Optical modulation amplitude

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


 * $$\text{OMA} = P_1 - P_0 \, $$

where P1 is the optical power level generated when the light source is "on," and P0 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 $$P_{\text{av}} = (P_1+P_0)/2$$ and the extinction ratio $$r_{e} = P_{1}/P_{0}$$


 * $$ \text{OMA} = 2 P_{\text{av}} \frac{r_{e}-1}{r_{e}+1}$$

In the limit of a high extinction ratio, $$ \text{OMA} \approx 2P_{\text{av}} $$. 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.