Katzir is an expert in the fields of biomedical optics and fiber optics. His group at Tel Aviv University developed special fibers made of crystalline silver halides, which are among the few that are highly transparent in the middle- infrared (mid-IR). He and members of the group have been involved with research and development of new methods and new systems, based on these fibers. They made significant contributions to the use of mid-IR fibers for scientific, medical, industrial and environmental protection applications. In the course of this work, Katzir collaborated with leading scientists in major national laboratories, universities, research institutions and industrial companies, all over the world.