Comparison of FBT coupler and PLC Splitter

June 7, 2022
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According to the working principle, optical splitter can be divided into two types: fused coupler (also called FBT splitter) and planar waveguide splitter (PLC splitter). The fused coupler is formed by side fusion of two or more optical fibers; The optical waveguide splitter is an optical element type product, which uses lithography technology to form optical waveguides on the dielectric or semiconductor substrate to realize the branch distribution function. The principle of these two forms of optical splitting is similar. They can achieve different branch quantities by changing the evanescent field coupling (coupling degree, coupling length) between optical fibers and changing the fiber radius. On the contrary, they can also combine multiple optical signals into one channel, which is called a synthesizer.


Fused fiber coupler has become the mainstream manufacturing technology in the market because of its simple manufacturing method, low price, easy connection with external optical fibers, and resistance to mechanical vibration and temperature changes.


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The melting coupler pulling method is to close two (or more) coated optical fibers together in a certain way, melt them under high temperature heating, stretch them to both sides at the same time, and finally form a special waveguide structure in the form of double cones in the heating zone. Different splitting ratios can be obtained by controlling the torsion angle and stretching length of the optical fibers. Finally, the taper area is solidified on the quartz substrate with curing adhesive and inserted into the stainless steel tube, which is the optical splitter. Due to the inconsistency between the thermal expansion coefficient of the cured adhesive and that of the quartz substrate and the stainless steel tube, the degree of thermal expansion and cold contraction is inconsistent when the ambient temperature changes. This situation is easy to cause damage to the optical splitter, especially when the optical splitter is placed in the field, which is also the main reason for the damage of the optical splitter. For the production of splitter with more channels, it can be composed of multiple two-way splitter.


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The main parameters of the two devices are compared as follows:

Each has its own advantages in terms of performance and price. Both processes and technologies are constantly upgrading to overcome their respective shortcomings. The FBT splitter is used to solve the problems of small number of tapered pullers and poor uniformity. The PLC splitter has also made unremitting efforts to reduce the cost. At present, the cost of the two devices above 1x8 is almost the same. With the increase of the shunt channel, the price of the planar waveguide splitter is better.


When selecting devices, the key is to consider the use check and the needs of users. In applications where the volume and wavelength of a patch are not very sensitive, especially when there are few shunts, it is more economical to select fused optical splitter. For example, 1310nm FBT optical splitter is selected for independent data transmission, and 1550nm FBT optical splitter is selected for TV video network; Optical waveguide splitters (plc splitter) should be used in situations where three networks in one, FTTH, etc. require optical transmission from multiple factories and there are many users. At present, due to the mature technology and low cost of planar optical waveguide splitter, the universal planar optical waveguide splitter is basically started all over the world. In some special fields, where uneven distribution is needed, the application of the combination of fused and planar waveguide is gradually promoted, or the uneven planar waveguide splitter is directly used to replace it.