Hello, everyone!
Today, I want to continue to explain a new topic – ODN engineering and maintenance. Now, I will continue to explain ODN engineering.
The next measurement required is using OTDR. In principle, each fusion splice must be checked by OTDR. What I did not say in the last article, the optical cable is checked before installation, in order to establish possible damage to the optical cable and to avoid spending time and money on laying that optical cable. This is done when the optical cable is on the reel. Both VFL (Visual Fault Locator) and OTDR are used for it.
OTDR is a very important instrument. With it, we can measure the total attenuation of each optical fiber, the attenuationing and reflection of each event on the route, to find the location of the problem - fiber optic/cable break or macro band, etc. OTDR can be used to test both SM and MM optical fibers, different optical systems, of different lengths. But before testing, you need to adjust the OTDR to get reliable results. In general, most technicians use automatic measurements - with parameters already set. The most important parameters are mode of operation, wavelength, link length and pulse width.
When measuring OTDR you should measure dark fiber (mostly, although there are OTDRs that measure live fibers), always use OTDR with reference optical cable, optical connectors to be the same on OTDR and reference cable and reference cable and test cable. Measurements can be made at different wavelengths, as with OLTS, it depends on the optical system. For a GPON system, 1310 nm, 1490 nm or 1550 nm should be tested. Measurements are required at both ends to obtain reliable results. One of the problems that arises is "gain". By measuring with the OTDR instrument, it allows us to check the attenuation of all events and make corrections if there are deviations. OTDR is not used in indoor applications, for shorter links. Also, with PON systems, OTDR measurements are very complicated. It takes a lot of knowledge and experience.
This is the end of this article. I will continue to explain this topic in the next article >> ODN Engineering and Maintenance (24).
Thank you!
Reference:
HCIA-Access, ver. 2.5, Huawei Access Certification Training
