  We search for signatures of gravitational lensing in the binary black hole
events detected by Advanced LIGO and Virgo during their first two observational
runs. In particular, we look for three effects: 1) evidence of lensing
magnification in the individual signals due to galaxy lenses, 2) evidence of
multiple images due to strong lensing by galaxies, 3) evidence of wave optics
effects due to point-mass lenses. We find no compelling evidence of any of
these signatures in the observed gravitational wave signals. However, as the
sensitivities of gravitational wave detectors improve in the future, detecting
lensed events may become quite likely.
