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Multimode fiber is a common choice to achieve 10 Gbit/s speed over distances required by LAN enterprise and data center applications. There are several kinds of multimode fiber types available for high-speed network installations, and each with a different reach and data-rate capability. With so many options, it can be tough to select the most suitable multimode fiber. OM1 vs OM2 vs OM3 vs OM4 vs OM5, which to choose? You may get answer in this article.

Multimode fiber (MMF) is a kind of optical fiber mostly used in communication over short distances, for example, inside a building or for the campus. Multimode fiber optic cable has a larger core, typically 50 or 62.5 microns that enables multiple light modes to be propagated. Because of this, more data can pass through the multimode fiber core at a given time. The maximum transmission distance for MMF cable is around 550m at the speed of 10Git/s. It can transmit farther at lower data rates, such as going about 2km at 100Mb/s.

Identified by ISO standard, multimode fiber optic cables can be classified into OM1 fiber, OM2 fiber, OM3 fiber, OM4 fiber and newly released OM5 fiber. The next part will compare these fibers from the side of core size, bandwidth, data rate, distance, color and optical source in details.

OM1 fiber typically comes with an orange jacket and have a core size of 62.5 µm. It can support 10 Gigabit Ethernet at lengths of up to 33 meters. It is most commonly used for 100 Megabit Ethernet applications. This type commonly uses a LED light source.

Likewise, OM2 fiber also comes with an orange jacket and uses a LED light source but with a smaller core size of 50 µm. It supports up to 10 Gigabit Ethernet at lengths up to 82 meters but is more commonly used for 1 Gigabit Ethernet applications.

OM3 fiber comes with an aqua color jacket. Like the OM2, its core size is 50 µm, but the cable 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.

OM4 fiber is completely backwards compatible with OM3 fiber and shares the same distinctive aqua jacket. 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 40/100GB up to 150 meters utilizing a MPO connector.

OM5 fiber, also known as WBMMF (wideband multimode fiber), is the newest type of multimode fiber, and it is backwards compatible with OM4. It has the same core size as OM2, OM3, and OM4. The color of OM5 fiber jacket was chosen as 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. More details can be found at: Three Critical Focuses on OM5 Fiber Optic Cable

The prime distinction between multimode fibers rests on physical difference. Accordingly, physical difference leads to different transmission data rate and distance. Watch the following video to learn the differences between OM1, OM2, OM3, OM4 & OM5 multimode fibers.

Physical difference mainly lies in diameter, jacket color, optical source and bandwidth, which is described in the following table.

MMF Cable Type Diameter Jacket Color Optical Source Bandwidth OM1 62.5/125µm Orange LED 200MHz*km OM2 50/125µm Orange LED 500MHz*km OM3 50/125µm Aqua VSCEL MHz*km OM4 50/125µm Aqua VSCEL MHz*km OM5 50/125µm Lime Green VSCEL MHz*km

Multimode fibers are able to transmit different distance ranges at various data rate. You can choose the most suited one according to your actual application. The max multimode fiber distance comparison at different data rate is specified below.

MMF Category Fast Ethernet 1GbE 10GbE 40GbE 100GbE OM1 m 275m 33m / / OM2 m 550m 82m / / OM3 m / 300m 100m 70m OM4 m / 550m 150m 150m OM5 / / 550m 150m 150m

Core Diameter&#;Single mode fiber has a small diametral core(8.3 to 10 microns) that allows only one mode of light to propagate. Multimode fiber optic cable has a large diametral core(50 to 100 microns) that allows multiple modes of light to propagate.

Light Source&#;Multimode devices usually use a LED or laser as a light source. While single mode devices use a laser, or laser diode, to produce light injected into the cable.

Distance&#;Light travels a longer distance inside single mode cable than it does inside multimode. So multimode fiber is suitable for short haul application, allowing transmission distances of up to about 550m at 10Git/s. When distance is beyond 550m, single mode fiber is preferred.

Price&#;Multimode fiber usually cost less than single mode fiber.

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Bandwidth&#;The bandwidth of single-mode is higher than multimode as much as 100,000 GHz.

Know more infro about single mode vs multimode fiber here: Single-mode Cabling Cost vs. Multimode Cabling Cost

There are many multimode fiber connector types in circulation such as ST, SC, FC, LC, MU, E, MTRJ, SMA, DIN as well as MTP & MPO etc. The most commonly used fiber optic connector types include ST, SC, FC and LC. Each one has its own advantages, disadvantages, and capabilities. So what are the differences and what do they mean to your implementation? This table of common multimode fiber connectors gives an overview of strengths and weaknesses. Get more details about commonly used fiber optic connectors here: Fiber Optic Connector Types, Market, & Installation

MMF Connector Ferrule Size Typical Insertion Loss (dB) Cost(FS.com) Application Features SC φ2.5mm ceramic 0.25-0.5 US$ 0.65 Mainstream, reliable, fast deployment, filed fit LC φ1.25mm ceramic 0.25-0.5 US$ 0.78 High density, cost-effective,filed fit FC φ2.5mm ceramic 0.25-0.5 US$ 0.74 High precision, vibration environment, field fit ST φ2.5mm ceramic 0.25-0.5 US$ 0.61 Military, filed fit

Although single mode fiber patch cable is advantageous in terms of bandwidth and reach for longer distances, multimode fiber easily supports most distances required for enterprise and data center networks at a cost dramatically less than single mode fiber. Besides, multimode fiber optic cable still has many significant advantages.

