Topic 2 - Optical Fibres and Endoscopy Flashcards
optical fibre
Light can be transported along a thin flexible glass fibre by a series of ‘internal reflections’
The application of this principle is called fibre optics
An optical fibre consists of a glass core surrounded by cladding with a lower refractive index. This is coated in one or two reinforcing layers of resin or plastic.
The need for cladding
The dense glass core is of a communication fibre is surrounded by a cladding material. This cladding material is a type of glass with a LOWER refractive index than the core (to increase total internal reflection and prevent the ray escaping the fibre).
mechanical splicing
just a mechanical alignment device
hold the 2 fibre ends in a precisely aligned place
still 2 separate fibres not continues
fusion splicing
two fibre ends are aligned an then fused or welled together
use heat or electric arc
two fibres become continues
Endoscopy
An endoscope is a device that uses fibre optic bundles to see inside the body. It contains coherent bundles of optical fibres to carry the image, and non-coherent bundles to carry light into the area being examined
Endoscopes can be used to examine many parts of the body, such as the digestive and respiratory systems.
If necessary, a small incision can be made to allow access to the area.
Endoscopy can produce detailed images in full colour and real time, which makes it a very useful technique
Imaging with fibre optics
A bundle of optical fibres can be used to transmit an image. The bundle is manufactured so that the relative positions of the fibres are the same at either end. This is a coherent bundle
Each fibre forms a pixel in a digital camera. The more fibres that are packed into a small bundle, the higher the resolution of the image, but the more expensive it is to manufacture
Coherent optical fibres are each the diameter of a human hair and have a core, a cladding and a protective plastic coating
Keyhole surgery
This is a form of surgery that uses an endoscope with surgical attachments to perform an operation through small incisions in the skin.
It is used for procedures such as gall bladder or appendix removal, middle ear investigations, and joint operations
Comparing fibre optics with copper cabling
Copper cables suffer from electrical resistance
Fibre optic transmission is faster
Fibre optic cables are impervious to electromagnetic interference
Fibre optic cables cannot catch on fire
Fibre optic cables do not break as easily
Only very small incisions are required, which means that compared with conventional surgery …
the rate of recovery is much greater
the risk of infection is lowered
the cost of the procedure is reduced
the cosmetic result is better.
what is a coherent bundle
The bundle is manufactured so that the relative positions of the fibres are the same at either end
