How OTDR Launch Cable box work and function?
OTDR launch box, according to its function and working principle, has a lot of other names, like dead zone box, pulse suppressor, fiber ring, fiber optic launch cable, etc.
Optical time domain reflectometer (OTDR) is a necessary fiber optic testing tool which use light back-scattering technologies to analyze the optical fiber performance. It can test the light loss and locate the breaks, splices and connectors in fiber optic network. However, OTDR has "dead zone" which can affect the testing result if proper measure is not taken. To overcome the limitation of OTDR dead zone, OTDR launch box is being used. How can OTDR launch box 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 level of reflection and affected by the pulse width, might extend hundred meters from the OTDR. Full length of optical fiber is suggested to use before the optical fiber under test. Thus, the receiver of the OTDR can have enough time to settle. OTDR launch box, 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 box (shown in the following picture). Then, the fiber optic link under test won't be largely affected by the OTDR dead zone.
How to use OTDR Launch Cable?
The OTDR launch box comes in various packages, most commonly used is box type.It has a long spool of optical fiber with connectors at both ends. One end is input to connect with the OTDR, the other end is output 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 using of OTDR launch boxes seems really easy. However, the handling of them should be careful. If you want to get 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. OTDR launch box is like fiber optic cables, it has different types. And one cannot be used in all fiber link test. We should mainly focus on 2points:
1. Fiber type, connector type, both of them should be compatible with the fiber link interface.
2. Fiber length, the longer ,the better. But in order to save cost, the length should be longer than the dead zone, mostly is hundreds or thousands meters.