SFP stands for small form-factor pluggable it is a compact hot pluggable transceiver used for both telecom and the data applications. LC connectors are used to connect fibers to SFPs. SFP module has two sides, first side known as transmitter it has laser for transmitting and other side known as receiver side has a photo detector. So basically SFP is a transceiver module since it has transmitter and the receiver in a single unit.
SFPs are not standardized by any single body, but relatively are specified by a multi source agreement also called MSA. It is an agreement between several manufacturers to make products which are compatible among different vendors. SFP designed based on the bigger gigabit interface converter (GBIC) interface, but it has a much smaller size in order to increased port density, that is why SFP is also called mini- GBIC.
SFP modules are used in all types of network applications like data networks, telecommunication networks, SAN as well as SONED/SDH.
Typical SFP modules can be classified based on the working wavelengths and its working distance so let’s take a look at the list here:
For multimode fibers the SFP modules called SX (short reach) module, it use 850 nanometer wavelength. The distance that SX modules support depend on the network speed, for 1.25 gigabit per second speed the distance achieved is about 550 meters, whereas for 125 gigabit per second speed it supports up to 150 meters
For single mode fiber side there are lots of choices, following are the most common types:
For single-mode fibers the SFP modules called LX (long reach) module use 1310 nanometer wavelength laser and supports up to 10 kilometer. EX module use 1310 nanometer wavelength laser and supports up to 40 kilometer. ZX module use 1550 nanometer wavelength laser and supports up to 80 kilometer. EZX module use 1550 nanometer wavelength laser and supports up to 160 kilometer. CWDM and DWDM SFP transceivers are also used at different wavelengths for reaching several maximum distances. Also there are Gigabit Ethernet UTP copper cable modules available.
As mentioned earlier SFP module supports speed up to 4.25 gigabit per second and an enhanced version which is called SFP+ supports more than 10 gigabit per second and SFP+ is becoming more popular on 10 gigabit ethernet.
The enhanced small form-factor pluggable (SFP+) is an improved kind of the SFP that supports data rate up to 16 gigabit per second. SFP+ supports 8 gigabit per second Fibre Channel, 10 Gigabit Ethernet and Optical Transport Network standard OTU2.
10 gigabit per second or commonly called SFP+ modules, are precisely the same sizes as regular SFPs, permitting the equipment producer to re-use present physical designs for 24 and 48 port switches and modular line cards.
The advantages of using SFP or SFP+ is, these both transceivers are typically the size of an RJ-45 ethernet port. As compared to GBIC, XENPAK or XFP modules SFP and SFP+ uses small area and standardized size of connectors. SFP sockets are commonly found in Ethernet switches, routers, firewalls and Optical Line Terminal commonly called OLT.
Recent optical SFP transceivers also support Standard digital diagnostics monitoring (DDM). This feature is commonly known as digital optical monitoring (DOM). DOM capable SFP modules give end user the ability to observer parameters of the transceiver, such as transmitted optical power, received optical power, transceiver supply voltage, laser bias current, as well as temperature of SFP in real time. This feature is commonly applied for monitoring on switches, routers and optical equipment via SNMP.
Since these SFPs are specified by a multi source agreement, which permits compatibility among different vendors. So a single SFP purchased can be used from Cisco switch to Juniper Router and from HP server to Huawei OLT. Also SFP modules are hot pluggable, so unlike other network components/cards there is no need to power off the device when inserting the SFP.