![]() Some projects will also specify extended “Tier 2” testing that requires an Optical Time Domain Reflectometer (OTDR) to characterize the loss of individual splices and connectors. Both TIA and ISO standards use the term “Tier 1” to describe testing with an OLTS. An Optical Loss Test Set like Fluke Networks’ CertiFiber® Pro provides the most accurate insertion loss measurement on a link by using a light source on one end and a power meter at the other to measure exactly how much light is coming out at the opposite end. How to Test Insertion Loss in Optical Fiber Systemsīecause insertion loss is the primary performance parameter that impacts the ability of a fiber link to support a given application, it is required for fiber certification testing per industry standards. Learn more about calculating and ensuring loss budgets. The active equipment also needs to be considered per the equipment manufacturer’s specifications based on any differences between transmitters and receivers, as well as some margin to account for loss of power over time that can occur due to transmitter age. Based on manufacturer specifications for the fiber and connectors, as well as the maximum specified loss of any splices or splitters, fiber insertion loss budgets are calculated by adding the insertion loss for the length of fiber and for each planned connection point in the channel. For example, the 10 Gb/s application 10GBASE-SR over 400 meters of multimode fiber allows a maximum channel insertion loss of 2.9 dB, while the 100 Gb/s application 100GBASE-SR4 allows a maximum of just 1.5 dB.īased on the maximum insertion loss values published by industry standards for specific applications, loss budgets are determined early in the design phase to ensure that the cable plant does not exceed the maximum specification. Still, there are limits on the amount of insertion loss that specific fiber applications can handle, and higher bandwidth applications have more stringent loss requirements. For example, multimode fiber loses only about 3% (0.3 dB) of its original signal strength over a 100-meter distance while a Category 6A copper cable loses about 94% (12 dB) of its signal strength over the same distance. Insertion loss in optical fiber cabling systems is much less than copper, which is why fiber supports much greater distances and long-haul backbone applications. Learn more in our article about the difference between return loss and reflectance. Also expressed in dB, reflectance is a negative number. It’s important to note that in optical fiber applications, the inverse of return loss is reflectance, which measures the amount of back reflection created by a reflective event (i.e., connector) compared to the amount of light injected. A higher return loss also generally correlates to a lower insertion loss. In other words, if none of the signal was reflected, there would be an infinite return loss. Decreased reflections result in a higher return loss. However, unlike insertion loss, the higher the number, the better the performance. Like insertion loss, return loss is also a positive number. Rather than measuring the amount of loss over a link, return loss measures the amount of power injected from the source compared to the amount reflected back toward the source. Like insertion loss, return loss is another parameter that is important in both copper and fiber systems. Because insertion loss is directly related to distance and the number of connection points, industry standards call out insertion loss limits and specify the number of connections and distance limitations for specific applications. If insertion loss is too high, it can prevent the signal from properly being received and interpreted by active equipment at the far end of a link. The lower the insertion loss, the better the performance. It is typically a positive number that is calculated by comparing the input power of the signal at the source to the output power at the far end. Insertion loss is also caused by any connection points along a cable link (i.e., connectors and splices).Ī key performance parameter for both copper and fiber applications, insertion loss is measured in decibels (dB). ![]() ![]() This reduction of signal, also called attenuation, is directly related to the length of a cable-the longer the cable, the greater the insertion loss. It is a natural phenomenon that occurs for any type of transmission-whether it's electricity or data. Insertion loss is the amount of energy that a signal loses as it travels along a cable link.
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