  We propose and experimentally demonstrate a microwave photonic intensity
differentiator based on a Kerr optical comb generated by a compact integrated
micro-ring resonator (MRR). The on-chip Kerr optical comb, containing a large
number of comb lines, serves as a high-performance multi-wavelength source for
implementing a transversal filter, which will greatly reduce the cost, size,
and complexity of the system. Moreover, owing to the compactness of the
integrated MRR, frequency spacings of up to 200-GHz can be achieved, enabling a
potential operation bandwidth of over 100 GHz. By programming and shaping
individual comb lines according to calculated tap weights, a reconfigurable
intensity differentiator with variable differentiation orders can be realized.
The operation principle is theoretically analyzed, and experimental
demonstrations of first-, second-, and third-order differentiation functions
based on this principle are presented. The radio frequency (RF) amplitude and
phase responses of multi-order intensity differentiations are characterized,
and system demonstrations of real-time differentiations for a Gaussian input
signal are also performed. The experimental results show good agreement with
theory, confirming the effectiveness of our approach.
