Identify the communications medium that transports data as pulses of laser light through strands of glass or plastic fibers.

Introduction:
Choosing the correct physical medium is fundamental to network performance. One medium stands out for its extremely high bandwidth, low attenuation, and immunity to electromagnetic interference: the optical fiber link that carries digitally modulated light pulses over long distances.

Given Data / Assumptions:

• The description references laser light and glass fibers.
• We are selecting the medium, not a service, device class, or software.
• Modern networks use both single-mode and multi-mode fibers.

Concept / Approach:
Fiber optic cables guide light through a core using total internal reflection. Data is encoded by modulating light sources (lasers or LEDs), enabling very high symbol rates and long-reach transmission. Compared to copper, fiber offers greater bandwidth, lower signal loss, and resilience to electromagnetic noise, which is why it dominates backbones, data centers, and submarine cables.

Step-by-Step Solution:
1) Match “pulses of laser light” and “glass fibers” to optical fiber technology.2) Exclude cellular (a radio access network, not a cabled medium).3) Exclude processors and software (they are components and programs, not transmission media).4) Select Fiber optic cables.

Verification / Alternative check:
Typical standards include ITU-T G.652 (single-mode) and OM3/OM4 multi-mode fibers used with high-speed Ethernet optics.

Why Other Options Are Wrong:

• Cellular phone systems: wireless RF service, not a fiber medium.
• Telecommunications processors/software: functional components, not physical links.
• None of the above: invalid because fiber is correct.

Common Pitfalls:
Confusing “optical network” services with the underlying medium; here the medium itself is the subject.

Final Answer:
Fiber optic cables