Standard splice between two asymmetric fiber geometries can lead to high insertion loss and degradation of the beam quality. A mode field adapter overcome this using an adiabatic taper between the two fibers to gradually expand or compress the mode field to achieve maximum signal transmission and M2 beam quality. Our Mode Field Adapters efficiently expand the mode field of an SM optical fiber or large-mode-area (LMA) fiber to match the LP01 mode of a larger LMA fiber. The PM Mode Field Adapter similarly expands the mode field of a PM optical fiber to match the LP01 mode of a polarization-maintaining LMA (PLMA) fiber while maintaining a high PER. These devices are bidirectional and can also be used in reverse to compress the mode field when the output end is used as an input. We offer standard configurations for most application scenarios. Customer parts are available with a NRE fee for different optical fibers, power levels, and package configurations by email.