Why is fiber connectivity and performance testing important?
With the increased demand for faster transmission speeds on the enterprise network brought by new versions of Wi-Fi supporting multi-gig speeds, servers having to transfer terabytes of data, and applications that have tighter loss budgets, the demand for bandwidth has led to an increase in the size of Ethernet fiber optic networks. Because of that it is now more important than ever to test optical paths post-installation to make sure they are performing as needed. This approach ensures that the installed cabling will be able to handle current and future data transmission loads.
In this blog we will discuss the most important causes of fiber optic connectivity and give you a step-by-step guide on how to troubleshoot them.
Table of Contents
What are optical fibers and how do fiber data transmissions work?
Optical fibers are long, thin strands of glass about the diameter of a human hair that are arranged in bundles called fiber optic cables and then used to transmit light signals over long distances.
The light transmitted through the fiber is a form of carrier wave that is used to carry information, and it travels down a fiber optic cable by bouncing off the walls of the cable repeatedly.
There are two main types of fiber optic cables normally used for networking:
- Single Mode – Typically used for cable TV, internet, and telephone applications, where the signals are carried by single mode fibers wrapped into a bundle.
- Multimode – About ten times larger than a single mode cable, these cable types can only send data over short distances. Because of that, they are normally used for interconnecting computer networks.
Fiber is preferred over copper wiring when high bandwidth, long distance, or immunity to electromagnetic interference is required.
What are the most common causes of fiber optic connectivity and performance problems?
As fiber optic signals travel through the network, many variables can affect the quality of the transmission and thus impact network connectivity or performance. Some of the most common reasons for fiber connectivity problems are:
- Broken fiber because of excessive bending
- A disconnected cable
- Signal loss due to a cable being too long
- Signal loss due to a bad connector
- Signal loss due to faulty splices or too many splices
- Incorrect transmit power
- Faulty connections on a patch panel
Meanwhile, when it comes to intermittent fiber optic connectivity or performance problems, the most common causes are:
- Too much of a loss budget was allowed when installing the fiber
- Dust, fingerprints, scratches or humidity in connectors or splices
How to troubleshoot common fiber optic problems?
Some of the most common fiber optic connectivity and performance problems can be easily resolved by validating that connectors are fully engaged or verifying that splices are properly seated and connected with their mate. Still, many times special tools may be required.
- Visual Fault Locators (VFL) – This tool uses a bright laser beam of light that can be easily seen with the naked eye. VLFs are great for testing continuity from one end of the link to the other and finding breaks in cables, connectors or splices. They can also be used as a tracing tool for locating the other end of a single fiber terminated within a rack.
- Light Source and Power Meter (LSPM) – LSPM are considered to be the most accurate tools for measuring loss. They can be used for troubleshooting by comparing the output power from a switch to the end of the fiber cable (or to splices). Which helps you identify problems with signal loss due to the cable being too long, bad connectors, faulty splices, or having too many splices.
- Optical Fault Finders – Optical fault finders measure length and identify high loss events and brakes on multimode up to 4,921 feet (1,500 meters). This single-ended optical fault locator sends a laser light pulse through the fiber and measures the power and timing of light reflected from high loss connections and from the end of the fiber to help identify the distance to a fault.
- Optical Time Domain Reflectometers (OTDR) – OTDRs calculate signal loss based on the amount of reflected light, or backscatter, that it detects. Which allows it to be used for locating breaks, bends, splices, and connectors, plus measure the loss caused by these specific events. OTDRs are more expensive than VFLs, LSPMs and optical fault finders, and they require some expertise to use. Still, because they measure the location, loss and characteristics of individual events, they are considered advanced troubleshooting tools.
Step-by-step Guide
Conducting fiber connectivity tests with NetAlly testers is simple as they can be used as an LSPM to measure loss. Follow these steps to get started:
- Use a Small Form-factor Pluggable (SFP) to connect your NetAlly tester to one side of the fiber cable to be tested. Note: NetAlly testers are SFP agnostic, so SFPs from any manufacturer should work.
- Connect the other side of the cable to an SPF slot in a switch.
- Use the built-in Switch app to run the test. Here’s a video that you can use to follow along with.
- Analyze the results to identify the amount of loss in the cable and determine if it will be able to support your specific application. Here’s a table provided by the Fiber Optic Association that shows the loss margin for most fiber optic links. If the loss of the cable plant is less than the maximum loss allowed for the link, it should work. Still, we recommend you always leave a little margin.
Meanwhile, using a NetAlly tool to detect intermittent problems or validate fiber network performance can be done as follows:
- Use an SFP to connect your NetAlly tester to one side of the fiber cable to be tested.
- Connect the other side of the fiber cable to a physical loopback plug or a second NetAlly tester.
- Use the built-in LANBERT app to run the test. Here’s a video that you can use to follow along with.
- Analyze the results to validate if your fiber cable can support the speeds your applications require. You could also let the LANBERT test run for up to 24 hours and use the different graphs available to identify intermittent issues (errors over time).
Besides allowing you to run the tests mentioned above, NetAlly tools will also allow you to use USB based fiber inspection cameras or VFL to quickly and easily test for continuity or find breaks in cables, connectors or splices. Just plug in your fiber inspection camera or visual fault locator to a USB port in your NetAlly tester and use your preferred third-party app to run your tests.
Conclusion
Making sure that your fiber network can support the increased demand for faster speeds doesn’t have to be difficult. We encourage all network professionals to implement regular fiber connectivity and performance testing as part of their network maintenance routine. Having the right tools is essential for quick and simple fiber optic troubleshooting and validation. By understanding the function and capabilities of each tool, you can confidently and knowledgeably address issues within fiber optic networks and maintain their reliability and performance.
Ready to take your network performance to the next level? Explore NetAlly’s range of fiber testing solutions and start optimizing your network today!
