The STK-AM series electro-optic intensity modulator utilizes the electro-optical effect of lithium niobate and push-pull Mach-Zehnder interference structure to achieve intensity modulation of optical signals. You can use EOIR to support concept development, design, field-testing, and operations. Please click here for more info. Required Capability Install: For versions 12. 10 and earlier of the STK software, this lesson requires the installation of. With STK's Electo-Optical Infrared (EOIR) tool, you can build your systems in space, on the ground, and in the air using STK's physics-based engine.