The Telecommunications Industry Association (TIA) recently released a new Telecommunications Systems Bulletin, TSB-4979, whose official title is Practical Considerations for Implementation of Encircled Flux Launch Conditions in the Field.
According to TIA, TSB-4979 “outlines precise specifications that define the launch condition of test sources into multimode fiber which have been standardized and are mandatory for testing optical attenuation of installed multimode cabling per TIA-568.” The association adds that the purpose of TSB-4979 is “to identify user-friendly, low-complexity solutions for implementing multimode launch conditions that meet EF-based requirements.”
To accomplish that purpose, the document describes two possible implementation methods, as follows.
A “universal controller,” which can be used with any light source, be it overfilling or underfilling, from any test supplier.
A “matched controller”—a light source and launch cord combination (with the launch cord including a controlling device), perhaps from a specific test supplier, that together meet the EF requirements.
TSB-4979 describes the advantages and disadvantages of each implementation method, and also provides uncertainty of measurement and best-practices advice.