Abstract: An optoelectronic device is used with an optical fiber for data transmission and has a transmitter mounted on a printed circuit board (PCB) to emit light. A collimation lens on a lens block receives the light incident thereto. A microstructure on a reflective surface of the lens block has sections that reflect the light into attenuated portions. A focusing lens on the lens block focuses a first attenuated portion from first sections of the reflective surface to the optical fiber. Meanwhile, second sections of the reflective surface reflect a second attenuated portion to another reflective surface on the lens block. The second attenuated portion passes out of a refractive surface on the lens block to an receiver, which is mounted on the PCB adjacent the transmitter. The second attenuated portion of the light can be used to monitor the optical output of the transmitter.