you will see a thick grey line between the markers, indicating the best fit to the trace, averaging all the noise.

The OTDR makes its measurements on the fiber, not the cable, so one must otdr tutorial the cable length. The OTDR uses this “backscattered light” to make measurements along with reflected light from connectors or cleaved fiber ends. There is also a noticable difference in the reflectance at the splice.

It will also read the difference between the power levels of the two points where the markers cross the trace and calculate the loss, or difference in the two power levels in dB. Fiber Attenuation by Least Squares Method The OTDR measures distance and loss between the two markers but calculates the best fit line between the two points mathematically using the “least squares” method to otdr tutorial noise.

Looking the opposite way, from a low attenuation fiber to a high attenuation fiber, we find the backscatter goes up, making the measured loss less than it actually is. In some cases, the fiber loss at the far end connection should also be tested. Same brand, same quality, same warrenty, why not choose the cheaper one? All three are otdr tutorial in many OTDRs, with user control of some of the selections. Generally, premises cabling uses the shortest possible pulse and long haul uses a medium pulse for the first test.

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There are some calculations otdr tutorial. Ghosts are very confusing, as they seem to be real reflective events otdr tutorial connectors, but will not show any loss. We once saw a cable that was tested with an OTDR and deemed bad because it was broken in the middle. In this way, the OTDR dead zone will happen in otdr tutorial additional optical fiber.

The Introduction of EXFO OTDR

Comparing Traces Comparing two traces in the same window is useful for confirming otdr tutorial collection and contrasting different test methods on the same fiber. If the fiber looks nonlinear at tutoria end, especially near a reflective event like a connector, avoid that section when measuring loss. You can see another good way to determine OTDR splice loss is untrustworthy with even 2.

You will see this effect in the next section on comparing otdr tutorial.

Index of Refraction The index of refraction is the calibration for the speed of light in the fiber which the OTDR uses to calculate tktorial in the fiber. Otdr tutorial should not be used for measuring insertion loss in the fiber optic cable – that task is better left to a fiber optic test source and power otdr tutorial.

If you have a long length of cable with distances marked otdr tutorial it, you can measure it with the OTDR and use the index of refraction to calibrate to the actual cable length. Operators increase investments for fiber optic network year by year.

A real “gainer” – a splice 35 km away in an installed fiber link. The blue line top otdr tutorial the attenuation coefficient of the cable in at nmthe green line bottom represents the otdr tutorial cable measured at nm.

All OTDRs are saled with a very reasonable price and warrenty for one year. When the markers are selecting the noisy part of the fiber trace, the least otdr tutorial attenuation 2-pt LSA tool can be applied to calculate otdr tutorial dB loss between uttorial cursors. Note how the slope of the curve is much higher in the fiber in this segment?


Measurements of connector loss or splices with some reflectance will look very similar, except you will see a peak at the connector, caused by the back reflection of the connector.

OTDR Archives – Tutorials Of Fiber Optic Products

Using launch fiber to overcome OTDR dead zone is the choice in most cases, otdr tutorial for long optical fiber testing. The ghost at 80 otdr tutorial looked otdd the end of the cable to him!

A receive cable may be used on the far end to allow measurements of the connector on the end of the cable under test also. If you need more resolution, average more with shorter test pulses. otdr tutorial

Otdr tutorial amount of light scattered back to the OTDR is proportional to the backscatter of the fiber, peak power of the OTDR test pulse and the length of the pulse sent out. This dead zone might be hundreds or thousands meters long. Then peak will have a flat top and tail on the far end, indicating the receiver was overloaded.

Then an analysis of the otdr tutorial will tell the operator how otdr tutorial select the right compromise. OTDR launch fiber comes in different types of packages. If you need more backscattered light to get good measurements, you can increase the pulse peak power or pulse width or send out more pulses and average the returned signals.