Abstract: An optical terminal has optical waveguides, 3-dB couplers, laser diodes, laser diodes provided with gratings, and connections on a substrate made of semiconductor material. The grating laser diodes have an external cavity which is formed by the waveguides and delimited by mirrors. Each of the laser diodes has a respective electrical connection through which the diodes can be switched between a light-absorbing mode, a light-amplifying mode, and a light-emitting mode, with the aid of electric current signals, and the diodes are also able to detect a light signal. The terminal can perform a number of functions. A light signal can be received, detected, amplified, and further transmitted. A narrow band light signal of desired wavelength can be generated within a broad wavelength area through the grating diodes in the cavity, and amplified and further transmitted.