In telecommunications, optical modulation amplitude (OMA) is the difference between two optical power levels, of a digital signal generated by an optical source, e.g., a laser diode.
It is given by
where P<sub>1</sub> is the optical power level generated when the light source is "on," and P<sub>0</sub> is the power level generated when the light source is "off." The OMA may be specified in peak-to-peak mW.
The OMA can be related to the average power and the extinction ratio
In the limit of a high extinction ratio, . However, OMA is often used to express the effective usable modulation in a signal when the extinction ratio is not high and this approximation may not be valid.