Fiber Optic Cable Types : Single Mode vs Multimode Fiber Cable
Although single mode fiber (SMF) and multimode fiber (MMF) optic cable types are widely used in diverse applications, the differences between single mode fiber and multimode fiber optic cables are still confusing. This article will focus on the basic construction, fiber distance, cost, fiber color, etc., to make an in-depth comparison between single mode and multimode fiber types.
Overview of Single Mode vs Multimode Fiber Optic Cable
Single mode means the fiber enables one type of light mode to be propagated at a time. While multimode means the fiber can propagate multiple modes. The differences between single mode and multimode fiber optic cable mainly lie in fiber core diameter, wavelength & light source, bandwidth, color sheath, distance and cost.
Single mode fiber core diameter is much smaller than multimode fiber. Its typical core diameter is 9 µm even if there are others available. And multimode fiber core diameter is 50 µm and 62.5 µm typically, which enables it to have higher "light gathering" ability and simplify connections. The cladding diameter of single mode and multimode fiber is 125 µm.
The attenuation of multimode fiber is higher than SM fiber because of its larger core diameter. The fiber core of single mode cable is very narrow, so the light that passes through these fiber optical cables is not reflected too many times, which keeps the attenuation to a minimum.
|9/125 Single Mode Fiber Simplex
|50/125 OM3 Multimode Fiber
|Attenuation at 1310nm
|Attenuation at 850 nm
|Attenuation at 1550nm
|Attenuation at 1300 nm
Wavelength & Light Source
Due to the large core size of multimode fiber, some low-cost light sources like LEDs (light-emitting diodes) and VCSELs (vertical cavity surface-emitting lasers) that works at the 850nm and 1300nm wavelength are used in multimode fiber cables. While the single mode fiber often uses a laser or laser diodes to produce light injected into the cable. And the commonly used single mode fiber wavelength is 1310 nm and 1550 nm.
Multimode fiber bandwidth is limited by its light mode and the maximum bandwidth at present is 28000MHz*km of OM5 fiber. While single mode fiber bandwidth is unlimited theoretically because it allows only one light mode to pass through at a time.
According to the TIA-598C standard definition, for non-military applications, single mode cable is coated with yellow outer sheath, and multimode fiber is coated with orange or aqua jacket. Find more details about the Fiber Optic Cable Color Code here.
Single Mode vs Multimode Fiber Distance
It’s known that single mode fiber is suitable for long-distance applications, while multimode optical fiber is designed for short-distance runs. Then when it comes to single mode vs multimode fiber distance, what’s the quantifiable differences?
|Fiber Optic Cable Type
|Fast Ethernet 100BA SE-FX
|1Gb Ethernet 1000BASE-SX
|1Gb Ethernet 1000BA SE-LX
|10Gb Base SE-SR
|25Gb Base SR-S
|40Gb Base SR4
|100Gb Base SR10
|Single mode fiber
|550m(mode conditioning patch cable required)
From the chart, we can see that single mode fiber distance is much longer than that of multimode fiber cables at the data rate from 1G to 10G, but OM3/OM4/OM5 multimode fiber supports a higher data rate. Because multimode optical fiber has a large core size and supports more than one light mode, its fiber distance is limited by modal dispersion which is a common phenomenon in multimode step-index fiber. While single mode fiber is not. That’s the essential difference between them. In addition, OS2 single mode fiber could support longer distances in 40G and 100G links, which is not listed in the table.
Single Mode vs Multimode Fiber Cost
“Single mode vs multimode fiber cost” is a hot topic in some forums. Numbers of people have expressed their own opinions. Their views mainly focus on the optical transceiver cost, system cost and installation cost.
Frequently Asked Question about Single Mode vs Multimode Fiber Optic Cable
Q: What is better single mode or multimode fiber type?
A: As has been mentioned above, single mode fiber and multimode fiber cable have their own advantages on cost and applications. There is no such thing that single mode optical fibers are better than multimode ones. Just choosing the best-fit one for your applications is ok.
Q: Can I mix single mode and multimode fiber type?
A: This answer for this question is “no”. Multimode fiber and single mode fiber have different core sizes, and the number of light modes that they transmit is also different. If you mix the two fibers, or connect them together directly, you’ll lose a large amount of optical loss, resulting in a link flapping or being down. Keep in mind that never mix different types of cabling randomly.
Q: Can I use a multimode transceiver on single mode fiber optic cable?
A: Generally speaking, the answer is "no". Large optical loss will occur if a multimode transceiver is connected with single mode fiber. However, the opposite will work. For example, 1000BASE-LX single mode SFP can work on multimode fiber cable by using mode conditioning fiber cable. Sometimes, fiber media converters also can be used to solve such problems between single mode transceivers and multimode transceivers.
Q: Single mode vs multimode fiber optic cable type: which should I choose?
A: When making a decision between single mode and multimode fiber cables, the first factor to consider is the fiber distance which you need actually. For example, in a data center, multimode fiber cables are enough for the distance of 300-400 meters. While in applications that require distance up to several thousands of meters, the single mode fiber is the best choice. And in applications that can use single mode and multimode fiber, other factors like cost and future upgrade requirements should be taken into consideration for your choice.
From the comparison between single mode vs multimode fiber optic cable, it can con
Contact Person: Mrs. Alice