# FREE Registered Communications Distribution Designer (RCDD): Mastering Telecommunications Standards Questions and Answers

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#### Which of the following options closely resembles the concept of Wave Division Multiplexing (WDM)?

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The correct answer is Frequency division multiplexing. Among the options provided, Frequency Division Multiplexing (FDM) is the one that closely resembles the concept of Wave Division Multiplexing (WDM). Both FDM and WDM involve the simultaneous transmission of multiple signals over a single medium by utilizing distinct frequencies or wavelengths to separate and carry each signal. This allows for efficient utilization of the communication channel and increased data capacity.

#### Given an optical fiber with a core diameter of 62.5 micrometers and a numerical aperture (NA) of 0.275, determine the angle of acceptance (in degrees) applicable to this particular optical fiber.

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The correct answer is 33.7 degrees. The angle of acceptance for an optical fiber is calculated using the formula θ = sin^(-1)(NA), where NA is the numerical aperture. In this case, with a given NA of 0.275, the angle of acceptance is approximately 33.7 degrees. This angle represents the maximum angle at which light can enter the core of the optical fiber and be guided effectively through it.

#### Which one of the following options does NOT represent a nominal wavelength commonly associated with laser light sources?

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The correct answer is 700 nm. The nominal wavelengths provided are commonly associated with laser light sources used in optical communications. However, 700 nm is not among these commonly used wavelengths. Laser light sources often include wavelengths like 850 nm, 1300 nm, and 1310 nm due to their suitability for various applications in optical fiber-based systems.

#### Composite conductors, while typically not suggested, might find application in specific situations due to their various benefits. However, which of the subsequent advantages is not among those offered by composite conductors in such cases?

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The correct answer is Have good digital transmission characteristics. Composite conductors, although occasionally employed under special circumstances, do not inherently possess the advantage of having excellent digital transmission characteristics. This is in contrast to some of their other benefits like being inexpensive, easy to produce, and easily embeddable into other materials.

#### A SONET OC-1 channel has the capability to accommodate 672 voice signals, operating at a data rate of 51.84 Mbps. On the other hand, an SONET OC-48 channel is designed to accommodate 32,256 voice channels. What is the LEAST data rate that is necessary for the OC-48 channel to function effectively?

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The correct answer is 2.5 Gbps. An OC-48 channel is designed to accommodate 32,256 voice channels, and since an OC-1 channel carries 672 voice signals, the minimum data rate required for the OC-48 channel can be calculated as 32,256 (channels) multiplied by 51.84 Mbps (data rate of OC-1), which results in 1.6777728 Gbps. Since the question asks for the minimum data rate, the correct answer rounds up to 2.5 Gbps. This is because OC-48 operates at 2.48832 Gbps, and the minimum data rate must be at least sufficient to carry the specified number of voice channels.

#### When combining two sinusoidal signals with identical amplitude (A) and frequency (f), but differing by a phase of 180 degrees, what is the resulting amplitude of the resultant sinusoidal signal formed by their summation?

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The correct answer is Zero. When two sinusoidal signals of the same amplitude and frequency but with a phase difference of 180 degrees are added together, their peaks and troughs align perfectly, resulting in complete cancellation. As a result, the amplitude of the resultant signal becomes zero. This phenomenon is known as destructive interference, where the waves destructively interact, leading to the elimination of the signal's presence.

#### To which category does this question pertain: What attribute represents an advantage of copper-based media in comparison to optical fiber cable?

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The correct answer is Susceptibility to EMI. It relates to the susceptibility of copper-based media to electromagnetic interference (EMI) in contrast to optical fiber cable. EMI can potentially affect the performance of copper-based systems, making this an important consideration when comparing different transmission media.