[en] Several applications of a few-cycle optical probe-pulse (fc-probe pulses) in Laser Wakefield Acceleration (LWFA) experiments on the JETI 40 TW laser system in Jena will be described. These investigations are motivated by the need for high-resolution diagnostics of the wakefield to gain a deeper insight into the physics underlying the acceleration process and to benchmark numerical simulations which have so far been the only source for detailed information. Various measurements using the fc-probe pulses were performed during a LWFA experimental campaign. Here, a gas-cell filled with a 95:5 Helium:Nitrogen mixture was used as the target material. Interferometric measurements of the electron plasma density were done and compared using both a Mach-Zehnder interferometer and a polychromatic wavefront sensor. Further measurements implementing the relationship between spectral bandwidth and temporal resolution of the fc-probe pulses were performed as an investigation into multi-frame, single-shot shadowgraphic techniques.