General-purpose programmable photonic processor for advanced radiofrequency applications.

A general-purpose photonic processor can be built integrating a silicon photonic programmable core in a technology stack comprising an electronic monitoring and controlling layer and a software layer for resource control and programming. This processor can leverage the unique properties of photonics in terms of ultra-high bandwidth, high-speed operation, and low power consumption while operating in a complementary and synergistic way with electronic processors. These features are key in applications such as next-generation 5/6 G wireless systems where reconfigurable filtering, frequency conversion, arbitrary waveform generation, and beamforming are currently provided by microwave photonic subsystems that cannot be scaled down. Here we report the first general-purpose programmable processor with the remarkable capability to implement all the required basic functionalities of a microwave photonic system by suitable programming of its resources. The processor is fabricated in silicon photonics and incorporates the full photonic/electronic and software stack.

Modeling amplified arbitrary filtered microwave photonic links and systems.

Microwave photonic (MWP) links and systems will have more losses as their complexities increase and there will be a need for incorporating optical amplification. Here, we report results of an analytical model developed for amplified arbitrary filtered MWP systems that provides the expressions of the main figures of merit for intensity modulation direct detection. It contemplates the cases of power, intermediate and pre amplification. The model is applied to a long MWP link and then it is evaluated in a MWP reconfigurable filter implemented by means of a programmable waveguide mesh photonic integrated circuit.

Multipurpose self-configuration of programmable photonic circuits.

Programmable integrated photonic circuits have been called upon to lead a new revolution in information systems by teaming up with high speed digital electronics and in this way, adding unique complementary features supported by their ability to provide bandwidth-unconstrained analog signal processing. Relying on a common hardware implemented by two-dimensional integrated photonic waveguide meshes, they can provide multiple functionalities by suitable programming of their control signals. Scalability, which is essential for increasing functional complexity and integration density, is currently limited by the need to precisely control and configure several hundreds of variables and simultaneously manage multiple configuration actions. Here we propose and experimentally demonstrate two different approaches towards management automation in programmable integrated photonic circuits. These enable the simultaneous handling of circuit self-characterization, auto-routing, self-configuration and optimization. By combining computational optimization and photonics, this work takes an important step towards the realization of high-density and complex integrated programmable photonics.

Auto-routing algorithm for field-programmable photonic gate arrays.

Programmable multipurpose photonic integrated circuits require software routines to make use of their flexible operation as desired. In this work, we propose and demonstrate the use of a modified tree-search algorithm to automatically determine the optimum optical path in a field-programmable photonic gate array (FPPGA), based on end-user specifications, circuit architecture and imperfections in the realized FPPGA arising, for example, from fabrication variations. In such a scenario, the proposed algorithm only requires the hardware topology and the location of the connections of the FPPGA defining the optical path to be programmed. The routine is able to optimize the path over multiple and competing objectives like the overall length, accumulated loss and power consumption. In addition, should any region of the circuit suffer from any potential damage that may affect the device performance, this algorithm is also able to provide basic self-healing and fault-tolerance capabilities by supplying alternative paths through the photonic arrangement.

Integrated photonic tunable basic units using dual-drive directional couplers.

Photonic integrated circuits based on waveguide meshes and multibeam interferometers call for large-scale integration of Tunable Basic Units (TBUs) that feature beam splitters and waveguides. This units are loaded with phase actuators to provide complex linear processing functionalities based on optical interference and can be reconfigured dynamically. Here, we propose and experimentally demonstrate, to the best of our knowledge, for the first time, a thermally actuated Dual-Drive Directional Coupler (DD-DC) design integrated on a silicon nitride platform. It operates both as a standalone optical component providing arbitrary optical beam splitting and common phase as well as a low loss and potentially low footprint TBU. Finally, we report the experimental demonstration of the first integrated triangular waveguide mesh arrangement using DD-DC based TBUs and provide an extended analysis of its performance and scalability.