The polarization and orbital angular momentum properties of light are of great significance in optical science and technology , especially in the fields of high-precision optical measurement and high-capacity optical communication. ln this experiment, we demonstrate a high-precision optical voltage measurement method that uses a Sagnac interferometer to make two beams of light with polarization perpendicular to each other carryorbital angular momentum ( OAM ), and combine them with birefringent crystals to obtain a “ fan-shaped' optical rotator carrying OAM beams by using the interference effect. This experiment applies abstract physical theoretical knowledge to conerete practice , which helps to improve students’ interest in scientific research and stimulate students’ innovative thinking.