When any fiber characteristic is not defined by a protocol, the value you will use becomes determined by the cable manufacturers' desire to avoid their products appearing inferior to other products.
In all other cases, the fiber attenuation rate depends upon the competitive nature of the market. The fiber attenuation rate will be defined in the case of networks designed to comply with TIA/EIA-568-A or -B. Once you define the maximum bit rate, the fiber attenuation rate will either be defined or easily determined.
This characteristic is required for protocols that support multiple bit rates, such as asynchronous transfer mode (ATM) and Fiber Channel. In addition to link length and protocol, you may need to define the maximum bit rate to run on the link. More specifically, these two characteristics of the network define the fiber: core diameter, clad diameter, numerical aperture (NA), wavelength, bandwidth distance product and the main characteristics of the transmitter-receiver pair. With most protocols, the link length and the protocol define the fiber to be used. You will calculate and compare the power loss to the maximum loss allowed by the protocol. The length and number of connections will define the power loss between the transmitter and receiver. The map defines number of fiber to fiber connections. The endpoints of each link, which are the locations of the transmitter and receiver, define the link length.
LAN design starts with your definition of three characteristics of the network: the end points of each link, a map of each fiber path between these end points, and the protocol to be run over the network. Not simple, mind you, but straightforward, as you will see. In fact, the design process is now straightforward. However, the evolution of fiber optic LANs and standards has significantly simplified this process. To those unfamiliar to fiber optics, the process of local area network (LAN) design may seem complicated and tricky.
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