Single Mode vs Multimode Fiber, What is The Difference?

Initial Published: December 22, 2022

In this in-depth single mode vs. Multimode Fiber comparison, I will compare those two fiber optic cables, helping you learn the difference and determine which best suits your fiber cabling system.

In this post, I’ll discuss how both Multimode and Single mode fiber compare in terms of:

• Core diameter
• Wavelength
• Bandwidth
• Attenuation
• Color code
• Distance
• Cost
• Application
• FAQs

But first, what exactly are single mode and multimode fiber?

What is single mode fiber? 

Single mode fiber, short as SMF, is a fiber cable that only allows one mode of light to transmit. Typically, this fiber includes a small light-carrying core of about 9µm diameter. These feature a small modal dispersion for vast-distance signal transmission.

In contrast with multimode fiber, single mode enables the concentration of light to travel quicker and farther, which is crucial for high-speed networks over a long distance. 

What is multimode fiber?

Unlike single mode, multimode fiber (MMF) allows multiple light modes to transmit and pass through. Typically, this fiber includes a large light-carrying core of about 50µm or 62.5µm diameter. That makes manufacturing easier and offers a lower cost ratio on the same length.

However, modal dispersion limits the most significant length of transmission connections. So, these fibers are mainly for the short-distance transmission of signals.

Commonly, multimode fiber can be divided into five types:

• OM1: it has a diameter of 62.5µm and an orange jacket. With 200/500 MHz*km overfilled launch (OFL) bandwidth at 850/1300nm, it is suitable for 100 Megabit and 1G Ethernet applications. 
• OM2: it has a diameter of 50µm and an orange jacket. With 200/500 MHz*km overfilled launch (OFL) bandwidth at 850/1300nm, it is suitable for 100 Megabit, 1G, and 10G Ethernet applications. 
• OM3: The laser-optimized MMF fiber supports 2000 MHz*km effective modal bandwidth. With a diameter of 50µm and an aqua jacket.
• OM4: A further laser-optimized fiber supports 4700 MHz*km EMB bandwidth. Sutitable for 10 Gb/s, 40 Gb/s, and 100 Gb/s transmissions.
• OM5: also known as WBMMF (wideband multimode fiber), uses two fibers to transfer data at speeds ranging from 40 GB/s, 100 GB/s and 400 GB/s. 

Single mode vs multimode fiber, what is the difference?

Now that we have learned their definitions, it is time to compare their differences.

Based on the different factors, we took the below benchmarks into their comparison.

1. Core Diameter

Single mode and multimode fibers have different physical core dimensions.

The figure below shows the different core diameters compared.

The core size of single mode fibers is small, with the most common typical diameter being 9µm, although other sizes are available. It has lower attenuation, supporting higher bandwidths and longer transmission distances.

The multimode core size is much larger, typically 62.5µm or 50µm. Depending on the fiber type, OM1 is 62.5µm in diameter, while OM2/OM3/OM4/OM5 are all 50µm in diameter. 

Although there is a clear difference in size, it isn’t easy to see these differences with the naked eye. That is because they are all smaller than the width of human hair. Usually, you can check the printed code on the fiber optic cable to see. 

However, single mode and multimode fibers are 125µm in diameter if they have protective cladding.

2. Wavelength

Multimode fiber is usually suitable for 850nm and 1300nm short wavelengths. Because it has a large fiber core, the industry can offer the transceiver with lower-cost components like LEDs (light-emitting diodes) and VCSELs (vertical-cavity surface-emitting lasers). 

Compare	OM1	OM2	OM3	OM4	OM5	OS2
Wavelength	850nm, 1300nm	850nm, 1300nm	850nm, 1300nm	850nm, 1300nm	850nm, 953nm, 1300nm	1310nm, 1490nm, 1550nm, CWDM&DWDM

Single mode usually supports long wavelengths like 1310nm, 1490nm, 1550nm, and WDM. A tiny fiber core diameter allows for highly accurate coupling and a much longer distance. The wavelength is usually created by FP, DFB, and EML light sources.

3. Bandwidth

These two types of fibers offer different bandwidths. Let’s make a simple comparison.

Because single mode fiber optic cable supports a single light source mode, it has lower attenuation and less dispersion. As a result, it can provide a nearly unlimited amount of bandwidth. That makes it the preferred choice for high-speed interconnections over long distances in telecommunications.

