Two monolithically integrated frequency tuners have been analyzed, designed and fabricated. The potential applications for WDM have also been studied. The frequency tuners use 3D micromirrors integrated with single-mode Fabry-Perot laser diodes and anti-reflection coated optical fibers. The difference between the two frequency tuners is that one uses the movable 3D micromirror driven by comb-drive to change the external cavity length, and the other uses the rotatable 3D micromirror driven by thermal-actuator to change the external feedback strength. For the frequency tuner that uses movable 3D micromirror, a wavelength tunability of 16 nm is obtained using 3V driving voltage. As for the frequency tuner that uses rotatable 3D micromirror, a wavelength tunability of 7nm is obtained while using 10mA driving current.