The frequency stability required for an amplitude modulated (ASK) optical coherent communications system is ±10 MHz. If the local oscillator laser emits at 1.55 μm wavelength and its frequency drifts at a rate of 14 GHz K-1 calculate:
(i) The fractional stability necessary for the laser;
(ii) The maximum temperature change permissible in the absence of external control;
(iii) The maximum transmission bandwidth allowed by the frequency stability.