Towards a universal RF photonic integrated circuit architecture for microwave applications

There has been a plethora of publications over the last decade that have described essentially the same Generalized Mach-Zehnder Interferometer (GMZI) circuit architecture: a 1 × N splitter directly interconnected to a N × 1 combiner via an array of N electro-optic LiNbO
₃
-based phase modulators, each circuit adapted to particular design goals. This paper introduces a novel extension of the circuit architecture that subsumes all these MZI circuits in the prior art by replacing the N × 1 combiner of a GMZI-based architecture by an N × N optical Discrete Fourier Transform (DFT) network to generate a frequency comb with regularly spaced harmonics of frequency qω
_RF
where ω
_RF
is the frequency of the RF drive signal applied to the phase modulators. All harmonic orders equivalent modulo N to the output port number p exit that port. As the circuit generates N spatially separated phase correlated subcarriers, it can be used to provide multi-carriers for transmission formats such as orthogonal frequency division multiplexing (OFDM) that will enable the satisfaction of the terabit data ratedemands anticipated in the near future. The proposed circuit can be implemented practically in any material platform that offers linear electro-optic phase modulators.