Design of compact polarization-insensitive multimode interference triplexer

Abstract

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 SiN_x in the Si/SiN_x/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 × 234.5 µm², 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.

KEYWORDS:

• FTTH
• multimode interference
• photonic crystal
• polarization-insensitive
• sandwiched structure

PACS::

• 42.79.-e
• 42.82.-m

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported in part by the Natural National Science Foundation of China [grant number 61571237] and the Natural Science Foundation of Jiangsu Province [grant number BK20151509].