Need more information. Temperature is dependent on thermal resistance and power dissipation, a thermal engineer would tell you the same thing.
To answer this we would need to know
A) The heatsink that is being used with the diode
B) The power dissipation of the diode (can be found by subtracting input power from optical output)
C) Ambient air temperature
Simply put:
T_diode = T_ambient + power dissipated by the heatsink * total thermal resistance from the diode to the heatsink fins