Novel low‐loss waveguide delay lines using Vernier ring resonators for on‐chip multi‐λ microwave photonic signal processors

Abstract

In this paper, novel photonic delay lines (DLs) using Vernier/non‐identical ring resonators (VRRs) are proposed and demonstrated, which are capable of simultaneous generation of multiple different delays at different wavelengths (frequencies). The simple device architectures and full reconfigurability allow the DLs to be integrated with other functional building blocks in photonic integrated circuits to realize on‐chip, complex multi‐λ microwave photonic signal processors with reduced system complexity. To prove the concept, DLs using VRRs in cascaded and coupled configurations have been fabricated in TriPleXTM waveguide technology, which enables a very low delay‐induced loss of approximately 0.18 dB/100 ps. The fabricated DLs demonstrated simultaneous generation of four incremental delays, where a maximum incremental step of 550 ps and a corresponding top delay of 1650 ps were measured for a bandwidth up to 1 GHz. To our knowledge, this is the first report on VRRs for delay generation functionalities.

Programmable optical processor chips: toward photonic RF filters with DSP-level flexibility and MHz-band selectivity

“…An alternative approach to address this issue is to create delay lines that are able to simultaneously provide multiple different delays at different wavelengths or optical carrier frequencies. We proposed and experimentally demonstrated such delay lines using the Vernier configurations of RRs [66], namely combining RRs of different FSRs. Two types of Vernier configurations were considered as shown in Figure 9, that is, the serial cascade and coupled configurations, where the former features easier control and the latter less chip area.…”

Nonlinear Integrated Microwave Photonics

“…The chip consists of three main sections: two long spiral waveguides for wavelength multicasting and multiplexing based on cascaded FWM processes, and reconfigurable optical filter based on a network of ring resonators that can be tuned using thermo-optics effect. This ring network might host a mixture of all pass ring filters, adddrop rings, as well as Vernier (cascade of non-identical) rings which have been recently exploited for tunable delay lines in a multi-wavelength beamformer [16]. The programmability of the ring network will allow the chip to be reconfigured in real time, to synthesize different responses according to the user demand.…”

Programmable photonic signal processor chip for radiofrequency applications

“…In integrated microwave photonics, many key RF functions have been demonstrated using on-chip photonic signal processors, including spectral filters [9][10][11], phase shifters [12], integrators [13], differentiators [14], pulse shapers [15,16], frequency discriminators [17,18], tunable delay lines [19,20], and beamformers [21,22]. Next to the general advantages of photonic integration in terms of device size, robustness, power efficiency, and low-cost potential [23][24][25][26], some salient works showed remarkable features such as THz processing bandwidths [27], subvolt control [28], filter extinction ratios greater than 60 dB [29], and multioctave continuous frequency shifting [19].…”

“…A more flexible approach would be to design a universal photonic circuit whose topology can be reconfigured, post manufacture, similar to a field-programmable electronic processor, e.g., a field-programmable gate array (FPGA) [30]. This would have variable circuit parameters [9][10][11][12][13][14][15][16][17][18][19][20][21][22] but also a flexible circuit topology to suit a wide range of signal-processing functions. Recently, Pérez et al presented the concept of software-defined processing in microwave photonic systems, addressing the anticipated flexibility requirements in future RF applications [31].…”