Electron-beam pumped transverse flow lasers suffer from turbulence and acoustic wave induced optical perturbations which degrade optical beam quality. Existing diagnostic technologies give limited low resolution information about these phenomena. The successful use of the high resolution digital heterodyne interferometer to obtain high quality measurements of these phenomena is described. The interferometer was equipped with multiple detectors with parallel outputs, each simultaneously reporting optical path difference measurements. Phase resolution of lambda/300 was demonstrated simultaneous with a 10-microsec time resolution. Substantial and unique information on flow and acoustic phenomena was obtained that was not previously available.