Page 91 - 2020 Interconnect Innovations eBook
P. 91

As fiber connectors have achieved smaller footprints, it has become even more challenging to engage and disengage them from transceivers and patching locations, especially as density increases. To overcome this challenge, the new USFF/VSFF connectors employ an innovative push-pull boot design in which the strain relief is the mechanism used to guide connectors into place, latch them, and provide a means for removal without disrupting adjacent connectors or requiring awkward removal tools or pull tabs/stalks.
These USFF/VSFF design innovations increase density over LC duplex connectors by 2x in SFP-DD and 4x in QSFP-DD and OSFP transceivers; they also have the ability to increase density in patching fields. In the same M-3 cutout of the tried and true LC duplex coupling adapter, USFF/VSFF connectors triple the density over LC. In other words, in the space of a single traditional LC duplex connector, you can fit three USFF/VSFF duplex connectors. This allows for up to 432 fibers or 216 duplex connectors per rack unit while still enabling clean cable management and easy moves, adds, and changes.
The final advantage of these USFF/VSFF connectors is that in spine/leaf architectures you can connect any spine to any leaf using discrete cabling. This enables ultimate design flexibility and virtually unlimited growth, as the assemblies are not limited to precision breakout lengths, which is often the case with traditional array-type harnesses. Another potential side benefit of this point-to-point cabling ability is an additional rack unit reduction due to elimination of intermediate patching locations.
ยป In this illustration of a spine/leaf architecture, each core router is connected to every spine, every spine is connected to every leaf switch, and every leaf switch is connected to every top of rack switch, forming a mesh topology. As these architectures grow, adding new switches can create connection challenges to the mesh, including physical space, length, and routing restrictions for harness-type assemblies. USFF/VSFF connectors enable discrete point-to-point path routing from transceiver to transceiver.
Dust-Insensitive Connectivity
For as long as we have had fiber connectivity, dirt and contamination have been the enemy. Numerous studies have been conducted to establish the true impact of contamination in fiber networks. A 2010 study by NTT-AT Research determined that 80% of network problems were due to dirty connectors and the top cause of fiber network failures was contaminated connectors.
Contamination varies widely in terms of both type and source. There are two primary classifications of contaminate: fixed and loose. Fixed contaminate typically originates in the manufacturing process and usually requires a solvent or liquid to remove, which can lead to other troublesome issues, especially in the field. Loose contaminate, on the other hand, is typically introduced in transit or during initial installation. Most reputable manufacturers will remove any and all fixed contaminate before it leaves the factory, so the issue driving the development of dust-insensitive connectors is loose contaminate.
Why is contamination so critical in fiber connectivity and why is it so hard to control? First, we have to look at the optical fiber itself. Optical fiber is comprised of a glass core that carries the signal and an outer glass layer with a

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