Spectral Classification and Cloning of Photonic Integrated Filters for Volume Testing

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.