QSFP, QSFP+ and QSFP28. What’s the Difference?
This abbreviation stands for Quad Small Form Factor Pluggable.
This type of cable support Infiniband, Fibre Channel, Ethernet and Sonet/SDH standards as well as other types of proprietary interconnects.
They are available for use in either singlemode or multimode applications and is able to support 4 independent channels that can individually transmit at up to 1.25 Gbp/s per channel for an aggregate combined speed of 4.3Gbp/s. However, due to technology advancements these type of optics are seldom used.
This abbreviation stands for Quad Small Form Factor Pluggable Plus. This interface type supports Ethernet, Fibre Channel and Infiniband at 10Gbps per channel up to a maximum of 4 channels (Quad) for a combined aggregate data rate of 40Gbps or 56Gbps. Like the QSFP interface, this QSFP+ version also supports transmission over both singlemode and multimode infrastructures to a maximum distance of 40km.
Line cards / ports that accept QSFP+ modules are typically used in one of two ways.
Connecting two switches together with 40G or 56G connectivity
Connecting one switch transmitting / receiving a 40G data rate to 4 devices each working at 10G
Direct Connect QSFP+ to QSFP+
The most common methods for creating a QSFP+ to QSFP+ link is to use either a Direct Attach Copper cable or two QSFP+ transceivers and a fibre cable. For short distances either method is possible but for distances over 10m only the 2nd method works.
Direct Connect one QSFP+ Port to 4 four SFP+ Ports
A second common requirement for network managers is to be able to connect one QSFP+ 40G port to multiple 10G ports. Both Direct Attach Copper (DAC) cables and QSFP+ transceivers with fibre cables offer this as an option. The fibre cable required with QSFP+ transceivers is an MTP – LC fibre breakout cable. Again for short distances, DAC breakout cables offer the most cost effective connection but these cables are limited to transmission distances of around 10m. QSFP+ transceivers and MTP breakout cables offer network connectivity for distances up to 400m.
For distances over 400m QSFP+ transceivers and singlemode fibre are required. Two options are available; LR4 duplex networking or PLR4 (PMS4) parallel networking.
The QSFP28 is also based on the QUAD interface. The QSFP28 ramps up the data speeds to 100G by using 28Gbps per channel. Unlike the older 100G CFP, CFP2 and CFP4 interfaces, the newer QSFP28 interface offers a much smaller form type. Due to its size this interface is becoming the standard interface choice for 100G transmission.
The QSFP28 interface is highly flexible and can be used in the following combinations.
2 X 50Gbp/s
4 X 25Gbp/s (SFP28)