Design of compact polarization-insensitive multimode interference triplexer

A compact polarization-insensitive multimode interference (MMI) triplexer is proposed. The triplexer can process signals among three wavelengths of 1310, 1490 and 1550 nm in the fibre-to-the-home (FTTH) systems. The polarization insensitivity is obtained by adjusting the refractive index of SiNx in the Si/SiNx/Si sandwiched structure. A triangular lattice array air-hole photonic crystal embedded in the MMI waveguide can transmit and reflect downstream and upstream signals, respectively. Furthermore, a cascaded MMI structure is used to separate two downstream signals. The performance parameters of the triplexer are analysed by three-dimensional finite-difference time-domain method. The results show that the size of the triplexer is only 5.5 x 234.5 mu m(2), the insertion loss and crosstalk are as low as 0.45 dB and -27.2 dB respectively. Besides, the triplexer has a large 3 dB bandwidth up to 105 nm, and it has potential application value in the FTTH systems.

Automated summary

A compact polarization-insensitive multimode interference triplexer has been proposed, utilizing material refractive index adjustment to achieve polarization insensitivity. Performance analysis shows that the triplexer is small in size, low in insertion loss, and has a large bandwidth, making it potentially valuable for FTTH applications.