Shielded Fibre Optic Audio Cable

Fibre optic cables transmit audio as pulses of light. Light is immune to electromagnetic interference. This is the universally accepted principle upon which optical audio transmission is based. But at Equatorial Audio, we ask a question that others have not considered: what about the light that is not inside the fibre?

Every optical fibre exhibits a phenomenon known as evanescent field leakage — a small but measurable portion of the guided light wave that extends beyond the physical boundary of the fibre core into the surrounding material. This evanescent field, while containing only a fraction of the total optical power, is susceptible to perturbation by external electromagnetic fields. Changes in the local electromagnetic environment modulate the evanescent field, which in turn modulates the boundary conditions of the guided mode, introducing timing variations in the optical pulses arriving at your DAC. The effect is small. We believe it is audible.