Editing Optical time-domain reflectometer (section)

==Reliability and quality of OTDR equipment==

The reliability and quality of an OTDR is based on its accuracy, measurement range, ability to resolve and measure closely spaced events, measurement speed, and ability to perform satisfactorily under various environmental extremes and after various types of physical abuse. The instrument is also judged on the basis of its cost, features provided, size, weight, and ease of use.

Some of the terms often used in specifying the quality of an OTDR are as follows:
:'''Accuracy''': Defined as the correctness of the measurement i.e., the difference between the measured value and the true value of the event being measured.

:'''Measurement range''': Defined as the maximum attenuation that can be placed between the instrument and the event being measured, for which the instrument will still be able to measure the event within acceptable accuracy limits.

:'''Instrument resolution''': Is a measure of how close two events can be spaced and still be recognized as two separate events. The duration of the measurement pulse and the data sampling interval create a resolution limitation for OTDRs. The shorter the pulse duration and the shorter the data sampling interval, the better the instrument resolution, but the shorter the measurement range. Resolution is also often limited when powerful reflections return to the OTDR and temporarily overload the detector. When this occurs, some time is required before the instrument can resolve a second fiber event. Some OTDR manufacturers use a “masking” procedure to improve resolution. The procedure shields or “masks” the detector from high-power fiber reflections, preventing detector overload and eliminating the need for detector recovery.

Industry requirements for the reliability and quality of OTDRs are specified in the Generic Requirements for Optical Time Domain Reflectometer (OTDR) Type Equipment.<ref name= "Telecordia Sep 2010">{{Citation|title = Generic Requirements for Optical Time Domain Reflectometer (OTDR) Type Equipment| publisher = Telcordia (Ericsson Inc)| date = Sep 2010 | url = http://telecom-info.njdepot.ericsson.net/site-cgi/ido/docs.cgi?ID=SEARCH&DOCUMENT=GR-196&| access-date = 15 April 2015}}</ref>