642-321 Study Guide / 642-321 Testing Engine / 642-321 Videos

Best CCIE Training and CCIE Exams
and more Cisco exams log in to Certkingdom.com

---

QUESTION 1
What is the phenomenon called where different wavelengths of light travel at different speeds?

A. attenuation
B. OSNR
C. dispersion
D. light skew

Answer: C

---

QUESTION 2
Why are the 1300 nm and 1550 nm regions of the fiber spectrum primarily used for optical
communications?

A. They are both regions of lowest loss.
B. They are both regions of low index of refraction.
C. They are both regions of low chromatic dispersion.
D. They are both regions of low reflections.
E. They are both regions of low Polarization Mode Dispersion (PMD).

Answer: A

---

QUESTION 3
For lasers with tightly controlled wavelengths, approximately how far apart are the centers of
adjacent wavelengths when 100 GHz spacing is used in a DWDM system?

A. 0.8 nanometers
B. 1.6 nanometers
C. 0.4 nanometers
D. 1.2 nanometers
E. 0.6 nanometers

Answer: A

---

QUESTION 4
Which device creates an OEO conversion?

A. fiber-optic cable
B. regenerator
C. optical receiver
D. optical switch
E. attenuator
F. amplifier
G. light emitter

Answer: B

---

QUESTION 5
If node 2 is accepting line timing from node 1, node 2 will send _____ to node 1 as its SSM
messge.

A. SMC
B. AMI
C. ESF
D. PRS
E. DUS
F. B8ZS

Answer: E

---

Best CCNA Training and CCNA Certification
and more Cisco exams log in to Certkingdom.com