Amplified spontaneous emission in cladding-pumped L-banderbium-doped fiber amplifiers

Propagation of amplified spontaneous emission (ASE) in cladding-pumped long-wavelength-band erbium-doped fiber amplifiers (EDFAs) is analyzed numerically. Forward and backward ASE power dependence on cladding area is analyzed for both pumping directions. ASE power propagating counterdirectionally to the pump is found to experience strong dependence on the cladding area. Increasing the cladding area results in more uniform pump distribution along the EDF, preventing short-wavelength gain and ASE buildup. Quantum conversion efficiency in cladding-pumped L-band EDFAs is discussed     

Scalability of a Metropolitan Bidirectional Multifiber WDM-Ring Network

We analyze the scalability of a metropolitan bidirectional multifiber wavelength-division-multiplexed (WDM) ring network. The analysis is carried out by using a bidirectional transmission model for optical networks and by building an experimental network. The model includes major limiting factors in WDM-ring networks such as relative intensity noise (RIN) due to multiple Rayleigh backscattering, amplified spontaneous emission (ASE) accumulation in a cascade of bidirectional erbium-doped fiber amplifiers (EDFA), tilting of the EDFA gain spectrum and input saturation power of the EDFA. We found that in metropolitan areas the scalability of a WDM-ring network using bidirectional transmission is not mainly limited by the RIN arising from the Rayleigh backscattering. The result was verified experimentally. The maximum size of the demonstrated network is 33–43 nodes with a spacing of 5–10 km between nodes. With this spacing, which is typical in metropolitan areas, the scalability of the network is mainly limited by the gain tilt and the input saturation power of the EDFA.