Multiple pins extend from the outside to the inside of an optical sub-assembly. A light receiver or a light transmitter is arranged inside the optical sub-assembly. A receiver circuit and transmitter circuit (TX) are arranged inside the optical sub-assembly and connected between the multiple pins and the light receiver and the light transmitter. The receiver circuit comprises a receiver communication interface in order to transform an output signal of the light receiver into a communication signal, and wherein the transmitter circuit comprises a transmitter communication interface to transform a communication signal into an input signal of the light transmitter. A control interface is connected with the receiver circuit and the transmitter circuit arranged inside the optical sub-assembly, wherein the control interface is connectable to two of the multiple pins.