A wafer includes multiple optical devices that each includes one or more optical components. The optical components include light-generating components that each generates a light signal in response to application of electrical energy to the light-generating component from electronics that are external to the wafer. The optical components also include receiver components that each outputs an electrical signal in response to receipt of light. The wafer also includes testing waveguides that each extends from within a boundary of one of the optical devices across the boundary of the optical device and also provides optical communication between a first portion of the optical components and a second portion of the optical components. The first portion of the optical components includes one or more of the light-generating components and the second portion of the optical components include one or more of the receiver components.