Ali Al-Bermani

The robustness of subcarrier-index modulation in 16-QAM CO-OFDM system with 1024-point FFT.

We present in numerical simulations the robustness of subcarrier index modulation (SIM) OFDM to combat laser phase noise. The ability of using DFB lasers with SIM-OFDM in 16-QAM CO-OFDM system with 1024-point FFT has been verified. Although SIM-OFDM has lower spectral efficiency compared to the conventional CO-OFDM system, it is a good candidate for 16-QAM CO-OFDM system with 1024-point FFT which uses a DFB laser of 1 MHz linewidth. In addition, we show the tolerance of SIM-OFDM for mitigation of fiber nonlinearities in long-haul CO-OFDM system. The simulation results show a significant penalty reduction, essentially that due to SPM.

Real-Time Phase-Noise-Tolerant 2.5-Gb/s Synchronous 16-QAM Transmission

The 2.5-Gb/s coherent 16-quadrature amplitude modulation data is optically transmitted over 75 km and synchronously received by self-homodyning in a real-time in-phase and quadrature receiver, with bit-error ratio below forward-error correction threshold. To this purpose, a phase-noise-tolerant hardware-efficient feedforward carrier recovery was implemented.

Fiber nonlinearity tolerance of SIM-OFDM in CO-OFDM transmission

We present the tolerance of subcarrier-index modulation OFDM which is a new method for mitigation of fiber nonlinearities in CO-OFDM transmission. Simulation results show a significant penalty reduction, essentially that due to SPM.

Hardware-Efficient Phase Estimation for Digital Coherent Transmission With Star Constellation QAM

In order to build optical transmission systems for 100 Gb/s and above on a single wavelength division multiplexing channel, transition from quadrature phase-shift keying (QPSK) to higher quadrature amplitude modulation (QAM) formats seems to be inevitable. Instead of the usual square constellation QAM, we focus on regular star constellation QAM formats and present a hardware-efficient phase-estimation algorithm that is suitable for all regular star constellations, together with preliminary simulation results.

A novel method for IQ imbalance compensation in CO-OFDM systems

We propose a novel IQ imbalance compensation for coherent optical OFDM. One test tone is used. The results show good imbalance tolerance improvements when large laser phase noise and a dispersive channel are considered.

Phase noise robustness of SIM-OFDM in CO-OFDM transmission

We present the robustness of subcarrier-index modulation OFDM to combat laser phase noise. Simulation results show the ability of using DFB lasers with SIM-OFDM in 16-QAM CO-OFDM system with 1024-point FFT.

RF-pilot-based nonlinearity compensation in frequency domain for CO-OFDM transmission

The effects of fiber nonlinearity in Coherent Optical Orthogonal Frequency-Division Multiplexing (CO-OFDM) transmission, such as self-phase modulation (SPM) and cross-phase modulation (XPM), are a major concern. In this paper, we investigate the use of RF-Pilot (RFP) based nonlinearity compensation scheme in frequency domain to compensate for fiber nonlinearity in a coherent OFDM optical system. It shows that the RFP-based compensation scheme has superiority over a conventional pilot-based compensation scheme at FEC threshold.

Nonlinear effect of IQ modulator in a realtime synchronous 16-QAM transmission system

Different operation points of a 16-QAM modulator are tested in realtime. An optimal condition is found which minimizes BER. The FEC threshold was reached for a receiver input power below -30 dBm.

Realtime implementation of square 16-QAM transmission system

Combination of quadrature amplitude modulation with coherent detection is attractive for optical transmission systems, since it permits an increase of data rate without increasing the symbol rate or the required bandwidth. 16-point Quadrature Amplitude Modulation (16-QAM) is most interesting in this context. In-phase (I) and quadrature (Q) signals transmit 2 bit each. Together with polarization division multiplex this amounts to 8 bit/symbol. 2.5 Gbit/s synchronous coherent 16-QAM data is transmitted and received in a realtime intradyne setup with BER below FEC (7% overhead) threshold. A phase noise tolerant feedforward carrier recovery concept with hardware-efficient implementation was tested. Transmission was error-free in a back-to-back electrical test for various PRBS lengths. The carrier recovery does not contain any feedback loop and is therefore highly tolerant against laser phase noise.

Implementation Of Coherent 16-QAM Digital Receiver With Feedforward Carrier Recovery

1.25 Gbit/s synchronous coherent 16-QAM data is transmitted and received in a real-time intradyne setup with BER below FEC threshold. A phase noise tolerant feedforward carrier recovery concept with hardware-efficient implementation was tested.