Measurement precision is a key figure of merit in optical measurements. However, precision in ratiometric fluorescence thermometry is constrained by its underlying physical principles. We identify weak signals as a major source of temperature uncertainty and propose optical signal uncertainty optimization to improve thermometric precision. In a representative thermally coupled system, optimization increases the maximum relative sensitivity to 2.1 times its original value and reduces the minimum temperature uncertainty by approximately 45%, both at 563 K. This method offers a route to improved precision in ratiometric optical measurements with asymmetric signal uncertainties.
