25 Gbit/s differential phase-shift-keying signal generation using directly modulated quantum-dot semiconductor optical amplifiers

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 106, 213501 (2015) and may be found at https://doi.org/10.1063/1.4921785.Error-free generation of 25-Gbit/s differential phase-shift keying (DPSK) signals via direct modulation of InAs quantum-dot (QD) based semiconductor optical amplifiers (SOAs) is experimentally demonstrated with an input power level of −5 dBm. The QD SOAs emit in the 1.3-μm wavelength range and provide a small-signal fiber-to-fiber gain of 8 dB. Furthermore, error-free DPSK modulation is achieved for constant optical input power levels from 3 dBm down to only −11 dBm for a bit rate of 20 Gbit/s. Direct phase modulation of QD SOAs via current changes is thus demonstrated to be much faster than direct gain modulation

40 GBd D(Q)PSK and OOK amplification using o-band quantum-dot semiconductor optical amplifiers

Error-free (bit-error ratio < 10−9) generation and amplification of phase-coded signals are presented with a symbol rate up to 40 GBd using quantum-dot (QD) based semiconductor optical amplifiers (SOA) emitting at a wavelength of 1.3 µm. Phase-coded signal generation is demonstrated via direct modulation of a QD SOA exhibiting a linear fiber-to-fiber gain of 8 dB. In comparison to gain modulation, the phase modulation of the QD SOAs via the current is found to be much faster. Various symbol rates from 10 to 25 GBd and input power levels from −11 dBm to 3 dBm are investigated. The amplification of a 40 GBd differential (quadrature) phase-shift keying (D(Q)PSK) signal is investigated using QD SOAs exhibiting a linear fiber-to-fiber gain of 26 dB. The input-power dynamic range is determined and discussed, based on bit-error ratio and error-vector magnitude measurements using differential detection and coherent detection receivers. Finally, investigations of the influence of a 40 GBd OOK neighboring channel (5 nm grid) on a 40 GBd DQPSK channel in dependence of the input power levels of both signals are presented