Fiber optic cables are used to transmit optical signals in modes. The mode is a path that the light beam travels along with the fiber. According to the number of modes, fiber optic cables can be divided into single-mode and multi-mode fiber cables.
Single-mode fiber is also called OS or Optical single-mode fiber, it contains a very thin core about 5-10 microns (millionths of a meter) in diameter. All signals go straight from the middle without bounce off the edges (yellow line in the diagram).
Single model fiber has the simplest structure, it can be divided into OS1 and OS2, their main difference is cable construction rather than optical specifications. The OS1 type cable uses a tight buffer structure, while the OS2 is a loose tube or blown cable structure.
Each OS1 fiber has its own double layer of protective coating, one layer is plastic and the other layer is waterproof acrylate. This tight-buffered cable has a smaller, lighter weight cable, which is more flexible and crushes resistant than Loose Tube. As there is no gel to clean, and no connector terminals for fan-out components, the installation is easier.
Application: OS1 single-mode fiber can support speeds up to 10G and distances up to about 10km (6 miles). It is mainly used indoor, such as moderate distance telco local loops, LANs, and point-to-point links in cities, buildings, factories, office parks, or campuses.
Apart from the outer coating, all fibers of OS2 are essentially bare, and each fiber has a colored coating for identification. In addition, the fiber “floats” in a strong, wear-resistant, oversized tube, which usually filled with optical gel to protect the fiber from moisture. The connector terminal requires a fan-out assembly.
Application: OS2 single-mode loose tube cable can support speeds up to 100G and distances up to 200km (124 miles). It is widely used in outdoor applications, such as high fiber count, long-distance telco backbone and backhaul lines, direct bury applications along streets and railroads.
Single-mode fiber is the standard choice for high data rate or long-distance transmission. Compared with multi-mode fiber optic cable, single-mode fiber can transmit signals at a higher speed with less signal attenuation and external interference.
In a multimode fiber cable, the size of each fiber is about 10 times that of a single-mode fiber. It means that the light beam can pass through the core in a variety of different modes (yellow, orange, blue, and cyan lines).
As the multimode fiber optic cable disperses the light propagating along with the core into multiple paths, this allows higher bandwidth in short and medium distances. However, in a long cable operation, multiple paths of light will cause distortion at the receiving end, resulting in unclear and incomplete data transmission.
Therefore, Multimode is usually only used for short-distance applications such as data centers.
Here are the types of multimode fiber cable and their specifications:
As OM1 and OM2 fiber cables can’t reach higher speeds, OM3 and OM4 have become the mainstream for multimode fiber supporting 25G, 40G, and 100G Ethernet.
In the past 30 years, multimode fiber cable has made great progress so far OM5 has been developed in data centers to expand the advantages of multimode fiber.
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