Nearly-penalty-free, fully TDM 100-Gbit/s optical transmission by using two tunable mode-locked Er-doped fiber lasers

Abstract

In 100-Gbids optical transmission, the influence of fiber dispersion becomes critical and causes bit-to-bit cross talk. In our previous report of polarization-multiplexed 100-Gbit/s trans-mission,1 the 20-ps time slot between the neighboring same-polarization pulses produced the tolerance to the cross talk between pulses. In fully time-division-multiplexed (TDM) 100-Gbit/s optical transmission, however, the problem of dispersion increases because the time slot is halved. Moreover, another problem is that a restriction is placed on the signal wave-length by the operation condition of the all-optical nonlinear loop mirror (NOLM) demultiplexer at the receiver. The NOLM demultiplexer uses a fixed-wavelength gain-switched laser diode as the control light source, and the wavelength difference be-tween optical signal and the optical control pulse determines the switching characteristics.1 The use of two tunable mode-locked Er-doped fiber (EDF) lasers,4 one for the signal and the other for the control pulses, is the solution to this problem. This report describes the realization of fully TDM 100-Gbids, 50-km optical transmission with a power penalty of less than 0.5 dB by optimizing t e wavelengths of both optical signal and control pulses. Also discussed is the wavelength dependency of the power-penalty characteristics.