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These fiber testing methods play a distinct role in detecting faults, measuring signal loss, and ensuring integrity of optical networks
An optical fiber rarely draws attention or curiosity from people. Yet this unassuming piece of technology forms the super-highway that brings the internet to us every minute of every day.
Encased inside protective tubes of varying thickness, otherwise called cables, these delicate strands of glass carry everything from late-night texts to training data for trillion-parameter AI models, all in the form of light beams.
So although the last mile wireless connection may make them invisible to the public eye, silent defects or physical damages in fiber lines can make connectivity disappear like it never existed. That’s what fiber testing seeks to prevent.
The scope of fiber testing today is expansive. It goes from detecting manufacturing defects in new fibers in factories to measuring signal loss and verifying integrity in existing fiber optic networks to detecting degradation remotely in real time.
There are a few different methods of testing that exist today, each consisting of different procedures, toolsets, and standards. Regardless, they all aim to ensure that components within a deployment are working as they should to support high-speed, error-free data transmission.
Optical Loss Test Sets or OLTS is the most widely used method of fiber testing. It entails measuring the loss of light in a fiber optic link. A light source is placed on one end of the link and a power meter consisting of a photodetector is placed at the other end. As the light source produces waves of light, the meter measures the optical power of the light coming through the line. The results reveal the measure of light lost during the passage. OLTS is known for its high accuracy and is described as “Tier 1” testing by standards bodies.
Optical Time-Domain Reflectometer or OTDR is another form of testing that is widely used by technicians. Unlike OLTS, OTDR testing involves measuring the amount of light reflected, rather than received — as the name suggests. Once again, light pulses are sent through the fiber, while measuring devices capture and compute the difference between reflections at the near and far ends.
OTDR is used to characterize link loss for individual splices and connectors, detect fiber faults, mismatches, macro bends, and connector misalignment, making it an essential test procedure for short-reach, single-model applications.
For certain deployments, OLTS and OTDR tests are performed in tandem, an approach referred to as “Tier 2”.
Other test methods include visual fault locators or VFL which use a visible light laser to identify breaks and bends in the cables, and fiber inspection probes that are used by technicians to detect dirt, debris, and damages in fiber connectors that impede connectivity.
Industry standards for fiber optic testing today are defined by three key organizations:
- Telecommunications Industries Association (TIA)
- International Electrotechnical Commission (IEC)
- International Organization for Standardization (ISO)
These bodies are responsible for setting standards for fiber optic cable systems, test procedures and parameters, and quality and assurance, respectively. Manufacturers and operators are required to adhere to the national and international standards to guarantee performance, reliability and interoperability.
