Optical fiber amplifier system and methods of using same

An optical fiber system configured to provide amplified radiation, the system comprising:

• an active optical fiber having an active dopant, an absorption spectrum associated with the active dopant, the active optical fiber having a first end and a second end;
• a plurality of grating-locked pump sources arranged to pump the active optical fiber, each grating-locked pump source having a gain bandwidth and a grating having a spectral width, each grating-locked pump source having an output optically coupled to the first end or the second end of the active optical fiber, each grating-locked pump source being configured to output pump radiation having a spectrum that substantially overlaps with the absorption spectrum associated with the active dopant of the active optical fiber, the pump radiation having a power that depends on a drive current input to the grating-locked pump source;
• one or more temperature sensors, configured to measure a temperature associated with one or more of the grating-locked pump sources;
• and
• a control system configured to accept measurements from the one or more temperature sensors and, for a desired total pump power output, to provide to one or more of the grating-locked pump sources a set of drive currents suitable to provide the desired total pump power output, wherein for each of the one or more grating-locked pump sources to which current is to be provided, the drive current is controllable such that, based on the measured temperature associated with that grating-locked pump source,
• the gain bandwidth of the grating-locked pump source remains in substantial overlap with the spectral width of the grating,
• wherein for each of the grating-locked pump sources, the control system is configured to provide a first range of drive currents to the grating-locked pump source at a first measured temperature, and to provide a second range of drive currents to the grating-locked pump source at a second measured temperature at least 10° C. more than the first measured temperature, the second range of drive currents being substantially different from the first range of drive currents, wherein the second range of drive currents has a substantially lower maximum current, a substantially lower minimum current, or both a substantially lower maximum current and a substantially lower minimum current than the first range of drive currents.

A method for providing amplified radiation form an optical fiber system including an active optical fiber having an active dopant and a plurality of grating-locked pump sources, the grating-locked pump sources being substantially identical to one another, arranged to pump the optical fiber, said method comprising, at a first time,

• providing a total pump power to the active optical fiber by
• measuring a temperature associated with each of one or more of the grating-locked pump sources;
• based on the total pump power to be provided to the active optical fiber and the measured temperature(s), determining how many of the grating-locked pump sources are to be activated, and selected a set of the grating-locked pump sources to be activated and at least one grating-locked pump source to not be activated;
• refraining from providing substantial drive current to the at least one grating-locked pump source to not be activated;
• and
• based on the measured temperature associated with each grating-locked pump source to be activated, providing a drive current thereto, the drive current being selected such that
• the gain bandwidth of the grating-locked pump source to be activated remains in substantial overlap with the spectral width of the grating, and
• the pump radiation output by the grating-locked pump source to be activated has a spectrum that substantially overlaps with the absorption spectrum associated with the active dopant of the active optical fiber,
• wherein the drive currents are selected to provide the total pump power to the active optical fiber from the one or more grating-locked pump sources;
• and amplifying radiation in the active optical fiber to provide the amplified radiation.