What are multicore fibers characterized by?

Multicore fibers are characterized by having multiple cores or channels within a single optical fiber, allowing them to transmit light through these separated cores. This design enables the simultaneous transmission of multiple data streams or signals, making multicore fibers highly efficient for data communication.

However, it's essential to clarify that option B mentions a "single fiber with multiple holes for cables," which is not an accurate representation of multicore fibers. Instead of holes, multicore fibers feature multiple refractive index regions or cores that can carry light independently, enabling parallel data transmission.

The correct characterization would emphasize their ability to transmit multiple wavelengths simultaneously through different cores, which corresponds to option D. This characteristic allows multicore fibers to significantly enhance data capacity and improve overall network performance while maintaining compact designs suitable for various applications.