Difference between Single Mode SFP and Multimode SFP

Increase in demand for higher bandwidth and fast speed requirement has enhanced the growth of fiber optic cable assemblies market. Singlemode SFP and multimode SFP both work with different types of optical fibers i:e single mode fiber and multimode respectively. Both are used in diverse applications but the major differences are still confusing. In this article, we will focus on the transmission factors such as data rate, distance, attenuation, time to travel and so on. Other factors like dimensions, color and types are also included to make an in-depth comparison between single mode and multimode fiber.

Singlemode SFP

Single-mode SFP has tighter tolerances for optic used. The core is smaller and thus laser wavelength is narrower. This directly states that SMF has the capability to carry out a higher bandwidth at much longer transmission distances. Single mode work mainly in the 1310nm and 1550nm wavelengths and is mostly used in a long distances transmission environment reaching (2-10-40-60-80-120) km. The bale clasp and color arrow on labels are generally blue, yellow or purple and color of compatible fiber optic patch cord is yellow.

• Blue is the 1310nm module
• Yellow is the 1550nm module
• Purple is the 1490nm module

Multimode SFP

Multimode Fiber uses a much bigger core than Singlemode SFP and uses a longer wavelength of light. So, the optics used in MMF has a higher capability to gather light from the laser. In terms of cost, this means the optics are cheaper. The common multimode SPF work in 850 nm wavelength and is only used for short distance transmission reaching 100m and 500m. It can transport many kinds of optical signals though it’s not able to transport for long distance. The bale clasp and color arrow on labels are black and fiber optic patch cord used is usually orange.

Comparison of factors:

1. Core Diameter As discussed earlier single mode fiber core diameter is much smaller than multimode’s. The typical core diameter is 9µm even if there are various sizes available. Multi-mode fiber has a core diameter of 50µm and 62.5µm, which shows it has a higher “light gathering” ability and simplify connections. The cladding diameter of single mode and multimode fiber is the same 125µm.
   
   
2. Wavelength & Light Source Low-cost light sources like light-emitting diodes (LEDs) and vertical cavity surface-emitting lasers (VCSELs) are used in multimode fiber cables. These work at 850nm and 1310nm wavelength and are best for large core size of the multimode fiber. On another hand, single-mode often uses a laser or diodes to produce light which is injected into the cable. The wavelength of 1310nm and 1550nm is used commonly for single mode fiber.
3. Bandwidth Multimode fiber bandwidth is limited by its light mode and the maximum bandwidth is 28000MHz*km of OM5 fiber. The single mode fiber bandwidth is unlimited and it allows one light of mode to pass through at a time.

Single Mode vs Multimode Fiber Distance

We read in the above sections that single-mode fiber is suitable for long distance applications, and the multimode optical fiber is designed for short distance runs.

In multimode optical fiber, distance is limited by model dispersion due to large core size and support of more than one light mode.

Installation Cost

Single-mode optical fiber costs less than multimode fiber. When building a 1G fiber optic network that has to go 10G or faster, the savings on the cost of fiber for single-mode saves about half-price. Though single-mode optics are more expensive, the labor costs of replacing the multimode are significantly higher in OM1-OM2-OM3-OM4. 

Finally, when we are choosing the SFP module, we must confirm the transmission distance and wavelength we want to use it. This helps to choose the right SFP types more efficiently.