Fibre-Optic Communications MCQ Quiz in मल्याळम - Objective Question with Answer for Fibre-Optic Communications - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

Explanation:

The primary purpose of the metallic shield in a coaxial cable is to protect against electromagnetic interference (EMI). Understanding the role of the metallic shield involves delving into the construction, principles, and functionalities of co-axial cables as well as the nature of electromagnetic interference.

Co-axial Cable Construction:

A co-axial cable is designed to transmit electrical signals with high efficiency and minimal interference. It consists of several layers:

• Core Conductor: The innermost part of the cable, typically made of copper or aluminum, which carries the electrical signal.
• Dielectric Insulator: Surrounding the core conductor, this layer insulates the signal-carrying conductor from the outer layers and helps maintain the integrity of the signal.
• Metallic Shield: This layer, often made of braided copper or aluminum, surrounds the dielectric insulator. Its primary function is to shield the inner conductor from external electromagnetic fields and to prevent electromagnetic interference (EMI).
• Outer Jacket: The outermost protective layer that shields the cable from environmental factors such as moisture, physical damage, and wear.

Electromagnetic Interference (EMI):

Electromagnetic interference is the disturbance generated by external sources that affect an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction. EMI can degrade the performance of electrical devices, cause data loss, or create noise in communication systems. In the context of co-axial cables, EMI can introduce unwanted signals that interfere with the transmission of the desired signal.

Function of the Metallic Shield:

The metallic shield in a co-axial cable serves several critical functions:

• EMI Protection: The metallic shield acts as a barrier to external electromagnetic fields, preventing them from penetrating the cable and causing interference with the transmitted signal. This ensures the integrity and clarity of the signal, which is especially important in high-frequency applications such as television broadcasting and internet data transmission.
• Signal Containment: It also prevents the electromagnetic fields generated by the signal within the cable from radiating outward and causing interference with other nearby electronic devices and cables.
• Grounding: The shield can serve as a grounding path, providing a reference point for the signal and improving overall signal stability and quality..

Explanation:

Which chemical is avoided for fiber optic cleaning?

Correct Option Analysis:

The correct option is:

Option 1: Acetone

Acetone is avoided for fiber optic cleaning due to several reasons. Acetone is a highly aggressive solvent and can cause damage to the delicate materials used in fiber optic components. The aggressive nature of acetone can lead to the dissolution or degradation of the plastic cladding or buffer material that surrounds the fiber optic glass core. This can compromise the integrity of the fiber optic cable, leading to signal loss or even complete failure of the communication link.

Moreover, acetone evaporates very quickly and can leave residues or streaks on the fiber optic surface. These residues can interfere with the transmission of light signals, causing signal attenuation and reducing the overall performance of the fiber optic system. The fast evaporation rate of acetone also makes it challenging to control during the cleaning process, increasing the risk of improper cleaning and potential damage.

In addition, acetone is highly flammable and presents a safety hazard in the workplace. The use of acetone in an environment with electrical equipment or open flames can lead to fire or explosion risks. Therefore, for safety and performance reasons, acetone is not recommended for cleaning fiber optic components.

Additional Information

Analysis of Other Options:

Option 2: Isopropyl alcohol

Isopropyl alcohol (IPA) is widely used for cleaning fiber optic components because it is effective at removing dust, oils, and other contaminants without damaging the fiber optic materials. IPA evaporates relatively quickly, leaving little to no residue, making it an excellent choice for maintaining the cleanliness and performance of fiber optic connections. It is important to use high-purity IPA (typically 99% or higher) to avoid introducing contaminants during the cleaning process.

Option 3: Ethyl alcohol

Ethyl alcohol (ethanol) is another solvent that can be used for cleaning fiber optic components. Like isopropyl alcohol, ethanol is effective at removing contaminants and evaporates quickly without leaving significant residues. However, isopropyl alcohol is generally preferred over ethanol because it is less hygroscopic (absorbs less moisture from the air), reducing the risk of moisture-related issues in the fiber optic system.

