Code reservation enabled PAPR reduction of digital CDM based channel aggregation for mobile fronthaul.

A code reservation technique is proposed to reduce the peak-to-average power ratio (PAPR) of digital code-division multiplexing (CDM) based channel aggregation for mobile fronthaul. We numerically investigate the relationship between the PAPR and the number of aggregated channels during the CDM based channel aggregation, and experimentally verify the transmission performance with the code reservation technique. The PAPR of aggregated signal, which is composed of 48x20MHz Long Term Evolution (LTE) signal mapped with 64 quadrature amplitude modulation (QAM), is reduced with the help of code reservation technique.

Pump RIN-induced impairments in unrepeatered transmission systems using distributed Raman amplifier.

High spectral efficiency modulation format based unrepeatered transmission systems using distributed Raman amplifier (DRA) have attracted much attention recently. To enhance the reach and optimize system performance, careful design of DRA is required based on the analysis of various types of impairments and their balance. In this paper, we study various pump RIN induced distortions on high spectral efficiency modulation formats.

Relative phase noise induced impairment in CO-OFDM optical communication system with distributed fiber Raman amplifier.

In this Letter, we demonstrate that the interplay between Raman pump relative intensity noise and cross-phase modulation leads to a relative phase noise (RPN) that brings non-negligible performance degradation to coherent optical orthogonal frequency-division multiplexing (CO-OFDM) transmission systems with co-pumped Raman amplification. By theoretical analysis and numerical simulation, we proved that RPN brings more system impairment in terms of Q-factor penalty than the single carrier system, and relatively larger walk-off between pump and signal helps to suppress the RPN induced impairment. A higher-order modulated signal is less tolerant to RPN than a lower-order signal.

Relative phase noise estimation and mitigation in Raman amplified coherent optical communication system.

The interplay between the stochastic intensity fluctuation of Raman pump laser and cross-phase modulation (XPM) effect in transmission optical fiber leads to additional phase noise, namely, relative phase noise (RPN) of signal in multi-level modulated coherent optical communication system. Both theoretical analysis and quantitative simulation have been performed to investigate the characteristics and impact of RPN. Being low-pass in nature, RPN is different from XPM induced phase noise in PSK/OOK hybrid system, and has not been considered yet.

Relative phase noise induced impairment in M-ary phase-shift-keying coherent optical communication system using distributed fiber Raman amplifier.

We show for the first time, to the best of our knowledge, that, in a coherent communication system that employs a phase-shift-keying signal and Raman amplification, besides the pump relative intensity noise (RIN) transfer to the amplitude, the signal's phase will also be affected by pump RIN through the pump-signal cross-phase modulation. Although the average pump power induced linear phase change can be compensated for by the phase-correction algorithm, a relative phase noise (RPN) parameter has been found to characterize pump RIN induced stochastic phase noise. This extra phase noise brings non-negligible system impairments in terms of the Q-factor penalty.