Passive spectral gain control of a four-channel WDM link employing twin-core erbium-doped fiber amplifiers

WDM is proving to be the preferred choice for expanding the capacity of optical communication systems. Using this technique bit rates exceeding 1 Tbits/s have been demonstrated. However, due to the combination of the gain spectrum and the predominantly homogeneous properties of erbium ions in silica glass the different wavelength channels will diverge. A new technique to overcome this problem is presented employing twin-core erbium-doped fiber amplifiers (TC-EDFAs) that induce inhomogeneous broadening in the gain medium at room temperature. A four-channel WDM link using cascaded TC-EDFAs is presented. It is demonstrated experimentally that the TC-EDFA can passively compensate for the wavelength dependence of the erbium gain spectrum thus allowing nondivergent and self-regulating propagation of individual channel powers