Emerging demand of higher bandwidth and faster speed connections has significantly enhanced the growth of fiber optic cable assemblies market over the past several years, especially the single mode fiber (SMF) and multimode fiber cable (MMF). However, though these two types of optical cables are widely used in diverse applications, the problem—single mode vs multimode fiber: what’s the difference—is still confusing. Therefore, the following article will focus on the basic construction, fiber distance, cost and fiber color, to make an in-depth comparison between single mode and multimode fiber.
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 difference between single mode and multimode fiber mainly lies in fiber core diameter, wavelength, light source and bandwidth.
Single mode fiber core diameter is much smaller than multimode fiber. The typical core diameter is 9µm even if there are others available. And multimode fiber core diameter is 50µm and 62.5µm typically, which enables it has higher “light gathering” ability and simplify connections. The cladding diameter of single mode and multimode fiber is 125µm.
Due to the large core size if 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 1310nm wavelength are used in multimode fiber cables. While the single mode often uses a laser or laser diodes to produce light injected into the cable. And the commonly used single mode fiber wavelength is 1310nm and 1550nm.
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 due to it allows one light of mode to pass through at a time.
In addition, there are also some differences between single mode and multimode fiber color, read the article to get clear infro: How to Identify the Fiber Optic Cable Color Code?
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||Fiber Cable Distance|
|Fast Ethernet 100BA SE-FX||1Gb Ethernet 1000BASE-SX||1Gb Ethernet 1000BA SE-LX||10Gb Base SE-SR||40Gb Base SR4||100Gb Base SR10|
|Single mode fiber||OS2||200m||5000m||5000m||10km||/||/|
|Multimode fiber||OM1||200m||275m||550m (mode conditioning patch cable required)||/||/||/|
From the chart, we can see as 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 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 model dispersion which is a common phenomenon in multimode step-index fiber. While single mode fiber is not. That’s the essential difference between them.
“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.
Compared to single-mode transceivers, the price of multimode transceivers is nearly two or three times lower. The following table takes FS.COM Cisco compatible single-mode transceivers and multimode transceivers as an example.
|Speed||Transceiver||Transceiver Description||Price||Price Difference|
|1G||Single-mode SFP||Cisco GLC-LH-SMD Compatible 1000BASE-LX/LH SFP 1310nm 10km DOM Transceiver||US$ 7.00||US$ 1.00|
|Multimode SFP||Cisco GLC-SX-MMD Compatible 1000BASE-SX SFP 850nm 550m DOM Transceiver||US$ 6.00|
|10G||Single-mode SFP+||Cisco SFP-10G-LR Compatible 10GBASE-LR SFP+ 1310nm 10km DOM Transceiver||US$ 34.00||US$ 18.00|
|Multimode SFP+||Cisco SFP-10G-SR Compatible 10GBASE-SR SFP+ 850nm 300m DOM Transceiver||US$ 16.00|
|40G||Single-mode QSFP+||Cisco QSFP-40G-LR4 Compatible 40GBASE-LR4 and OTU3 QSFP+ 1310nm 10km LC DOM Transceiver||US$ 340.00||US$ 285.00|
|Multimode QSFP+||Cisco QSFP-40G-SR4 Compatible 40GBASE-SR4 QSFP+ 850nm 150m MTP/MPO DOM Transceiver||US$ 55.00|
|100G||Single-mode QSFP28||QSFP28 Cisco QSFP-100G-LR4-S 100GBASE-LR4 1310nm 10km Compatible Transceiver||US$ 2800.00||US$ 2400.00|
|Multimode QSFP28||QSFP28 Cisco QSFP-100G-SR4-S Compatible 100GBASE-SR4 850nm 100m Transceiver||US$ 400.00|
From the table, we can see that the price difference gains greatly with the speed increasing.
To utilize the fundamental attributes of single-mode fibers, which are generally geared towards longer distance applications, requires transceivers with lasers that operate at longer wavelengths with smaller spot-size and generally narrower spectral width. These transceiver characteristics combined with the need for higher-precision alignment and tighter connector tolerances to smaller core diameters result in significantly higher transceiver costs and overall higher interconnect costs for singe-mode fiber interconnects.
Fabrication methods for VCSEL based transceivers that are optimized for use with multimode fibers are more easily manufactured into array devices and are lower cost than equivalent single-mode transceivers. Despite the use of multiple fiber lanes and multi-transceivers arrays, there are significant cost saving over single-mode technology employing single or multichannel operation over simplex-duplex connectivity. Multimode fiber system offers the lowest system cost and upgrade path to 100G for standard-based premises applications using parallel-optic based interconnects.
Single-mode optical fiber often costs less than multimode fiber. When building a 1G fiber optic network that you want to be able to go to 10G or faster on eventually, the savings on cost of fiber for single-mode saves about half-price. While the multimode OM3 or OM4 fiber increase 35% in cost for SFP modules. The single-mode optics are more expensive, but the labor costs of replacing the multimode are significantly higher, especially if those followed OM1—OM2—OM3—OM4. If you are willing to look at used ex-fiberchannel SFPs, the price of single-mode 1G drops through the floor. If you have budget and need for 10G short connections, the economics at last check still support multimode. Keep an eye on those economics though, as history suggests that the price premium for single-mode will drop.
As has 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.
This answer for this question is “no”. Multimode fiber and single mode fiber have different core size, and the numbers of light mode that they transmit is also different. If you mix the two fibers, or connect them together directly, you’ll lose large amount of optical loss, resulting in a link flapping or being down. Keep in mind that never mix different types of cabling randomly.
Generally speaking, the answer is “no”. Large optical loss will occur if 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 converter also can be used to solve such problems between single mode transceiver and multimode transceiver.
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 is 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 which 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—single mode vs multimode fiber, it can conclude that both single-mode optics and multimode optics have their own features. Single-mode fiber cabling system is suitable for long-reach data transmission applications and widely deployed in carrier networks, MANs and PONs. Multimode fiber cabling system has a shorter reach and is widely deployed in enterprise, data centers and LANs. No matter which one you choose, on the basis of total fiber cost, choosing the one that best suits your network demands is an important task for every network designer.
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