  A high fraction of massive stars are found to be binaries but only a few of
them are reported as photometrically variable. By studying the populations of
SB2 in the 30 Doradus region, we found a subset of them that have photometry
from the OGLE project and that display variations in their light curves related
to orbital motions. The goal of this study is to determine the dynamical masses
and radii of the 26 binary components to investigate the mass-discrepancy
problem and to provide an empirical mass-luminosity relation for the LMC. We
use the PHOEBE programme to perform a systematic analysis of the OGLE V and I
light curves obtained for 13 binary systems in 30 Dor. We adopt Teff, and
orbital parameters derived previously to obtain the inclinations of the systems
and the parameters of the individual components. Three systems display eclipses
in their light curves, while the others only display ellipsoidal variations. We
classify two systems as over-contact, five as semi-detached, and four as
detached. The two remaining systems have uncertain configurations due to large
uncertainties on their inclinations. The fact that systems display ellipsoidal
variations has a significant impact on the inclination errors. From the
dynamical masses, luminosities, and radii, we provide LMC-based empirical
mass-luminosity and mass-radius relations, and we compare them to other
relations given for the Galaxy, the LMC, and the SMC. These relations differ
for different mass ranges, but do not seem to depend on the metallicity
regimes. We also compare the dynamical, spectroscopic, and evolutionary masses
of the stars in our sample. While the dynamical and spectroscopic masses agree
with each other, the evolutionary masses are systematically higher, at least
for stars in semi-detached systems. This suggests that the mass discrepancy can
be partly explained by past or ongoing interactions between the stars.
