A systematic way has been developed for cavity design of reflection-type two-wavelength modulators based on coupled cavity structures. By inserting a properly designed additional reflector between the two quantum well absorbing layers with different designed operating wavelengths, two modulator structures can be combined with different operating wavelengths in one device and they can be made to operate almost independently. In this paper, three types of two-wavelength cavity designs including the simple cavity, the balanced cavity, and the decoupled cavity, are described. Their merits and drawbacks in overall modulation performance are compared. The three designs have also been realized experimentally. All of the three devices show clearly independent two-wavelength operation and the measured characteristics agree with the theoretical predictions.