Design of a 2D fiber mode converter using a planar 2D multi-mode interference structure

Abstract

In this work, we present a new design of a fiber mode converter using a two dimensional multi-mode interference waveguide (2D MMI) Structure. The proposed structure allows the conversion of the fundamental fiber mode LP01 to the second order LP21 fiber mode in multimode fiber. The 2D MMI is used as a 1 × 4 splitter and followed by a phase shifter to construct the proper phase map of the higher order LP21 mode. The design is based on the self- imaging properties of the 2D MMI structure and can thus be generalized to higher order modes. The proposed structure shows an insertion loss of about −0.96 dB and a Wavelength Dependent Loss (WDL) of about 0.4 dB over a spectral range of 140 nm around 1550 nm.