Simple In-Line M–Z Interferometer Based on Dual-Core Photonic Crystal Fiber

We experimentally demonstrated a simple dual-core photonic-crystal-fiber-based M-Z interferometer by use of femtosecond laser drilling and fiber splicing. A higher order mode is excited in one fiber core by introducing a conical air hole at the splice point, which interferes with the fundamental mode in the other fiber core. Sensing applications to strain and temperature of the interferometer are experimentally demonstrated in this letter, and the sensitivities are obtained to be 2.18 pm/με and 6.8 pm/ °C, respectively. The device is compact and robust with a very simple structure, and can find applications in liquid environment.