Fiber Optics- Definitions Essay
Fiber Optics- Definitions
1.Crosstalk – The coupling or transfer of unwanted signals from one pair within a cable to another pair. Crosstalk can be measured at the same (near) end or far end with respect to the signal source. Crosstalk is considered noise or interference and is expressed in decibels. 2.Waveguides – A structure that guides electromagnetic waves along their length. The core fiber in an optical-fiber cable is an optical waveguide. 3.FTTH – (fiber-to-the-home): Fiber reaches the boundary of the living space, such as a box on the outside wall of a home. Passive optical networks and point-to-point Ethernet are architectures that deliver triple-play services over FTTH networks directly from an operator’s central office. 4.Simplex – A link that can only carry a signal in one direction. A fiber-optic cable or cord carrying a single fiber. Simplex cordage is mainly used for patch cords and temporary installations.
5.Half-Duplex – A system in which signals may be sent in two directions, but not at the same time. In a half-duplex system, one end of the link must finish transmitting before the other end may begin. 6.Full-Duplex – A system in which signals may be transmitted in two directions at the same time. 7.Photodiode – A component that converts light energy into electrical energy. The photodiode is used as the receiving end of a fiber-optic link. 8.Amplitude Modulation – A method of signal transmission in which the amplitude of the carrier is varied in accordance with the signal. With respect to optical fiber cabling, the modulation is done by varying the amplitude of a light wave, common in analog/RF applications. 9.Analog Transmission – A signal that varies continuously through time in response to an input. A mercury thermometer, which gives a variable range of temperature readings, is an example of an analog instrument. Analog electrical signals are measured in Hertz (Hz). Analog is the opposite of digital.
10.Digital Transmission – Refers to transmission, processing, and storage of data by representing the data in binary values (two states: on or off). On is represented by the number 1 and off by the number 0. Data transmitted or stored with digital technology is expressed as a string of 0s and 1s. Digital signals are used to communicate information between computers or computer-controlled hardware. 11.Sample Rate – The sampling of the analog signal’s voltage at regular intervals and converted into binary numbers that represent the voltage at each interval. This sampling frequency is measured in terms of cycles per second, or hertz, so a rate of one sample per second would be designated 1Hz. 12.Electromagnetic Wave – The combination of an electrical field and a magnetic field, formed at right angles to each other and at right angles to their path of travel through open space or air at approximately 300,000km/s (kilometers per second).
13.Refraction – The bending of a beam of light as it enters a medium of different density. Refraction occurs as the velocity of the light changes between materials of two different refractive indexes. 14.Medium – A medium is any material or space through which electromagnetic radiation can travel. 15.Total Internal Reflection – The reflection of light in a medium of a given refractive index off of the interface with a material of a lower refractive index at an angle at or above the critical angle. Total internal reflection occurs at the core/cladding interface within an optical fiber cable. 16.Fresnel Reflection – Reflection of a small amount of light passing from a medium of one refractive index into a medium of another refractive index. In optical-fibers, reflection occurs at the air/glass interfaces at entrances and exit ends. 17.Tensile Strength – Resistance to pulling or stretching forces.
18.Dispersion – A broadening or spreading of light along the propagation path due to one or more factors within the medium (such as optical fiber) through which the light is traveling. There are three major types of dispersion: modal, material and waveguide. Modal dispersion is caused by differential optical path lengths in a multimode fiber. Material dispersion is caused by a delay of various wavelengths of light in a waveguide material. Waveguide dispersion is caused by light traveling in both the core and cladding materials in single-mode fibers and interfering with the transmission of the signal in the core. If dispersion becomes too great, individual signal components can overlap one another or degrade the quality of the optical signal. Dispersion is one of the most common factors limiting the amount of data that can be carried in optical fiber and the distance the signal can travel while still being usable; therefore, dispersion is one of the limits on bandwidth on fiber-optic cables. It is also called pulse spreading because dispersion causes a broadening of the input pulses along the length of the fiber.
19.Bandwidth – Indicates the transmission capacity of media. For copper cables, bandwidth is defined using signal frequency and specified in Hertz (Hz). For optical fibers, wavelength in nanometers (nm) defines bandwidth. Also refers to the amount of data that can be sent through a given channel and is measured in bits per second. 20.Polarity – Identifies which side of an electrical circuit is positive and which is negative. 21.Absorption – The loss of power (signal) in an optical fiber resulting from conversion of optical power (specific wavelengths of light energy into heat. Caused principally by impurities, such as water, ions of copper or chromium (transition metals), and hydroxyl ions, and by exposure to nuclear radiation. Expressed in dB/km (decibels per kilometer). Absorption and scattering are the main causes of attenuation (loss of signal) of an optical waveguide during transmission through optical fiber.
22.Scattering – A property of glass that causes light to deflect from the fiber and contributes to losses. The redirection of light caused by atomic structures and particles along the light’s path. 23.Equilibrium Mode Distribution – A condition in which the light traveling through the fiber populates the available modes in an orderly way. 24.Personal Protective Equipment – Consists of anything that you would wear to protect yourself from materials or situations. PPE can include protective gloves and eyewear for cutting and grinding operations, respirators for working with chemicals that put out harmful vapors, and specialized goggles for working with lasers. 25.Good Work Habits – The simplest and most effective means to working safely. Good work habits can help you prevent accidents and spot potential problems in time to correct them.