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Q25: What is Single-Mode Fiber?
A25:Single-mode fiber has a core diameter in 10 micron to allow only
single mode of light to propagate.This eliminates the main limitation
to bandwidth and modal dispersion.However,the small core of a single-mode
fiber makes coupling light into the fiber more difficult,and thus expensive
lasers must be used as light sources. The main limitation to the bandwidth
of a single-mode fiber is material (chromatic) dispersion.Laser sources
must also be used to attain high bandwidth, because LEDs emit a large
range of frequencies,and thus material dispersion becomes significant.
Single-mode fiber is capable of supporting much longer segment lengths
than multi-mode fiber.Segment lengths of 5000 meters and beyond are supported
at all Ethernet data rates through 1 Gbps.Single-mode fiber is significantly
more expensive to deploy than multi-mode fiber because of the high laser
equipment cost.
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