ccna question with answer

ccna question with answer.There are two types of fiber used for data connections: multimode fiber (MMF) and single-mode fiber (SMF) Multimode fiber transmits at wavelengths of 850 or 1300nanometers (nm) (infrared light invisible to the naked eye) MMF has a diameter of 62.5/125 microns, including the cladding (the actual diameter of the fiber optic cable) of 50 to 100 microns.) is 50 ~100 μm. The wavelength of 850/1300nm corresponds to a frequency of THz class. The light source is an LED, and as the light travels, it is reflected by the cladding surrounding the core. the relatively large core of the MMF allows multiple beams of light of a given wavelength to be transmitted (the light travels along different paths), hence the term multimode. Multiple beams cause dispersion (signal expansion), which limits the data transmission speed of the fiber to a few hundred Mbit/so The following scenario is a good illustration of dispersion: when a flashlight is turned on and shone on a wall, the farther the flashlight is from the wall, the larger the circle of light formed on the wall.A single-mode fiber transmits light at wavelengths of 1300 or 1550 nm and uses a laser emitter as the light source. Because the laser emitter has a higher output power than the LED, SMFs can transmit over 10 km and at speeds of up to 100 Gbit/so Because the SMF has a small core, only one beam of light of a given wavelength can be transmitted, hence the term single mode. Because only one beam of light is propagated, SMF has a lower degree of dispersion (signal expansion) than MMF and therefore supports much higher data speeds (over 100 Gbit/s) than MMF.In the last decade, the use of optical fiber has gained tremendous popularity, with one of the major improvements being Wavelength Division Multiplexing (WDM) and Dense Wavelength Division Multiplexing (DWDM).0 WDM allows optical fibers to propagate multiple wavelengths of light (multiple signals), thereby increasing the number of connections.DWDM further increases the number of wavelengths, allowing a single fiber optic cable to propagate more than 200 different wavelengths of light simultaneously.DWDM - an obvious DWDM has the obvious advantage of providing flexibility and transparency in the protocols and traffic carried by the fiber. DWDM offers scalability, allowing operators to provide new connections without laying new fiber optic cables, which allows them to add new connections in a very short period of time after receiving an order.Here are some terms related to fiber and their impact on transmission speed and distance. Fiber optic cables contain an outer protective layer (coating) and an inner cladding layer (cladding). The cladding is very tight and is able to reflect light. In the center of the fiber optic cable is the core, which is used to transmit the signal. The refractive index (IOR) affects the speed of light transmission, which refers to the ratio of the speed of light transmission in a vacuum to the speed of light transmission in an optical fiber. In a vacuum, transmission is not affected in any way, but when transmitting a signal through a medium such as fiber optic cable or copper cable, the properties of the medium will affect transmission, which in turn will cause delays.IOR is used to measure this difference: the IOR measure is basically the density of the fiber. The higher the density of the fiber, the lower the speed at which light travels through it.The depletion factor refers to how much the signal is depleted to reach the other end of the fiber. Splice depletion refers to the depletion caused by the splice used to connect two fibers together: this signal depletion is relatively small. Also, the longer the fiber, the greater the likelihood that the signal will degrade in strength once it reaches the other end of the fiber, which is known as attenuation.There are two other terms that describe signal degradation. Microbending refers to optical signal distortion caused by folds in the fiber (usually located where the fiber cable is slightly bent); macrobending refers to optical signal leakage at the bend in the fiber cable. To solve this problem over long distances, optical amplifiers can be used; they are similar to Ethernet transponders and hubs. Good amplifiers, such as clamp-doped fiber amplifiers (EDFAs), amplify the optical signal directly, achieving the best possible reproduction of the original signal; other amplifiers convert the optical signal into an electrical signal, and then into an optical signal, which can lead to degradation of the signal quality.There are two main standards that regulate the transmission of signals in optical fiber: SONET (Synchronous OpticalNetwork) and SDH (SynchronousDigital Hierarchy). SONET was developed by the Exchange Carriers Standards Association (ECSA) and the American National Standards Institute (ANSI) and is commonly used in North America; SDH is an international standard and is used in most parts of the world except North America. Both standards specify the physical layer framing method used to transmit optical signals. Optical signals also have transmission overheads, and these are divided into 3 categories.. Segment overhead (SOH): the overhead of the link between devices (e.g., transponders).