WHAT IS AN OTDR (OPTICAL TIME-DOMAIN REFLECTOMETER)?

by www.fiber-mart.com

An OTDR is the optical equivalent of an electronic time domain reflectometer. It injects a series of optical pulses into the fiber under test and extracts, from the same end of the fiber, light that is scattered (Rayleigh backscatter) or reflected back from points along the fiber.

 

 

The scattered or reflected light that is gathered back is used to characterize the optical fiber. This is equivalent to the way that an electronic time-domain meter measures reflections caused by changes in the impedance of the cable under test. The strength of the return pulses is measured and integrated as a function of time, and plotted as a function of fiber length.

 

 

The common types of OTDR-like test equipment are:

 

Full-feature OTDR:

Full-feature OTDRs are traditional, optical time domain reflectometers. They are feature-rich and usually larger, heavier, and less portable than either the hand-held OTDR or the fiber break locator.

Often a full-feature OTDR has a main frame that can be fitted with multi-function plug-in units to perform many fiber measurement tasks. The full-feature OTDR often has a greater measurement range than the other types of OTDR-like equipment. Often it is used in laboratories and in the field for difficult fiber measurements. 

Hand-held OTDR and Fiber break locator:

Hand-held (formerly mini) OTDRs and fiber break locators are designed to troubleshoot fiber networks in a field environment, often using battery power.

 

Hand-held OTDRs are commonly used to measure fiber links and locate fiber breaks, points of high loss, high reflectance, end-to-end loss, and Optical Return Loss (ORL).

 

Fiber break locators are intended to be low-cost instruments specifically designed to determine the location of a catastrophic fiber event, e.g., fiber break, point of high reflectance, or high loss. The fiber break locator is an opto-electronic tape measure designed to measure only distance to catastrophic fiber events.