Phase Noise Effects on High Spectral Efficiency Coherent Optical OFDM Transmission

Abstract

Abstract-There are three major advantages for coherent optical orthogonal frequency-division multiplexing (CO-OFDM) transmission using digital signal processing. First, coherent detection is realized by digital phase estimation without the need for optical phase-locked loop. Second, OFDM modulation and demodulation are realized by the well-established computation-efficient fast Fourier transform (FFT) and inverse FFT. Third, adaptive data rates can be supported as different quadrature amplitude modulation (QAM) constellations are software-defined, without any hardware change in transmitter and receiver. However, it is well-known that coherent detection, OFDM, and QAM are all susceptible to phase noise. In this paper, theoretical, numerical, and experimental investigations are carried out for phase noise effects on high spectral efficiency CO-OFDM transmission. A transmission model in the presence of phase noise is presented. By using simulation, the bit error rate floors from finite laser linewidth are presented for CO-OFDM systems with high-order QAM constellations. In the experiments, the phase noise effects from both laser linewidth and nonlinear fiber transmission are investigated. The fiber nonlinearity mitigation based on receiver digital signal processing is also discussed.

Performance analysis of 2×2 STBC in DFT-spread PDM-CO-OFDM comunication systems

“…Then, the compensated signal is fed into the IDFT for inverse conversion to M-ary QAM signal. For RPN compensation, the common phase error (CPE) [7] method is used in the final process. Finally, the M-ary QAM de-mapping is followed to de-mapping the M-ary QAM into binary bit streaming as shown in Fig.…”

“…CO-OFDM, also PDM-CO-OFDM, is very sensitive to random phase noise (RPN) [5,7] and nonlinear impairment [8]. In general, the nonlinear impact occurs from peak to average power ratio (PAPR) behavior [8] which is one drawback of OFDM.…”

Investigation of Tolerable Laser Linewidth for Different Modulation Formats in CO-OFDM Systems

“…Latest technological advancements in microelectronics such as high speed digital signal processors, analog to digital converters and digital to analog converters have made possible the use of digital signal processing in communication systems. This has further led to the development of software defined optical transmission [1]. A number of channel impairments such as chromatic dispersion, phase noise etc.…”

“…Therefore, the hardware and cost involved are more. Digital phase estimation, computationally efficient FFT and IFFT, adaptive data rates due to software defined QAM constellations are the major advantages offered by COOFDM systems [1]. The software defined capability in COOFDM system presents numerous advantages in terms of different modulation formats for different subcarriers, mitigation of various imperfections such as laser drift, channel dispersion, optimization of various OFDM system parameters by monitoring of transmission channel characteristics.…”

160 Gbit/s photonics wireless transmission in the 300-500 GHz band

“…The limitation is mainly associated with the typical opto-electronic approach of generating THz carriers by using free-running lasers for heterodyne photo-mixing in the UTC-PD, which intrinsically leads to a beat-note with high phase noise. However, it has been commonly known that spectrally efficient modulation formats are all susceptible to phase noise, 16,17 even if digital algorithm-based carrier phase estimation can to some extent mitigate the influence of phase noise. Therefore, generation of THz carriers with high purity and low phase noise will be expected to increase the capacity of THz wireless systems, from communication system viewpoint.…”