Issue link: https://www.e-digitaleditions.com/i/1386104
July/August/September 2021 I 9 4 optical channels (8 total SM fibers-MPO). Each channel operates at 100Gb/s. 4 optical channels multiplexed onto 1 pair (2 total SM fibers-LC). Each channel operates at 100Gb/s. 8 optical channels (16 total MM fibers-MPO). Each channel operates at 50Gb/s. NEW TRANSCEIVER FORM FACTORS AND SWITCHES There are two major transceiver form factors for 200 and 400 Gb/s: Quad small form-factor pluggable, double density (QSFP-DD) and octal small form-factor pluggable (OSFP). Various switch manufacturers are offering one or the other and in some cases both. The QSFP-DD trans- ceiver can support up to 32 ports in a 1RU switch, and it is backward compatible to QSFP+ and QSFP28 options. The transceiver accepts LC, MPO, and CS connectors. The OSFP can also support up to 32 ports and accepts the same connector types. It can become backward compatible with QSFP ports with the use of an adapter. It is designed to handle future generations, such as 800 Gb/s. The first 400 Gb/s switches on the market are from Arista, Cisco, and Juniper: • Arista 7060 top-of-rack switches offer 32 ports of 400 Gb/s in 1RU, using either QSFP-DD or OSFP transceiver options. • The Cisco 3432 top-of-rack switch also offers 32 ports of 400 Gb/s in 1RU, using QSFP-DD transceivers. In addition, its 3408 switch provides a 4RU 8-slot chassis option. • The Juniper QFX5220-32D 1RU top-of-rack switch also offers 32 ports with QSFP-DD transceivers. TRANSCEIVER OPTIONS FOR 200 AND 400 GB/S One variable yet to be resolved is the number of optical fiber strands used to deliver 200 and 400 Gb/s. Currently, switch manufacturers have plans for connectors with 2, 8, 16, 24, and even 32 fibers. Because the market is quickly responding to higher speeds, some of the options introduced are proprietary or based on MSAs. Between proprietary and standards-based offerings, there are now a range of options, and a few favorites are emerging. The latest transceivers for 200 and 400 Gb/s introduce several new terms that indicate the number of channels and fiber modes as shown in Figure 2: SR8, DR4, and FR4. The "SR" prefix denotes short reach 100 meter (≈328 ft) multimode, with "8" indicating 8 optical chan- nels. The "DR" refers to a 500 meter (≈1640 ft) reach, with "4" for 4 optical channels. The "FR" denotes a 2 kilometer (≈1.2 mi) reach with the "4" for 4 optical channels. FIGURE 2: Shows three new transceiver options for delivering 200 and 400 Gb/s. The new 400 Gb/s switches, based on 12.8 Tb/s chips, provide much faster speeds and greater network density.