Fibre vs Copper

Technology

Trends... What should we use?

Tech Laws

Moore's Law (1973)

Gordon Moore, founder of Intel, the simplified version of this law states that processor speeds, or overall processing power will double every two years. Today Moore’s Law has transcended silicon chips. It has become a way of saying that all digital stuff, from PCs to cell phones to music players, get twice as good every 18 to 24 months–at the same price point.

Nielsen's Law (1998)

Nielsen's Law addresses the more normal high-end user who is willing to pay a premium but still wants well-tested equipment that can be bought in a regular shop. It states that:
A high-end user's connection speed grows by 50% per year.

More on Nielsen's Law

Gilder's Law (2000)

George Gilder, visionary author of Telecosm, proposed that "bandwidth grows at least three times faster than computer power." This means that if computer power doubles every 18-24 months (Moore's Law), then communications power should double every 6-8 months.

Tech Trends over Time

Note the Marker of 'broadband' (around 2003) this is when telstra looked at seriously considering upgrading their networks to provide higher speeds (FTTN) but abandoned it in favor of waiting for fibre based solutions.

We have kept up thus far by relying on software work-arounds and optimizations, however we have reached the limit of what the current physical links can provide in terms of bandwidth compared to what is and will be required.

The longer we wait the more exorbant the cost will be to get communication tech up to a level that will enable us to make more efficient use of computing and storage solutions.

Standard Tech Development curve

A standard development curve extrapolated from moore's law and superimposed on adoption rates of users.

Note the relationship of the initial investment made to offset R&D (implementation).

Naturally adoption rates will not remain linear and will generally more closely mimic that of the dev / implementation curve itself. The important point is as long as adoption rates remain fairly consistent we can adjust the other factors and recieve ROI on the initial capital offset accordingly.

Wireless / LTE

Shared Bandwidth

While it's true mobile broadband has been increasing in marketshare, ANY type of wireless technology available currently can never replace fixed line solutions in terms of speed and reliability for a vast userbase. Like GPON's, the bandwidth for wireless is shared, however unlike most other technology wireless speed is stated per cell in comparison to a speed per connection as is the case with fixed line. Why does this matter? Well take the latest standard 5G / LTE for example:

1 user 1000Mbps / 1 1000Mbps per user
2 users 1000Mbps / 2 500Mbps per user
10 users 1000Mbps / 10 100Mbps per user
40 users 1000Mbps / 40 25Mbps per user
1000 users 1000Mbps / 1000 1Mbps per user

This does make wireless suitable for small scale implementations where population is sparsely distributed and there are a limited number of users. Currently contention ratios (bandwidth on demand at any one time) over wireless is pretty low even in the suburban / metro area's so it is possible to acheive reasonable speeds because the primary access method is fixed line.

Also implementing QoS rules on these connections can make the percieved latency much less meaning while your speed maybe only 7Mbps you can still stream a HD clip requiring 8Mbps due to these rules being in place and buffering.

If everyone switched to wireless however, to acheive even the minimum stated speeds that fibre and even 'properly implemented FTTN' can attain, every 40 people would need their own wireless tower. That equates to Australia's current population 23,200,000 / 40 = 580,000 wireless towers.

That is the main reason for wireless being unfeasable at this point in time, there are of course other reasons:

  • Contention Rates: The above assumes that a fixed number of people remain in the same area all the time... People commute, go on vacation, what about tourists or natural disasters? All these scenarios present changes in population density that a purely wireless network just could not cope with.
  • Coverage: The above assumes that area's occupied are in relatively close proximity to each other, but given the size and population density of Australia 600,000 towers would be the minimum if communities were side by side.
  • Limited spectra: There are only a limited number of frequencies that we can use.
  • Wireless tech deficiencies: There are problems inherent with using wireless, of particular concern however are those of interferance and security.

Note that while the percentage of mobile users has increased in market share the primary method of accessing the internet remains fixed line.
As Evidence of this examine the latest ABS figures note the volume of data downloaded in Dec 2012 for fixed line connections is a little over 18 and a 1/2 times that of wireless.

Comparison

Which is the Superior Medium?

