The interference and gravitational redshift effect of long waves passing a binary black hole

We investigate the interference of electromagnetic long waves passing a binary black hole based on the approximate binary black hole metric. The interference pattern of long waves demonstrates strong contrast intensity and changes with respect to different wavelengths and incoming angles. A bright semicircular arc emerges from the interference pattern and bridges the two black holes when the binary black hole rotates to certain angle. The angular momentum of the binary black hole causes asymmetric gravitational redshift distribution along the relative position vector of the two black holes. The angular momentum of the binary black hole is measurable based on the interference pattern of long waves and gravitational redshift.