Fiber Optic Coupler Types and How to Make Couplers

[MasterPeaC1]

I was thinking on the second TREE coupler on that picture (Nx1), combiner.

[FiberOptics4Sale]

Tree couplers split all wavelength power evenly to all output ports. If the light contains 1550nm and 1560nm wavelengths, for a 1x4 tree coupler, you will get 25% of 1550nm and 25% of 1560nm power on each output port.

WDM (multiplexers) output each wavelength to its own output port. (100% 1550nm to port 1, 100% 1560nm to port 2, 100% 1570nm to port 3, etc.)

[MasterPeaC1]

What is the difference between optical TREE couplers (2:33) and multiplexers?