PE1-2.2 Signal Distortion, Connectors & Splicing

Work through these

• Attenuation: absorption, scattering and bending losses

  Why the signal gets weaker, split into three causes with different wavelength behaviour. Rayleigh scattering setting the floor at short wavelengths is what pushed systems to longer ones.

• Core and cladding losses

  Losses attributable to each region of the fibre separately. It is the detailed version of the item above.

• Information capacity determination

  How much information the fibre can carry, which is set by dispersion rather than loss over short distances. It is the bridge to the next two items.

• Material dispersion and waveguide dispersion

  Two causes of pulse spreading that exist even in a single mode fibre. They have opposite signs in some wavelength ranges, which is why a zero dispersion wavelength exists.

• Intermodal dispersion; pulse broadening in graded index fibre

  The spreading caused by different modes travelling different distances, and how grading the index reduces it. It is the dominant effect in multimode fibre.

• Connector types and single mode fibre connectors; connector return loss

  Joining fibre to equipment, which is where a great deal of practical loss appears. Return loss matters because a reflection travels back into the source.

• Splicing techniques; splicing single mode fibres

  Joining fibre to fibre permanently, by fusion or mechanically. Single mode splicing needs alignment to a fraction of the core diameter, which is why the equipment costs what it does.

• Fibre alignment and joint loss: multimode and single mode joints

  What actually causes loss at a joint: lateral offset, angle and gap. Knowing which dominates tells you what to fix when a link comes up short.