A photonic integrated circuit includes a main light source, a redundant light source, a controller, an optical switch, and a modulator. The main light source outputs main light through a main light input waveguide. The redundant light source outputs redundant light through a redundant light transmission waveguide. The controller generates a first switch signal based on a fault state of the main light source. The optical switch selectively provides the redundant light from the redundant light transmission waveguide to a redundant light input waveguide based on the first switch signal. The modulator modulates main light from the main light input waveguide or redundant light from the redundant light input waveguide and outputs a first optical signal.