This paper presents the performance of optically controlled MESFETs as photodetectors. The optical performance characteristics such as optic-to-electric responsivity, and BER for a π/4-QPSK signal are experimentally investigated. Measurements are performed by using MMIC compatible MESFETs. Experimental results are also evaluated in comparison with calculated PIN-PD limit. Optic-to-electric responsivity has high gain at lower received optical powers. It is shown experimentally that MESFET photodetectors improve the permissible optical power by 6 dB compared to the PIN-PD limit. Optically controlled MESFETs will provide a novel receivers for fiber-optic systems.