Fibre Copper

Capability


(Max)

Advantages

  • Greater bandwidth
  • Low attenuation over greater distance
  • Better Security
  • Immune to EMI / RFI
  • Di-electric, no possibility of sparking / less of a fire hazard
Cheaper to terminate

No special skills or tools are required to terminate a copper connection as opposed to fibre, this means labour is cheaper.

Limitations

  • Signal needs to be regenerated

    How much? this will depend upon the type of cable bing used and the power of the endpoints, however in current practices for the access layer of the network (from FDH to premesis) a distance of 15 - 20km is available without the need to regenerate.

  • The glass can be affected by various chemicals including hydrogen gas (a problem in underwater cables.)
    Only when not insulated properly and is still more resistant to corrosion then copper.
  • Despite extensive military use it is known that most fibres become opaque when exposed to radiation.
    If we start testing / dumping nuclear materials, start to worry.
    Radiations Effects on Fibre
    NASA Research
  • Signal needs electricity to propagate
  • Signal needs to be regenerated
  • Attenuation increases with a greater number of factors
  • Bandwidth is limited by frequency

Attenuation

Simply put, it is a measure of signal degradation. So what affects this? On fibre? Very little, within the copper network however...

Distance

The length of the cable (or loop length). A simple analogy would be if you talk normally, I can hear you when you're 5m away. But I can't hear you at 60m unless you shout.

Cable Joints

Lead-in joints, pair repair joints, CV joints, and gel filled joints are all susceptible to crosstalk and moisture exposure which can accelerate oxidation.

Oxidation

Oxidation is a build up of 'rust' (patina, looks green) on the surface of copper. This causes interferance with signals being sent 'over the wire' as an AC system, signal transmission travels along the surface of the wires (see skin effect).

"The main catalyst for the process of oxidation is water. The metal doesn't need to be submerged in water, moisture in the air is often enough to get the reaction underway."

The higher the frequency being used (to achieve higher speeds), the thinner the 'skin effect' will be, therefore the more oxidation can interfere.

Read more

EMI

Electromagnetic Interferance (crosstalk) is a phenomenon caused by running power through conductors. The magnetic field generated by the actively powered one can induce unwanted current flow in the other. While there are ways to limit the effects, poorly insulated cables and the endpoints are still vulnerable.

"The higher the frequency goes the worse this crosstalk is going to become"

Implementation

More fibre vs More Copper?

Terminology

Fibre to the Node: Roughly the same as FTTC, only the street cabinet can be further away (up to several km away) with the rest of the distance to your house being covered by regular copper wiring.
Fibre to the Cabinet: Fibre-optic cables run all the way to the cabinet in the street, which can be up to 300m away.
Fibre to the Basement:
Fibre to the Home: A more accurate description to be using when referring to a a fibre network that has more universal coverage of the general population.

NOTE: FTTP, Fibre to the premesis, is the broad term used by professionals and industry when speaking about connecting fibre to a specific location i.e. homes, hospitals, banks, factories, etc.

FTTH FTTN

Performance


Capability + Reliability
  • Capability:
    Is only limited by the endpoints, it is not unusual for a single fibre to easily be able to transmit 1Gbps or more over 15-40km.

    As tech law's dictate performance / efficiency are increasing over time, opening up the possibility of Terabit speeds or greater being available to home users as is currently available over under-sea cables.
    submarine cable map

    Reliability:
    Highly reliable and stable, it is a passive network:

    No electrical power is required to propagate signals over the fibre, power is only required at the endpoints to transmit and recieve.

    It also has other advantages over copper that make it a much better choice when implementing infrastructure here in Australia. (see above).

  • Capability:
    Up to (not guaranteed) 80Mbps, with respect to attenuation factors.

    Reliability:
    See above (limitations / attenuation)

Lifespan

  • The french work off 25 years, Bouygues Telecom (page 12)

    The French Regulator is conscious of the need to anticipate cable depreciation and suggests to shorten the lifespan from 25 years to 13 years (in practice, the tilted annuity mechanism will cause 35% of the depreciation process to occur within the last 3 years).

    This choice of a lifespan is completely arbitrary and fits into one single scenario assuming that a majority of French consumers will switch to fibre by 2024.

Maintenance

Ongoing Costs
Connectors are effectively sealed from dirt in patch panels, and splices are sealed in enclosures that prevent moisture from entering. There is no need to disconnect terminations to clean, inspect or test them, which adds to the reliability and lifespan of the connections.