Today, multimode fibers (MMFs) of the OM3 and OM4 classes are the preferred media for Ethernet and Fiber Channel applications operating at 850 nm with NRZ modulation. If the data rate is to be increased, the effective bandwidth is limited by the modal dispersion of the MMF and the low VCSEL bandwidth.
To overcome this limitation, parallel fiber links operating at 10 and 25 Gbps line speed are used to multiply the capacitance. However, this approach requires an infrastructure based on multi-fiber connection technology (MPO). To continue the proven 2-fiber structures is a 100 Gbps solution and moreover, using a single MMF would be preferable. In this context, WDM techniques can be used. For comparison, an OM4-MMF provides a high modal bandwidth, but only a narrow wavelength range centered at 850 nm, limiting its WDM capabilities.
The cost-effective operation of at least four WDM channels, each with 25 Gbps, requires high-bandwidth broadband MMFs over an extended wavelength range of 100nm. For backward compatibility, the 850nm wavelength was maintained, resulting in the operating window of 850 to 950nm (see FIG. 1). The performance of MMF in a system is related to the effective bandwidth, which is a function of the effective modal bandwidth (EMB) and chromatic dispersion.