Quantum key distribution (QKD) at telecom wavelengths (1260nm to 1625nm) has the potential for fast deployment due to existing optical fibre infrastructure and telecom technologies. At these wavelengths, indium gallium arsenide (InGaAs) avananche photodetectors (APDs) have to be used for photon detection. Similar to their silicon counterparts used at shorter wavelengths, they exhibit fluorescence from recombination of electron-hole pairs generated in the avalanche breakdown process. This fluorescence may open side channels for attacks on QKD systems. Here, we characterise the breakdown fluorescence from two commerical InGaAs single photon counting modules (ID220 ID Quantique), and find a spectral distribution between 1000nm and 1600nm. We also show that with application of spectral filtering, this side channel can be greatly suppressed.