We measure the dipole moment of InGaAs/GaAs self-assembled quantum dots by investigating the propagation of femtosecond light pulses interacting resonantly with the ground to excited state transition. The measurement involves coupling light into a waveguide containing quantum dots in the core and time resolving the output. The advantages are increased interaction length with the weakly absorbing quantum dots and observation of the decay of light pulses over successive cavity round trips. The large uncertainty in waveguide coupling efficiency that has hindered the determination of the absolute dipole moment in similar experiments' does not affect our results.