Polarization-Insensitive 3-dB Coupler for Polarization and Wavelength Division Multiplexed Systems

We propose and experimentally demonstrate a polarization-insensitive 3-dB coupler by using tapered three-guide structure based on the silicon-on insulator. Owing to the symmetrical and tapered structure, the dependency on wavelength and polarization are both alleviated. The coupling length of the 3-dB coupler is about 120 μm. The measured wavelength-dependent power imbalance is less than 1.1 dB and the maximum polarization-dependent imbalance is about 1.0 dB in the wavelength region from 1520 to 1600 nm. This letter shows potential applications in polarization and wavelength division multiplexed systems.