In my last quiz, I challenged your knowledge on fiber optic testing. Fiber optic test results are usually expressed in decibels (dB), a term that can be very confusing. Do you understand decibels, and do you know how to interpret test data expressed in decibels?
Created by: Jim Hayes
1. The term “Bell” was chosen in recognition of ________.
A. The Liberty Bell
B. Alexander Graham Bell
C. The sound of a bell
D. The Gaussian bell curve
2. When making measurements, dB is used in measurements of ________.
A. Signal power
B. Signal attenuation (per km)
C. Signal loss
D. All of the above
3. Decibels are used for measuring other systems besides fiber optics, such as electrical, wireless/radio and acoustics/sound.
4. Changes in optical power, for example when measuring loss of a fiber optic cable plant, are expressed in ________.
B. decibel-milliwatts (dBm)
C. Either dB or dBm
5. When measuring the actual optical power output from a fiber optic transmitter or the input power at a receiver, the reading is expressed in ________.
6. Since dB is a logarithmic term based on a factor of 10, a change of power of 10 times is represented by a change of 10 dB and a factor of 100 times change in power is ________.
A. 13 dB
B. 20 dB
C. 100 dB
D. 200 dB
7. “0 dBm” is a typical power output of a laser transmitter, which has an output of ________.
A. 1 microwatt
B. 1 milliwatt
C. 1 watt
D. 1 micron
8. If a “0 dBm” laser transmitter is used on a fiber optic link with 10 dB loss, the receiver power measured in a fiber optic power meter will be ________ dBm.
9. A typical multimode fiber has an attenuation of 3 dB/km. At the end of 1 km, the power transmitted into the fiber will be reduced by ________%.
10. When you calculate or measure loss with a light source and power meter, the result in decibels is a negative number, but most optical loss test sets and optical time-domain reflectometers display a positive number when they measure loss.