The visible red light travels along the fibre core until it reaches a fault, where it leaks out of the fiber. Light leaking through the fault can be seen through plastic coatings and jackets under suitable illumination. Infrared light in the signal leaks out at the same point, but your eyes cannot see it. The tester emits Class II red laser beam, making the light escaping from the damaged fiber easily visible from a distance.

Attenuation of glass fibres is much higher at 630 to 670nm wavelengths of red light than in the 1300 to 1650nm transmission window, but the red light can still travel up to 5km through standard fibers. Note that the fibers must be exposed to use fiber optic cable tester effectively. If the red light leaks out inside a thick cable wrapped in black plastic, you can’t see it.

This technique is particularly valuable in equipment bays and other places inside buildings where fibres are exposed.

Shining a flashlight beam down a multimode fiber can serve the same function, and has long been used to trace fiber continuity as well. However, the flashlight couples little light into a single mode fiber.

Whether installing or troubleshooting, the fiber optic cable tester is an essential tool that quickly and easily locates problem areas in fiber cables. By pinpointing the exact location of fiber damage, technicians can diagnose, troubleshoot, and fix the problem effectively. The cable tester is also used for conducting continuity tests and performing fibre identification.

The Continuous/Flash control button lets operators choose between continuous or flashing illumination.

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FC optical attenuators come in several types for a variety of applications.

:: Male to Female Doped Fiber Plug Type FC Fixed Attenuator

This type of attenuators are also called build out types. They contain doped fiber suitable for both 1310nm and 1550nm operation. Fixed attenuation values are available in 1dB increments from 1 to 20dB.

The build out FC attenuators are installed between an mating sleeve and a connector (plug). Because they are based on doped fiber, this type of attenuators have exceptional optical performance and reliability.

:: Female to Female Absorption Filter Adapter Type FC Fixed Attenuator

This type of attenuators are also called bulkhead type. They incorporate absorption filters in the centers of the adapter housings. In use, the filters are interposed between the end-faces of mating plugs.

Bulkhead attenuators utilize a wavelength sensitive neutral density filter to achieve attenuation. They can be inserted easily between jumpers or permanently mounted in a fiber distribution cabinet. This type of FC attenuators can be used for either multimode or single mode applications.

They use a filter to induce attenuation and are wavelength dependent, so you need to choose between 1310nm or 1550nm versions.

:: Applications

FC attenuators are widely used in telecom and data networks, power equalization in DWDM networks, CATV and multimedia applications, testing instruments, Fiber to the Home, and more.

Colin Yao is the sales manager at Fiber Optics For Sale Co. and an expert on optic cabling technologies and products.

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