Multimode fiber features carrying multiple signals at the same time in the same line. Most importantly, the total power inside the signals carries almost no loss. Therefore, the network user can send more than one packet in the cable at the same time, and all information will be delivered to their destination with out any interference and keep unchanged.

Multimode fiber can support many data transfer protocol, including Ethernet, Infiniband, and Internet protocols. Therefore, one can use the cable as the back bone of a series of high value applications.

With a larger fiber core and good alignment tolerances, multimode fiber and components are less expensive and are easier to work with other optical components like fiber connector and fiber adapter, and multimode patch cords are less expensive to operate, install and maintain than single mode fiber cables.

Due to its high capacity and reliability, multimode fiber is usually used for backbone applications in buildings. In general, mmf cable continues to be the most cost-effective choice for enterprise and data center applications up to the 500-600 meter range. But it&#;s not to say that we can substitute single mode fiber with multimode fiber cable, as for whether to choose a single mode fiber patch cord or multimode patch cord, it all depends on applications that you need, transmission distance to be covered as well as the overall budget allowed.

Related Article: Single Mode Fiber: How Much Do You Know?

For fiber optic cable, theoretically speaking, its bandwidth is infinitely high, transmission capacity is infinitely large and the transmission distance is infinitely far. Besides, optical fiber cable is also light in weight, and all of these features make it an ideal medium for data transmission, which is capable of transmitting unlimited and TV signal. However, in the current application of optical cable, the result is far from the theory. Regardless of the fragile physical properties of silicon, the transmission capability of fiber optic cable has opened a few windows.

In May , the ITU-T organization divided the fiber optical communication system into six bands as O, E, S, C, L and U6. Multi-mode optical fiber at 850nm is known as the first window,  single-mode optical fiber at O band is referred to as the second band. C band is called as the third window, L band is the forth window and E band is the fifth window. The following table shows the  wavelength bands for both multimode fiber optic cable and single-mode fiber optic cable.

Frequency band Window Wavelength range (nm) Frequency range (THz) / 1 850(770-910) / Original band 2 - 237.9-220.4 Extended band 5 - 220.4-205.3 Short wavelength band / - 205.3-195.9 Conventional band 3 - 195.9-191.6 Longer wavelength band 4 - 191.6-184.5 Ultralength wavelength band / - 184.5-179.0

The frequency range in the table above refers to the frequency of light. According to the formula  speed = wavelength x frequency, we can easily figure out the frequency of light. Its relation to the transmission loss of fiber optic cable and wavelength has been displayed as follow:

In the early days of fiber optic communication the LED was employed as a light source due to its low price. Multi-mode fiber optic cables that operate at 850nm and nm became the first choice for building small network, while single-mode optical fiber cables, working at nm and nm with laser as the light source , were the foundation for constructing large network. If there were more windows available for single-mode optic cable, one fiber optic cable would achieve ultra high speed transmission by transmitting signals at different wavelength at the same time by employing WDM (wavelength division multiplexing) technology, thus maximizing the potential of single mode fiber. and network and be using at the same time via ADSL (asymmetric digital subscriber line) modem. That&#;s because voice and data use different frequency. And this principle is similar with WDM and ADSL technology, which are usually applied in main networks that require higher bandwidth.

For intelligent building, the mainly adopted fiber optic cable are multi-mode optical cable which supports short distance transmission, such as multi-mode optical fiber cable that operates at 850nm or nm with LED as the light source, or multi-mode optical fiber cable working at 850nm with VCSEL laser. Single-mode fiber optic cable is often adopted in buildings that with a longer distance to each other.

Intelligent building applications, fiber optic cable is often close to support multi-mode-based, such as multi-mode fiber optic cable with the emission wavelength of 850nm or nm LED light source, or 850nm VCSEL laser wavelength. Single-mode used in long distance system buildings, single-mode fiber optic cable with emission wavelength nm or nm FP or DFB laser, means that most of the fiber optic cable is only open a window. Single-mode fiber optic cable works together with FP or DFB which transmit wavelength of nm or nm. That&#;s to say most optical cable only open one window.

Whether the transmission windows of fiber optic cable can be opened or not and how many windows can be opened will be subject to several factors as dispersion, loss, WDM as well as light source and network equipment. In the long term, fiber optic cables that supports multiple windows are bound to have stronger practicability, compatibility and scalability.

Related Article: How to Identify the Fiber Optic Cable Color Code?

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