  We investigate the capability of ongoing radio telescopes for probing Faraday
rotation measure (RM) due to the intergalactic magnetic field (IGMF) in the
large-scale structure of the universe which is expected to be of order $O(1)
{\rm rad/m^2}$. We consider polarization observations of a compact radio source
such as quasars behind a diffuse source such as the Galaxy, and calculate
Stokes parameters $Q$ and $U$ assuming a simple model of the Faraday dispersion
functions with Gaussian shape. Then, we perform the Fisher analysis to estimate
the expected errors in the model parameters from QU-fitting of polarization
intensity, accounting for sensitivities and frequency bands of Australian
Square Kilometer Array Pathfinder, Low Frequency Array, and the Giant Meterwave
Radio Telescope. Finally, we examine the condition on the source intensities
which are required to detect the IGMF. Our analysis indicates that the
QU-fitting is promising for forthcoming wideband polarimetry to explore RM due
to the IGMF in filaments of galaxies.
