[Daily Question] Registered Cost Engineer – Installation Measurement, Multiple Choice Questions, 12/31/2021

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Characteristics of single-mode fiber (). A. The core is thick, allowing only one mode of light to be transmitted. B. It has low inter-mode dispersion, resulting in a wide bandwidth. C. It can be used in conjunction with light-emitting diodes. D. It offers good confidentiality, making it suitable for long-distance communication. 【Answer】BD 【Explanation】 Single-mode fiber: Since the core is extremely thin (about 10μm), only one mode of light can be transmitted, which is why it is called single-mode fiber. The advantage of single-mode fiber is its very low inter-mode dispersion, which allows for a wide transmission bandwidth; it is suitable for long-distance communication, with a bandwidth of up to 10 GHz per kilometer. The disadvantage is that the core wire is thin, resulting in less coupled optical energy. The interfaces between the fiber and the light source, as well as between fibers themselves, are more difficult to handle compared to multi-mode fibers. Single-mode fibers can only be used with laser diode (LD) light sources, and not with light-emitting diodes (LEDs) that have a larger divergence angle and a wider spectrum. Therefore, the transmission equipment for single-mode fiber is more expensive.