Focus On Fiber Optic Link Loss

We know that, no natter what component you use, there must insertion loss in your fiber optic cabling. Therefore, in order to make your fiber optic cabling system perform at high level, calculating the amount of insertion loss before cable plant is necessary. This article will focus on fiber optic link loss.

Overview of Link Loss And Link Loss Budget

The link loss and link loss budget are measured in dB. Link loss is the total insertion loss of all optical components in an optical network. While link loss budget is the amount of loss that a cable plant should have. It is calculated by adding the average losses of all the components used in the cable plant to get the total estimated end-to-end loss. The link loss budget has two important functions: during the design stage to ensure the cabling being designed will work with the links intended to be used over it and; after installation, comparing the calculated link loss to test results to ensure the cable plant is installed properly.

How to Calculate Link Loss?

Usually, the loss of four parts need to be calculated: mated pair connector loss, fiber optic splicing loss, fiber optic cable loss and other loss.

link loss calculation

  • Mated Pair Connector—EIA/TIA 568 standard allows 0.75 max per connector

Connector or “connection” loss is the total loss of the mated pair connectors. It’s standard to assume a 0.3 dB loss for most ultras polished connectors. In order to measure the loss of the connectors, you must mate them with similar connectors, or you are likely to experience different losses. Also, a high quality connector is required when testing matted pairs.

  • Fiber Optic Splicing—EIA/TIA 568 max loss is 0.3 dB per splice

According to the Fiber Optic Association (FOA), multimode splices are commonly made using mechanical splices. Best construction practices dictate that even with multimode fiber fusion splicing is ideal. Both forms of splicing generally result in satisfactory results, however fusion splicing proves to be more reliable in adverse surroundings. Single mode fibers that have been fusion spliced will typically have less than 0.10 dB loss. A good average for a skilled installer is generally around 0.05 dB loss.

  • Fiber Optic Cable

EIA/TIA 568 spec for multimode fiber is 3.5 dB/ km at 850 nm and 1 .5 dB/km at 1310 nm. This specification translates into a loss of approximately 0.1 dB per 100 feet for 850 nm, 0.046. dB per 100 feet for 1300 nm. For example, 300 ft multimode fiber optic cable at 850 nm would approximately equal 0.3 dB loss. While for single mode fiber, the loss is 0.5 dB per km at 1310 nm, 0.4 dB per km for 1550 nm.

  • Other Loss—Passive Components and Margin

Don’t forget to count any other passive components you are using in your network. For example, if you are using splitters or filters, add the insertion loss for those components. In addition, it is recommended to add margin to your link loss calculation to adjust for any unforeseen losses. The amount may vary by designer or application but typically 2-3 dB will allow for sufficient headroom in you network link loss calculation.


The fiber optic link loss calculation and analysis are vital in cable plant. After the cable plant is installed, the calculated loss values are compared with the test results to ensure the link can operate properly. Besides, to reduce the link loss, high quality components are required. Quality is everything when gigabit and higher speeds are required. FS.COM provides high quality fiber optic connector, fiber optic cable and fiber optic transceiver at reasonable price. Also, they have test tools, such as light source and power meter.

A Closer Look at OM5

We know that for short-reach optical interconnects, multimode fiber is a cost-effective solution. As data centers are constantly moving towards faster speeds and higher densities, the multimode fiber also has evolved over time, from OM1, OM2 to OM3 and OM4 multimode fiber. Now, OM5 is coming. This article will guide you to have a closer look at OM5.

Overview of OM5

OM5, also known as wide-band multimode fiber (WBMMF), is recognized within both the Telecommunications Industry Association (TIA) and International Electrotechnical Commission (IEC) standards. It is designed to support shortwave wavelength division multiplexing (SWDM) which would use 850nm, 880nm, 910nm and 940nm for transferring signals.


Characteristics of OM5

What makes OM5 different? What are characteristics of OM5? The following part will make a summary.

Size: OM5 fiber is laser optimized multimode fiber (LOMF) of 50 micron core. Therefore, OM5 cabling supports all legacy applications at least as well as OM4, and is fully compatible and intermateable with OM3 and OM4 cabling.

Color: TIA has specified lime green as the official cable jacket color for OM5.

Bandwidth: The operating band of OM5 is from 850 to 953nm and its effective modal bandwidth is specified at the lower and upper wavelengths: 4700 at 850nm and 2470 at 953nm.

Speed: OM5 can support 40G, 100G and 400G Ethernet by accommodating SWDM. And it is designed and specified to support at least four WDM channels at a minimum speed of 28Gbps per channel through the 850-953 window.

Distance: When transferring signals at the speed of 10 Gb/s, OM5 can achieve 550 meters; when transferring signals at the speed of 40 Gb/s, OM5 can achieve 440 meters; when transferring signals at the speed of 100 Gb/s, OM5 can achieve 150 meters.

Working principle: Since SWDM will enable 40G and 100G over few fiber strands, when using 25GBASE-SR specifications, 100 gigabit OM5 fiber links could be created using 2-fiber 25 gigabit channels on 4 different wavelengths. Similarly, using 100GBASE-SR4 specifications, 400 gigabit OM5 fiber links could be created using 8-fiber 100 gigabit channels on 4 different wavelengths.

Cost: As the matter of fact, OM5 cabling will costs about 50% more than OM4.

Comparison Among OM5, OM4 And OM3

By comparison, it is not difficult to find that there are many differences between OM5, OM4 and OM3.

  • OM5 carries at least 4X more capacity than OM4 over a meter of fiber and carries 5.7X more capacity than OM3 over a meter of fiber.
  • The color of OM5 fiber is lime green, while standard OM3 and OM4 fiber is aqua.
  • The effective modal bandwidth for OM5 is 4700 at 850nm and 2470 at 953nm. While OM4 is 4700 at 850nm and OM3 is 2000 at 850nm.
  • For 100 transmission speed, OM5 uses 2-fiber 25 gigabit channels on 4 different wavelengths, while OM4 and OM3 requires the use of 8-fibers via 100GBASE-SR4.
  • OM5 supports transmission distance of 440 meters for 40G SWDM system and 150 meters for 100G SWDM system. While OM4 can only achieve 350 meters for 40G SWDM system and 100 meters for 100G SWDM system; OM3 can support 40G SWDM system with distance of 240 meters and 100G SWDM system with 75 meters.


As a new type of multimode fiber, OM5 fiber does have a breakthrough in some aspects. However, it is not very popular on the market. Maybe because its strength is not prominent. Therefore, for OM5, it still has a long way to go.