Difference between multimode and single mode sfp

 
With the convergence of single-mode and multi-mode SFP optical modules in recent years, the application of single-mode has become mainstream. Taking Fiberstore as an example, what are the differences between single-mode and multi-mode SFP optical modules?

Operating methods:

1. Multi-mode SFP: Almost all multi-mode fiber sizes are 50/125µm or 62.5/125µm, and the bandwidth (information transmission capacity of the fiber) is usually between 200MHz and 2GHz. Multi-mode optical transceivers can transmit up to 5 kilometers through multi-mode fibers. They use light-emitting diodes or lasers as light sources. The ring or external color is black. They can be divided into various wavelengths such as 850nm/1310nm/1550nm/1490nm/1530nm/1610nm. The SFP multi-mode module has a transmission distance of below 2KM at a wavelength of 850nm.
 
2. Single-mode SFP: The size of single-mode fibers is 9-10/125µm, and they have infinite bandwidth and lower loss compared to multi-mode fibers. Single-mode optical transceivers are mostly used for long-distance transmission, sometimes up to 150 to 200 kilometers. They use laser diodes or LEDs with narrower spectral lines as light sources. The ring or external color is blue, yellow, or purple. SFP single-mode modules have a transmission distance above 2KM at wavelengths of 1310/1550nm.
 

3. Here are some concepts and differences between single-mode and multi-mode SFP that I have learned:

3.1 Difference 1: They can be divided into various wavelengths such as 850nm/1310nm/1550nm/1490nm/1530nm/1610nm.

The modules with a wavelength of 850nm are multi-mode and have a transmission distance below 2KM, while those with a wavelength of 1310/1550nm are single-mode and have a transmission distance above 2KM. These three wavelengths are relatively cheaper compared to the other three.

3.2 Difference 2: Bare modules can be easily confused without identification. Generally, manufacturers distinguish them by the color of the ring.

For example, black ring modules are multi-mode with a wavelength of 850nm; blue modules have a wavelength of 1310nm; yellow or green modules have a wavelength of 1550nm; purple modules have a wavelength of 1490nm, and so on.

3.3 Difference 3: Single-mode fiber is cheaper, but single-mode devices are much more expensive compared to similar multi-mode devices.

Single-mode devices can run on both single-mode and multi-mode fibers, while multi-mode devices are limited to multi-mode fibers only.
 

3.4 Difference 4: Different applications

Single-mode modules are mostly used in line construction with relatively high transmission rates and long distances, such as metropolitan area networks. Multi-mode modules are suitable for short-distance transmissions with multiple network nodes and connectors. Additionally, multi-mode devices can only run effectively on multi-mode fibers, while single-mode devices can operate on both single-mode and multi-mode fibers, but the performance on multi-mode fibers is not guaranteed.

3.5 Difference 5: Different fiber types

 
Fibers can be divided into single-mode fibers and multi-mode fibers according to the transmission mode of the optical module in the fiber. The diameter of multi-mode fibers (MMF) is generally 50/125μm or 62.5/125μm, while the diameter of single-mode fibers (SMF) is 9/125μm.
 

3.6 Difference 6: Different light sources

The light source of single-mode modules is laser diodes (LD) or LEDs with narrower spectral lines, while the light source of multi-mode modules is light-emitting diodes (LEDs) or lasers.
 

4. Precautions for using single-mode and multi-mode modules.

4.1 When using single-mode modules, it is important to ensure that the actual received optical power is smaller than the overload optical power, so it is necessary to measure the transmitting and receiving optical powers and selectively use attenuators.
4.2 When using single-mode modules, there should be sufficient margin for received power.
4.3 Multi-mode modules can only transmit signals of one wavelength and cannot be used with multiplexers.
4.4 Multi-mode modules are limited to operation on multi-mode fibers.
 
With the convergence of single-mode and multi-mode SFP optical modules in recent years, the use of single-mode cables and modules has become mainstream. Single-mode has obvious advantages over multi-mode in terms of usage.