This paper provides a description of electric field sensing using the slab coupled optical fiber sensor (SCOS) with an emphasis on the detection electronics. This analysis includes estimated signal strength and the main noise sources. With all noise eliminated except for the shot noise in the photodetector, thermal noise in the terminating resistor, and the thermal noise in the low noise amplifier the theoretical sensitivity is calculated to be 0.85 V/m Hz^0.5. The signal is measured using an electrical spectrum analyzer and found to have a sensitivity of 1.34 V/m Hz^0.5.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.