The multimode fiber optic cable is commonly applied in short distance communication. It has the properties of low insertion loss, good repeatability, high return loss and excellent temperature stability, which is largely used nowadays. However, it has a serious disadvantage of large dispersion. The longer the distance the signal transmits, the larger the dispersion is. Therefore, the multimode fiber optic cable is suggested to be used in the applications for short distance transmission.
Comparison With Single-mode Fiber Optic Cable
Clearly different from the single-mode fiber optic cable, the multimode fiber optic cable can carry more than one light signal in the different modes, which requires a much longer diameter of its core. In general, the core diameter of multimode fiber optic cable is about 50-100 µm. However, because of its large dispersion, the multimode fiber optic cable is only suitable for short communication.
Figure 1. Structure of single-mode fiber optic cable and multimode fiber optic cable
Furthermore, the multimode fiber optic cable is only suitable in 1 Gigabit Ethernet., while the single-mode fiber optic cable is able to transmit signals in 10 Gigabit Ethernet. But considering the manufacturing cost of single-mode fiber optic cable, it can’t be largely used in 10 Gigabit Ethernet. Therefore, improving the performance of multimode fiber optic cable to support 10 Gigabit Ethernet has become an inexorable trend.
Development of Multimode Fiber Optic Cable
With the improvement of network applications, 10 Gigabit Ethernet seems to have been inevitable. To meet the requirement of fiber optic market, the advanced multimode fiber optic cables are developed which can be also applied in 10 Gigabit Ethernet. As for the cost, the advanced multimode fiber optic cable is a little bit more expensive than original multimode fiber optic cable.
At present, there are four types of multimode fiber optic cables in fiber optic market, OM1, OM2, OM3 and OM4. The word “OM” is the acronym of optical multimode.
As for the four types of multimode fiber optic cables, they have different properties and can be used in different applications. In general, OM1 is always used to support 100 Megabit Ethernet applications; while OM2 is more commonly applied in 1 Gigabit Ethernet. As for OM3, it is designed to support the applications of 10 Gigabit Ethernet. And OM4 is more superior which can support 100 Gigabit Ethernet.
Basic Differences Between OM1, OM2, OM3 and OM4
The multimode fibers can be distinguished by their core and cladding diameters. All cladding diameters of the four multimode fibers are 125 µm. But their core diameters are different. The core diameter of OM1 is 62.5 µm, while the core diameters of OM2, OM3 and OM4 are 50 µm.
OM1 and OM2 have the orange jackets and their optical source is LED. Different from OM1 and OM2, OM3 and OM4 have aqua jackets and their optical source is 850nm VCSEL.
They can also be described by different bandwidth. OM1 has 200 MHz*km bandwidth, and OM2 has 500 MHz*km bandwidth. As for OM3, it provides sufficient bandwidth to support 10 Gigabit Ethernet, which is 2000MHz*km. To be used in 100 Gigabit Ethernet, the design of OM4 maximizes the bandwidth, so that OM4 has 4700MHz*km bandwidth, much wider than previous types.
Figure 2. Basic differences between OM1,OM2,OM3 and OM4
OM1, OM2, OM3 and OM4 in Different Applications
All of the four types of multimode fiber optic cables can support 100 Megabit Ethernet for communication at lengths up to 2000 meters.
In 1 Gigabit Ethernet, the transmission distances of OM1 can be 275 meters; the transmission distances of OM2 and OM3 are 550 meters at most; and the transmission distances of OM4 is the longest, 1000 meters.
In 10 Gigabit Ethernet, OM1 can only transmit signals at lengths up to 33 meters; OM2 has the performance of 82 meters transmission distance; OM3 can transmit longer, 300 meters; and OM4 can transmit longest, 550 meters.
In order to support 40 Gigabit Ethernet and 100 Gigabit Ethernet, OM3 and OM4 have been developed. It should be noted that OM3 can be used in both 40 Gigabit Ethernet and 100 Gigabit Ethernet with 100 meters transmission distance. As for OM4, it is a further improvement that can support both 40 Gigabit Ethernet and 100 Gigabit Ethernet at lengths up to 150 meters.
Figure 3. OM1,OM2,OM3 and OM4 in different applications
In short, OM1 is always used for 100 Megabit Ethernet applications which can transmit 2000 meters with the lowest cost; while OM2 is more commonly used in 1 Gigabit Ethernet. These two multimode fiber optic cables are not very suitable for high-speed communication nowadays. Therefore, to fulfill the need of the fast network development, advanced multimode fiber optic cables OM3 and OM4 are invented. OM3 is designed to support the applications of 10 Gigabit Ethernet, and OM4 is more superior that can support 100 Gigabit Ethernet at lengths up to 150 meters.
Conclusion
With the fast development of network, the multimode fiber optic cables would be improved to support 40 Gigabit Ethernet and 100 Gigabit Ethernet with longer transmission distance, which is the future development prospect in fiber optics market.
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