Optical Fiber Transmission Modes, Network Switching, and Routing Fundamentals

Posted on Aug 7, 2024 in Computers

Optical Fiber Transmission Modes and Applications

1. Modes of Transmission in Optical Fibers

Optical fibers transmit light beams through different paths called modes of propagation. The type of propagation mode determines whether the fiber is classified as multimode or singlemode.

Multimode Fiber

Multimode fiber allows light beams to travel through multiple modes or paths simultaneously. This type of fiber can support over a thousand light propagation paths. Multimode fibers are cost-effective and commonly used in short-distance applications, typically less than 1 km, with a maximum distance of 2 km. They utilize low-level laser diodes for light transmission.

Singlemode Fiber

Singlemode fiber, as the name suggests, allows only one mode of light propagation. This is achieved by reducing the core diameter of the fiber to a size (8.3 to 10 microns) that permits only a single propagation mode. Light transmission occurs parallel to the fiber axis. Unlike multimode fibers, singlemode fibers can transmit data over long distances (up to 100 km) at high data rates (tens of Gb/s) using high-intensity lasers.

2. Applications of Terrestrial Microwave Systems

Terrestrial microwave systems find applications in various domains, including:

• Bluetooth
• Wi-Fi (802.11 b and g)
• Mobile communications
• Microwave radars (e.g., speed detectors)
• Cable television
• Long-distance transmissions

Network Switching and Its Role in Data Communication

3. Switching in Telecommunications Networks

Switching in telecommunications networks involves connecting different nodes located at various distances. This process establishes an efficient path for communication between two users. Switches play a crucial role in managing network traffic by reducing congestion and enhancing bandwidth utilization. They are particularly effective in alleviating congestion in Ethernet LANs.

Examples of switching devices include:

• Routers
• Switches

4. Purpose of Switching Nodes in Data Packet Transmission

Switching nodes perform essential functions in data packet transmission:

• Store and Forward: Intermediate nodes store incoming data packets and forward them towards their destination, effectively establishing a logical path.
• Routing: Nodes determine the optimal path for packet transmission by selecting the appropriate next hop for each packet.

Packet switching networks operate by transmitting data packets through interconnected nodes. While packets may travel different routes, the network strives to ensure reliable delivery.

5. Phases of Circuit Switching Communication

Circuit switching communication involves three distinct phases:

1. Circuit Establishment: A dedicated communication channel is established between the source and destination stations. This phase involves reserving resources like bandwidth and defining service parameters.
2. Data Transfer: Once the circuit is established, data transmission commences. The transmission mode (analog or digital) and direction (unidirectional or full-duplex) depend on the network service and requirements.
3. Circuit Disconnection: After data transmission is complete, the circuit is disconnected, releasing the reserved resources for use by other communications.

Virtual Circuit Switching and Packet Switching Techniques

6. Subdivisions of Virtual Circuit Switching

Virtual circuit switching encompasses two main types:

• Permanent Virtual Circuit (PVC): A pre-determined route is established between two terminals, providing a dedicated communication path.
• Switched Virtual Circuit (SVC): The path is dynamically established during the call setup phase. Each packet carries a virtual circuit identifier for routing.

7. Packet Switching Techniques

Packet switching is a widely used method in computer networks where data is divided into packets for transmission. Each packet includes a header containing source and destination addresses, control information, and the data segment. Packet switching optimizes transmission capacity by efficiently utilizing available bandwidth.

Two primary techniques employed in packet switching are:

• Virtual Circuit Packet Switching: Packets belonging to the same communication flow follow the same pre-established virtual circuit, ensuring in-order delivery.
• Datagram Packet Switching: Each packet is routed independently, and the network does not guarantee packet order or path control.

Routing in Data Networks and Its Significance

8. Purpose of Routing

Routing is the process of determining the optimal path for data packets to travel across a network. The goal is to find the”best rout” based on specific metrics, such as:

• Number of Hops: Minimizing the number of intermediate nodes traversed.
• Transit Delay: Minimizing the time taken for a packet to travel from source to destination.
• Cost: Minimizing the expense associated with using specific network links.

Effective routing aims to achieve:

• Low average transit delay
• Bounded delay between network nodes
• High-speed and efficient data delivery
• Cost-effectiveness

Types of Routing Algorithms

Routing algorithms can be categorized as:

Deterministic or Static Routing

Static routing relies on manually configured routing tables that remain unchanged unless manually updated. While simple to implement, static routing lacks adaptability to network changes.

Adaptive or Dynamic Routing

Dynamic routing algorithms adapt to network conditions by adjusting routing tables based on real-time information. They offer better resilience to traffic fluctuations and network failures. Dynamic routing can be further classified into:

• Centralized Routing: A central node collects network information and calculates routing tables for all other nodes.
• Distributed Routing: Each node calculates its routing table based on information exchanged with neighboring nodes. Examples include distance-vector and link-state routing protocols.
• Isolated Routing: Each node makes routing decisions based on local information, such as in flood routing.

Routing Protocols and Autonomous Systems

Routing protocols facilitate the exchange of routing information between routers. Autonomous Systems (AS) represent groups of networks under a single administrative domain. Routing protocols can be categorized based on their scope:

Interior Gateway Protocols (IGPs)

IGPs operate within a single AS. Examples include:

• RIP (Routing Information Protocol)
• OSPF (Open Shortest Path First)
• EIGRP (Enhanced Interior Gateway Routing Protocol)
• IS-IS (Intermediate System to Intermediate System)

Exterior Gateway Protocols (EGPs)

EGPs exchange routing information between different ASes. BGP (Border Gateway Protocol) is the primary EGP used in the internet.

9. Routing Table Example

Please refer to the provided image for the network topology and link costs.

Node A Routing Table

Note: The routing table for Node A is constructed using the shortest path (least cost) to each destination based on the provided link costs.