Conventional Triple band wavelength demultiplexer is proposed based on MMI coupler.

Tapers are included at input and output ports of second MMI to improve the performance of demultiplexer device for this pair of wavelength and given refractive index.

Demultiplexer based on MMI-II also works as 3 dB power divider for S-band wavelengths 1481 nm and 1526 nm.

The 3-dB bandwidth of insertion loss for wavelength band 1300 nm, 1510 nm and 1550 nm are 80 nm, 20 nm and 10 nm.

It has an important role in optical communication such as Fiber-to-the-home (FTTH) based, passive optical networks (PON).