How can I ensure that the linearity of an optical measurement is maintained even at higher cell densities?

The standard procedure for optical off-line measurement is that at higher cell densities the original suspension is diluted before the measurement. The result of the measurement can then be "back-calculated" using the known dilution factors.

In case of measurement in a reactor, the dilution of the culture medium is not possible. In-line sensors with a wide linear range by using both transmission and reflection optical measurements (like Dencytee Arc) are the best option to prevent any signal loss at higher cell densities.