Photonics offers the bandwidth and a potentially seamless integration with the fiber-wireless technology (Fi-Wi) for 5G communications. Commercially available terahertz generators are often based on photonics, i.e., lasers, too. One particularly promising technique to generate the microwave or sub-terahertz signal is to use the comb generated by modulating a continuous-wave laser signal. By filtering two non-adjacent comb lines, a beat signal is generated that has a frequency that is an integer multiple of the electrical modulator driving signal. In this way, frequency multiplication is achieved using microwave photonics. Photodetectors and/or photomixers can then be used to convert the beat signal to a millimeter-wave. However, the energy-efficiency of these techniques – and how they compare to all-electronic solutions – has not been analyzed yet.
In this paper we will present this energy-efficiency analysis, based on a silicon photonics implementation. Silicon photonics has the potential to miniaturize such systems, for ubiquitous and low-cost implementation. Silicon-based modulators, however, are not ideal phase modulators, and simulation tools need to incorporate this. The regimes, in terms of signal power and frequency, where photonics compares favorably over electronics, will be discussed.