Splitter in GPON Network

An interesting (and strange) fact is that attenuation of light through an optical splitter is symmetrical. It is identical in both directions. Whether a splitter is combining light in the upstream direction or dividing light in the downstream direction, it still introduces the same attenuation to an optical input signal (a little more than 3 dB for each 1:2 split).

There are two basic technologies for building passive optical network splitters: Fused Biconical Taper (FBT) and Planar Lightwave Circuit (PLC). Fused Biconical Taper is the older technology and generally introduces more loss than the newer PLC splitters, though both PLC splitter and FBT splitters are used in PON networks.
A Fused Biconical Taper 1:2 optical splitter is diagrammed below. A Fused Biconical Taper (FBT) splitter is made by wrapping two fiber cores together, putting tension on the optical fibers, and then heating the junction until the two fibers are tapered from the tension and fused together. FBT attenuation tends to be a bit higher than attenuation from PLC splitters.

June 10, 2011

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