Although 10/40G Ethernet nowadays still captures the major position in the world of telecommunication, service providers and enterprise data centers are actually undertaking an infrastructures transformation. Which fuels the demand for higher speeds and better performance 100G transceiver, making migration to 100G an inevitable trend. Optical transceiver modules always pertain to an integral part of overall system design, as for 100G CFP modules, the options vary widely. This article makes a comparison between the most common two CFP transceivers: 100G SR10 and 100G LR4 CFP modules.
Basics of 100G CFP Modules
CFP transceiver is a hot pluggable form factor designed for optical networking applications. CFP is the acronym of 100G (here C equals 100 in Roman numerals) form factor pluggable. The name clearly indicates that CFP modules are designed typically for 100G interfaces. To make it easier, let’s begin with general CFP modules architecture. It basically consists of two parts—electrical interface interacting with equipment, and line card interface and optical line interface. The following figure displays the general architecture of 100GBASE CFP transceiver.
From equipment line card to electrical interface, CFP transceiver has several “M-Lines” with 10Gbps speed. If CFP modules are working 100GBase-LR4 mode, then it has 10 x 10Gbps M-Lines. As for 40GBase-LR4, it uses 4 x 10Gbps M-Lines. The so called “gear box” is electrical 10:4 mux/demux module aggregating up to 10 M-Line interfaces in maximum 4 N-Line interfaces. Each N-Line is 25Gbps for 100GBase-LR4 and 10Gbps for 40GBase-LR4. The N-Line is converted to optical signal with different wavelength and all four wavelengths are transmitted to CFP transceiver line interface using built in passive optical multiplexers.
100G SR10 and 100G LR4 CFP Modules Overview
100G CFP modules offer connectivity options for a wide range of service provider transport, data center networking, and enterprise core aggregation applications. The basic information of CFP-100G-SR10 and CFP-100G-LR4 module is provided below.
CFP-100G-SR10 is an IEEE standardized CFP transceiver supporting link lengths of 100 m and 150 m respectively on laser-optimized OM3 and OM4 multifiber cables. It primarily enables high-bandwidth 100-gigabit links over 24-fiber ribbon cables terminated with MPO/MTP-24 connectors. It can also be used in 10 x 10 Gigabit Ethernet mode along with ribbon to duplex fiber breakout cables for connectivity to ten 10GBASE-SR optical interfaces. 100G SR10 CFP interface serves as a more cost-effective solution, which is optimized for data center application but limited to short distances.
CFP-100G-LR4 is standardized by IEEE using standard LC dual fiber interface with single-mode cable, but running four optical wavelengths each direction (1295.56 nm, 1300.05 nm,1304.59 nm, 1309.14 nm) and muxing/demuxing of these wavelengths happening inside CFP module. Each wavelength is running at 25.78 Gbps and it is possible to achieve up to 10 km. Compared to 100G SR10 CFP, 100G LR4 CFP delivers much better reach for long-haul applications, but at a cost premium.
Comparison Between 100G SR10 and 100G LR4 CFP Modules
In this section, we’re trying to figure out the difference between CFP-100G-SR10 and CFP-100G-LR4 from the perspective of connectors and cabling used on each. For connectors, 24-fiber MPO/MTP connector is for 100GBASE-SR10 CFP transceiver while dual SC/PC connector for 100GBASE-LR4. Note that only patch cords with PC or UPC connectors are supported. The cabling specification and features for 100G SR10 and 100G LR4 CFP modules are presented in the following diagrams.
Service providers and data centers are embracing the trend of 100G network migrations, while IT managers must think twice when choosing from those various 100G transceiver options. 100G SR10 is preferred due to lower cost over 100G LR4, but its reaching distance is limited. Whereas 100GBASE-LR4 CFP transceiver enables data transmission up to 10 km with higher price. This article generally offers some basic knowledge of each CFP modules, the decision actually depends on your specific demands or the application requirements. Always be aware of what you need, which will work best for you.