Patent ID: 7068879

Claim:
A gain flattening device for an optical fiber amplifier having first and second amplification fibers for amplifying input optical signals by induced emission of excited ions, comprising: a first end portion having first and second ends for receiving an amplified optical signal from the first amplification fiber via the first end; a second end portion having third and fourth ends for outputting a part of the amplified optical signal to the second amplification fiber via the fourth end; and an optical coupling portion between the first and second end portion having a first connector for connecting the first end to the third end, a second connector for connecting the second end to the fourth end, and at least one reflective grating, the optical coupling portion for coupling the amplified optical signal from the first connector to the second connector in a first coupling region that includes a common adjacent length of the first and second connectors such that the first and second connectors are closer to each other over said common adjacent length than in any other area, and outputting a second part of the amplified optical signal reflected from the reflective grating via the second end.