This paper reports the radiation tolerance of small form factor multimode optical transceivers designed for extended temperature and vibration environments. The transceivers are based on specifically designed VCSELs and PIN photodiodes and packaged such that the transceiver functions over an extended temperature range (beyond -40 to +85°C) without affecting performance or dynamic range. These transceivers are capable of multi-Gigabit per second transmission with bit error ratio of less than 1e-12 in non-irradiated conditions. To characterize these transceivers, we have measured their response to dose rate, total dose, and neutron fluence environments. For the dose rate test, we report the upset, latch-up, and burnout thresholds of the transceiver. In the total dose test, we measure the total dose level that does not significantly affect the transceiver and characterize the degradation for increasing total dose levels. For the neutron fluence test, we measure the fluence level that does not significantly affect the transceiver and characterize the degradation for increasing fluence levels. With this radiation data on the performance limits and penalties of the transceiver, high speed fiber optic links may now be considered for platforms previously off limits due to their irradiated environments.