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How Much Do You Know About Multimode Fiber Optic Cables

If the multimode fiber is mentioned, most of you may be familiar with this term. As a significant member of the large fiber optic cable family, multimode fiber optic cable also consists of many sub-branches. However, not all the people are clear about these subbranches. Therefore, in this article, we will introduce the multimode fiber optic cable and its subbranches to you.

What Are Multimode Fiber Optic Cables

In optical fiber technology, the multimode fiber is a kind of optical fiber that is designed to carry multiple light rays or modes concurrently, each at a slightly different reflection angle within the optical fiber core, typically 50 or 62.5 μm for its core diameter. Mostly, the multimode fiber is used for communications over short distances, such as within a building or on a campus for the reason that its modes tend to disperse over longer lengths (this is called modal dispersion).

Applications of Multimode Fiber

Typical multimode transmission speed and distance limits are 100 Mbit/s for distances up to 2 km (100BASE-FX), 1 Gbit/s up to 1000 m, and 10 Gbit/s up to 550 m. In addition, the equipment used for communications over multimode optical fiber is less expensive than that for single-mode optical fiber. Because of its high capacity, reliability, and cheap price, the multimode optical fiber mostly is used for backbone applications in buildings, aerospace and LAN network, storage area networks.

Types of Multimode Fiber

Identified by ISO 11801 standard, multimode fiber optic cables can be classified into the OM1, OM2, OM3, OM4, and OM5 fiber. Specified by that Standard, “OM” is abbreviated for optical multimode. These five types will be presented in the following parts.

OM1 Fiber

Wearing an orange jacket, OM1 fiber cable possess a core size of 62.5 µm, supporting 10 Gigabit Ethernet at lengths of up to 33 meters. It is most commonly used for 10/100 Megabit Ethernet applications. This type is commonly used as an LED light source.

OM2 Fiber

Just like OM1, OM2 fiber also comes with an orange jacket and uses an LED light source. But, its core size is 50 µm, supporting up to 10 Gigabit Ethernet at lengths up to 82 meters and more commonly used for 1 Gigabit Ethernet applications.

Figure 1: OM2 Fiber
OM3 Fiber

Like OM2, the OM3 fiber cable’s core size is 50 µm, but it wears an aqua jacket and is optimized for laser-based equipment. OM3 supports 10 Gigabit Ethernet at lengths up to 300 meters. Besides, OM3 is able to support 40 Gigabit and 100 Gigabit Ethernet up to 100 meters. However, 10 Gigabit Ethernet is most commonly used.

Figure 2: OM3 Fiber
OM4 Fiber

Being backward compatible with OM3 fiber, the OM4 fiber shares the same aqua jacket with it. The OM4 was developed specifically for VSCEL laser transmission and allows 10 Gig/s link distances of up to 550m compared to 300M with OM3. And it’s able to run at 40/100GB up to 150 meters utilizing an MPO connector.

Figure3: OM4 Fiber
OM5 Fiber

 

OM5 fiber, also known as WBMMF (wideband multimode fiber), is the newest type of multimode fiber, and it is backward compatible with OM4. It has the same core size as OM2, OM3, and OM4. The color of the OM5 fiber jacket was lime green. It is designed and specified to support at least four WDM channels at a minimum speed of 28Gbps per channel through the 850-953 nm window.

Figure 4: OM5 Fiber

Conclusion

Through this article, we will have a basic idea of what the multimode fiber cable is and how many types it has. In general, multimode fiber cable continues to be the most cost-effective choice for enterprise and data center applications up to the 500-600 meter range. However, since the fiber patch cable is a very large family, every kind has its own features. Before making a choice, the key point is we need to understand whether our demands match the patch cable we want to choose.

What Can Do Damages to the Fiber Cables?

