  The coherent nature of gravitational wave emanating from a compact binary
system makes it possible to detect some interference patterns in two (or more)
signals registered simultaneously by the detector. Gravitational lensing effect
can be used to bend trajectories of gravitational waves, which might reach the
detector at the same time. Once this happens, a beat pattern may form, and can
be used to obtain the luminosity distance of the source, the lens mass, and
cosmological parameters such as the Hubble constant. Crucial question is how
many such kind of events could be detected. In this work, we study this issue
for the future space-borne detectors: DECIGO and its downscale version,
B-DECIGO. It is found out that there can be a few tens to a few hundreds of
lensed gravitational wave events with the beat pattern observed by DECIGO and
B-DECIGO per year, depending on the evolution scenario leading to the formation
of double compact objects. In particular, black hole-black hole binaries are
dominating population of lensed sources in which beat patterns may reveal.
However, DECIGO could also register a considerable amount of lensed signals
from binary neutron stars, which might be accompanied by electromagnetic
counterparts. Our results suggest that, in the future, lensed gravitational
wave signal with the beat pattern could play an important role in cosmology and
astrophysics.
