CHAPTER 12 – Erbium-Doped Fiber Amplifiers for Dynamic Optical Networks

Light-wave networks are evolving from centrally planned provisioned circuits to intelligent dynamic network elements supporting point and click provisioning and simplified operations with reduced capital and operational costs. In recent years, the emphasis of light-wave networks has shifted from point-to-point line system to a more 2D architecture involving multi-wavelength networking capability via optical add/drop multiplexers and optical cross-connects. Erbium-doped fiber amplifiers (EDFAs) are a key element of these wavelength division-multiplexing (WDM) systems. WDM systems require high output power and low noise EDFAs with a high level of gain flatness over a wide and well-managed bandwidth. The capacity of lightwave communication systems has undergone enormous growth during the last few years due to huge capacity demand for data transmission. The chapter discusses the fundamentals of EDFAs including design considerations and system and network issues related to EDFAs. The issues related to EDFAs in dynamic WDM networks are also described. The chapter also focuses on several control schemes to limit the impairments caused by fast power transients. These include fast pump control, link control via insertion of compensating signals, gain clamping by lasing in an all-optical feedback loop, and three schemes, pump control, link control, and laser control, suitable for controlling the signal channel power transients.