Fiber cables are widely applied in today’s communication network. They are buried under the street or under the sea. Fiber cables are quite indispensable for information transmission and data providing. They are just like the veins of communication systems. Once fiber cables are damaged or cut, network will be interrupted. You may be not able to watch TV or even suffer a great loos. So, what can destroy the fiber cables?

Bad Weather & Natural Disasters

Bad weather like hurricanes, mud slides, flood and ice storms etc. and natural disasters are nightmare not only to our personal life and property, but also the fiber cables. When there is a heavy snow, we are glad to make snowman. But for cable installers, they have to o an emergency network repair under such harsh conditions in order to avoid additional damage and downtime. Because water that enters a splice enclosure will be frozen, crushing the fiber strands and leaving you with a costly network outage. Additionally, lightning is also a factor to destroy fiber cables. When lightning strikes the ground, it will search for the best conductor available, even if it’s underground. If that happens to be the armor or trace-wire of your fiber cable, then cable sheath or the fiber is likely to be broken.

Animals Chew & Bite

The damages to fiber cables caused by animals are annoying. We don’t know how to avoid that. Squirrel, a furry little nut eater, seems to be deeply fond of fiber cable sheathing besides nuts. We even doubt that the cable manufacturers using peanut oil in the sheathing. Squirrel often gnaw fiber optic cable. Even metal armored cable can get cut in two by this furry critter. In addition, undersea cables aren’t exempt from cuts. Because there is another animal under ocean like to bite cables. It is shark. Why shark would like to eat fiber cables? Effect by magnetic fields is one of the explaining at present. We have no idea how we can combat these wayward rodents. Now, the only thing we can do is always looking for ways to improve.

shuck-bite

Construction Damage

During the construction, people may cut the fiber cables with excavators. Tools like backhoes, post-hole augers and even hand shovels can all bring network traffic to a halt. Because some of them don’t even care if there are fiber cables underground before digging. So construction may do harm to fiber optic cable.

excavator

Vehicle Damage

How can vehicle damage the fiber cables? Here we mainly refer to big trucks, or maybe small airplane. For example, a cable damage accident causing by a truck happened in Pennsylvania. A trucker got lost and accidently turned down a residential street. His rig got tangled up in a mess of overhead phone cables. But that didn’t stop him! He kept pushing forward until his rig was tied up like a Christmas present. He was dragging a 20 foot section of broken telephone pole down the street before he stopped to see what was impeding his progress. To address this situation, we can forbid trucks from entering the residential street or city by limiting the height of the vehicles. However, accident always happens with all kinds of tricks, e.g. a small airplane will destroy the fiber cables. This happened in California. A small airplane was attempting to land at the Burbank International Airport and overshot the runway and crashed in a residential area. It clipped the poles that the aerial fiber was attached to, causing everything to come down. Though it is just a small probability event, it really refresh the record of fiber cut causing by vehicle.

Artificial Destruction

Since fiber optical cable is valuable, some people try to steal it. They cut the fiber into pieces. The most classical event is that a 75 year-old woman in Georgia (country in Asia) was digging with her spade, looking for copper, which she wanted to sell for scrap, when she accidentally cut the fiber optic cable that provided internet to 90% of Armenia. It is ridiculous. It is fiber but not copper! In addition, people vandalize the fiber cable in other ways, e.g. for gun practice. This especially happens in the rough parts of town which makes the cable repair work become dangerous. Furthermore, land disputes may also causes artificial malicious damage to fiber.

Cable Protection, Repair and Recovery

No matter damages caused by nature or human, we can’t predict. So the only thing we can do is to take a good protection for our fiber cables. Waterproof fiber cables, armored fiber cables and the other outdoor cables which are designed to protect fibers in a harsh application environment are widely used in this field. More better protection methods will be developed in the future. Of course, there are some other factors which cause signal loss and cut the network. Repairs and recovery service are necessary. There is a group of people who are willing to get down into the trenches in the first time, make the necessary repairs and recovery service every time when network is down. They are great and worthy of respect.