If we were to make a composite wire-wound music string constructed around a multifilament tow core of raw carbon fibres it would enclose a number of approximately 1 micron sq. section capillary spaces, each space being bounded by three adjacent fibres.

Imagine what would occur within this string if it were to be immersed in boiling water.

Water vapour, condensing as it cools within the capillaries will draw liquid water into the string core.

Unable to wet the carbon fibres' surfaces due to the carbon/water mutual antipathy, this water forms spontaneously into surface-tension, meniscus-suspended 'water-strings' each one surrounded by a 'tri-lobed tube' of air.

Each 'water-string' can then function as an efficient fibre-optic, every one centred in its own capillary space within the multifilament string core.