4A0-205: Nokia Optical Networking Fundamentals

Services are transported over trails; that is, services are clients with respect to trails. A service is a logical connection that is used to transport data from one point to another. It is created over a trail, which is a physical connection that is established by using multiple wavelengths. As such, services are clients with respect to trails, as they are transported over them.

The OSNR is defined as the ratio between the average optical signal power and the average optical noise power over a specific spectral bandwidth. This is also known as the signal-to-noise ratio (SNR), and it is a measure of how much signal is present in the optical signal compared to the noise, usually expressed in decibels (dB).

Yes, during the segment creation phase or editing. It is possible to select the fiber type independently for each segment while designing a network in EPT. This can be done during the segment creation phase or when editing an existing segment. This allows for more flexibility when designing the network and allows for more efficient use of resources.

A star topology is a network design where all devices are connected to a central hub, which acts as a central point of control and management for the network. This type of topology is commonly used in access networks, where a central node is used to aggregate traffic from multiple users or devices, and then forward it to the core network. This design allows for efficient use of resources and easy management of the network.

Reference:

"Computer Networking: A Top-Down Approach" by James Kurose and Keith Ross (Chapter 3) "Data Communications and Networking" by Behrouz A. Forouzan (Chapter 2)

Different wavelengths propagate at different speeds within the same media and therefore different colors travel in the fiber with different speed. This phenomenon is known as chromatic dispersion and causes light to spread out as it travels through the fiber over distance, leading to signal attenuation and distortion. The fiber attenuation does not introduce inter-channel interference, but it can cause attenuation of the signal. Different channels have different bandwidths, but this does not affect CD performance.

The Metro Area Network (MAN) is a telecommunications network that spans a metropolitan area and connects multiple local area networks (LANs) or business networks together. It typically covers an area that is larger than a LAN but smaller than a wide area network (WAN). The purpose of a MAN is to provide a high-bandwidth, low-latency communication infrastructure for businesses and other organizations in a metropolitan area.

Reference:

Cisco, "Metro Ethernet Services," https://www.cisco.com/c/en/us/solutions/service-provider/metroethernet-services/index.html

Techopedia, "Metro Area Network (MAN)," https://www.techopedia.com/definition/26896/metroarea-network-man

A trail is a transparent transport of a client signal. A trail is a physical link between two points in an optical network, allowing for the transport of a client signal from one point to the other. It is a loworder signal, such as a 10G Ethernet or a Fibre Channel signal, encapsulated into a high-order container, such as a 40G or 100G signal. This allows for the transport of the client signal over longer distances, increasing the power budget of the optical link.