Telecommunications Systems Essay Research Paper Everything You

Telecommunications Systems Essay, Research Paper Everything You Ever Wanted to Know About dB But Were Afraid to Ask Telecommunications systems used electrical signals and copper wire to transmit voice messages long before lasers, lightwaves and fiber optic cable. To describe and measure power levels in electrical systems, telecommunication engineers used the standard unit of decibels to express gain or loss and relative power levels.

Telecommunications Systems Essay, Research Paper

Everything You Ever Wanted to Know About dB But Were Afraid to Ask Telecommunications systems used electrical signals and copper wire to transmit voice messages long before lasers, lightwaves and fiber optic cable. To describe and measure power levels in electrical systems, telecommunication engineers used the standard unit of decibels to express gain or loss and relative power levels. Meanwhile, scientists working with fiber optic signals were using units of milliwatts (mW) to determine the amount of light traveling down a fiber or the amount of light coupling from one fiber to another (as would be expected with optical radiation). As the telecommunications industry began to use fiber it did not adopt the milliwatts terminology. Just the opposite happened, fiber optics adopted the traditional telecommunications language of decibels or dB.Decibel is defined as a unit used to express relative difference in power, usually between acoustic or electric signals, equal to negative ten times the common logarithm of the ratio of the two levels. The main reason dB is used is because it makes power levels more manageable. Thus, it’s easier to add up power losses in a system. For example, a system with 4.0dB of fiber loss, 2.5dB of connector loss,3.0dB of splitter loss and0.5B of splice loss results in a 10dB system loss or the sum of each component loss. Translating 10dB into a percentage based upon the formula given earlier results in a signal that is 10% of the original intensity. Because dB can be used to describe both gain and loss, it is important to carefully consider the given optical parameter. A decibel expressing loss is a negative unit. However, in the fiber optics industry, it is common practice to omit the negative sign and speak of a 3dB loss rather than-3dB. For example, a back reflection level of *-40dB and *40dB are generally taken to mean the same thing (reflected light *0.01% or light is reduced by 99.99%) and therefore one must keep in mind the overall context when making system calculations. An additional point of confusion is the difference between dB and dBm. dB is a comparison of a signal to a reference signal without any specified unit of measurement: dBm is used when 1 milliwatt is the reference signal level: For example, a value of -3dBm means that P is 3dB (50%) less than than 1mW or .5mW. Conversion tables for dB to percent and dB to mW are shown below:

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