OTDR

The OTDR (optical time domain reflectometer) has long been used to determine these measurements. CertiFiber is challenging the OTDR by offering a repeatable, accurate, and faster methodology for testing LAN fibers

An OTDR was used to measure the length and loss of a spool of multimode LAN fiber. 1310 nm laser wavelengths were used in our lab experiment. A simple wave form, set by professor Vito was obtained in order to examine the differences that can result when the measurement setup parameters are varied. Individual waveforms were acquired and stored, and the waveform was analyzed to determine the two-point losses and distances. While performing the OTDR measurements, we first engaged the automatic event detection and waited while the OTDR completed both the acquisition and auto event detection. I noticed that each time there was a variance in the measurements. This shows the inaccuracy of the OTDR as little as it may be

OTDRs are the original and widely accepted test systems used to measure length and loss of fiber optic cables. An OTDR uses a time-of-flight technique by injecting extremely powerful pulses of laser light into the near end of an arbitrarily long fiber and then detecting and measuring the amount of light that returns to the near end. By measuring the reflected light as a function of time, losses and distances to losses can be determined with high accuracy. Because OTDRs have been used with utility since the origin of fiber optics, they have become the de facto standard for testing newly installed and restored fiber optic systems. This practice persists even though no official standard regarding OTDR testing has ever been put into general use. This is in contrast to optical loss measurements, which have been specified in several international standards.

OTDR tests demonstrate that the OTDR can be used to determine loss and length of installed LAN fiber optic cables as well. OTDR test results can be more reliable than using a power meter but usually consume more time and a higher level of skill. Unfortunately, the OTDR doesn't have the ability to test according to accepted fiber loss test standards nor can it commission a LAN link according to established communications protocols, which competitors of the OTDR such as CertiFiber test tool can do. There is a lot of information on CertiFiber, which can be found in my sources. Information on the CertiFiber is outside the scope of this paper. This latter point is a distinct advantage over the OTDR, whose test parameters are limited to length, and loss, and do not perform pass/fail certification tests against cabling or networking standards. OTDR is a great tool to learn from and does meet the required level needed for our lab environment. If you have any questions please e-mail me at