Fiber-Optic Cable Signal Loss, Attenuation, And Dispersion; Signal Loss In Multimode And Single-Mode Fiber-Optic Cable - Juniper PTX1000 Hardware Manual

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Figure 26: LC Duplex Connector
Transceiver
Fiber-optic cable

Fiber-Optic Cable Signal Loss, Attenuation, and Dispersion

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Signal Loss in Multimode and Single-Mode Fiber-Optic Cable | 65

Attenuation and Dispersion in Fiber-Optic Cable | 66
Signal Loss in Multimode and Single-Mode Fiber-Optic Cable
Multimode fiber is large enough in diameter to allow rays of light to reflect internally (bounce off the walls
of the fiber). Interfaces with multimode optics typically use LEDs as light sources. However, LEDs are not
coherent sources. They spray varying wavelengths of light into the multimode fiber, which reflects the
light at different angles. Light rays travel in jagged lines through a multimode fiber, causing signal dispersion.
When light traveling in the fiber core radiates into the fiber cladding, higher-order mode loss results.
Together these factors limit the transmission distance of multimode fiber compared with single-mode
fiber.
Single-mode fiber is so small in diameter that rays of light can reflect internally through one layer only.
Interfaces with single-mode optics use lasers as light sources. Lasers generate a single wavelength of light,
which travels in a straight line through the single-mode fiber. Compared with multimode fiber, single-mode
fiber has higher bandwidth and can carry signals for longer distances.
Exceeding the maximum transmission distances can result in significant signal loss, which causes unreliable
transmission.