Optical amplifier having a substantially flat gain spectrum

An optical amplifier comprising:

• a first segment of optically amplifying fiber configured to receive a plurality of optical signals at a first end portion, each of said plurality of optical signals being at a respective one of a plurality of wavelengths, said first segment of doped optical fiber having a second end portion;
• an optical circulator having first, second and third ports, said first port of said optical circulator being coupled to said second end portion of said first segment of doped optical fiber, said optical circulator being coupled to circulate said plurality of optical signal from said first port to said second port;
• a second segment of optically amplifying fiber having a first end portion coupled to said second port of said optical circulator and a second end portion;
• a first plurality of in-fiber Bragg gratings, each configured to reflect a respective one of a first group of said plurality of optical signals;
• a third segment of optically amplifying fiber coupled to said first plurality of in-fiber Bragg gratings;
• and
• a second plurality of in-fiber Bragg gratings, each configured to reflect a respective one of a second group of said plurality of optical signals, said second plurality of in-fiber Bragg gratings being coupled to said third segment of optically amplifying fiber.

A method of amplifying a plurality of optical signals, wherein each of said plurality of optical signals being at a respective one of a plurality of wavelengths, said method comprising the steps of:

• non-uniformly amplifying said plurality of optical signals with a first optically amplifying fiber;
• supplying said amplified plurality of optical signals to a second optically amplifying fiber;
• non-uniformly amplifying said plurality of optical signals with said second optically amplifying fiber;
• reflecting said amplified plurality of optical signals from said second optically amplifying fiber back to said second optically amplifying fiber;
• selectively attenuating said reflected optical signals with a power spectrum that substantially compensates a power spectrum associated with said plurality of optical signals after a single pass through said first segment of optically amplifying fiber and two passes through said second segment of optically amplifying fiber;
• and
• non-uniformly amplifying said reflected and attenuated plurality of optical signals with said second optically amplifying fiber such that said plurality of optical signals having substantially the same power level.