Recent studies have shown that a compact self-mixing interferometer can be used for the characterization of shock waves. It measures dynamically (> 10 MHz) the changes in the refractive index induced by the shock wave. Associated to an appropriate acousto-optic model, the pressure profile is computed with a 34 mbar resolution. In the present work, we compare shock wave induced refractive index variations measurements by another method using a Michelson-type fiber- optic interferometer with phase analysis that has been developed for Photonic Doppler Velocimetry applications. The output signals of this system are processed in triature, which consists in analyzing the phase shift between the three interferometric signals. This bulkier system provides, in theory, a better resolution than the self-mixing interferometry sensing scheme. In the present paper, we compare these two optical methods to measure a shock wave pressure through experiments that were carried out with an open shock tube instrumented with commercial, bandwidth limited, pressure sensors. This configuration creates a spherical shock wave similar to those observed during on-field experiments with explosives. We describe the two measurement systems and the experimental setup design used for overpressure characterizations. Both sensing approaches have been carried out in the same experimental conditions and with shock wave pressure peak amplitudes of a few bars. We detail the two types of signal processing and we discuss the results obtained with the two optical methods, which are also compared to a piezoelectric reference sensor.