  The expansion of telecommunications incurs increasingly severe crosstalk and
interference, and a physical layer cognitive method, called blind source
separation (BSS), can effectively address these issues. BSS requires minimal
prior knowledge to recover signals from their mixtures, agnostic to carrier
frequency, signal format, and channel conditions. However, previous electronic
implementations of BSS did not fulfill this versatility requirement due to the
inherently narrow bandwidth of radio-frequency (RF) components, the high energy
consumption of digital signal processors (DSP), and their shared weaknesses of
low scalability. Here, we report a photonic BSS approach that inherits the
advantages of optical devices and can fully fulfill its "blindness" aspect.
Using a microring weight bank integrated on a photonic chip, we demonstrate
energy-efficient, WDM-scalable BSS across 19.2 GHz of bandwidth, covering many
standard frequency bands. Our system also has a high (9-bit) resolution for
signal demixing thanks to a recently developed dithering control method,
resulting in higher signal-to-interference ratios (SIR) even for
ill-conditioned mixtures.
