Generally speaking, there are two types of fibers: those that support multiple propagation paths or transverse modes are called multi-mode fibers (MMF), and those that support a single mode are called single-mode fibers (SMF). But what is the difference between them? Reading this article will help you get the answer.
Overview of Single Mode vs Multimode Fiber Optic Cable
Single mode fiber allows the propagation of only one light mode at a time, while multimode fiber can propagate multiple modes. The key differences between them are in fiber core diameter, wavelength & light source, bandwidth, color sheath, distance, cost, etc.
Single Mode vs Multimode Fiber, What is The Difference?
Time to compare single mode vs. multimode fiber and understand their differences.
Core Diameter
Single Mode Fiber has a small core size, typically 9µm, enabling lower attenuation, higher bandwidths, and longer transmission distances.
In contrast, Multimode Fiber has a larger core size, usually 62.5µm or 50µm, with OM1 at 62.5µm and OM2/OM3/OM4/OM5 at 50µm. Although there is a difference in size, it’s not easily visible to the naked eye as they are smaller than a human hair’s width. Checking the printed code on the fiber optic cable can help identify the type.
With a protective cladding, both single mode and multimode fibers have a diameter of 125µm.
Wavelength & Light Source
Multimode fiber, with its large core size, uses low-cost light sources like LEDs and VCSELs at 850nm and 1300nm wavelengths. In contrast, single mode fiber utilizes lasers or laser diodes to produce light injected into the cable, commonly at wavelengths of 1310nm and 1550nm.
Single Mode vs Multimode Wavelength & Light Source Comparison
| Compare | OM1 | OM2 | OM3 | OM4 | OM5 | OS2 |
| Wavelength | 850nm, 1300nm | 850nm, 1300nm | 850nm, 1300nm | 850nm, 1300nm | 850nm, 953nm, 1300nm | 1310nm, 1490nm, 1550nm, CWDM&DWDM |
Bandwidth
These two fiber types differ in bandwidth capabilities. Single-mode fiber offers nearly unlimited bandwidth due to its support for a single light source mode, resulting in lower attenuation and dispersion. It is the preferred choice for high-speed telecommunications over long distances.
On the other hand, multimode fiber can transmit multiple optical modes, but it has higher attenuation and larger dispersion, limiting its bandwidth.
Single-mode fiber outperforms multimode fiber in terms of bandwidth capacity.
Single Mode vs Multimode Bandwidth Comparison
| 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 |
Attenuation
Single-mode fiber has lower attenuation, while multimode fiber is more susceptible to attenuation.
Single Mode vs Multimode Attenuation Comparison
| 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 |
Distance
Single mode fiber’s lower attenuation and mode dispersion enable much longer transmission distances than multimode. Multimode is cost-effective but limited to short links (e.g., 550m for 1Gbps), while single mode is used for very long-reach transmission.
Single Mode vs Multimode Distance Comparison
| Fiber Type | 1000Base/1Gb（SX）Ethernet | 1000Base/1Gb（LX）Ethernet | 10Gb Ethernet | 40Gb Ethernet | 100Gb Ethernet |
| OS1/OS2 single mode fiber（1310nm） | 5Km | 20Km | 40Km | 40Km | 80Km |
| OM1 multimode fiber（850nm） | 275m | 550m | 33m | / | / |
| OM2 multimode fiber（850nm） | 550m | 550m | 82m | / | / |
| OM3 multimode fiber（850nm） | 550m | 550m | 300m | 100m | 100m |
| OM4 multimode fiber（850nm） | 550m | 550m | 550m | 150m | 150m |
| OM5 multimode fiber（850nm） | / | / | 550m | 440m | 150m |
Cost
When considering the total cost, three segments play a crucial role.
- Installation Cost
The installation cost for single-mode fiber is often perceived to be higher than multimode fiber due to its advantages. However, the reality is the opposite, thanks to more efficient manufacturing, saving 20-30% compared to multimode fiber. For the pricier OM3/OM4/OM5 fibers, single-mode can save up to 50% or more. However, the optical transceiver cost must also be taken into account. - Optical Transceiver Cost
The optical transceiver is a significant cost component in fiber cabling, accounting for a substantial portion, sometimes up to 70% of the total cost.
Single mode transceivers generally cost 1.2 to 6 times more than multimode ones. This is because single mode utilizes high-power laser diodes (LD), which are more expensive, while multimode devices typically use lower-cost LEDs or VCSELs. - System Upgrade Cost
With the rapid advancement in technology, cabling systems often require upgrades and expansion. Single mode fiber cabling offers greater scalability, flexibility, and adaptability.
Multimode fiber, due to its limited bandwidth and short distance capabilities, may struggle to meet future demands for long-distance and high-volume signal transmission.
Upgrading a single mode fiber system is more straightforward, involving only changing the switch and transceivers without the need to lay new fibers.
In contrast, for multimode fiber, upgrading from OM2 to OM3 and then to OM4 for higher-speed transmission would incur significantly higher costs, especially when changing the fibers laid under the floor.
In summary, multimode is cost-effective for short distances, while single mode is ideal for medium to long distances.
Color
Color coding simplifies cable type identification. TIA-598C provides the industry’s suggested color code for easy recognition.
- Multimode OM1 and OM2 usually have the orange jacket.
- OM3 usually have Aqua color jackets.
- OM4 usually have Aqua or Violet color jackets.
- OM5 was colored lime green.
- Single mode OS1 and OS2 typically with Yellow jackets.
Application
Single mode fiber is primarily used in long-distance backbone and metro systems in telecom, datacom, and CATV networks.
On the other hand, multimode fiber is mainly deployed in relatively short-distance applications such as data centers, cloud computing, security systems, and LANs (Local Area Networks).
Frequently Asked Question about Single Mode vs Multimode Fiber
Q: Which is better, single mode or multimode fiber?
A: Both have their advantages. Choose the one that best fits your application.
Q: How do I choose between single mode and multimode fiber?
A: Consider the required distance. Multimode is suitable for shorter distances, while single mode is for longer ones.
Q: How far can single mode fiber go?
A: Up to 160 kilometers, or more with dispersion-compensating fibers.
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 and 0.4dB/km for 1550nm sources.
Q: How far can multimode fiber go?
A: It varies with data speed and fiber type but is generally less than 2 kilometers.
Q: What is the acceptable dB loss for multimode fiber?
A: According to EIA/TIA 568, the MMF loss is about 3dB/km for 850nm and 1dB/km for 1300nm sources.
Q: How to identify single mode and multimode fiber?
A: Different color jackets: yellow for single mode, orange or aqua for multimode.
Q: Can I use a multimode transceiver on single mode fiber?
A: Generally no, as it results in high optical loss. However, the reverse can work with mode conditioning cables.
Q: Can I use single mode fiber for a short distance?
A: Yes, but you may need to add optical attenuation to avoid receiver overload or damage.
Q: Can multimode fiber support 10Gb?
A: Yes, but the link distance varies based on the grade. Use higher-grade OM3 or OM4 for 10Gb networks.
Conclusion
In conclusion, single-mode fiber cabling is ideal for long-reach data transmission in carrier networks, MANs, and PONs. Multimode fiber cabling, on the other hand, is more commonly used in enterprise, data centers, and LANs due to its shorter reach. The key is to choose the fiber type that best fits your network requirements while considering the total fiber cost. As a network designer, making this decision is crucial for an efficient and reliable network setup.
