BiDirectional Testing of Fiber Optic Cabling

Bi-directional testing of fiber optic cable is important to insure the quality of a fiber network. The main reason for this is due to the fact that no two glass fibers are exactly same. Whether the fiber optic cables are manufactured by different companies or they happened to come off another reel, their fibers may have slightly different core sizes due to core-cladding concentricity mismatches.

Self-Supporting Drop Optical Cable

For example, if the transmitting light travels from a larger core to a slightly smaller one or if the cores are offset during the fusion splice or connection process, you will witness more attenuation in one direction than the other.  Therefore, it is essential to measure both directions. Once you have gathered the bi-directional measurements you calculate the average which is known as the ‘average link loss.’ Using the bi-directional average enables networkers to adequately measure splice loss.

Generally, network operators use optical time domain reflectometers (OTDR) to determine loss. Simply, the OTDR sends light through the fiber and then measures the amount that is reflected back, as well as how much time it took. In addition to attenuation, these meters have the ability to locate breaks in fiber, splices and connectors and reflection properties at multiple wavelengths.

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