SC/APC fibre attenuators listed on your website (208-558). We have had issues with attenuators operating over low temperatures (down to -40°C) previously, where presumed misalignment of the component leads to significant extra attenuation.
Misalignment would be a reason for a significant increase in attenuation. SC/APC connectors should offer correct alignment and stable attenuation loss even at temperatures as low as -40°C.