Reconfigurable broadband microwave photonic intensity differentiator based on an integrated optical frequency comb source

Abstract

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 the first-, second-, and third-order differentiation functions based on this principle are presented. The radio frequency 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.

Microcomb-Based Photonic RF Signal Processing

“…The transversal structure, similar to the concept of finite impulse response digital filters, is a fundamental tool for photonic RF signal processing. With the proper design of the tap weights, any transfer function can be arbitrarily realized for different signal processing functions such as bandpass filters, differentiators and Hilbert transformers [23][24][25][26][27][28][29][30][31][32][33][34].…”

“…In addition, for photonic RF channelizers, with a given bandwidth for each wavelength channel, the total operation bandwidth (i.e., the maximum bandwidth of the input RF signal that can be processed) will depend on the number of wavelengths, and thus can be greatly enhanced with microcombs. Based on these advantages, a wide range of RF applications have been demonstrated, such as optical true time delays [23][24][25], transversal filters [25][26][27], signal processors [28,29], channelizers [30,31] and others [32][33][34]. Here, we review the recent advances of RF signal processing functions made possible through the use of microcombs, highlighting their potential and future possibilities.…”

Advanced RF and microwave functions based on an integrated optical frequency comb source

“…Kerr micro-comb sources [32][33][34][35][36][37][38][39], particularly those based on CMOS-compatible platforms featuring a high nonlinear figure of merit [34][35][36], offer many advantages over discrete laser sources, such as the potential to provide a much higher number of wavelengths, a greatly reduced footprint and complexity, as well as significantly improved performance. In particular, for RF transversal functions the number of wavelengths dictates the available channel number of RF time delays.…”

“…First, Kerr combs were generated based on an integrated MRR. When the wavelength of the pump light was tuned into one of the MRR resonances, with the pump power high enough to provide sufficient parametric gain, optical parametric oscillation occurred [32][33][34][35][36][37][38][39], ultimately generating Kerr optical combs with nearly equal line spacing (as shown in Fig. 1(a)).…”

Microwave and RF Photonic Fractional Hilbert Transformer Based on a 50 GHz Kerr Micro-Comb

“…This holds true for recent reports of an integrated reconfigurable microwave processor [11] as well as a a simple, wideband and direct route to realize continuously tunable FHT based on a Bragg grating [12]. In practice, however, the FHT of the temporal intensity profiles associated with radio frequency (RF) and microwave signals, and not the complex optical fields, is required in many applications such as ultra-wideband frequency generation, RF measurement, and RF signal reshaping [13][14][15][16].…”