For multimode fiber, as the speed increases, parallel optics is the primary technology standardized by the IEEE 802.3 Ethernet and Fiber Channel Standards bodies, and parallel optics will be the technology of choice for at least the next 20 years. In 2021 however, there will be one Ethernet specified 400 Gb/s solution that will, in fact, use two wavelengths (400GBASE-SR4.2).
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