You Mimura, Kazuyou Mizuno, Syu Namiki, Yoshio Tashiro, Yoshihiro Emori, Mariko Miyazawa, Toshiaki Tsuda, Kazuhiko Nishiyama, Yasuo Uemura, Toshihiko Ohta
With the steadily increasing demand for fiber-optic communications, hope is more and more being placed in the method known as wavelength division multiplexing, or WDM. The key device supporting WDM technology is the erbium-doped fiber amplifier (EDFA), and such amplifiers need to have a flat gain spectrum. A problem arises, however, in the fact that the loss profile and gain spectra of erbium-doped fiber are temperature dependent, resulting in temperature-dependent changes in the EDFA gain spectra. The authors took note of long-period fiber gratings having a large wavelength shift temperature dependence, and have combined the grating with a conventional gain-flattening filter (GFF) in a compound GFF that provides stabilization of EDFA gain spectra over a wide range of temperatures.