Issue link: https://www.e-digitaleditions.com/i/1386104
July/August/September 2021 I 19 AN MPO TESTER IS NOW A NECESSITY The amount of singlemode fiber is increasing in the data center due to its virtually unlimited bandwidth combined with more cost-effective singlemode transceivers that are helping to drive down the cost of equipment. While singlemode fiber can support speeds of 400 gigabit per second (Gb/s) and beyond over a duplex fiber cable using wavelength division multiplexing (WDM) technology that transmits signals over multiple wavelengths of a fiber, expensive WDM equipment is used primarily for long-haul fiber links in service provider networks. More cost-effective 200 and 400 Gb/s short-reach single- mode applications that are on the rise in the data center use parallel optics technology that transmit signals over multiple fibers via multi-fiber push on (MPO) connec- tivity. Higher speed multimode fiber applications also use parallel optics and MPO connectivity, even those like 400GBASE-SR4.2 that combine both parallel optics and short-wave WDM technology to transmit 50 Gb/s over two separate wavelengths on each fiber to enable 100 Gb/s per lane. Table 1 shows the leading singlemode and multi- mode data center applications currently being deployed. It clearly demonstrates that parallel optics, and therefore MPO connectors, are here to stay. With all multimode fiber applications above 200 Gb/s and emerging short-reach 200 and 400 Gb/s singlemode data center applications requiring MPO connectors, the use of a certification tester that supports MPO testing has become a necessity for anyone testing in the data center space. Using a tester that can only test traditional duplex fiber interfaces is an extremely time-consuming process that requires the use of MPO to LC fanout cords or MPO-to-LC cassettes that separate the multiple fibers into single fiber channels. The standards-recommended (i.e., TIA-568, ISO-14763-3) default 1-jumper method references out the loss of the test reference cord connectors to include the loss of connections at both ends of the link. However, testing MPO connectors with fanout test reference cords requires the time-consuming 3-jumper method to reference out the duplex connectors that should not be included in the final test result. This involves first verifying and setting the duplex test reference cords used on both ends of the link, then verifying a third duplex reference cord and removing it before connecting to the first pair of fiber on the fanout cable. This process needs to be repeated for each pair of the fanout cable. For a 100 Gb/s, 100GBASE-SR4 application that transmits Speed (Gb/s) Application Fiber Type Transmission Type Speed per Lane (Gb/s) # of Fibers Max Length (meters) 40 40GBASE-SR4 Multimode Parallel 10 8 150 50 50GBASE-SR Multimode Duplex 50 2 100 100 100GBASE-SR4 Multimode Parallel 25 8 100 100 100GBASE-SR2 Multimode Duplex 100 2 100 200 200GBASE-SR4 Multimode Parallel 50 8 100 400 400GBASE-SR16 Multimode Parallel 25 32 100 400 400GBASE-SR8 Multimode Parallel 50 16 100 400 400GBASE-SR4.2 Multimode Parallel & WDM 100 8 100 (OM4), 150 (OM5) 50 50GBASE-FR Singlemode Duplex 50 2 2 km 100 100GBASE-DR Singlemode Duplex 100 2 500 200 200GBASE-DR4 Singlemode Parallel 50 8 500 400 400GBASE-DR4 Singlemode Parallel 100 8 500 and receives 25 Gb/s over four fibers, each link would need to be tested four times. For a data center with 50 of these links, that equates to 200 tests using the time-consuming 3-jumper method. This method of testing MPO links is not only extremely time consuming, but the process also inherently lends itself to the potential for greater inconsistencies because it is more difficult to keep all the connectors clean during the process. Using a tester with an on-board MPO connector ulti- mately tests about 90 percent faster than using a duplex tester, while significantly reducing inconsistencies. TABLE 1: Among the latest multimode and singlemode data center applications for 40 Gb/s and above, parallel optics and MPO connectivity remain dominant.