In this contribution we present the small signal net modal gain measurement results of single-layer InAs/InP(100) quantum dot amplifiers in 1.6 to 1.8 μm wavelength range. The material shows sufficient optical gain to be used in the long-wavelength optical coherence tomography. The modal gain has been observed as a function of current density and temperature. An improved rate equation model has been applied to analyse the measurements. A good fit of the theory to the measurements was obtained with a temperature dependent carrier injection efficiency which is below 2%.