In a linear combustion channel (LCC) with an initial pressure of 50 kPa, interferometric flow visualization was conducted on detonation waves using Fizeau interferometry. The visualization, which was compared with the numerical results, revealed the detonation waves propagating through the premixed fuel and oxidant jet trains. By using Fizeau interferometry, the density profile across the detonation waves was clearly determined while previous study was not able to extract quantitative information of the density profile across the detonation waves. The experimental and numerical results for the propagated wavefronts aligned well. The next goal of this research is to simulate a real gas environment inside a rotating detonation engine by developing a double-ignition mechanism for the LCC, which will result in a mixture of burnt and unburnt fuel gases in front of the detonation waves.