Dozens of copper coils in an MRI scanner pick up the faint response from tissues, like microphones trying to catch a whisper in a noisy hall. Each microphone drags a thick bundle of wires behind it. The wires press on each other, create electrical interference, heat up, and add risk for the patient.

A team of researchers proposed replacing that copper tangle with optical fibers. In the Light Coils architecture, the signal from each coil is converted into light using a Mach-Zehnder modulator — a tiny device that varies the brightness of a laser beam in sync with the radio signal. Power for the preamplifiers is delivered over the same fiber: a powerful laser lights a photovoltaic cell, turning light into electricity. Even the coil's detuning during the scanner's RF pulse is triggered by an optical command — no galvanic connection at all.

Tests on a clinical 3 Tesla scanner showed that a single "light coil" produces brain images of a living human that are indistinguishable in quality from the traditional coaxial connection. Moreover, signals from four coils were transmitted over a single fiber by wavelength-division multiplexing, like different colors in a rainbow. The optical isolation between channels exceeded 28 decibels, and noise correlation was lower than with the copper counterpart.

This opens the path to lightweight, modular, and potentially ultra-dense receiver coil arrays based on integrated photonics. Instead of a heavy bundle of cables — a few transparent threads. Instead of electrical interference — pure light. Now the whisper in the hall can be listened to with dozens of microphones, without fear of them tangling in their own wires.