Nonlinear optical frequency conversion techniques have now existed for 60 years; frequency combs have now also been important scientific tools for two decades. Nonlinear optics is a vital piece of experimental realizations of frequency combs in the form of f-2f interferometry for stabilization of the carrier envelope offset frequency. Frequency combs, owing to their unparalleled frequency stability, broad spectral bandwidths, and coherent link between microwave and optical frequencies, have similarly had an impact on the field of optical frequency conversion.The work in this thesis demonstrates the important symbiotic relationship between nonlinear optics and optical frequency combs – combs could not have existed without nonlinear optics, and combs continue to push the boundaries of what is possible in nonlinear optics. In this work, I show the generation of few-cycle pulses from Er:fiber oscillators, approaching the picture of frequency combs being delta functions in the time and frequency domain. With these ultrashort pulses, I show mid-infrared frequency comb generation with intrapulse difference frequency generation. Dual comb spectroscopy in the mid-infrared shows the applicability of these combs. I also show a novel comb stabilization technique relying on offset frequency detection in the mid-infrared. With ultrashort near-infrared pulses, I show mid-infrared comb measurement techniques using electro- optic sampling and discuss the current noise limits. Finally, this dissertation also provides an outlook on future techniques enabled by frequency combs aimed at measuring light sources beyond coherent laser frequency combs
