Issue link: https://www.e-digitaleditions.com/i/1113055
EDUCATION Page 28 Tech Tip: Optical Fiber Cable Testing By Gerry Ward, RCDD Testing fiber optic cabling is one of the biggest technical challenges a technician faces. But using the current generation of testers, many of the old problems have been eliminated. Here are some Tech Tips on how to make your fiber testing a snap… Fiber testing should be performed after all cabling is completed and prior to system cutover. The horizontal cabling should be tested from the telecommunications outlet (TO) to the telecommunications room (TR). Standard system testing should be performed using a bidirectional end-to-end power meter test. The system loss measurements should be measured and recorded at 850 and 1300 nanometers for multimode fibers and 1310 and 1550 nanometers for singlemode fibers. All results should then be saved for warranty or archive purposes. A Few TIPs Before You Start • Field-test instruments shall have current calibration verifications on file. • Field-test instruments should have the latest software and firmware installed. • Properly clean each fiber port before inserting the test reference cord into it or you will contaminate the test patch cord and cross-contaminate each fiber port. • Use ANSI/TIA/EIA-526-14A, Method B or an adaptation of Method B (see Figures 1 and 2) to reference the test reference cords and test the link. This is the proper method for premise cable testing in which the connectors make up the bulk of the attenuation. Setting the Reference The following example is for LC-LC cable testing, using Fluke Networks equipment (drawings and procedures are borrowed heavily, courtesy of Fluke). Adapt your reference jumpers for the connector configuration you are testing. The leading cause of negative loss/optimistic looking results is the use of the two-jumper reference. That's where the reference is set using two jumpers and a bulkhead adapter (shown below). Although we may have been doing this for the past 20 years, this reference method is incorrect for the testing of installed links! Figure 1 - Referencing the Old (Wrong) Way