Optical frequency comb optimization for satellite payload applications based on multitone phase modulation

We investigate the generation and shape manipulation of an optical frequency comb (OFC) by using a phase modulator (PM) driven by multiple RF signals.The rationale is to use the OFC to act as the light source of dense wavelength division multiplexing (DWDM) or to achieve photonically-assisted mm-wave generation, e.g., 15 GHz -60 GHz (Ka/V IEEE bands) and to be able to integrate these key functionalities onto satellite payloads.We propose to externally modulate a narrow-linewidth continuous wave (CW) laser using an electro-optic phase modulator driven by multiple RF signals.The shape of the comb can be controlled by setting the frequencies, the amplitudes and the relative phases of the driving signals.Consequently, we can attenuate the undesired frequencies leaving just two tones whose frequency difference is equal to the desired mm-wave.In this work, we present an extinction ratio between the two desired tone and the strongest undesired one of approximately 10 dB.Heterodyne detection with a photodiode generates the mm-wave signal.Moreover, controlling the OFC shape allows the generation of an ultra-flat OFC.We present an OFC of 13 lines and 3 GHz spacing showing an amplitude difference between the strongest and weakest line of 0.5 dB.This technique avoids the use of an intensity modulator, exploiting the good insertion loss performance of the PM, shows good power efficiency and is extremely simple and cheap with respect to other OFC generation techniques such as modelocked lasers.