Unit 9. Exercise 1 1. Forward Biased LED – Semiconductor diode with a positive voltage applied to the p-region and a negative voltage to the n-region.

2. Incoherent Light – Light in which the electric and magnetic fields of photons are completely random in orientation. Incoherent light is typically emitted from light bulbs and LEDs.

3. Laser – Acronym for light amplification by stimulated emission of radiation. The laser produces a coherent source of light with a narrow beam and a narrow spectral bandwidth (about 2cm). Lasers in fiber optics are usually solid-state semiconductor types. Lasers are used to provide the high-powered, tightly controlled light wavelengths necessary for high-speed, long-distance optical fiber transmissions.

4. Output Pattern – LED and laser semiconductors used in fiber-optic light sources are packaged to couple as much light as possible into the core of the optical fiber. The output pattern or NA of the light source directly relates to the energy coupled into the core of the optical fiber.

5. Output Power – This power of light sources used in fiber-optic communication systems varies dramatically depending on the application. LEDs are typically designed to support transmission distances of up to 2km while laser light achieves distances in excess of 80km. Laser optical power output levels can exceed LED optical output power levels by more than 20dB.

6. Modulation Speed – One factor that can limit the performance/bandwidth of a fiber-optic communication system via the light source.

7. Core Diameter Mismatch – Occurs when there is a difference in the core diameters of the two optical fibers. A los may occur when the core diameter of the transmitting optical fiber is greater than the core diameter of the receiving optical fiber.

8. Current – Flow of electrons in a conductor.
9. PIN Photodiode- A diode with a wide lightly doped near intrinsic semiconductor region between a p-type semiconductor and an n-type semiconductor region.

10. Avalanche Photodiode- Highly sensitive semiconductor electronic device that exploits the photoelectric effect to convert light to electricity.

11. The state or fact of having a duty to deal with something or of having control over someone.

12.

16. Optomechanical Switch this type of switch redirects an optical signal by moving fiber or bulk optic elements by means of mechanical devices.

17 Optical Subassembly guides the light energy from the optical fiber to the photodiode.

18. Optical Isolator - reduces the effects of interference.

19. Wavelength Division Multiplexing is the combining of different optical wavelengths from two or more optical fibers into just one optical fiber.

20. Passive Optical Network A network that does not used electrically powered equipment or components to get the signal from one place to another.

21. FTTH a type of PON that uses optical fiber from the central office to the home.