Compare	OM1	OM2	OM3	OM4	OM5	OS2
Minimum overfilled modal bandwidth length	200MHz-km @850nm 500MHz-km @1300nm	500MHz-km @850nm 500MHz-km @1300nm	1500MHz-km @850nm 500MHz-km @1300nm	3500MHz-km @850nm 500MHz-km @1300nm	3500MHz-km @850nm 1850MHz-km @953nm 500MHz-km @1300nm	NA
Minimum effective modal bandwidth length	Not required	Not required	2000 MHz-km@850nm	4700MHz-km @850nm	4700MHz-km @850nm	NA

However, a multimode fiber optic cable can transmit in multiple optical modes. Moreover, the attenuation is high, and the dispersion is large. This is why its bandwidth is limited. 

In this regard, single-mode fiber is the winner.

4. Attenuation

Typically, single mode fiber has lower attenuation than multimode fiber, which is more vulnerable to attenuation. 

The table below compares fiber attenuation.

Compare	OM1	OM2	OM3	OM4	OM5	OS2
Maximum attenuation	3.5dB/km @850nm 1.5dB/km @1300nm	3.5dB/km @850nm 1.5dB/km @1300nm	3.0dB/km @850nm 1.5dB/km @1300nm	3.0dB/km @850nm 1.5dB/km @1300nm	3.0dB/km @850nm 2.3dB/km @953nm 1.5dB/km @1300nm	0.5dB/km @1310nm 0.5dB/km @1550nm

5. Color Code

Different colors allow us to distinguish cable types easily. TIA-598C defines the suggested color code for the industry. 

• Multimode OM1 and OM2 usually have the orange jacket. 
• OM3 and OM4 usually have Auqa color jackets.
• OM5 was colored green.
• Single mode OS1 and OS2 typically with Yellow jackets.

6. Distance

Due to the less attenuation and mode dispersion, single mode provides a much longer transmit distance than multimode. 

As a result, multimode fiber cabling is only used in short links (e.g., 550m for 1Gbps) while providing low cost. However, single mode cabling is mainly used for very long-reach transmission. 

Compare	OM1	OM2	OM3	OM4	OM5	OS2
Distance	200m (100Mbps) 275m (1Gbps)	200m (100Mbps) 275m, (1Gbps) 82m (10Gbps)	200m (100Mbps) 550m, (1Gbps) 300m, (10Gbps) 100m, (40Gbps) 100m,(100Gbps) 100m (400Gbps)	200m (100Mbps) 550m (1Gbps) 400m (10Gbps) 150m (40Gbps) 150m (100Gbps) 100m (400Gbps)	200m (100Mbps) 550m (1Gbps) 400m (10Gbps) 300m (40Gbps) 300m (100Gbps) 100m (400Gbps) 100m (800Gbps)	180km (100Mbps) 180m (1Gbps) 100km (10Gbps) 80km (40Gbps) 80km (100Gbps) 80km (400Gbps) 80km (800Gbps)

7. Cost

When discussing it, we consider the total cost based on three segments: fiber cabling, transceiver, and system upgrade. Now, let us discuss the details of that cost.

7A. Fiber cabling cost

Because of the many advantages of single mode fiber, many people might think that single-mode cable is more expensive than multimode cable.

However, the opposite is true. Isn’t that strange? 

The reason is that single-mode fiber is more efficient to manufacture, saving an average of 20~30% compared to multimode fiber. If you consider the more expensive OM3/OM4/OM5 fibers, single mode can save about 50% or even more.

However, we must consider another critical cost – the optical transceiver.

7B. Transceiver cost

As an essential segment of fiber cabling, the optical transceiver takes up a large percentage of the cost-sharing. Sometimes, it may share 70% of the total cost.

In most cases, single mode transceivers typically cost 1.2~6 times more than multimode. Because single mode usually utilizes a high-power laser diode (LD), which is much more expensive. Meanwhile, multimode devices typically use the lower-cost LED or VCSEL laser. 

Taking the Optcore transceiver as an example, we compare the costs in the table below. 

Transceiver	Description	Price
Single mode SFP	Generic 1000BASE-LX/LH SFP 1310nm 20km Transceiver	US$ 5.90
Multimode SFP	Generic 1000BASE-SX SFP 850nm 550m Transceiver	US$ 5.90
Single mode SFP+	Generic 10GBASE-LR SFP+ 1310nm 10km Transceiver	US$ 15.00
Multimode SFP+	Generic 10GBASE-SR SFP+ 850nm 300 Transceiver	US$ 11.00
Single mode SFP28	Generic 25GBASE-LR SFP+ 1310nm 10km Transceiver	US$ 37.00
Multimode SFP28	Generic 25GBASE-SR SFP+ 850nm 100 Transceiver	US$24.00
Single mode QSFP28	Generic 100GBASE-LR4 QSFP28 1310nm 10km Transceiver	US$ 49.90
Single mode QSFP28	Generic 100GBASE-SR4 QSFP28 850nm 100m Transceiver	US$ 329.00

7C. System upgrade cost

The dramatic growth in thought drives the cabling system to upgrade and expand. Generally speaking, single mode fiber cabling provides more scalability, flexibility, and elasticity.

