Lasers for gravitational wave detectors need to fulfill tight requirements in amplitude stability, which can only be met by means of feedback control loops. Ultimately, power stabilization control loops are limited by the shot noise of their sensor. The power noise increases linearly with the amount of detected power, while the shot noise grows with the square root. Increasing the detected power is therefore a suitable means to reach a lower sensing noise but it is limited by the power handling capabilities of the photodiodes. An alternative way of improving the sensitivity is the optical AC coupling technique, which exploits the high pass behavior of an optical resonator to reduce the optical power on the detector without compromising its sensitivity above the corner frequency. In this paper we investigate the optical AC coupling technique at the aLIGO Livingston gravitational wave detector. We measured an optical AC coupling gain of 10 dB in the gravitational wave detection band, which offers the potential to improve the laser power stability by the same factor. [ABSTRACT FROM AUTHOR]