Patent ID: 6236498
Filing Date: 2001-05-22
Classification: H01S,H04B,H04J

Abstract:
A multistage fiber amplifier system for amplifying a plurality of channel signals comprising:an input amplifier stage and an output amplifier stage each comprised of a rare earth doped fiber and having an inherent gain profile over a gain spectrum, said input amplifier stage coupled to receive as input a plurality of channel signals;a plurality of pump laser sources with outputs combined for providing pump power for pumping said input and output amplifier stages;a gain flattening filter provided between said input and output amplifier stages, said gain flattening filter providing a filter shape characteristic with low attenuation across the gain band of said input amplifier stage; andsaid pump power to said input and output amplifier stages upgradable via an input connector to provide a second plurality of pump laser sources with outputs combined for providing pump power for pumping said input and output amplifier stages via optical pump power split such that the system is upgraded with an increase in channel capacity to maintain said input amplifier stage in a high inversion state maintaining substantially the same signal to pump power ratio with system upgrade so that said gain flattening filter characteristics remain applicable to the power upgraded multistage fiber amplifier system.