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2007-08-01 15:47:53 · 3 answers · asked by Flash 2 in Science & Mathematics Engineering

3 answers

Fibre optics as the wave front progresses down the fibre it reflects off of the sides. In multi-mode fibre if can reflect at a number of angles. The light at the sharper angles hits the sides more times for each meter it travels down the fibre. The light that hits at shallower angles reflects fewer times traveling a straighter path. As the wavefront goes farther down the fibre it spreads out the shallower portion of the light gets farther from the other light. If it went far enough the beginning of one bit (shallow angle) could catch the end (sharper angle) of the preceding bit. To compensate you can slow the bit rate making the beginnings and endings farther apart.
Electrically (in wires) as wires go through other magnetic fields (near other wires with electricity) they will get very weak electric charges induced upon them also know as noise. The wires work like antennas. Wires that are longer will tend to pick up stronger noise and more noise from more sources. As the signal progresses the noise may begin to overwhelm data bits that is a low signal may get a brief pulse that may be read as a high signal. By slowing down the data rate so that a brief pulse is recognized as just noise the system becomes more reliable.
Radio waves.As a radio wave progresses through space it weakens quickly. Other sources of radio waves such as wires carrying electrical power or data will create weak radio waves. Natural sources geologic or in space create radio waves. The more noise the more difficult it is to pick out the signal To compensate you can slow the data rate.
Anther way to compensate in all 3 examples) would be to put in parity codes or check-sums that help you determine if the data read was correct. But these schemes use some data bits so a message that needs 128 data bits may need 128 +16 for instance to transmit. the bit rate is the same but the message takes more bits now. If you determine that you did not get valid data you may resend but now the portion of the message not received the first time takes twice as much data!

2007-08-01 17:22:12 · answer #1 · answered by zydecojudd 3 · 0 0

When a data signal travels down a signal wire it is attenuated. As the signal is attenuated the signal to noise ratio decreases. As the signal to noise ratio decreases so does the maximum data rate that can be sent down the transmission line reliably. If the reliability of the communication link deteriorates the "bit error rate" at the receiver will increase. Many data communications systems can detect this and will automatically shift to a lower data rate so that fewer packets need to be resent.

2007-08-01 19:30:01 · answer #2 · answered by Anonymous · 0 0

In any data transmission there is noise.
Signals are also attenuated with distance, especially in wireless transmission.
so the longer the distance, weaker the signal and higher probability to get corrupted by noise, which decreases effective data rate.

2007-08-01 17:03:03 · answer #3 · answered by TV guy 7 · 0 0

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