Fiber U Basics

Lesson #4, Fiber Optic Datalinks

FOA Reference Guide To Fiber Optics
And Study Guide To FOA Certification

FOA Reference Guide to Fiber Optics

Answers To Chapter Questions

Chapter 4 Quiz -Datalink


    1.    ANS:    T
Most systems operate by transmitting in one direction on one fiber and in the reverse direction on another fiber for full duplex operation. It's possible to transmit both directions on one fiber but it requires couplers to do so and fiber is less expensive than couplers.

    2.    ANS:    F
LEDs have much lower power outputs than lasers. LEDs have much less bandwidth than lasers and are limited to systems operating up to about 250 MHz or around 200 Mb/s.


    3.    ANS:    B
As many premises systems using multimode fiber have exceeded bit rates of 1 Gb/s, lasers (mostly VCSELs) have replaced LEDs. 

    4.    ANS:    A
The restricted launch of the VCSEL or any laser makes the effective bandwidth of the fiber higher, but laser-optimized fiber, usually OM3, is the choice for lasers.

    5.    ANS:    A
Silicon photodiodes are used for short wavelength links (650 for POF and 850 for glass MM fiber).

    6.    ANS:    C
Long wavelength systems usually use InGaAs (indium gallium arsenide) detectors as they have lower noise than germanium which allows for more sensitive receivers.

    7.    ANS:    D
 In telephony, fiber amplifiers combine with DWDM (dense wavelength division multiplexers) to overcome the inefficiencies of DWDM couplers for long haul transmission.
The typical fiber amplifier works in the 1480-1650 nm band.


    8.    ANS:    C, D
See table: Typical Fiber Optic Source Specifications

    9.    ANS:    A, B, C
See table: Typical Fiber Optic Source Specifications


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