Intense optical fields interact nonlinearly with materials to create very wide spectra, or supercontinua. Supercontinua created with ultrafast lasers in very nonlinear optical fiber have revolutionized the precision and ease with which optical frequencies are measured. I will describe the unique properties of the supercontinuum that make these measurements possible. Many other applications stand to benefit from this bright, phase coherent light source, as well. However, large fluctuations in the amplitude of the supercontinuum dramatically limit its utility. I present the first detailed investigation of noise on supercontinuum generation in microstructure fiber, both experimental and theoretical. We have identified the predominant source of large broadband noise to be fundamental quantum fluctuations (shot noise).