Why OTDR Launch Cable ? OTDR Extension Test Line Fiber Ring Introduction

(Optical Fiber Test Extension Line)

Optical time domain reflectometer (OTDR) is a necessary fiber optic testing tool which uses light backscattering technologies to analyze the optical fiber performance. It can test the light loss and locate the breaks, splices and connectors in fiber optic networks. However, OTDR has "dead zone" which can affect the testing results if proper measures are not taken. To overcome the limitation of OTDR dead zone, OTDR launch box is being used.

OTDR launch cable, according to its function and working principle, has a lot of other names, like dead zone box, pulse suppressor, fiber extension cable, fiber ring, fiber optic launch cable, etc. How can OTDR launch cable minimize the effect of OTDR dead zone during fiber optic testing? The following explains the detail.

The dead zone of OTDR, caused by high return levels of reflection and affected by the pulse width, might extend hundreds of meters from the OTDR. Full length of optical fiber is suggested to be used before the optical fiber under test. Thus, the receiver of the OTDR can have enough time to settle. OTDR launch cable, which is actually a long spool of optical fiber inserted between the fiber under test and OTDR, can ensure that the OTDR dead zone happens in the OTDR launch cable (shown in the following picture). Then, the fiber optic link under test won't be largely affected by the OTDR dead zone.

02 OTDR Launch Cable Usage Guide

The OTDR launch cable comes in various packages. The box-design is the most commonly used one with the advantage of durability. It has a long spool of optical fiber with a pigtail on two ends. One of the pigtails is for input, which is used to connect with the OTDR. The other pigtail on the opposite end is for the output, which is used to connect with the optical fiber under test. After connecting the input end and output end to the corresponding port, the OTDR launch box can be used to test the attenuation of the fiber link.

The use of OTDR launch boxes seems really easy. However, the handling of them should be careful. If you want to get an accurate test result of the fiber link the length of the optical fiber inside the OTDR launch box should be long enough to cover the whole dead zone.

03 Which OTDR Launch Box Fit Your Applications?

The selection of OTDR launch box is like selecting fiber patch cable. You should basically consider about the fiber type, connector type terminated on pigtails and the polishing type of the connectors. Another important factor that should be considered is the length of optical fiber of OTDR launch box as mentioned above mentions. The optical fiber of OTDR launch box should be longer than the dead zone. Thus, most of fiber OTDR launch boxes can support hundreds or thousands of meters. Check right reference forms to select correct fiber cable.

Following as our product manual : 

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