Due to its limited bandwidth and short distance, multimode fiber will make it challenging to meet future long-distance and high-volume signal transmission needs.

Plus, for the single mode fiber, you could easily upgrade the system by changing only the switch and transceivers; you don’t need to lay any new fibers.

For multimode fiber, you must replace the OM2 with OM3 and then OM4 for higher-speed transmission. However, changing the fibers Lying underneath the floor will cost much more.

To summarize, MMF provides a lower total cost for short distances. Single mode fiber is the best choice for medium to long distances.

Sidenote: When comparing systems, remember to consider the total cost. Consider the cost of all three parts instead of only one. Otherwise, your system may cost more, even though you save on the single fiber cabling.

8. Application

Given the above comparison, single mode is mainly for long-distance backbone and metro systems in telecom, datacom, and CATV networks. 

Multimode fiber is mainly used for comparatively short-distance applications, such as data centers, cloud computing, security systems, and LANs (Local Area Networks). 

Single Mode vs Multimode Fiber FAQs

Q: How far can single mode fiber go?

A: For most applications, the maximum distance of single mode cable is around 160 kilometers. However, the dispersion-compensating fibers can support more than 200 kilometers.

Q: How far can multimode fiber go?

A: It varies with the data speed and fiber type. Take the common OM2 as an example. It supports a maximum of 550m at 1Gbps and 82m at 10Gbps. However, the maximum distance for all multimode fibers will be less than 2km.

Q: What is the acceptable dB loss for single mode fiber?

A: According to EIA/TIA 568, the SMF loss is around 0.5dB/km for 1310nm sources and 0.4dB/km for 1550nm sources. 

Q: What is the acceptable dB loss for multimode fiber?

A: According to EIA/TIA 568, the MMF loss is around 3dB/km for 850nm sources and 1dB/km for 1300nm sources. 

Q: Can I use multimode fiber with single mode?

A: No, you can not. Because they have different core diameters and transmit a different number of light modes, mixing the two fibers or connecting them directly will incur a significant optical loss, resulting in a link flapping or going down. 

Q: How do you identify single-mode and multimode fiber?

A: Identify most fibers with different-colored jackets. Yellow stands for Single mode, while Orange or Aqua stands for multimode.

Q: Can I use single mode fiber for a short distance?

A: Yes, it may be. However, you must add appropriate optical attenuation to avoid overloading or damaging the receiver. 

Q: Can multimode fiber support 10gb?

A: All multimode fiber supports 10Gb, but the link distance varies depending on the data speed. OM1 only supports a max of 33m, and OM2 supports 82m. So, it is not recommended to use OM1 and OM2 for 10G networks. Using higher-grade OM3, OM4, or OM5 fiber for 10Gb networks is better.

Q: Can a multimode transceiver be used with single mode fiber?

A: In general, no. A significant optical loss will result if a multimode transceiver connects with a single mode fiber. However, the reverse will work. For example, utilizing mode conditioning fiber cable, a 1000BASE-LX single mode transceiver may function on a multimode fiber with reduced distance. 

Q: Is single mode better than multimode fiber?

A: In most cases, single mode fiber provides better performance and wide application. However, we can not say it is better than multimode fiber because of its cost and advantages in application. Therefore, you should choose the best one based on your application and budget.

Final words

After reading this post, we know the main difference between single mode and multimode fiber. Simple to say, is the core size, light mode, distance, bandwidth, and application. Multimode cable is widely used in LANs, enterprises, cloud computing, and data centers. Singlemode is suitable for medium and long-reach applications, such as telecom, datacom, and CATV networks.

Remember to calculate the total system cost and consider future bandwidth needs regardless of which fiber you choose. It will save you more in the future.

Read more:

• What is SFP Module? An Ultimate Guide
• Understanding Armored Fiber Optic Cable: A Beginner Guide
• Fiber Optic Cable Basics Tutorial
• 16 Tips On How To Save Fiber Cabling Cost

Reference:

• https://www.thefoa.org/tech/loss-est.htm
• https://www.geeksforgeeks.org/single-mode-vs-multimode-fiber-cable/