Option 4: Fiber cleaner

Fiber cleaners are specialized cleaning solutions specifically formulated for cleaning fiber optic components. These cleaners are designed to effectively remove contaminants without damaging the fiber optic materials or leaving residues. Fiber cleaners are typically available in convenient packaging, such as pre-moistened wipes or spray bottles, making them easy to use in the field or in a laboratory setting. They are considered the best choice for fiber optic cleaning due to their effectiveness and safety.

• A laser is a device that emits coherent light through a process called stimulated emission
• Coherent light is a light in which the electromagnetic waves maintain a fixed and predictable phase relationship with each other over a period of time
• The acronym of LASER is Light Amplification by Stimulated Emission of Radiation

Explanation:

Cleaning the Core of an Optical Fiber Cable (OFC)

Definition: Optical Fiber Cable (OFC) is a type of cable that uses light to transmit data at high speeds. The core of the optical fiber is the central part of the fiber where the light travels. To ensure optimal performance, it is crucial to clean the core of the optical fiber properly before use.

Cleaning Process: Before cleaning the core of an optical fiber cable, several layers of the cable must be removed. These layers include the jacket, buffer coating, and Kevlar. Let’s understand each of these layers:

1. Jacket: The outermost layer of the optical fiber cable is the jacket. It provides protection against physical damage and environmental factors. The jacket is typically made of durable materials like polyethylene or PVC.

2. Buffer Coating: Beneath the jacket, the buffer coating is applied directly over the optical fiber. This layer protects the fiber from moisture and mechanical damage. The buffer coating is generally made of plastic or acrylate materials.

3. Kevlar: Kevlar is a synthetic fiber known for its high tensile strength. It is used as a reinforcing layer in optical fiber cables to provide additional strength and durability. Kevlar helps prevent the fiber from breaking when the cable is bent or pulled.

To clean the core of the optical fiber, all these layers must be removed carefully. Here is a step-by-step process for removing these layers and cleaning the core:

1. Remove the Jacket: Use a cable stripping tool to remove the outer jacket of the optical fiber cable. Be careful not to damage the inner layers while stripping the jacket.
2. Remove the Kevlar: After removing the jacket, you will see the Kevlar strands. Use scissors or a Kevlar cutter to trim the Kevlar strands. Ensure that you cut the strands close to the edge of the buffer coating.
3. Remove the Buffer Coating: Use a fiber stripping tool to remove the buffer coating. This tool is designed to strip the coating without damaging the fiber. Carefully place the fiber into the stripping tool and pull the tool along the length of the fiber to remove the coating.
4. Clean the Core: Once the core is exposed, use a lint-free wipe and an appropriate cleaning solution (usually isopropyl alcohol) to clean the core. Gently wipe the core to remove any dirt, dust, or residues.

This thorough cleaning process ensures that the optical fiber core is free from any contaminants that could interfere with data transmission.

Correct Option Analysis:

The correct option is:

Option 4: All of these

This option correctly states that all the layers (jacket, buffer coating, and Kevlar) need to be removed before cleaning the core of the optical fiber cable.

Additional Information

Understanding the importance of each layer in the optical fiber cable helps in appreciating the careful process required for cleaning the core. The jacket provides overall protection, the Kevlar adds strength, and the buffer coating protects against moisture and mechanical damage. Removing all these layers ensures that the core is exposed and can be thoroughly cleaned to maintain the cable’s performance and reliability.

• Modal dispersion is a distortion mechanism occurring in multimode fibers and other waveguides, in which the signal is spread in time because of different propagation velocities for all modes. As we know, light rays entering the fiber at different angles of incidence will go through different paths/modes.
• Some of these light rays will travel straight through the center of the fiber (axial mode) while others will repeatedly bounce off the cladding/core boundary to zigzag their way along the waveguide, as illustrated below with a step-index multimode fiber. Whenever there is a bounce-off, modal dispersion (or intermodal dispersion) happens.
• The longer the path is, the higher the model dispersion will be. For example, the high-order modes (light entering at sharp angles) have more model dispersion than low-order modes (light entering at smaller angles).

