As we all know, optical fiber because of light weight, corrosion resistance, immunity to electromagnetic interference image, in the area of environmental adaptability than cable, fiber optic line quality is good or bad depends on the cable quality and construction process. According to the structure of the
fiber optic cable, cable construction process, in strict accordance with the specifications construction, fiber optic cable by the injury a chance. Once the fiber optic cable construction requires the help of
OTDR in order to understand the status of the fiber-optic lines by the human eye is not known, it is in the maintenance and operation of the fiber optic cable lines, with OTDR testing fiber link is very important and necessary.
OTDR in fiber construction process testing generally need four tests: Incoming test,Welding before testing, After welding testing and acceptance testing after construction.
(1) before laying the fiber optic cable for each fiber in the fiber optic cable must first be tested, because the fiber optic transport from the factory to the buyer unit and then transported to the site through the middle of the up and down loading, unloading, there is no guarantee optic cablefrom damage. So, tested before laying fiber optic cable in order to draw the lines of responsibility, which is make sure the fiber optic cable is good before construction. Maintenance operations perspective, the test has two purposes: First, to ensure the cable is not damaged due to the construction, the second is to determine long cable lines, in order to avoid not long enough.
(2) Cable laying continues must also re-test, which is due to the advancement of technology, fiber splicing machines weld quality has been greatly improved, making the weld point loss is no longer the main factor of the fiber line loss. Because of splice loss is small, the optical signal after passing through the point, the changes in the optical power is not obvious when the OTDR test, not easy to judge out, but is also easy to find a test curve of the optical fiber link to splice point, On the future operation and maintenance, which will generate a lot of inconvenience: First line maintenance, resulting in picking difficult because I do not know just how long the paragraph cable; line change then not easy change contact general should be selected in the jointsthe position, because of the curve in the welding point is not obvious, may not find the fusion point can not be changed then. So, before connecting again testing to prevent the occurrence of such problems, and can verify that the fiber optic cable in the arm when no cable damage. Connection before testing and OTDR test the same way, just splice in the cable before the first test cable length and the loss of data stored, to establish the length of the line segment and the loss of the database, as an important reference for future line maintenance.
(3) Cable welding again with OTDR testing, the test has two effects: First, test weld point splice loss does not exceed the stipulated requirements, once found excessive point can again re-welding, the second is the use of testand control cable core wire, weld to hundreds-core optical fiber there is no guarantee that it will not take wrong.
Many welding cable link, link the individual excessive weld point, generally speaking, there are two reasons: First, the fiber of the reasons, that successive points at both ends of the fiber numerical aperture difference is too large, may be due to differentthe manufacturers, however, with the advances in optical fiber manufacturing technology, this difference is getting smaller and smaller; another weld reasons, caused by human negligence or fault of welding machine.
Identify failed weld point fiber link with OTDR must be carefully tested and carefully judged on unqualified to be taken seriously, otherwise this point may cause deterioration of the fiber link special fast the most direct reason.
(4) After the completion of the fiber optic cable project, but also the final test of the line, the construction side of the test cable link self-test, self-examination, self-test, the test data can be used as the reference when the subsequent acceptance, acceptance-square test according to the standardacceptance testing requirements, the length of the fiber optic cable link, link loss and splice loss, the establishment of a database of test data, as an important reference for future operation and maintenance.
Final test also can take advantage of the light source, optical power meter,, and OTDR three instruments common, before they are used to test the wear and tear of the optical signal transmission within the actual link with OTDR is to find the bad linkweld point and location.
Fiber optic link loss is measured by the light source and the
optical power meter, the measurement, the transmitting end and the receiving end of each take one person, before the test, the two sides of the optical fiber in the cable of the test sequence (according to the color of the optical fiber coating material) can be agreed doingAnother advantage is that timely detection the miswiring fiber.
