Study on Mach-Zehnder optical isolator based on magneto-optic photonic crystal fiber

Optical isolators are important components in fiber optic communication and sensing systems. Conventional optical isolators, including bulk and in-line fiber types, mainly rely on the Faraday rotation effect and require external magnetic fields, which result in structural complexity and integration challenges. In this paper, a fiber-type optical isolator based on magneto-optic photonic crystal fiber (MO-PCF) is proposed, which utilizes non-reciprocal phase shifts (NRPS) in a Mach-Zehnder configuration. The full-vector finite element method (FV-FEM) is used to analyze the transmission characteristics. In the proposed isolator, the PCF cores are filled with magnetic and non-magnetic materials, to enhance the non-reciprocity of light by applying a magnetic field perpendicular to the polarization direction and propagation direction. Based on these analyses, the designed MO-PCF structure achieves a NRPS per wavenumber of 0.863 × 10^-3 rad/μm. In the optical isolator, the coupling length is 612.3 μm, ensuring the function of an optical isolator.