OM5: Hip or Jive?

by Doug Coleman Manager of Technology & Standards Distinguished Associate, Corning Optical Communications

The time for fiber is now! I made this proclamation approximately 15 years ago, where I spoke about 10G Ethernet IEEE 802.3ae standards at a BICSI Conference. Since that time, there has been an ongoing, insatiable demand for higher network bandwidth that has led to the standardization of higher Ethernet data rates (40/100/200G) as well as future Ethernet roadmap data rates (400G/800G/1.6 Tb). “The time for fiber is now” proclamation quickly came to fruition, as optical fiber is the primary connectivity media solution in the data center.

Corning multimode and single-mode fiber structured cabling solutions support Ethernet standard 10/40/100/200G data rates and provide a migration path to emerging 400G and future 800G/1.6 Tb data rates. Data center operators clearly expect connectivity solutions to support multiple Ethernet data rate generations to ensure a 10- to 15-year service life is maintained.

After much discussion with ASIC, transceiver and switch vendors, the solutions today (40/100/200GbE) and in the future (400/800GbE and 1.6 Tb) all converge on duplex-fiber serial and 8-fiber parallel transmission with some interim solutions along the way.

With current transceiver and switch vendor trends leading to 2- and 8-eight fiber transceivers, there is a need for optimized optical connectivity solutions. Traditional MTP^®-based solutions are based on 12-fiber connectors, which is not always divisible by eight. Based on this information, to simplify network design and operation, improve fiber utilization, and reduce costs and attenuation in an optical link, an 8-fiber-based infrastructure provides the optimal solution.

A base-8 infrastructure (illustrated in Figure 1) consists of backbone trunks that have 8-fiber legs and modules that have four ports (8 fibers) and 8-fiber harnesses. Since parallel connectivity uses eight fibers out of the available 12 fibers in the connector, the issue arises with a base-12 infrastructure to either leave the four middle fibers dark or use some type of conversion device. A conversion device can convert two 12-fiber links into three 8-fiber links. This allows all fibers to be utilized, giving you three parallel links for each 24 fibers of the installed base-12 trunk cables. This is not necessary when a base-8 infrastructure is installed.

Migration from duplex to parallel links is easy without the added complexity since the infrastructure is already eight fibers (each trunk cable has 8-fiber legs). The conversion is made easy by removing the modules used for duplex communication and replacing them with MTP adapter panels. MTP-to-MTP array jumpers would provide the link from the trunks to the QFSP+ transceivers. The installation of a base-8 infrastructure allows for 100 percent fiber utilization when migrating to parallel links without the need for conversion modules or harnesses. Figure 2 illustrates base-8 connectivity for SFP and QSFP transceivers that interfaces to the electronics.

I will celebrate 40 years of service with Corning in March 2019. I have been fortunate to witness and participate in optical fiber’s adoption into most all communications applications spaces (long haul, metro, access, CATV, enterprise, etc). Since 10G implementation, data centers have made optical connectivity the de facto solution.  The future is bright for optical fiber connectivity as the data center industry moves to terabit data rates.