This invention is to control and monitor a solar module by optical communication using solar cells in the solar module as a receiver of the incoming optical signal. The optical communication is by way of solar cells in a solar module as sensors and/or receivers, and busbars of the solar module as conduits to transfer the incoming signal to a control circuitry. Such control includes, but is not limited to, on/off control of power output from a solar module, and such monitoring includes, but is not limited to, reading, data keeping and displaying current operating performance status of the solar module. With this invention, solar modules can be turned off and on without physically disconnecting and reconnecting wires. Such control and monitoring enables more efficient and accurate operation and maintenance of a solar power system of any size.