We present the results of 7 years of K -band monitoring of the low-mass X-ray binary GRS 1915+105 .
Positive correlations between the infrared flux and the X-ray flux and X-ray hardness are demonstrated .
Analysis of the frequency spectrum shows that the orbital period of the system is P _ { orb } = 30.8 \pm 0.2 days .
The phase and amplitude of the orbital modulation suggests that the modulation is due to the heating of the face of the secondary star .
We also report another periodic signature between 31.2 and 31.6 days , most likely due to a superhump resonance .
From the superhump period we then obtain a range for the mass ratio of the system , 0.05 < q < 0.12 .