Power budgets for long-haul optically amplified systems

Power budgets are used in the system planning of all submarine and terrestrial optical systems. They enable system owners and suppliers to identify the margin that exists in the system design and to compare this with the specified performance objectives. The author considers how a power budget can be developed for an optically amplified system. Two possible starting points for these are computer system simulations or a simple model of amplifier noise concatenation; the benefits and drawbacks of each are considered. Both give a measure of the expected performance for an idealised system, that is there are a number of effects that are not taken into account. The power budget is used to subtract from this idealised system performance these additional impairments to give the actual expected performance. These additional impairments are identified and considered individually