An electro-absorptive optical modulator module monolithic-integrated on a semiconductor substrate, which includes a distributed feedback laser having a grating for oscillating light and to output the oscillated light through a first end and a second end of the module. An electro-absorptive modulator modulates a first light output through the first end of the distributed feedback laser, and an optical detector provides detection of a second light output through the second end of the module. The optical detector is formed opposite to the second end of the distributed feedback laser on the semiconductor substrate. A first inner window permits attenuation of the intensity of the second light and electrically insulates the distributed feedback laser and the optical detector from each other, with the first inner window being arranged between the distributed feedback laser and the optical detector.