Researchers at the National Institute of Standards and Technology (NIST) have demonstrated a prototype device capable of absolute measurements of optical power delivered through an optical fiber.

The device is the world's first fiber-coupled cryogenic radiometer that links optical fiber power measurements directly to fundamental electrical units and national standards. It uses a microscopic forest of carbon nanotubes—the world's darkest material—to measure values that are about one-thousandth of the levels typically attained with a cryogenic radiometer lacking direct fiber input capability.

Source: NIST Tech Beat