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Can I use a multimode SFP on single mode fiber?
Knowledge Base + 2023.12.07

No, you should not use a multimode SFP on single mode fiber. Multimode SFPs are designed to work with multimode fiber, which has a larger core diameter than single mode fiber. Using a multimode SFP on single mode fiber can cause signal degradation, loss of data, and potentially damage the equipment. It is important to use the correct SFP and fiber type for your specific network requirements.

You might be interested in 10G SFP+ Tunable DWDM 25G SFP28 Tunable DWDM

Multi-mode has a larger core than the Single-mode, 50 to 100 microns. Its light is much more bulky and because of this, light-waves are dispersed in numerous ways through the cable. This won’t be a problem for short distances, however in distances greater than 1 kilometer this can cause a light distortion at the far end resulting in incomplete data transmission.

What if you have to connect Multi-mode and Single-mode? Even though, installing a Multi-mode on a Single-mode transceiver is possible, it is highly advisable to use compatible equipment. When trying to mix up the installation it’s highly advisable to pay attention to the device’s specifications which can be found in the device’s datasheet.

The main things to know when using these types of cables are:

- Mode Conditioning Patch Cords require a MC Cable to be connected on each side of the installation.

- When using equipment equipped with LC or SC connectors it’s crucial to keep in mind that the single-mode part of the cable must be connected to the transmit side of the equipment, and the multi-mode part of the cable must be connected to the receive side of the equipment.

Please note that this solution does not have the best quality. Depending on the bandwidth transmissions on multi-mode fibers are limited in their distance.

For this reason it is always recommended to use the multi-mode or single-mode fiber patch cords to match the transceiver to achieve the best connection quality.

What is SFP Connector?

SFP connector or SFP plug is another name of SFP as SFP (small form-factor pluggable) is a compact and hot-pluggable interface connector. The SFP connector module functions as the intercommunication media between the network devices and cables to achieve photoelectric and electro-to-optical conversion. SFP interface is commonly used in SFP port network equipment such as Ethernet switches, firewalls, routers, network interface cards (NICs) for both data communication and telecommunication applications.


Figure: the optical interface of the 1000BASE-SX SFP connector module is located at the side of the dust cap. Once unplug the cap, will you see the optical interface.

According to transmission media, there are SFP copper connectors and SFP fiber connectors. Copper SFP uses an RJ45 SFP connector interface, whereas fiber SFP uses SFP lc connector, SFP sc connector, and SFP MTP/MPO connector interface as typical ones. According to the SFP forms, different SFP form factors often utilize corresponding SFP connectors.

The table below shows the SFP connector interface types for different SFP types.

SFP TypesMediaConnector
100 Mbit/s SFP
LC, RJ45
1 Gbit/s SFP
Fiber, copper
1 Gbit/s cSFP
10 Gbit/s SFP+
Fiber, copper, DAC
LC, RJ45
25 Gbit/s SFP28
Fiber, DAC
50 Gbit/s SFP56
Fiber, DAC
4 Gbit/s QSFP

40 Gbit/s QSFP+
Fiber, DAC
50 Gbit/s QSFP28
Fiber, DAC
100 Gbit/s QSFP28
Fiber, DAC
200 Gbit/s QSFP56
Fiber, DAC
400 Gbit/s QSFP-DD
Fiber, DAC

What Type of Connector is Used with an SFP Port?

SFP ports are frequently found in Ethernet network switches. These switches with 1G SFP ports as the major functional switch ports are called gigabit SFP switches.

SFP port on SFP switch supports both SFP copper connector and SFP fiber connector while RJ45 port can only take copper SFP module RJ45 connector. SFP connector types that 1G SFP port can take are RJ45 SFP connector, SFP lc connector, SFP sc connector.

FAQs about SFP Transceiver

Can We Use SFP Hardware in SFP+ Slots?

In many cases, the SFP+ port accepts SFP optics, but the speed will be down to 1G instead of 10G. However, SFP+ optics can not be plugged into the SFP port, because SFP+ does not support speed under 1G. In addition, almost all SFP+ ports on Cisco switches can support SFPs, but many SFP+ ports of Brocade switch only support SFP+ optics.

Can I use a 1000base-LX sfp for 1000base-SX fiber?

Generally, they are not interchangeable. 1000Base SX and LX are two optics standards with different operation wavelengths.1000Base LX SFP transceiver usually operates at 1310nm and uses single-mode fiber to connect, while 1000Base-SX usually is 850nm SFP and works with multimode fiber.

Can you aggregate multiple SFP ports?

Of course, you can. Link aggregation provides benefits like increased bandwidth, redundancy, and load-balancing. That will ensure that one link can immediately switch to a second available link when it fails. Therefore, aggregation on SFP ports is critical for enterprise networks where performance and security are more important. But note that, before connecting the SFP ports, please make sure that the switches have been configured for link aggregation. Otherwise, it will cause network loops.