Evaluation of the rejection ratio of an MMI-based higher order mode filter using optical low-coherence reflectometry

The multimode interference (MMI)-based higher order mode filter is effective in improving the characteristics of devices that employ highly confined waveguides. However, the characteristics of fabricated devices are not well known due to the difficulties of higher order mode loss measurement. We determined the characteristics of simple MMI-based higher order mode filters experimentally by using optical low coherence reflectometry.