O-band EML and 4-bits DAC enabled 112 GBaud PAM8 transmission over a 10 km SSMF without optical amplifiers.

The increasing traffic of intra-data center networks creates an urgent demand for low-cost and high-speed intensity modulation/direct detection (IM/DD) transmission. In this Letter, we propose a joint scheme combining nonlinear lookup table (NL-LUT) pre-distortion, digital pre-emphasis (DPE), and a digital resolution enhancer (DRE) to achieve high-speed and low-cost IM/DD optical links using a low-resolution digital-to-analog converter (DAC). The NL-LUT and DPE are responsible for the system nonlinear impairments and channel attenuation at high frequency, respectively, while DRE handles the quantization noise (QN) caused by high peak-to-average ratios (PAPRs) and low-resolution DAC.

Countermeasure to the side effect of polarization demultiplexing in Stokes space.

We propose a new method to solve the side effect of polarization demultiplexing in Stokes space. The scheme calculates the phase difference between the two polarization states according to the boundary of the projection of the signal on the S2-S3 plane in Stokes space and completes the compensation by a phase retarder. According to the analysis results, this scheme can effectively solve the side effect caused by polarization demultiplexing in Stokes space.

Joint equalization of EEPN, RSOP, and CD with the sliding window assisted extended Kalman filter for a high baud rate Stokes vector direct detection system.

Equalization-enhanced phase noise (EEPN) has emerged as one of the major impairments that cannot be ignored for a high baud rate Stokes vector direct detection (SVDD) system. When EEPN interacts with the rotation of state-of-polarization (RSOP) and chromatic dispersion (CD), the joint impairment effects become even more complicated. To achieve the joint equalization of EEPN, RSOP, and CD impairments of a high baud rate SVDD system, this paper first derives a joint impairment model of these three kinds of impairments, and then proposes a joint equalization scheme of EEPN, RSOP, and CD with a sliding window assisted extended Kalman filter (SWA-EKF).

Blind frequency offset estimation using the optimal decision threshold-assisted QPSK-partition method for probabilistically shaped MQAM systems.

Moderate or strong shaping conditions reduce the occurrence probability of the outermost ring constellation points of probabilistically shaped (PS)-M quadrature amplitude modulation (QAM) signals, which easily causes the peaks in the 4 power periodogram of received signals be submerged, accordingly the classical frequency offset estimation (FOE) scheme using 4 power fast Fourier transform (FFT) cannot be applied in PS-MQAM system. To solve this issue, we have proposed an optimal decision threshold assisted quadrature phase shift keying (QPSK)-partition blind FOE scheme. Firstly, the proposed scheme utilizes an optimal decision threshold assisted method for the symbol decision of received symbols, then chooses the symbols on multiple specific QPSK-shape rings.

Blind modulation format identification based on improved PSO clustering in a 2D Stokes plane.

Blind modulation format identification (MFI) is indispensable for correct signal demodulation and optical performance monitoring in future elastic optical networks (EON). Existing MFI schemes based on a clustering algorithm in Stokes space have gained good performance, while only limited types of modulation formats could be correctly identified, and the complexities are relatively high. In this work, we have proposed an MFI scheme with a low computational complexity, which combines an improved particle swarm optimization (I-PSO) clustering algorithm with a 2D Stokes plane.