Study of the attenuator for the high extinction ratio testing system

In order to improve the measuring accuracy of the intelligence high extinction ratio measuring system,the polarization interference principle is used to study and design an attenuator used in the system,and the attenuator's principle is analyzed carefully.The attenuator is consisted of three polarization prisms,one λ/4 wave-plate(λ=632.8nm),and two stepper motors.It can continuously adjust intensity of light within the range of about 0~60dB and the insertion lossof less than 1.5dB,so the aberration generated by changing attenuator with fixing attenuation value can be canceled effectively.If the attenuator is used to measure the extinction,the extinction ratio better than 10-7 can be obtained.The attenuator can be used not only in the high extinction ratio measuring system,but also in other optical measuring systems.The attenuator can adjust kinds of wavelength lights with achromatic plate in place of λ/4 wave-plate,so the useful range can be expanded.