Guide To Multimode Fiber (62.5um & 50um, OM1 to OM5)

What is multimode fiber optic glass?

Multimode fiber optic cable (or glass) is a common specification of optical fiber that offers a much wider core size or core diameter of 50-62.5 microns (µm) compared to the 9 microns (µm) core diameter of single-mode fiber.

Multimode fiber typically operates at a wavelength of 850 nm as it allows for the use of lower-cost, light-emitting diode (LED) sources as the light source over shorter distances. LEDs have a relatively broad emission spectrum, and the 850 nm wavelength is within the range that can be efficiently generated by these sources. OM1 fiber can transmit data up to 33 meters at a data rate of 1 Gbps, while OM5 fiber can transmit data up to 550 meters at a data rate of 100 Gbps. This represents a more than 16-fold increase in transmission distance.

On the other hand, Single-mode fiber typically operates at a wavelength of 1310 nm or 1550 nm because it allows for the use of laser diodes as the light source. Laser diodes have a very narrow emission spectrum and therefore can achieve higher bandwidth and longer distance transmission compared to LED.

The 850 nm wavelength also has lower attenuation (or signal loss) in the fiber than longer wavelengths, which allows for longer distances to be covered with multimode fiber than would be possible with single-mode fiber. So really the choice of operating wavelength for multimode fiber is a balance between cost-effectiveness and performance. The use of 850 nm allows for the use of lower-cost LED sources while still providing acceptable performance for short-distance applications. While most of the long-span cables used in extended distances use SM glass, interbuilding/campus links often utilize multimode fiber.



Overview of common multimode glass types: OM1, OM2, OM3, OM4, and OM5

With many options, it can be tough to select the most suitable multimode cable for your network needs. You may find yourself asking – What’s the difference between OM1 multimode cable and OM5 multimode cable? What about all those other fiber types in between? And which one is right for my network? This quick read will help to improve your understanding.

As mentioned earlier, there are 5 commonly used multimode fiber types used in most industries worldwide. The most common optical multimode fiber types are OM1, OM2, OM3, OM4, and OM5. Beyond these widely used variations, some industries such as mining or sensing applications may utilize multimode fiber with a plastic core instead of glass, while some applications require fiber with a much larger core diameter of 200+ micron (called MM200). We won’t discuss these uncommon but interesting types of glass today and only focus on the most common variations from OM1 to OM5.

The letters “OM” stand for optical multi-mode. OM1 has a glass core diameter of 62.5μm (micrometers). The rest of the fiber types – OM2, OM3, OM4, and OM5 – have a smaller core diameter of 50μm, which is better optimized for use with modern lasers. But, most importantly, the practical differences between all the multimode fiber types are the various thresholds for carrying data over certain distances.


Multimode FIber Comparison Chart

Multimode FIber Comparison Chart

  • OM1 Glass is used for 10Gb Ethernet at lengths up to 33 meters (110 ft). This type commonly uses an LED light source and can be identified by an orange jacket.
  • OM2 Glass is able to carry 10Gb Ethernet at a data rate of 1 Gbps up to 82 meters (270 ft) on an LED light source. It can be found in both orange and aqua jackets.
  • OM3 Glass is laser-optimized glass and has a diameter of 50 microns. It can transmit data over longer distances than OM2 fiber, up to 300 meters at a data rate of 10 Gbps. This type of cable can also be distinguished by an aqua jacket.
  • OM4 Glass is a type of fiber cabling used for high-bandwidth applications such as data centers and enterprise networks. It can transmit laser signals up to 150 meters, and with extra technology like SWDM or DWDM, up to 400 meters. It is usually aqua-colored, but a magenta variant is also available. Magenta is used to differentiate it from other fiber types.
  • OM5 Glass can provide high bandwidth over short-range distances using fewer cables often by utilizing WDM technology. Traditionally, 400Gb Ethernet was achieved using 16 transmit and receive cables, but with OM5 cables you can accomplish this with just four transmit and receive cables. It always comes in a lime-green jacket.

How is OM5 glass different?

Optical Multimode 5, or OM5, is a new type of optical multimode fiber (OMF) that is designed to support higher bandwidth and longer distances than previous versions of OMF, such as OM3 and OM4. OM5 uses a wavelength of 850 nm, which is the same as OM4, but it also uses a wavelength of 953 nm. The addition of the 953 nm wavelength allows for better support of new shortwave wavelength division multiplexing technology like SWDM4 (also known as SWDM-4F, 4-Fiber, and SWDM-4X, 4-wavelength) for increased transmission capacity using less fiber.

SWDM4 is a technology that allows multiple data streams to be transmitted over a single optical fiber by using different wavelengths of light, it uses four wavelengths centered around 850 nm. The four wavelengths used in SWDM4 are 850nm, 880nm, 910nm, and 940nm. One of the key advantages of SWDM4 is its ability to utilize the existing multimode fiber infrastructure, which can be less costly than upgrading to single-mode fiber. In the data center and enterprise networks, OM5 is typically used to connect switches and servers across short distances. The high modal bandwidth and support for SWDM technology of OM5 allow for the use of 10GBASE-T and 40GBASE-T, which provide higher data transfer rates than previous versions of BASE-T. This allows data centers to support more servers and storage devices and to provide faster data transfer speeds to users.


Diagram showing TX and RX, SWDM4 over OM5 WBMMF

Diagram showing TX and RX, SWDM4 over OM5 WBMMF

What are some key considerations when specifying multimode glass for your application?


Distance and data rate: The distance and data rate requirements of the application will determine the type of multimode glass that should be used. Higher data rates typically require higher bandwidth multimode glass, while longer distances typically require lower attenuation multimode glass.

Wavelength: The wavelength of light that the glass will be used to transmit will also be important to consider. Different types of multimode glass will have different transmission characteristics at different wavelengths, so it’s important to choose a glass that is optimized for the wavelength of light that will be used.

Modal dispersion: Modal dispersion is caused by the multiple modes of light that can propagate through the fiber, it causes signal distortion and limits the distance of data transmission, it’s important to choose a glass that has lower modal dispersion.

Cost: The cost of the glass and associated equipment will also be an important consideration. Some types of multimode glass may be more expensive than others, and the cost of the equipment that is used to transmit the light through the glass will also be a consideration.

Compatibility: The compatibility of the glass with the rest of the network is also important to consider. It’s important to ensure that the glass is compatible with the other equipment that will be used in the network, such as the transceivers and the switches.


Multimode Fiber Optic Patch Cables

Product Photo of Multimode LC Patch Cable

Multimode (OM1, OM2, OM3, OM4 & OM5) Patch Cables manufactured by Megladon are built to reference grade performance and geometrical standards. We build with both standard and bend-insensitive fiber types, and have selected industry recognized connectors to maintain high performance standards. Our assemblies are designed to support the trend of higher data rates and will prepare your network for 10gig and beyond.

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About Megladon

A global industry leader in fiber optics and your premier partner for fiber optic connectivity, Megladon has spent over a decade developing fiber optic technology and perfecting the HLC interconnect. Our patented technology and process results in a reference grade interconnect that is reliable, rugged, repeatable and provides maximum performance. With millions of our products deployed worldwide, our fiber optic technology has been proven time and again to solve many of the problems encountered in network deployment and maintenance. We have also been able to use HLC as the foundation piece to develop unique and passive fiber optic solutions for our customers.