The light-emitting device has a fiber stub part, a semiconductor optical amplifying
device, a photodiode, and a bench as its main parts. The fiber stub part is composed
of a ferrule and a grating fiber. The fiber stub part and the semiconductor optical
amplifying device are mounted on the bench, and optically coupled together. An
optical cavity is composed of the light-reflecting face of the semiconductor optical
amplifying device and the diffraction grating of the grating fiber. The light-emitting
device, which does not use a pigtail fiber, can be downsized and can provide laser
light with a desired wavelength.
