The mode field diameter fiber array (Short for MFD FA) provides a method of low loss coupling to waveguides with small mode fields, using a small section of ultra-high numerical aperture single-mode fiber (UHNA) spliced to the pigtail of standard SM or PM fiber, keeping the fusion point and the surface of the fiber array close to 7mm to achieve mode field conversion. HYC provides a variety of choices of fiber arrays, such as the number of fiber array channels, core spacing and polish angle can be customized.