Thermal actuators are among the most consolidated and widespread devices for the active control of photonic integrated circuits (PICs). As a main drawback, mutual thermal crosstalk among actuated devices integrated onto the same photonic chip can affect the working point of the PIC and can reduce the efficiency of automated tuning and calibration procedures. In this work, a strategy to cancel out the effects of the phase coupling induced by thermal crosstalk is presented. In our technique, that we named Thermal Eigenmode Decomposition (TED), all the actuators of the PIC are controlled simultaneously according to the eigensolution of the thermally coupled system. The effectiveness of the TED method is validated by numerical simulations and experiments carried out on coupled microring resonator (MRR) and switch fabrics of Mach-Zehnder interferometers (MZIs). With respect to individual control of phase actuators, where thermal crosstalk can hinder the convergence of automated tuning algorithms, with the TEDtechnique convergence is always reached, requires a lower number of iterations, and is less sensitive to the initial state of the PIC. The proposed TED method can be applied to generic tuning and locking algorithm, can be employed in arbitrary PIC architectures and its validity can be extended to systems where phase coupling is induced by other physical effects, such as mutual mechanical stress and electromagnetic coupling among RF lines.

This paper presents the key ingredients and the best practices for implementing simple, effective and robust control and calibration procedures for arbitrary photonic integrated circuit (PIC) architectures. Three main features are presented and discussed: a technique to cancel out the effects of mutual crosstalk among thermal tuners, the exploitation of labelling to identify different optical signals, the use of input modulated signal to automatically reshape the frequency response of the device.Examples of application are then illustrated to show the validity and generality of the approach, namely a cross-bar interconnect matrix router, a variable bandwidth filter and third order coupled microring filter. Further, the automatic and dynamic generation of the lookup table of add/drop hitless filters operating on a dense wavelength division multiplexing grid is demonstrated. The lookup table achieved with the proposed approach can dynamically update itself to new conditions of the chip or new requirements of operation, such as variations in channel modulation format or perturbation induced by neighboring devices due to a change in their working point.

Given the escalation of demand for high speed data interconnection, both between users and datacenters, high capacity optical networks need a boost in capacity, flexibility and efficiency. To stand up for those problems, the network reconfigurability is a key feature in a saturated and power hungry network operating scenario. In this paper, a reconfigurable optical node, using a commercial integrated photonics foundry was conceived, fabricated and tested. A novel application of automatic control of complex optical circuits involving locking and tuning of microring resonators is presented. The technique exploits a channel labeling strategy to identify a single optical channel amid a Dense Wavelength Division Multiplexing (DWDM) comb. The fabricated filter array provided add-drop ports with hitless channel reconfiguration and telecom graded specifications as 20 dB of in-band isolation, 40 GHz of channel bandwidth in a microring filter with 1 THz of Free Spectral Range (FSR).

Real‐time control of multiple cascaded devices is a key requirement for the development of complex silicon photonic circuits performing new sophisticated optical functionalities. This article describes how the dithering technique can be leveraged in combination with non‐invasive light probes to independently control the working point of many photonic components. The standard technique is extended by introducing the concept of orthogonal dithering signals to simultaneously discriminate the effect of different actuators, while the idea of frequency re‐use is discussed to limit the complexity of control systems in cascaded architectures. After a careful analysis of the problem, the article presents an automated feedback strategy to tune and lock photonic devices in the maxima/minima of their transfer functions with given response speed and sensitivity. The trade‐offs of this approach are discussed in detail to provide guidelines for the design of the feedback loop. Experimental demonstrations on a mesh of Mach‐Zehnder interferometers and on cascaded ring resonators are discussed to validate the proposed control architecture in different scenarios and applications.

Flexible optical networks require reconfigurable devices with operation on a wavelength range of several tens of nanometers, hitless tuneability (i.e. transparency to other channels during reconfiguration), and polarization independence. All these requirements have not been achieved yet in a single photonic integrated device and this is the reason why the potential of integrated photonics is still largely unexploited in the nodes of optical communication networks. Here we report on a fully-reconfigurable add-drop silicon photonic filter, which can be tuned well beyond the extended C-band (almost 100 nm) in a complete hitless (>35 dB channel isolation) and polarization transparent (1.2 dB polarization dependent loss) way. This achievement is the result of blended strategies applied to the design, calibration, tuning and control of the device. Transmission quality assessment on dual polarization 100 Gbit/s (QPSK) and 200 Gbit/s (16-QAM) signals demonstrates the suitability for dynamic bandwidth allocation in core networks, backhaul networks, intra- and inter-datacenter interconnects.