Effect of Cabling on Differential Mode Delay Measurement of Laser Optimized Multimode Fiber

摘要

Multimode fiber for 10 Gb/s 850 μm applications has been specified as OM-3 by ISO 11801 and 850-nm Laser Optimized 50 micron (850 LO 50) by TIA. These standards have been developed such that the fiber provides 2000 MHz-km of effective modal bandwidth (EMB) in installed systems using compliant 10 Gb/s transceivers. The only accepted way to characterize the 10 Gb/s system bandwidth for multimode fiber is with DMD (Differential Mode Delay) measurements and specifications as described in the relevant TIA and ISO/IEC fiber and cabling standards. The DMD is typically measured on fiber prior to cabling. It is assumed that the DMD measured on the fiber remains the same after the cabling process. OFS manufactured 36 spools 550 m of 10 Gb/s multimode fiber. The fibers were measured prior to cabling and had DMD mask widths ranging from 0.10 to 0.22 ps/m. After measurement, the fibers were sent to CommScope, Inc. for cabling. At CommScope, each spool was tight buffered with riser PVC under normal processing conditions. Minimum start-up scrap was used to maintain the integrity of the DMD study. The 36 spools of 900 |0m tight buffer were then cabled into three 12-fiber riser distribution cables. Each distribution cable contained 12 tight-buffered fibers in a 9@3 orientation, aramid yarn, a polyester ripcord, and a riser PVC outer jacket. The three completed cables measured approximately 500 meters. These cables were then sent to OFS for DMD characterization and comparison with the pre-cabling DMD values. It is shown that good agreement between the pre-cabling and post-cabling measurements is achieved when DMD measurements are conducted under proper conditions and a good cabling process is used.