As we know, QSFP28 is considered to be the mainstream form factor in today’s 100GbE optics market. There are many products with QSFP28 form factor include DAC (Direct Attach Copper) cables, AOCs (Active Optical Cables) and transceivers with various interface options, like SR4, LR4, PSM4, CWDM4, etc. Among these QSFP28 products, which one is the best for your data center 100GbE deployment? The selection of the most suitable 100G QSFP28 product depends on a few factors. The most basic factors may be the transmission distance you may want to reach and cable types you plan to use.
QSFP28 passive DAC products include QSFP28 to QSFP28 DACs and QSFP28 to 4x SFP28 DACs are ideal to use for reaches within 5 m, providing a very cost-effective I/O solution for 100GbE connectivity. In stead of discrete components, QSFP28 DACs offers a complete cable assembly for short distance connectivity in a cost-effective manner. If your 100GbE deployment is within 5m intra racks, the DAC is ideal for you.
For 100GbE cabling with multimode fiber between switches, there are two options. One is to use QSFP28 AOC which is the best fit for 3-20 meters. And the other option is to use QSFP28 SR4 transceiver with 12-fiber MTP OM3/OM4 cable. SR4 with 12-fiber OM4 MTP fiber cable can support reaches up to 100 m. If you want to use multimode fiber for connectivity, you could choose either QSFP28 AOC or SR4 transceiver with 12-fiber MTP cable. This depends on your reaches and cost consideration.
Reaches over 100 m but less than 2km are usually called mid-reaches. For most large data center operators, a 100GbE solution which can satisfy the mid-reach connectivity in a cost-effective way is their sweet-spot. PSM4 and CWDM4/CLR4 transceivers which can respectively support up to 500 m over 12-fiber MTP single-mode fiber cable and 2 km over duplex LC single-mode fiber cable are recommended here. For more details about PSM4 and CWDM4 in 100G Ethernet, you can visit the previous post by clicking here.
For very long span 100GbE deployment, such as connectivity between two building, mostly up to 10km, QSFP28-100G-LR4 with duplex LC single-mode fiber cable is the preferred option defined by IEEE. But now, cost of QSFP28 LR4 is still very high.
After reading the above content, do you know what is best for you now? FS.COM offers a full series of 100G products and professional service for you which helps you with your worry on 100G QSFP28 optics selection. For more information, please visit www.fs.com or contact email@example.com.
Resource: How to Choose the Right 100G QSFP28 Optical Transceivers?