Dynamic gain-controlled erbium-doped fiber amplifier repeater for WDM network

Wavelength-division multiplexing (WDM) networks using optical adddrop multiplexers and optical switches are effective for increasing not only capabilities but also transparency, and survivability against fiber cuts. In systems employing erbium-doped fiber amplifiers (EDFAs), per-channel output power control by a wavelength monitor is an important function, because a change in the number of channels caused by network reconfigurations or faults may bring a power transition in EDFA output. A wavelength monitor for an optical amplifier with cascaded fiber gratings and delay lines of optical fibers has been reported. We have recently developed an EDFA repeater for WDM networks that has a wavelength monitor for arbitrary wavelength and uses an acousto-optic tunable filter (AOTF).