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Fibre Optic cable vs Copper wire

  1. Feb 12, 2010 #1
    Is the fibre optic cable cheaper than copper wire for transmission? I believe there is still loses in a fibre optic cable. As the critical angle of glass is 42 degrees, thus about 50% of the signal would be lost. Is that true?
     
  2. jcsd
  3. Feb 12, 2010 #2

    berkeman

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    Not sure about the relative costs per meter, but your loss number is not right. Read about single-mode fiber. The losses are much lower.
     
  4. Feb 12, 2010 #3

    PhanthomJay

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    I can't directly answer your question, but miles and miles and miles of fiber optic cable have been or are being installed by telephone, cable tv, electric, and internet provider companies, etc, using light pulse signals, . I don't see any copper (using electric current) being installed. On a material cost basis, fiber probably costs more, but does a lot more. So its more than material cost, it's greater realized income. Mind you, this response is from a non expert in the communications field.
     
  5. Feb 12, 2010 #4
    Generally, yes? Although, it depends on the data rate and distance involved. Short distance and lower data rates are more conveniently handled and probably cheaper with a copper solution.

    Note that USB cables on computers are copper based because the distance is short; however, trans-atlantic telecommunications is done with fiber because the net cost is much much cheaper.

    There are losses in optical fiber, of course, but the loss is much less than copper.

    Note that the critical angle depends on the fiber type. There can be issues of coupling light into optical fiber due to the acceptance angle. However, this is generally not a big issue. This is because lasers and LEDs are available with high optical power, coupling methods achieve 50 % to 90 % coupling efficiency, and once the light is coupled into the fiber, it transmits with very much lower loss than copper.

    The exact value of the loss depends on the wavelength of light used and the type of fiber used. The most common fiber type is made from silica glass. For these, typical communications wavelengths are 800 nm, 1300 nm and 1550 nm, all in the infrared range. The low loss window is 1550 nm with a loss of about 0.2 dB/km. Note that this equates to loss of half the light after 15 km. There is another transmission at 1300 nm with a local minimum loss of about 0.4 dB/km. The loss at 800 nm is significantly higher, but still quite good.
     
  6. Feb 12, 2010 #5
    Is trans Atlantic cable done with fibre optics? Trans Atlantic cable was laid before the age of fibre optics. Why change it? The actual manufacturer price of the fibre optic and copper cable per metre. Which is cheaper?
     
  7. Feb 12, 2010 #6
    Fibre optics is cheaper and yes the trans-altantic cable has been laid several times and currently fibre optics are used.
     
  8. Feb 12, 2010 #7

    mheslep

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    No, the cost comparison depends on the length of the cable, the bandwidth required, and the environmental conditions. High temperature FO transceivers, for example, are expensive.
     
  9. Feb 12, 2010 #8

    berkeman

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    Links guys. My gut says fiber is more cost effective for BW/cost, but I haven't looked for supporting links...
     
  10. Feb 12, 2010 #9
    What is up with you? The OP asked the question is fibre optics cheaper, in the case of the transatlantic or any distance at which laying cables is needed. Fibre optics is preferable.
     
  11. Feb 12, 2010 #10

    berkeman

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    I'm only guessing, but for short distances and lower BW, UTP is cheaper overall. I agree that that's probably not the OP's question however.
     
  12. Feb 13, 2010 #11

    mgb_phys

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    Fibre can carry vastly more data.
    The early copper cables could carry telegrams at a few bits/second, modern fibre can carry several billion bits/second.
    The fibre cable is much smaller and cheaper to make and lay, especially if you are trying to lay 1000s of km of the stuff. It's also extremely low loss so fewer amplifiers and much less power is needed.

    This long, but utterly fascinating, account explains all about the wonderful world of international telecoms fibre http://www.wired.com/wired/archive/4.12/ffglass_pr.html
     
  13. Feb 13, 2010 #12
    I believe that was the primary driving force behind the decision to lay new cables with the additional pressure that more data would be needed to transferred in the future.
     
  14. Feb 13, 2010 #13

    mheslep

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    The OP didn't specify a distance at all, nor bandwidth, nor environmental conditions. You assumed 'transatlantic' or 'laying' cable distances and gave a blanket answer. Cables have to be terminated in connectors, and driven by a transceiver. IF the cable is relatively short, such as in network LAN, then the connector & transceiver cost make up a significant portion of the cost. Even the cheapest FO ST connectors are more expensive installed than a comparable Ethernet RJ-45 jack. If the BW is high enough, say greater than 5-Gbit, so that copper has to move from twister pair to coax, then the balance tips back in favor of FO again. Include the cost of the transceiver and FO looks much worse than even 1Gbit-Ethernet, again for short distances.
     
  15. Feb 13, 2010 #14

    mheslep

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    Agreed.
     
  16. Feb 13, 2010 #15

    mheslep

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    Cables to Go Ethernet 100Base-TX cable - RJ-45 - M - Stranded wire 5 ft: $2
    http://www.cablesondemand.com/category/LC-LC9/product/FO-LCX2SIMP00/URvars/Items/Library/InfoManage/FO-LCX2SIMP00.htm" [Broken]: $13.73
     
    Last edited by a moderator: May 4, 2017
  17. Feb 13, 2010 #16
    mheslep & OP:

    From http://www.thefoa.org/tech/fo-or-cu.htm

    by the Fibre Optic Association a international non-profit educational organization.
     
  18. Feb 13, 2010 #17
    Referencing a commercial website and comparing two dissimilar products is pathetic. Has it not crossed your mind that they can charge whatever they want for a fibre optic cable because they KNOW people will believe it is superior and are therefore likely to buy it, so why not take a huge profit on that item. Basic business.
     
    Last edited by a moderator: May 4, 2017
  19. Feb 13, 2010 #18

    mheslep

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    The all fiber LAN article has some interesting points, but its hype laden:

    :rolleyes:
    Yes, they're all simple rubes who don't know any better, waiting for enlightenment from the FOA.
     
  20. Feb 13, 2010 #19
    This may be true for computers, but for telecoms, using fibre optics is substantially more cheaper than using copper.
     
  21. Feb 13, 2010 #20

    mheslep

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    No, but wild assertions are.

    I for one don't believe its superior for all needs, and I buy FO cable by the km from the lowest bid when I need it. You're stacking assertion on top of assertion.
     
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