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4.1 | |
Background for Studying Frequency-Based Cable Testing | |
| 4.1.1 | |
Waves |
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A wave is energy traveling from one place
to another. There are many types of waves, but all can be described
with similar vocabulary.
It is helpful to think of waves as disturbances. A bucket of water that is completely still does not have waves, because there are no disturbances. Conversely, the ocean always has some sort of detectable waves due to disturbances such as wind and tide. Ocean waves can be described in terms
of their height, or amplitude, which could be measured in meters. They
can also be described in terms of how frequently the waves reach the
shore, using period and frequency. The period of the waves is the
amount of time between each wave, measured in seconds. The frequency
is the number of waves that reach the shore each second, measured in
Hertz. One Hertz is equal to one wave per second, or one cycle per
second. Experiment with these concepts by adjusting the amplitude and
frequency in Figure
Networking professionals are specifically interested in voltage waves on copper media, light waves in optical fiber, and alternating electric and magnetic fields called electromagnetic waves. The amplitude of an electrical signal still represents height, but it is measured in volts instead of meters. The period is the amount of time to complete one cycle, measured in seconds. The frequency is the number of complete cycles per second, measured in Hertz. If a disturbance is deliberately caused, and involves a fixed, predictable duration, it is called a pulse. Pulses are important in electrical signals because they determine the value of the data being transmitted.
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