Once the cable plant is installed and terminated, or likewise fiber optic cables get damaged as the time passes by. It is recommended to test the fiber optic segment. Thus it’s of prior need to get them tested on a regularly basis, so that possibilities of hindering data transmission efficiency can be lowered down or eliminated. This is where a crucial aspect of fiber optic testing is needed to be conducted.

Basically, the main purpose of testing is to evaluate how the cables are working, and to eliminate the faults, if perceived. Thus via this way quality of standards, as well as overall functioning of system gets improved. Usually, the components that are needed to be tested are: connectors, receiver, light source or LED, detectors and splices etc. The testing should be done according to TIA TSB-140 and the Acceptance Testing Notes guidelines. These documents provide additional guidelines for field-testing length, loss and polarity of a completed fiber optic link.

Test Equipment
Various types of testing equipment are available on the market, such as a fiber visual fault locator (VFL), a fiber power meter, a network cable tester or an optical time-domain reflectometer (OTDR). For troubleshooting, the OTDR is recommended.

Visual Fault Locator
The VFL is a red laser source; the tracer is a LED source. This instrument can be used to locate the breakpoint, bad splices, poor connections, bending or cracking on optical fiber cables. Visual fault locator is an efficient tool for tracing fiber, fiber routing, and continuity checking in optical networks, as well as to identify fibers and connectors in patch panels or outlets. It easily isolates high loss points and faults in fiber optic cables and is an ideal solution for applications in telecommunication, LAN, WAN, fiber data links and CATV systems.

Fiber Power Meter
Optic Power Meter is used for absolute light power measurement as well as fiber optic loss related measurement. For dBm measurement of light transmission power, proper calibration is essential. For measuring loss or relative power level in dB, fiber power meter is always used with an optical light source. There are general-purpose power meters, semi-automated ones, as well as power meters optimized for certain types of networks, such as FTTx or LAN/WAN architectures. It’s all a matter of choosing the right gear for the need.

Network Cable Tester
A network cable tester is used to test the strength and connectivity of a particular type of cable or other wired assemblies. Network cable tester can tell whether the cable is capable of carrying an Ethernet signal. If the cable carries the signal, this indicates that all the circuits are closed, meaning that electric current can move unimpeded through the wires, and that there are no short circuits, or unwanted connections, in the wire. There are a number of different types of cable testers, each able to test a specific type of cable or wire (some may be able to test several different types of cables or wires).

Optical Time Domain Reflectometer (OTDR)
The OTDR is a more sophisticated measurement instrument. It uses a technology that injects a series of optical pulses into the fiber under test and analyses the light scattering and the light reflection. This allows the instrument to measure the intensity of the return pulse in functions of time and fiber length. The OTDR is used to measure the optical power loss and the fiber length, as well as to locate all faults resulting from fiber breaks, splices or connectors.

Testing Guidelines
When do fiber optic testing, you should always according to TIA TSB-140 and the Acceptance Testing Notes guidelines. They provide additional guidelines for field-testing length, loss and polarity of a completed fiber optic link. For example, clean all connections and adapters at the optical test points prior to taking measurements.