A compact and stable three-port optical gate has been successfully fabricated by monolithically integrating a simple photodiode and an electroabsorption modulator. The gate shows an excellent DC logic "and" function with different load resistors. Its dynamical characteristics without packaging have also been measured. We observed a dynamic extinction ratio of over 7dB with a 95012 load resistor and a 7mW control light power at 622Mbit/s.