Volume testing is rapidly becoming a key step in the production chain of photonic integrated circuits (PICs), which are ever increasing their integration density and complexity, and are penetrating many market sectors. What makes PIC testing peculiar with respect to testing of electronic integrated circuits (EICs) is the fact that it generally requires also control and calibration procedures. Here, we present a method to perform time and cost-efficient volume testing of frequency-selective PICs. The described techniques enable to evaluate the deviation between the spectral responses of a device under test (DUT) and a reference (REF) device, without a direct measurement of the transfer function, which is a time and resource consuming procedure. Information on the DUT status is inferred from the integral power of a top-flat broadband optical source, which is shaped by the REF device and is transmitted through the DUT. In this way it is possible to classify the DUT according to specifically defined metrics, automatically tune it to replicate the REF spectral response and build LookUp Tables (LUTs) to be used in operative conditions. The proposed technique is validated experimentally on a reconfigurable silicon-photonics microring resonator filter implementing a Tuneable Optical Add/Drop Multiplexer, but we also provide conditions for its use for testing of frequency-selective devices.

Programmable photonic circuits require an electronic control layer to configure and stabilize the optical functionality at run‐time. Such control action is normally implemented by supervising the status of the circuit with integrated light monitors and by providing feedback signals to integrated actuators. This paper demonstrates that the control action can be effectively performed with electrical signals that are time‐multiplexed directly on the photonic chip. To this aim, the necessary electronic functionalities are monolithically integrated in a conventional 220 nm silicon photonics platform with no changes to the standard fabrication process. By exploiting a non‐conventional structure to implement metal‐oxide–semiconductor field‐effect transistors, an electronic controller is co‐designed into a programmable photonic circuit to enable a time‐multiplexed readout of integrated photodetectors and sequential activation of thermal phase shifters with on‐chip electronic memory. The accuracy of the time‐multiplexed control, achieved on a time scale of less than 10 ms, is demonstrated by penalty‐free routing of 10 Gbit s −1 modulated signals. This approach can be straightforwardly applied to large‐scale photonic chips to reduce the number of required electrical input/output connections.

Continuously variable true-time optical delay lines are typically subject to a constraint of the bandwidth-delay product, limiting their use in several applications. In this Letter, we propose an integrated topology that breaks the bandwidth-delay product limit. The device is based on multiple Mach-Zehnder Interferometers (MZIs) arranged in parallel, providing easier control and a larger bandwidth compared to ring resonator-based solutions. The functionality of this architecture is demonstrated with a 4-stage delay line by performing measurements in both the time and frequency domains. The delay line introduces a delay of 90 ps over a bandwidth of more than 22 GHz with a negligible group delay distortion, operates on a wavelength range of about 60 nm, and is scalable to a higher number of MZI stages.

This paper demonstrates the possibility of automatically stabilizing the working condition of an integrated Silicon Photonics microring modulator with a novel dithering-based control scheme.The proposed feedback strategy leverages a realtime acquisition of the modulator non-linear transfer function (TF) and operates by setting the target locking point to the zero of the TF second derivative, i.e.where the ring slope is maximum.This results in a control algorithm that is both power-independent and calibration-free.The paper shows that the operating point identified in this way has a negligible difference with respect to the optimum working condition of minimum Transmitter Penalty normally targeted and that the employed dithering signal does not affect the modulation quality.The control performances, made possible by an FPGA-based platform ensuring a 30 ms response time, are assessed in a 50 Gbit/s routing scenario, demonstrating effective compensation of wavelength and thermal variations and successful transmission even in demanding environments.

Automatic electrical IV measurements and optical spectral tuning of a 4-channels reconfigurable multiplexer is achieved using a probe-card approach. The full testing lasts less than 300 msec. The technique is suitable for PICs volume testing.

A silicon photonic integrated circuit, implementing a novel delay-line architecture, is proposed. The device, based on a set of four nested Mach-Zehnder Interferometers, overcomes typical delay-bandwidth product. Showing a minimum bandwidth of 20 GHz, group delay can be continuously tuned between 0 and 100 ps.

