PROCEEDINGS ARTICLE | October 13, 2005
Proc. SPIE. 5970, Photonic Applications in Devices and Communication Systems
KEYWORDS: Multimode fibers, Refractive index, Eye, Light emitting diodes, Modulation, Polarization, Interferometry, Single mode fibers, Data transmission, Local area networks
Multimode fiber (MMF) has found applications in high-speed computer interconnect, local area networks (LAN), and storage area networks (SAN) due to its ease of handling and high performance over short span. However, modal dispersion limits its bandwidth-distance product (BDP) to about 2 Gb/s-km. This limit has been extended by recent new generation of optimized MMF to 28 Gb/s-km, but there is evidence that a substantial portion of installed MMF have imperfect refractive index (RI) profiles due to defects during the manufacturing process, and the BDP might be at best no more than 500 Mbps-km. Different strategies have been proposed to address this issue by employing offset launch, multi-level subcarrier modulation, and mode spatial control. However, our studies have shown that end-to-end system performance of installed MMF can be highly dependent on input launch polarization. In this report, we investigate, for the first time to our knowledge, the relationship between RI profile defect, input launch condition, and transmission performance in commercial-grade MMF, both 50 μm and 62.5 μm. To this end, a number of techniques have been deployed. Two-dimensional (2D) MMF RI profile is obtained by a micro-reflectivity technique with a spatial resolution of ~400 nm. MMF transmission characteristics are interrogated using interferometric techniques. Data at 40 Gb/s are transmitted over the same MMF sample at different launch conditions, and the system performance is evaluated by bit-error rate measurements. These results are then analyzed to provide insights to correlate fiber RI profile defects and high-speed data transmission performance for installed commercial-grade MMF for optical access networks.
