In 2001 however, Büttner and Czarske presented an LDA they called Multi-Mode Laser Doppler Anemometer (MM-LDA) which circumvents signal degradation by choosing a wideband laser source such as a broad-area laser diode [13]. According to this work multimode fibers do not only allow the in-coupling of much higher laser powers, but also, at the same time, decrease the spatial coherence of the guided light due to the excitation of higher transverse guided modes. Usually, this effect is unwanted, but in the case of the MM-LDA it is beneficial as the low spatial coherence greatly decreases the volume of interference in the beam intersection. Thus, modulated scattering signals only occur in a small part at the center of the measurement volume as compared to the use of single mode illumination. This effect significantly increases the effective spatial resolution, see Fig. 2. The MM-LDA has successfully been utilized for the investigation of boundary layers in turbulent and laminar flows [14]. As the MM-LDA performance is mainly determined by laser source and optical fiber used in the set-up, optimal components were identified to best fit the investigation of flows in tubes with diameters of some millimeters.