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shpongle
What limits the speed of information through a copper wire? What is the speed of signal in optic fibres? Is it faster and why?
For a long line, it's normal to use the transmission line equation, which involves the characteristic impedance, rather than just considering the Capacitance. Depending on the terminating load, the line may look like a resistance, Capacitance or Inductance or, in the general case, an Impedance.gleem said:The speed of transfer is also intrinsically related to the capacitance of the transmitting cable, Before the final expected voltage shows up at the end it must charge the cable.
I am not sure whether you are talking about speed or data rate here - and I'm not actually sure which the OP really wants to know about.jerromyjon said:Makes me wonder if the biggest difference between electrical and optic transmission speed or at least density is the proximity effect?
I should have mentioned : speed of information transfer.sophiecentaur said:I am not sure whether you are talking about speed or data rate here - and I'm not actually sure which the OP really wants to know about.
I think you must mean 'rate' of transfer. That is Bits per second.shpongle said:I should have mentioned : speed of information transfer.
Haha Good pun!sophiecentaur said:Which bit of that link were you referring to?
Interesting thread! Most here have their engineering hats on. I come from linguistics and A.I., so the limits of the "information" transfer would depend on the local "neural" configurations much more than the medium - unless that medium gave more "information" about its relevance to the content.shpongle said:What limits the speed of information through a copper wire?
According to shannon's theorem http://en.wikipedia.org/wiki/Shannon–Hartley_theorem it is bandwidth and noise the main factors that affect the data throughput (bits per second) transmitted through a medium. If we care about latency , then the speed of the electromagnetic waves in the medium also plays a role. Optic fibers are better in all those 3 factors over copper wires or coaxial cables. Optic fibers offer enormous bandwidth, zerolike noise and speed of electromagnetic wave almost at theoretical maximum near c=3*10^8m/s^2. The usual twisted copper pair of wires has limited bandwidth because the signal frequencies attenuate the longer the wire is due to electromagnetic radiation and due to conversion of signal energy to heat. Coaxial cable is much better on these two factors as well as shielding the signal from external noise . Speed of the signal in twisted pair and coaxial cable is about 0.70c. As you see only optic fiber offer the absolut best in all factors.shpongle said:What limits the speed of information through a copper wire? What is the speed of signal in optic fibres? Is it faster and why?
Data rate and signal delay, due to path length are two different things - and you mention both. I am still not sure which the OP was asking, and that demonstrates how important the correct vocabulary is in these matters. Actual delay time between the transmission and reception of the information can sometimes be relevant but, very often, a delay is quite acceptable and can allow suitable coding that will actually increase the useful data rate. The word "bandwidth" is often mis-used when information rate is in fact what is meant (as in "broadband data"). Bandwidth is strictly an analogue term because there is no one-to-one relationship between the two. The channel noise level is equally important.Delta² said:According to shannon's theorem http://en.wikipedia.org/wiki/Shannon–Hartley_theorem it is bandwidth and noise the main factors that affect the data throughput (bits per second) transmitted through a medium. If we care about latency , then the speed of the electromagnetic waves in the medium also plays a role. Optic fibers are better in all those 3 factors over copper wires or coaxial cables. Optic fibers offer enormous bandwidth, zerolike noise and speed of electromagnetic wave almost at theoretical maximum near c=3*10^8m/s^2. The usual twisted copper pair of wires has limited bandwidth because the signal frequencies attenuate the longer the wire is due to electromagnetic radiation and due to conversion of signal energy to heat. Coaxial cable is much better on these two factors as well as shielding the signal from external noise . Speed of the signal in twisted pair and coaxial cable is about 0.70c. As you see only optic fiber offer the absolut best in all factors.
Now SophieCentaur can you tell me how the diameter of wire affects the speed of electromagnetic wave in it? at least using classical physics i don't see how one can arrive at this result.
Regarding waves not traveling in the wire, an alternative view might be that a longitudinal wave of compression propagates through the electron plasma which fills the wire. This then creates the fields surrounding the wire, and in some cases produces EM radiation.sophiecentaur said:Data rate and signal delay, due to path length are two different things - and you mention both. I am still not sure which the OP was asking, and that demonstrates how important the correct vocabulary is in these matters. Actual delay time between the transmission and reception of the information can sometimes be relevant but, very often, a delay is quite acceptable and can allow suitable coding that will actually increase the useful data rate. The word "bandwidth" is often mis-used when information rate is in fact what is meant (as in "broadband data"). Bandwidth is strictly an analogue term because there is no one-to-one relationship between the two. The channel noise level is equally important.