As the fiber optic networks are developed for long distances, high-speed wavelength Division multiplexing (WDM) fiber has been used in new wavelength ranges, now called Bands.

The wavelength division multiplexing has allowed multiple signals to share a single fiber.

∴ The order of their increasing wavelength is:

(d) original band (O-band)

(c) Extended band (E-band)

(b) Conventional band (C-band)

Explanation:

Fiber Optic Tools for Splicing

Definition: In fiber optic communications, splicing is the process of joining two fiber optic cables end-to-end. This is typically done to extend the length of the fiber, repair damaged cables, or connect different types of fiber. The tools used for splicing ensure that the fiber ends are properly aligned and the optical signal can pass through with minimal loss.

Correct Option Analysis:

The correct option is:

Option 2: V-block

The V-block is a crucial tool in the process of fiber optic splicing. It ensures that the two fiber ends are aligned precisely before they are fused together. The V-block holds the fibers in place, allowing for a smooth and accurate alignment which is essential for maintaining the integrity of the optical signal. Without proper alignment, the signal loss at the splice point can be significant, leading to poor performance of the fiber optic network.

Working Principle: The V-block holds the two fiber ends in a V-shaped groove. This groove ensures that the fibers are aligned in the same plane. Once the fibers are placed in the V-block, a microscope or camera system is used to make fine adjustments, ensuring exact alignment. After the alignment is confirmed, the splicing process, usually involving a fusion splicer, can proceed.

Advantages:

• Ensures precise alignment of fiber ends, reducing signal loss.
• Simple to use and highly effective in maintaining fiber position during splicing.
• Compatible with various types of fiber optic cables.

Disadvantages:

• Requires careful handling and proper setup to achieve the best results.
• May require additional tools for fine alignment adjustments.

Applications: V-blocks are widely used in the telecommunications industry, data centers, and any application where fiber optic cables need to be spliced. They are essential tools for field technicians and engineers working with fiber optic networks.

Explanation:

Correct Option Analysis:

The correct answer is option 2:

Option 2: 1 km

Long-distance underground (UG) cables are used to transmit electricity over large distances. These cables are designed to be durable and reliable, ensuring that the electrical supply is consistent and safe. One of the critical aspects of using UG cables is the need for joints. Joints are essential for connecting lengths of cable together, ensuring that the electrical supply can be maintained over long distances.

For long-distance UG cables, joints are typically made every 1 km. This is because the manufacturing and handling processes of these cables usually limit the cable lengths to around 1 km. By making joints every 1 km, it becomes easier to manage and install the cables. Additionally, these joints help in maintaining the integrity of the electrical connection, ensuring that the cables can efficiently transmit electricity over long distances without significant losses or interruptions.

Important Information:

It is crucial to understand why other options are not correct:

Option 1: 100 m

Making joints every 100 meters would be impractical for long-distance UG cables. This would require a significantly higher number of joints, increasing the chances of potential points of failure and maintenance issues. It would also increase the installation time and cost.

Option 3: 500 m

While 500 meters is a more feasible distance than 100 meters, it is still shorter than the typical manufacturing and handling limits of UG cables. This would result in more joints than necessary, leading to higher installation costs and maintenance efforts.

Option 4: 200 m

Similar to option 1, making joints every 200 meters would also be impractical. It would result in an excessive number of joints, increasing the complexity of the installation and the potential for maintenance issues. Additionally, it would not take full advantage of the manufacturing capabilities of UG cables, which can handle lengths of up to 1 km.

In summary, the optimal distance for making joints in long-distance UG cables is 1 km. This distance balances the manufacturing limitations, installation efficiency, and maintenance considerations, ensuring a reliable and cost-effective solution for transmitting electricity over long distances.