Tunable Gain-Clamped Linear Cavity Bismuth-Doped Fiber Amplifier Operating in the O-Band

The gain-clamping performance of amplifiers deserves to be scrutinized for dealing with transient bursts in optical transmission systems. Currently, there are fewer investigations on the gain control of bismuth-doped fiber amplifiers (BDFAs). In this paper, we first propose a linear cavity BDFA with tunable gain clamping operating in the O-band. Two fiber Bragg gratings are utilized to form a linear cavity inside the amplifier to generate a control laser. Specifically, a variable optical attenuator (VOA) is connected to the linear cavity by two circulators, and no losses other than gain clamping are introduced. Adjusting the loss of the VOA enables flexible control of the amplifier gain clamping. The relationships of pumping mode, wavelength, signal power, and VOA loss with the gain, gain float, and noise figure of the BDFA are discussed. This work provides a valuable reference for the study of O-band BDFA gain clamping and facilitates the application of BDFA to optical communication links.