Benefits of fiberoptic transmission, instead of copper media transmission include the following.

• Immunity to High-Altitude Electromagnetic Pulse (HEMP)
• Immunity to Electromagnetic Interference (EMI)
• No signal detection from radiated emissions (TEMPEST security, SCIF security)
• Fiber more difficult to physically tap (SCIF security)
• No conducted ground loops from different voltage potentials within system
• Power surges from lightning, etc. are not conducted

EMI is a common type of noise that is a product of the basic properties of electromagnetism. Shielding wire, such as coaxial cables, can reduce the radiated emissions, however some finite level of signal energy is radiated, and signal detection is possible. There are no radiated magnetic fields around optical fibers. Electromagnetic fields are confined within the core and cladding of the fiber. Since fiber optics do not radiate electromagnetic energy, emissions cannot be intercepted and physically tapping a fiber is quite difficult to achieve without detection. Thus, fiber is the most secure medium available for carrying sensitive data.

Facilities often are required to be protected against several EM environments including HEMP (or other EMP), EMI, electromagnetic compatibility (EMC), and lightning. The facility may also have TEMPEST requirements that impose the need for communications security through control of compromising EM radiation. Sensitive Compartmented Information Facilities (SCIFs) also require security procedures preventing EM radiated emissions.

EMC is defined as the ability of communications-electronics equipment, subsystems, and systems to operate in their intended environments without suffering or causing unacceptable degradation because of unintentional EM radiation or response. EMI results when EM energy causes unacceptable or undesirable responses, malfunctions, degrades or interrupts the intended operation of electronic equipment. RFI is a special case of EMI for which the radio frequency transmission (usually narrow-band) causes unintentional problems in equipment operation. For commercial electronic and electrical equipment, systems, or subsystems, the Federal Communications Commission (FCC) has regulations defining allowable emission and susceptibility levels. Military equipment is regulated by MIL-STD-461 and MIL-STD-462.

Any electrical conductive cables can carry power surges or ground loops. Fiber optic cables are valuable in eliminating ground loops and protecting electronic equipment from surge damage.

MIL-STD-188-125-1 defines the design and testing criteria for specifically designated fixed ground-based facilities in HEMP-hardened, critical, time-urgent C4I networks. Such nodes include subscriber terminals and data processing centers, transmitting and receiving communications stations, and relay facilities.

MIL-STD-188-125-1 recommends that all standard voice and data lines, whether shielded or unshielded, shall be converted to fiber optics outside the secure facility electromagnetic barrier and shall penetrate the facility HEMP shield on all-dielectric fiber optic cables. A main barrier transient suppression/attenuation device shall be provided on each penetrating conductor of electrical control and signal lines, whether shielded or unshielded. Nonmetallic fiber optic lines, however, do not require a transient suppression/attenuation device at the barrier.