Abstract Silicon photonic integrated circuits allow very efficient manipulation of light in a compact size but suffer from strong dependence on temperature variations and fabrication tolerances. Local stabilization of the working point of each photonic device in a circuit is thus needed, made possible by integrated sensors and actuators that are operated by an external electronic controller. However, this approach is what currently limits the scaling of photonic complexity to few tens of devices, due to practical limitations in the number of connections between the chip and the control electronics. Monolithic integration of electronic functionalities into the photonic systems is therefore essential to enable new sophisticated architectures, but it requires to fully preserve the optical quality. Here we demonstrate the possibility of fabricating CMOS integrated electronic circuits on a technological platform specifically conceived and optimized only for photonic devices. By exploiting the silicon waveguide layer and with zero changes to the photonic process flow, fully functional MOS transistors have been integrated on the side walls of the waveguide layer, showing a threshold voltage of 1.84 V, a gain factor of 4 μA/V^2, an Early voltage of 35 V and an inverse subthreshold slope of 250 mV/dec. By combining digital gates and analog switches, we demonstrate the operation of an analog multiplexer integrated into a 16-to-1 optical router to sequentially read 16 on-chip photodetectors with only one connection towards the external electronics. This enables time-multiplexed closed-loop control and stabilization of the router to thermal instabilities with less than 10 ms transient time and a power penalty of just 0.3 dB on the transmission of 10 Gb/s modulated signals. We envision that this first example of co-integrated electronic layer to support the optics and counteract its weaknesses can definitely unleash the full potential of the photonic technology towards a new realm of innovative architectures and applications.

A novel method to perform both electrical and optical testing of Photonic Circuit is presented. The use of probe card to electrically access and characterize the device enables the execution of a new approach for the calibration and cloning of filter-based devices.

On-chip optical power monitors are essential elements to calibrate, stabilize, and reconfigure photonic integrated circuits. Many applications require in-line waveguide detectors, where a trade-off has to be found between large sensitivity and high transparency to the guided light. In this work, we demonstrate a transparent photoconductor integrated on standard low-doped silicon-on-insulator waveguides that reaches a photoconductive gain of more than 106 and an in-line sensitivity as high as -60 dBm. This performance is achieved by compensating the effect of electric charges in the cladding oxide through a bias voltage applied to the chip substrate or locally through a gate electrode on top of the waveguide, allowing one to tune on demand the conductivity of the core to the optimum level.

We report on a novel integrated delay-line architecture enabling to break the delay-bandwidth product of Mach-Zehnder Interferometers delay-lines. A continuously tuneable delay from 0 to 100 ps is achieved across a bandwidth of 21 GHz.

We propose a technique for automated active compensation of nonlinear effects in silicon photonic coupled microring resonator filters. Transmission performances of 200 Gbit/s DP 16-QAM signals up to 20 dBm are evaluated.

Nonlinear effects limit the maximum amount of optical power that can be handled by silicon photonic integrated circuits (PICs). This limitation is particularly tight in resonant devices such as microring resonator (MRR) filters, suffering from a power-dependent resonance spread due to intracavity power enhancement. In this Letter, we present an automatic control system that can dynamically mitigate the nonlinear spectral distortion of silicon MRR filters by thermally controlling each MRR. The benefit of the proposed scheme is demonstrated on the spectral response of a polarization-transparent coupled-MRR filter operating on a 200 Gbit/s signal. The proposed technique, which does not require a priori information on the PIC topology and functionality, is scalable to more complex architectures and can be employed to compensate for generic nonlinear effects in different photonic platforms.

A coupled microring resonator architecture with non-integer Vernier ratio design and controllable loss is exploited to implement a polarization-transparent hitless tunable FSR-free filter operating over the extended C+L band (1520 nm–1620 nm).

We present a novel design for a reconfigurable silicon microring resonator filter exploiting non-integer Vernier ratio to achieve FSR-free spectral response. Hitless tunability across the extended C+L band (1520 nm-1620 nm) is achieved by introducing controllable loss in the MRRs of the filter.

We propose an approach to real-time compensate nonlinear phenomena in microring resonator silicon photonic filters. Transmission assessments are performed for 200 Gbit/s DP 16- QAM signals, up to 19 dBm.