Study On Faraday Effect Of ZF7 Flint Glass And Fiber

With the rapid development of the National Smart Grid and ultrahigh voltage transmission network,the traditional electromagnetic current transformer gradually cannot meet the measurement standards of ultrhigh voltage power system.The main development trend in the field of ultrahigh current measurement is the all-fiber optical current transformer based on the Faraday rotation effect and fiber sensing technique.The special flint glass fiber is the core element of the all-fiber optical current transformer.ZF7 flint glass is the main material of this special fiber.However,there are many problems hard to solve during its fabrication and application process such as birefringence and temperature drift.Currently,the single mode silica fiber with very low Verdet constant is still used in the sensing element of domestic all-fiber optical current transformers,the fabrication and application of flint fiber in the all-fiber optical current transformer are rarely reported.In this paper,ZF7 flint glass was selected and optimized as the research object.The properties of Faraday effect and birefringence of ZF7 flint glass are studied,the flint fiber is drawn and studied on its Faraday effect.Firstly,the Faraday effect of ZF7 flint glass is studied theoretically,The Verdet constant of ZF7 glass sample is measured.The scheme of comparation measurement of standard TGG crystal sample and ZF7 flint glass sample is adopted,the mean value measurment of Faraday rotation angle is proposed to reduce the error caused by polarizer's extinction ratio and axis angle.A method based on Jones matrix and Matlab simulation is studied and used to analyze the measurement error.In the third chapter,the birefringence property of ZF7 flint glass is analyzed and measured by two ways: A four-quadrant detector is proposed for the measurment of ZF7 flint glass' s linear birefringence,comparing with the traditional polarization-modulation scheme.The matrix theory is used to analyze and simulate the error of polarization.In this paper,the ZF7 flint glass preform is fabricated and used in flint fiber drawing,the fiber loss coefficient is measured experimentally.The flint fiber's Faraday effect is tested in the magnetic field generated by the solenoid,it is concluded that this flint fiber has the potential to be applied on all-fiber optical current transformer.