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Single-mode vs Multimode SFP: What’s the Difference?

GeorgeUpdated at Dec 20th 20231 min read

Single-mode SFP and multimode SFP are the two main types of hot-pluggable optical transceivers used in fiber optic networks. Both of them use LC connectors and are collectively referred to as LC SFP transceivers. The primary differences between them are the types of fiber they support and their transmission distances.
What is Single-mode SFP?
Single-mode SFP (SMF SFP) operates on single-mode fibers that have a core diameter of 9 microns and a cladding diameter of 125 microns. SMF SFP primarily operates at wavelengths of 1310 nanometers and 1550 nanometers. Therefore, it is suitable for long-distance data transmission applications such as 2 kilometers, 10 kilometers, 40 kilometers, 60 kilometers, 80 kilometers, and 120 kilometers. There are various types of single-mode SFP modules available, such as 1000BASE-LX and 1000BASE-EX.
What is Multimode SFP?
Multimode SFP (MMF SFP) operates on multimode fibers that have core diameters of 50 microns or 62.5 microns and a cladding diameter of 125 microns. Common multimode SFP works at a wavelength of 850 nanometers and is used for short-distance transmission. Typically, they can reach up to 100 to 550 meters. There are various types of multimode SFP modules available, including SFP1G-SX-85.
Single-mode vs Multimode SFP: What’s the Difference?
There are several main differences between single-mode SFP and multimode SFP.
Working Wavelength
Single-mode SFP module has a narrower laser wavelength, which works essentially in 1310nm and 1550nm wavelength. However, the multimode SFP module works in 850nm wavelength because of the bigger core size.
Transmission Distance
Single-mode SFP modules are designed for long-distance transmissions, typically ranging from 2 to 120 kilometers, depending on the specific module type. They are ideal for large-scale networks requiring high-speed connectivity over vast distances. Multimode SFP modules are better suited for shorter distances, generally covering 100 to 550 meters, making them a cost-effective choice for data centers and local area networks where shorter transmission ranges are sufficient.
Color Coding
The color coding for single-mode SFP module typically includes blue, yellow, or purple. For FS products, blue is used for 1310 nanometer modules, yellow for 1550 nanometer modules, and purple for 1490 nanometer modules. The compatible fiber patch cords for single-mode SFP modules are usually yellow. On the other hand, the color-coding for multimode SFP modules includes black for the label's color-coding and arrow, and orange for the fiber patch cords used.
Transmitter
Single-mode SFP and multimode SFP utilize various transmitters. VCSELs (Vertical Cavity Surface Emitting Lasers) are commonly used in multimode SFP transceivers. They can be tested at the wafer level and do not require hermetic packaging.
Edge-emitting lasers such as Fabry-Perot, DFB (Distributed Feedback), and DBR (Distributed Bragg Reflector) lasers are used in single-mode SFP modules for various spans and applications. They have complex layer structures and typically require hermetic packaging to achieve higher output power and stable single-mode operation. Therefore, edge-emitting lasers are more expensive than VCSELs.
Cost
From a cost perspective, single-mode SFP is more expensive than Multimode SFP. This cost difference is largely due to the transmitters used. Single-mode SFP modules require more powerful transmitters with higher RX/TX power ranges to support long-distance data transmission, which increases their cost compared to the less expensive transmitters used in Multimode SFPs.
Additionally, power budget considerations also play a role; Single-mode SFP modules require a higher power budget to maintain signal integrity over long distances. For more details on RX/TX optical power, you can refer to this article: Understanding the TX/RX Optical Power on the Transceiver. Therefore, Multimode SFP modules are generally more cost-effective.
The following table summarizes the main differences:
Features
Single-mode SFP
Multimode SFP
Working Wavelength
1310nm and 1550nm
850nm
Transmission Distance
2 to 120 km
100 to 550 m
Color Coding
Blue, Yellow, or Purple
Black
Transmitter
Edge-emitting lasers
VCSELs
Cost
High
Low
Tips on Utilizing Single-mode SFP and Multimode SFP
Single-mode SFP and multimode SFP modules are used in switch slots and support communication through fiber optic or copper network cables. When using single-mode SFP or multimode SFP, it is important to keep the following points in mind:
Conclusion
The choice between single-mode vs Multimode SFP mainly depends on cost and distance needs. Single-mode SFP suits long-distance transmission, while multimode SFP is ideal for short-distance with more economical solutions. FS offers a variety of LC SFP transceivers. If you have any needs, feel free to contact us.