A method and apparatus for characterizing light from an optical source using simplified chronocyclic tomography by modulating the phase of light from an optical source using alternating positive and negative quadratic temporal phase modulation at a desired alternating frequency .OMEGA.; generating an electric signal proportional to the optical power of the modulated light after propagation through an optical frequency resolving device, for a desired optical frequency .omega.; determining a time-invariant and time-varying components of the electric signal; repeating the generating and determining steps for a plurality of optical frequencies; and determining the spectral phase and spectral intensity of the light from the optical source using the time-invariant and time-varying components determined for the plurality of optical frequencies.