How Fiber Optics Work
Fiber optics or optical fibers are made of pure glass which has about the diameter of a human hair. They are bundled into optical cables which can transmit light signals and can contain hundreds up to thousands of fibers. The bundles are wrapped in an outer covering or jacket.
Single-Mode or Unimode Fibers (SMF)
- small core that transmits a single ray of infrared laser light
- Fiber Optics Equipment is more expensive than multi-mode
- Better at retaining the fidelity and accuracy of each light pulse over long distances
- Preferred method in scientific research such as medical or mechanical imaging
- larger core transmitting infrared light generated by LED’s
- Lower-cost than the more expensive laser resources and equipment required for SMF
- Traditionally used for short distance communication such as within a building or campus
- core can be 100 times larger than glass fiber and connectors as well as installation are less expensive than glass fiber
- Traditionally used for low-speed, short-distance (<= 100m) networks
Fiber Optics Basics
In optical fiber or fiber optic cable the light travels through the core by constantly bouncing along the cladding which is like a mirror-lined wall.
We all know that light travels in a straight line, so when you shine a flashlight beam down the hall it won’t illuminate what is around the corner. You could however place a mirror at the end of the hallway so the light beam would bounce of and reflect around the corner.
You might repeat this process by placing multiple mirrors at various corners and the light beam would just propagate. This is exactly what the cladding does in optical fiber.
Just as electrical signals though there is some degradation in light signal the further it travels. This is mostly because of impurities in the glass and the wavelength of the transmitted light. To compensate for this signal loss or degradation an optical regenerator is often spliced along the cable to boost the signal.
By using a special coating on a portion of optical fibers (Doping) the light that hits the doped coating is pumped with a laser beam that amplifies the signal.
Very-high-bit-rate Digital Subscriber (VDSL) uses fiber-optics to deliver Internet access to your home or business.
This can be achieved through Fiber to the Node (FTTN) or Local Exchange, Fiber to the Cabinet or Curb (FTTC), Fiber to the Building (FTTB) or for maximum speed Fiber to the home (FTTH).
In the case of FTTC the fiber runs all the way from the local telephony exchange to the street cabinet containing a DSLAM. From there on the signal is carried on to your house over metallic or copper wiring.
Suffice to say that the shorter the copper wire length, the higher the signal throughput. That is why FTTH is the fastest connection as there is no copper wire involved.
As mentioned before, FTTN means the fiber is terminated at the local Exchange while FTTC extends the fiber connection to a cabinet – containing a DSLAM – closer to your home or business before sending the signal over a copper wire.