With the help of GPS signals for synchronization, increasingly ubiquitous phasor measurement units (PMUs) provide power grid operators unprecedented system monitoring and control opportunities. However, the performance of PMUs is limited by the inherent deficiencies in traditional transformers. To address these issues, an optical sensor is used in PMU for signal acquisition to replace the traditional transformers. This is the first time the utilization of an optical sensor in PMUs has ever been reported. The accuracy of frequency, angle, and amplitude are evaluated via experiments. The optical sensor based PMU can achieve the accuracy of 9.03 × 10−4 Hz for frequency, 6.38 × 10−3 rad for angle and 6.73 × 10−2 V for amplitude with real power grid signal, demonstrating the practicability of optical sensors in future PMUs.