Novel silicon asymmetric optical switches with transverse injection structure have been proposed and fabricated which are based on total internal reflection and free-carrier effect. The switches have a quite short operation length of about 200 mum. The device performance was measured at the wavelength of 1.3 mum. It shows that the crosstalk is less than -11.4 dB at an injection current of 85 mA. Response time is 100 ns. They are very suitable for silicon monolithic optoelectronic integration