Nowadays, the development momentum of optical modules is unstoppable, among which the 100G optical modules take up most of the market share, such as 100G CFP and QSFP28. Then, what is 100G CFP? What is 100G QSFP28? How to choose between the two? This article will give a detailed introduction on 100G CFP vs. QSFP28 with their specific applications involved.
CFP, whose full name is C form-factor pluggable, is a multi-source agreement (MSA) to define the form-factor of the optical transceivers for high-speed digital signal transmission. This MSA was primarily developed for 100 Gigabit Ethernet systems and the “C” in “CFP” stands for the Latin letter C used to express the number 100. The electrical connection of a CFP uses 10x10 Gbit/s lanes in each direction (RX, TX). While, the optical connection can support both 10x10 Gbit/s and 4x25 Gbit/s variants of 100 Gbit/s interconnects. 100G CFP modules offer connectivity options for a wide range of service provider transport, data center networking, and enterprise core aggregation applications. Normally, there are four CFP module types: A Comprehensive Understanding of CFP Transceiver Modules.
Figure 1: 100G CFP
QSFP28 is a hot-pluggable transceiver module designed for 100G data connection in telecommunications, data centers and networking markets. The “Q” of QSFP28 means quad (4 channels). QSFP28 integrates 4 transmit and 4 receive channels. “28” means each lane carries up to 28G data rate. QSFP28 can do 4x25G breakout connection, or 1x100G connection depending on the transceiver used. For example, you can use 100G QSFP28 to 4 SFP28 DAC cables to realize 4x25G breakout connection and LC-interface based QSFP28 with a single mode fiber (or MTP/MPO-interface based QSFP28 transceiver with a 12-fiber MTP/MPO patch cable) to get 1x100G connection directly.
Figure 2: CFP vs QSFP28
CFP, one of the recommended 100G optical modules, is mainly applied in metro network and long-distance transmission (normally over 10 km).
As shown in the following picture, to achieve high cabling density and long-distance transmission with CFP transceiver, the architecture mixed a 16-channel dual fiber DWDM Mux Demux by adding MTP harness cable and WDM SFP+ OEO converter to transfer the regular SR wavelength to DWDM wavelengths. Thus, a long-distance DWDM network with 100G coherent CFP module is achieved.
Figure 3: 100G CFP Application
Nowadays, QSFP28 is considered to be the mainstream form factor of 100G optical modules. There are many QSFP28 products on the market, including QSFP28 DAC/AOC cables and QSFP28 optical modules such as 100G SR4/LR4/PSM4/CWDM4 of different types. These products are mainly divided into the following four applications according to the transmission distance.
Copper DAC Used Inside Racks Within 5 Meters
QSFP28 DAC cables are ideal to use in short-range connections within 5 meters. They can offer a complete cable assembly in a cost-effective manner. Therefore, if your 100G network is deployed inside racks in 5 meters, you can use QSFP28 DAC cables instead of 100G optical modules.
QSFP28 AOC/SR4 Transceiver for 5-100 m
There are two options for 100G multimode fiber cabling between switches away from 5 to 100 meters. One is to use QSFP28 AOC which is the best fit for 3-20 meters, and the other is to use QSFP28 SR4 transceiver with 12-fiber MTP OM3/OM4 cable, which can support a transmission distance of up to 100 m.
QSFP28 PSM4/CWDM4/CLR4 Transceiver for 100 m-2 km
For mid-reach connectivity like 100 meters to 2 km, QSFP28 PSM4 and CWDM4/CLR4 transceivers can offer cost-effective solutions. They can support up to 500 meters over 12-fiber MTP single mode fiber and 2 km over duplex LC single mode fiber respectively.
QSFP28 LR4/ER4/ZR4 Transceiver for Long Span
For long-span 100GbE deployment, such as connectivity between two buildings (mostly up to 10 km), QSFP28-100G-LR4 with duplex LC single mode fiber is the preferred option defined by IEEE. For longer distances (up to 40 km and 80 km), 100G QSFP28 ER4 and 100G QSFP28 ZR4 transceivers are better.
As for 100G CFP vs. QSFP28, which to use for your network construction? Actually, it depends on two main aspects: the port type of your hardware device and application scenarios. CFP modules have a much larger size than QSFP28 modules. 100G QSFP28 appears to be the mainstream and is mostly used in shorter distances (0-10 km) between switches or sometimes in long distances (up to 40/80 km) with QSFP28 ER4/ZR4 and single mode fibers. While, although 100G CFP can be used in short distances as well, it is more common in metropolitan area networks (MANs) and long-haul WDM transmissions.