Single/Dual channel extinction ratio tester can independently test polarization extinction ratio, optical power test, digital zeroing, digital calibration, manual or automatic range selection, equipped with USB(RS232) interface, upper computer software can automatically test, record and analyze data, and can easily form an automatic test system. Widely used in optical communication equipment, optical fiber, optical passive devices and optical active devices testing, wide power range, high test accuracy, cost-effective, good reliability