The wave does not travel "in" the wire but is directed by the wire. Also, there are only a very few systems for signal transmission that use only a single conductor. In a practical transmission line, the wires are supported by or even encased in insulators. That will affect the propagation speed (delay).
I cannot imagine any model based on that would produce a propagation speed of more than a small fraction of c. More like the speed of sound, I should have thought. Do you have any reference to that idea or is it one of your own?tech99 said:Regarding waves not traveling in the wire, an alternative view might be that a longitudinal wave of compression propagates through the electron plasma which fills the wire. This then creates the fields surrounding the wire, and in some cases produces EM radiation.
Are you really serious ??tech99 said:This then creates the fields surrounding the wire, and in some cases produces EM radiation.
\sophiecentaur said:Data rate and signal delay, due to path length are two different things - and you mention both. I am still not sure which the OP was asking, and that demonstrates how important the correct vocabulary is in these matters. Actual delay time between the transmission and reception of the information can sometimes be relevant but, very often, a delay is quite acceptable and can allow suitable coding that will actually increase the useful data rate. The word "bandwidth" is often mis-used when information rate is in fact what is meant (as in "broadband data"). Bandwidth is strictly an analogue term because there is no one-to-one relationship between the two. The channel noise level is equally important.
The wave does not travel "in" the wire but is directed by the wire. Also, there are only a very few systems for signal transmission that use only a single conductor. In a practical transmission line, the wires are supported by or even encased in insulators. That will affect the propagation speed (delay).
Delta² said:\
Yes the insulation affects the speed of the wave (which travels inside the wire as well, only the direction of travel is changing, from a direction say along the z-axis it becomes radial (speaking about a cylindrical wire)) BUT how the diameter of the wire (with or without the insulation) affects the speed of the wave?
Yes you are right about optical and wireless systems.jerromyjon said:I'm still a little unsure about a few things but sticking with the op's question... in electrical systems there are 2 wires in the twisted pair, both emitting unwanted radiation which causes interference to the signal, while only 1 conductor in that pair is carrying information? In optical systems, much like wireless, there is only the EM wave carrying the information?
Agree on that point.davenn said:Are you really serious ??
I'm not familiar with any case where an EM field isn't created by the movement of electrons in a wire/conductor
D
I am afraid it is my own idea, based on plasmons. I have been using this concept to explain surface waves and radiation.sophiecentaur said:I cannot imagine any model based on that would produce a propagation speed of more than a small fraction of c. More like the speed of sound, I should have thought. Do you have any reference to that idea or is it one of your own?
I thought that as the guided wave travels along, surrounding the wire, each electron in turn will give a back and forth kick as the wave passes. When viewed as a whole, this would constitute a longitudinal wave traveling in the wire at almost c.sophiecentaur said:I cannot imagine any model based on that would produce a propagation speed of more than a small fraction of c. More like the speed of sound, I should have thought. Do you have any reference to that idea or is it one of your own?
tech99 said:am afraid it is my own idea, based on plasmons. I have been using this concept to explain surface waves and radiation.
shpongle said:What limits the speed of information through a copper wire?
What is the speed of signal in optic fibres? Is it faster and why?
This involves two entirely different questions - qhich one do you want to discuss on this thread - the propagation speed or the bandwidth?Delta² said:\
When i say bandwidth i mean the bandwidth in frequency range in Hertz, not the data transmission rate. To tell you the truth i am not sure how delays allow for better coding schemes with faster data rate, but this is not my interest here.
Yes the insulation affects the speed of the wave (which travels inside the wire as well, only the direction of travel is changing, from a direction say along the z-axis it becomes radial (speaking about a cylindrical wire)) BUT how the diameter of the wire (with or without the insulation) affects the speed of the wave?
The maximum speed of information through a copper wire is determined by the speed of light, which is approximately 299,792,458 meters per second.
The length of the copper wire does not affect the speed of information directly. However, longer wires may experience more resistance, which can slow down the speed of information.
The speed of information through a copper wire is influenced by several factors, including the type and quality of the copper wire, the temperature, and the presence of any obstacles or interference.
Yes, the speed of information through a copper wire can be increased by using higher quality copper wire, minimizing the length of the wire, and reducing any potential sources of interference.
Copper wire has limitations in terms of the distance it can transmit information without experiencing significant signal loss. It also has a lower bandwidth compared to other materials, limiting the amount of data that can be transmitted at once.