“…The MZI is usually formed by splitting and later recombining different optical modes, i.e., core mode and cladding modes, at two separate fiber mode-coupling joints. The mode-coupling joints can be produced by fiber taper [4], [9], [14], dual-core fiber [15], lateral-offset splicing [16], or photonic crystal fiber collapsing [12]. Among these techniques, fiber taper is a favorable option because of its low cost and ease of operation with high reproducibility.…”