Page 84 - 2020 Interconnect Innovations eBook
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» A female MIL-T-29504 POF fiber optic terminal (top) and a male MIL-T-29504 fiber optic terminal (bottom) from XiOptics. Both are commonly used in M38999 connectors.
Optical fiber connector performance can be expressed by two data points: insertion loss and return loss. Measurements of these parameters are defined in IEC standard 61753-1, which gives five grades for insertion loss, ranging from A (best) to D (worst), plus M for multimode, and five rankings for return loss, ranging from 1 (best) to 5 (worst).
Most fiber optic connectors are spring-loaded plugs (male connectors) that feature a protruding ceramic, metal, or plastic ferrule that holds and aligns fibers to ensure optimal waveguide core alignment. These spring-loaded connectors press the fibers’ end faces together when connectors are mated and, by removing any air gap between the optical waveguides, minimize signal loss and maximize return loss to prevent noise from being returned to laser sources. A connector shell brings these plugs together with a screw-on or snap-in mating adapter.
» A typical connector backshell for circular M38999 fiber optic or copper termini.
Transmission Performance: If an application requires high-speed and/or high-bandwidth data transmission, fiber optic cabling is an ideal choice and is available in both single-mode and multimode configurations. The diameter of the waveguide core in single-mode fiber optic cable is much smaller than the diameter of the waveguide core in multimode fiber. Single-mode fiber has a typical core diameter of 8.5–10 microns, while multimode fiber core has a
Fiber Optic Installation Considerations
Signal Versus Power: Fiber optic cabling does not support power transmission in the classic sense and is thus not the best solution for applications that require power delivery. Power-by-light applications exist, but they are typically very specific to equipment designs. In general, fiber optics are not a viable option for powering more than a few milliwatts over any distance. Instead, power must be provided by parallel copper elements, which adds complexity and cost.
Shielding: Optical fibers transmit light, which does not have a polarity that can be affected by electromagnetic interference (EMI). This makes it ideal for applications where traditional cables and connectors would require heavy and expensive shielding to protect against EMI and optimize signal integrity.

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