Types of Coupler
Fiber Optic coupler
Fiber optic couplers are used to split the input signals into two or more outputs, they are called splitters in this case.
On the other hand, some types of couplers can be used to combine two or more inputs into one single output, they are called combiners in this case.
Y coupler
Y coupler is also called tap coupler.
This type of coupler simply divides the signal into two outputs. The power distribution ratio between two outputs can be precisely controlled, such as 10/90 percent, 20/80 percent, 30/70 percent, 40/60 percent or 50/50 percent.
T coupler
T coupler functions the same as Y coupler.
T couplers can be cascade to connect multiple terminals on a network, as shown below. The split ratio between two outputs should be 10/90 percent or 20/80 percent in order to have enough power left for next terminal in the link.
Star coupler
Star couplers have multiple inputs and outputs.
The input and output port number could be the same or not, such as 2×2, 4×4, 8×8, etc. Star couplers distribute the input power uniformly among the output fibers.
Directional Star Coupler
The first type is directional, mixing optical signals from all inputs and then distribute them among all outputs, as shown below. These are bidirectional devices because they also can transmit light in the opposite direction.
Non-Directional Star Coupler
The second type of star coupler is non-directional. It takes inputs from all fibers and then distribute them among all fibers, both input and output
Tree coupler
Tree couplers are also called 1xN couplers because they take one or two inputs and split it into multiple outputs
Tree couplers distribute the input power uniformly among the output fibers. Some may combine multiple inputs to one or two outputs, so they are actually combiners.
Most common configurations include 1×4, 1×8, 1×16, 1×32 and 2×4, 2×8, 2×16, 2×32 port ratios.