In Utrecht we are building an imaging polarimeter, ExPo (Extreme Polarimeter), to image circumstellar disk and characterize extra-solar planets. To test and calibrate ExPo, we have built a laboratory-based simulator that mimicks a star with a Jupiter- like exoplanet as seen by the 4.2 m William-Herschel Telescope. The star and planet are simulated using two single-mode fibres in close proximity that are fed with a broadband arc lamp. The unpolarized star has a flux of 10$^11$ photons s$^-1$, to simulate a mv=0 star, and the planet is partially linearly polarized, with a flux of as little as 10$^2$ photons s$^-1$ to simulate reflected star light with a contrast ratio of as much as 10$^-9$. The telescope is simulated with two lenses, and seeing can be included with a rotating glass plate covered with hairspray, while dispersion is approximated with a wedge prism. These are the first realistic laboratory simulations of imaging polarimetry for exoplanet detection and characterization.