What is described by a link budget in optical networks?

• A. The total optical power emitted by transmitter.
• B. The amount of electrical power required to energize the transceiver.
• C. The sum of optical losses that must not exceed transceiver power limits.
• D. The distance between transmitter and receiver.

Answer: (C)

A link budget is the calculation that determines how much optical loss the system can tolerate while still delivering enough power to the receiver. In practice, it compares the transmitter’s output power with the receiver’s minimum required power, taking into account all gains and losses in the path. The key idea is that the total optical losses along the link must not exceed the available margin provided by the transmitter power and any gains in the system, so the receiver can still detect the signal reliably.

That’s why the described option is the best: it captures the idea that the link budget is about the sum of optical losses that must not exceed the transceiver’s power limits. If you know the transmitter power and the receiver’s sensitivity, you can sum up all losses (fiber attenuation, connectors, splices, etc.) and ensure they stay within that margin. If the losses exceed the budget, the link won’t meet the required performance.

The other ideas aren’t the budget itself. The total optical power emitted is part of the inputs to the budget but doesn’t describe the path losses and margins. The electrical power to energize the transceiver is unrelated to the optical link budget. The distance between transmitter and receiver is a factor that affects losses, but the budget specifically represents the allowable cumulative losses given the transmitter power and receiver sensitivity.