Techniques for measuring optical modulation amplitude (OMA) are disclosed. For example, a technique for measuring an OMA value associated with an input signal includes the following steps/operations. The input signal is applied to a photodetector, wherein the photodetector is calibrated to have a given responsivity value R, and further wherein the photodetector generates an output signal in response to the input signal. The output signal from the photodetector is applied to a radio frequency (RF) power meter, wherein the RF power meter measures the root mean squared (RMS) power value of the output signal received from the photodetector. The OMA value associated with the input signal is determined in response to the root mean squared (RMS) power value measured by the RF power meter. The OMA value may be determined as a function of a factor F derived from a relationship between an amplitude of a data signal and the RMS value of the data signal.