Today, the transmission of optical fiber globally takes only a few seconds, receives information or images, videos. Compared to copper cables, information is being transmitted faster with higher speeds and its quality remains unchanged.
Not to mention the demand for higher bandwidth and faster speed connections has significantly boosted the growth of the optical fiber assembly market for years, especially Single Mode (SM) and Multimode (MM). However, although these two types of optical fiber are widely used in diverse applications, the difference of these two fiber is still not widely understood.
Therefore, the following article will focus on the basic structure, fiber distance, and fiber color, to compare deeply between Single Mode and Multimode.
1. Overview of Single Mode and Multimode
Single Mode optical fiber can only transmit 1 light at a time.
While Multimode can transmit up to 3 different types of light rays, causing dispersion which is not available in Single Mode optical fiber.
Therefore, the basic difference between SM and MM lies in the fiber core diameter, wavelength, light source, and bandwidth.
1.1. Fiber core diameter
The diameter of SM's fiber core is much smaller than that of MM.
SM: 9µm even if there are more parts.
MM: 50µm (OM1) and 62.5µm (OM2, OM3, OM4). Allow it to be able to collect higher light and simplify connections.
The cladding department, also known as the light reflection layer of both SM and MM, has a diameter of 125µm.
1.2. Wavelength and light source
SM is often used in laser diodes or lasers to produce light that is inserted into the cable, so the commonly used wavelength is 1310nm and 1550nm.
And MM due to its large core diameter should work better at the wavelength of 850nm and 1310nm, suitable for light emitting diodes (LEDs) and longitudinal surface emitting lasers (VCSEL)
1.3. Bandwidth
Theoretically, the bandwidth of SM optical fiber is not limited because it allows the light of passing mode at a time.
MM optical fiber has different types of bandwidth depending on each type:
- OM1: core diameter 62.5 μm, bandwidth reaches 200/500 MHz-km at wavelength of 850/1300 nm.
- OM2: core diameter of 50 μm, bandwidth of 500/500 MHz-km at wavelength of 850/1300 nm.
- OM3: 50 μm core diameter, laser emission source to increase bandwidth up to 2000 MHz-km, support 10 GE applications.
- OM4: 50 μm core diameter, 2 times more active bandwidth than OM3, reaching 4700 MHz-km, specially designed for 10, 40 and 100 GE applications.
2. The distance between SM and MM
It is known that optical fiber SM is suitable for long-distance applications, while MM optical fiber is designed to transmit short distances.
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Types of optical fiber
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Optical fiber distance
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|
Fast Ethernet
100BASE-FX
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1Gb Ethernet
1000BASE-SX
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1Gb Ethernet
1000BASE-LX
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10Gb Base
SE-SR
|
40Gb Base
SR4
|
100Gb Base
SR10
|
|
SM
|
OS2
|
200m
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5000m
|
5000m
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10km
|
/
|
/
|
|
MM
|
OM1
|
200m
|
275m
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550m (requires air condition patch mode)
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/
|
/
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/
|
|
OM2
|
200m
|
550m
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/
|
/
|
/
|
|
OM3
|
200m
|
550m
|
300m
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100m
|
100m
|
|
OM4
|
200m
|
550m
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400m
|
150m
|
150m
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From the chart, we can see that the SM fiber distance is much longer than the MM at 1G to 10G data rate, but the multi-mode OM3 / OM4 multimode fiber supports higher data rates. Because MM optical fiber has a large core size and supports more than one light mode, its fiber distance is limited by model dispersion, a common phenomenon in the MM step number thread. While SM yarn is not. That is the necessary difference between them.