Difference between single mode and multimode sfp module

With the rapid development of data centers and 5G applications, optical modules have gradually become known to more and more people and are widely used. As we all know, optical modules can be distinguished based on parameter types, such as the often-mentioned single-mode optical modules and multimode optical modules. Do you know what single-mode and multimode mean in these modules? What are the differences between them? And how to choose under different application scenarios? This article will explain the differences between the two and how to choose. You can continue reading with these questions in mind.

Multimode SFP:

Almost all multimode optical fiber sizes are 50/125µm or 62.5/125µm, with a bandwidth typically ranging from 200MHz to 2GHz. Multimode optical terminals can transmit up to 5 kilometers through multimode fibers and use LEDs or lasers as light sources. The loop or external color is black.

Single-mode SFP:

Single-mode fiber has a size of 9-10/125µm and has infinite bandwidth and lower loss characteristics compared to multimode fiber. Single-mode optical terminals are often used for long-distance transmissions, sometimes up to 150 to 200 kilometers. LD or narrow-spectrum LEDs serve as the light source. The loop or exterior color is blue, yellow, or purple.

Here are some concepts and differences between single-mode and multimode SFPs:

Difference 1:

Based on wavelengths, we have 850nm/1310nm/1550nm/1490nm/1530nm/1610nm. The 850nm wavelength is for multimode SFP with a transmission distance of less than 2Km, while 1310/1550nm wavelengths are for single-mode with a transmission distance of more than 2Km. Among them, the first three have a relatively lower cost than the latter three.

Difference 2:

Bare modules can easily be confused if not labeled. Manufacturers typically differentiate by the color of the loop: black is for multimode with an 850nm wavelength; blue is for 1310nm modules; yellow or green is for 1550nm modules, and purple is for 1490nm modules.

Difference 3:

Single-mode fiber is cheaper, but single-mode devices are much more expensive than their multimode counterparts. Single-mode devices can operate on both single-mode and multimode fibers, while multimode devices are limited to operating on multimode fibers.

Difference 4:

The types of fibers differ. They can be divided into single-mode (SMF) and multimode fibers (MMF) based on the transmission mode in the optical module. MMF typically has a diameter of 50/125µm or 62.5/125µm, while SMF is 9/125µm.

Difference 5:

Light sources differ. Single-mode modules use LD or narrow-spectrum LEDs, while multimode modules use LEDs or lasers.

Difference 6:

Applications differ. Single-mode modules are often used in lines with relatively high transmission rates and long distances, such as in metropolitan area networks. Multimode modules are often used for short-distance transmissions and are ideal for transmissions with many nodes and connectors.

Furthermore, while multimode devices can only effectively operate on multimode fibers, single-mode devices can run on both but might not guarantee effective performance on multimode fibers.

How to distinguish between single-mode and multimode optical modules: Single-mode (SM) modules are versatile and suitable for long-distance data transmission, while multimode (MM) modules can transmit light in multiple modes, suitable for short-distance transmission. The terms "single-mode" and "multimode" in optical modules refer to the type of fiber connected to the module.

Tips for using single-mode and multimode optical modules:

1.When using a single-mode module, ensure that the received optical power is less than the overload power. Consider measuring transmission and reception power, then selectively use optical attenuators.

2.The received power should have a margin when using single-mode modules.

3.Multimode modules can only send one wavelength signal and cannot be used with multiplexers.

4.Multimode modules are limited to operating on multimode fibers.

Frequently Asked Questions:

While we've detailed the concepts and differences between single-mode and multimode modules, many users still have questions:

Can single-mode modules connect to multimode fibers? For short-distance transmissions, they can. However, due to significant dispersion, performance isn't guaranteed. It's recommended to connect single-mode modules with single-mode fibers and avoid multimode fibers.

Can multimode modules connect to single-mode fibers? No, they cannot. This may cause significant loss and even communication failure.

Can single-mode and multimode modules be used interchangeably? In theory, if both module signals can be received and the optical power is within the reception range, they can. For instance, 100M LX single-mode and 100M FX multimode modules can be used interchangeably. However, this isn't recommended for modules above 1G.

Conclusion:

Through this article, you should have a clearer understanding of single-mode and multimode optical modules. To avoid link failures, it's recommended to choose based on your actual application needs. More importantly, it's best not to mix and match single-mode and multimode fibers and modules.