Kazuyou Mizuno, Yasuhiro Nishi, You Mimura, Yoshitaka Iida, Hiroshi Matsuura, Daeyoul Yoon, Osamu Aso, Toshiro Yamamoto, Tomoaki Toratani, Yoshimi Ono, An Yo
As a result of rapid increase of amount of traffic data and transmission rates in telecommunication, the wavelength division multiplexing (WDM) system has been studied. An erbium-doped fiber amplifier (EDFA) which is a key component in this system needs flat gain spectra. One of the gain-flattening technologies is usage of an optical gain-flattening filter that has a reverse loss profile against the gain profile of EDFA. We have developed a design method using nonlinear fitting upon an etalon-type gain-flattening filter, so we can design a gain-flattening filter that has less error against any gain spectra than conventional methods. Thereupon we have manufactured modules designed by the method, and we can get excellent performance upon gain-flattening filters. In this paper, we demonstrate the design method and report performances of several types of gain-flattening filters for optical amplifiers that have different gain spectra.