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Module Four - Activity 2 - Fibre Optic System Overview
Why fibre?

For the purposes of fibre optic systems for rural and remote communities, fibre optic technology will, in most cases, be used in one of two ways:

  1. as a way of extending the local ethernet, or
  2. As a way to establish a "backbone" link into a community.

Fibre optic technology is an extremely complex and technical subject. However, for the above purposes, there are some basic concepts in this overview which are designed to help give a basic understanding of this technology so that a community could decide how to use this technology, or if to use this technology.

Both the tools and the materials required for installing fibre optic technology are quite expensive. Also, personnel installing the technology must have a good understanding of the stringent installation requirements that must be adhered to in order for the technology to function. Most fibre optic installers are highly trained. However, fibre optic technology is still desireable: it's FAST, and it carries a LOT of data.

Equipment costs too high? Do most of the work yourself!

If a remote community wishes to install fibre, but finds the costs of the equipment too expensive, it is recommended that they purchase and install their singlemode loose tube fibre, and have a professional fibre optic installer contractor come in to complete either splicing or connectorization.

For more information on the cable types, see the section on cables. (Fibre Optic cable can be either gel-filled or not depending on their location and what is recommended by the supplier, either aerial self-supported cable or wire bound supported cable attached to a messenger cable, or underground fibre (either in conduit or not).

IF a community decides to standardize on connectors rather than splices, it is VERY IMPORTANT that the type of connector (and the type of cable) be STANDARDIZED. Once one kind is purchased, that should be the kind that is ALWAYS purchased. There are many different kinds of connectors, with different end polishes and finishes, and intermixing these causes problems. A good connector standard that is often used is an "SC" connector. These come in mechanical (crimp) as well as glue-on types, and costs will be a factor in choosing connectors types.

 
   

Do a loss budget

Before splicing or connectorization takes place, a loss budget will need to be completed. An individual can be trained to complete a loss budget, or an organization or contractor can prepare one for the community. A loss budget basically adds up every splice within a system, and the total loss of every device on the system. This total has to be within acceptable loss tolerances, or the system won't work.

In this way, fibre loss is comparable to a plumbing system - if there is a little leak here and there, the system may still work, but if there are large leaks in multiple places, it's unlikely that the water will continue to flow. So, if we think of the fibre optic cable as "pipe", there can't be too many "leaks" or the data will all drip out, causing the system to not work.

Having said this, automated splicing machines, if coupled with accurate cleaving instruments, should yield losses which are at, or at least close to zero every time. The closer the losses are to zero, the further the data will go.
   

Gizmos:

Most of the technology that makes the fibre optic system work is "plug and play," meaning that once it is purchased, it should just plug in and work. Beyond that, money equals distance. Different types of fibre equipment use different light sources, which send the data various distances. The more that a community pays for the equipment, the further that equipment should push (and pull) the data through the fibre.

There are several "levels' of technology, as follows, which basically translate into speeds (and again, costs.)

  • "Fast ethernet" is 100 mbps (megabits per second). This technology generally uses tranceivers and optical light sources such as lasers. It can generally travel about 170 kilometres, and costs about $6000-$7000 per end.
  • Gigabit SX technology uses directional LEDs, and can travel about two kilometres.
  • Gigabit LX technology uses lasers to send a signal, and is rated for about ten kilometres.
  • Gigabit ZX: “extra-long haul” Gbix tranceivers (?) Gigabit interface converters 70 kms at full gigabit.

The type of technology chosen when designing the system will depend on what the system is supposed to do, how far the data must be sent, how many devices will be on the line, and what sort of cable is being used. It is HIGHLY recommended that before designing a system, a community member take a course on fibre optic system design. The light Brigade is an excellent source for materials, videos, courses, and other fibre optic information. They, and other suppliers would also be able to provide up to date information on system design and recommended materials for what individual communities are trying to achieve.