As the network becomes more complex with requests for higher bandwidth, data rates, and density, the market has seen a wide variety of transceiver modules in the telecommunication industry. SFP, SFP+, SFP28, QSFP+, QSFP28, and OSFP are all form factor types of optical modules. The most typical function of these hot-swappable optical modules is to connect network switches and other network equipment (such as servers, etc.) for data transmission. QSFP and SFP are two Small Form-Factor Pluggable module types that have a significant influence on data communications. This post introduces QSFP vs SFP respectively and illustrates their difference in form factors, size, compatibility, and price.

What is SFP:

SFP (Small Form Pluggable) can be simply understood as an upgraded version of GBIC (Gigabit Interface Converter). It is an interface device that converts gigabit electrical signals into optical signals and can be hot-swapped. GBIC is an international standard interchangeable product. Gigabit Ethernet switches designed with GBIC interfaces have a significant market share due to their flexibility and interchangeability.
SFP (Small Form Pluggables) can be simply understood as an upgraded version of GBIC. SFP modules have approximately half the size of GBIC modules and can accommodate more than twice the number of ports on the same panel. Since SFP modules are functionally similar to GBIC, some switch manufacturers also refer to them as Mini-GBIC. SFP modules achieve size and power consumption reduction by placing CDR (Clock Data Recovery) and dispersion compensators outside the module. They are used in optical communication applications for telecommunications and data communication. SFP connects network devices such as switches, routers, etc., to the mainboard using fiber optic or UTP cables. SFP is an industrial specification supported by some fiber optic device providers. SFP supports SONET, Gigabit Ethernet, Fiber Channel, and some other communication standards.

What is QSFP:

QSFP (Quad Small Form-factor Pluggable): Quad Small Form-factor Pluggable (QSFP) is a solution developed to meet the market demand for higher density and higher-speed pluggable interfaces. This 4-channel pluggable interface achieves a transmission rate of 40Gbps. Many mature key technologies from XFP are applied to this design.
QSFP can serve as a fiber optic solution and offers higher speed and density compared to 4-channel CX4 interfaces. By supporting four channels of data transmission at 10Gbps per channel within the same port volume as XFP, QSFP achieves a density four times that of XFP products and three times that of SFP+ products. The 4-channel and high-density QSFP interface has been adopted by the InfiniBand standard.

QSFP vs SFP - What are the Differences Between SFP and QSFP?

Overview of the relationships between SFP and QSFP. In short, the SFP optics are developed from GBIC to offer a smaller size for high-density applications. QSFP modules are derivated from SFPs to provide fiber connectivity solutions with higher speed. The market utilizes 40G QSFP+ and 100G QSFP28 to meet higher-speed transmission requirements and gradually obliviates QSFP.

So what is it that highlights the difference between SFP and QSFP?

QSFP vs SFP Form Factor

Compact, hot-swappable, and optical fiber connector are their common features. However, one can easily identify one from the other with a glance. QSFP vs SFP form factor is the key. Form Factor describes the attributes related to the design of SFP hardware, such as size and shape. The picture below shows the form factors of the different optical transceivers. You can figure out their appearance with ease. Figure 3: QSFP vs SFP vs other transceivers form-factors comparison

QSFP vs SFP Specifications

QSFP vs SFP specification is the second identification. Detailed factors include standard, connector, fiber type, wavelength, data rate, transmission distance, etc.
 

	SFP	QSFP+	QSFP28
Standard	SFP MSA	EEE 802.3ba QSFP+ MSA SFF-8436 SFF-8636 Infiniband 40G QDR	IEEE 802.3bm QSFP28 MSA SFF-8665 SFF-8636
Fiber Type	OM1 OM2 OS1 OS2	OM3 OM4 OS2	OM3 OM4 OS2
Wavelength	850nm 1310nm 1550nm CWDM DWDM BIDI	850nm 1310nm 832-918nm	850nm 1310nm CWDM4
Data rate	55Mbps 622Mbps 1.25Gbps 2.125Gbps 2.5Gbps 3Gbps 4.25Gbps	40Gbps 41.2Gbps 42Gbps 44.4Gbps	100Gbps 103Gbps 112Gbps
Connector	LC/SC/RJ45	LC/MTP/MPO	LC/MTP/MPO-12
Max Distance	160km	40km	80km
DDM	NO or YES	YES	YES
Temperature	COM/IND	COM/IND	COM/IND

SFP is applied in SONET, Gigabit Ethernet, Fibre Channel, and other communications standards. QSFP+, as the expansion of QSFP, supports 10-Gigabit Ethernet, 10G Fibre Channel, and InfiniBand.
In function capacity, QSFP vs SFP differs in the channel quantities and data rates.

SFP has only one channel while QSFP has four. SFP speeds up to 1Gbps, and SFP+ up to 10Gbps. However, The initial QSFP supports 4Gbps, and the new version QSFP+ supports 40Gbps. Further, a QSFP+ functions the same as 4 separate SFP+ modules, which means an increase in port density and overall system cost-efficiency.

QSFP vs SFP Price

In general, for transceivers with optical fiber connectors, the higher the speed, the more expensive the price. The costs of single-mode and multimode transceivers are different. The table below shows SFPs (Incl. SFP+) and QSFPs (Incl. QSFP+, QSFP28) prices with single-mode and multi-mode as divisions.
 

1G SFP		10G SFP+		40G QSFP+		100G QSFP28
SFP-1G-SX	SFP-1G-LX	SFP-10G-SR	SFP-10G-LR	QSFP-4G-SR4	QSFP-40G-LR4	QSFP28-100G-SR4-S	QSFP28-100G-LR4-S
$4.6	$4.6	$9.9	$14.9	$33.9	$99	$46.9	$229

QSFPTEK SFP and QSFP price is quite low compared to the whole optical transceiver market. Taking multimode QSFP vs SFP price as an example, the Cisco GLC-SX-MM 1G SFP price is only $4.6 while the Cisco QSFP-40G-SR4 40G QSFP+ price is $33.9. However, single-mode 40G QSFP+ QSFP-40G-LR4 costs more than five times that of GLC-SX-MM.
 
The difference between QSFP+ and SFP+ optical modules lies in their transmission rate, protocol, and usage.

1. Transmission rate:

- QSFP+ optical module: QSFP+ has four 10G channels, with a transmission rate of up to 40Gbps.
- SFP+ optical module: SFP+ has only one 10G channel, with a transmission rate of 10Gbps.

2. Protocol:

- QSFP+ optical module: QSFP+ supports protocols such as SFF-8436 MSA and IEEE802.3ba 40GBASE-LR4.
- SFP+ optical module: SFP+ only supports the IEEE802.3ba 40GBASE-LR4 protocol.

3. Usage:

- QSFP+ optical module: QSFP+ supports MPO and LC fiber optic jumpers. It is mainly used for switches, routers, and host adapter buses.
- SFP+ optical module: SFP+ is usually connected with LC jumpers. It is mainly used for routers and host adapter buses.