Blind and low-complexity modulation format identification based on signal envelope flatness for autonomous digital coherent receivers

Abstract

Modulation format identification (MFI) is a critical technology for autonomous digital coherent receivers in next-generation elastic optical networks. A novel and simple MFI scheme, to the best of our knowledge, based on signal envelope flatness is proposed without requiring any training or other prior information. After amplitude normalization and partition, the incoming polarization division multiplexed (PDM) signals can be classified into quadrature phase shift keying (QPSK), 8 quadrature amplitude modulation (QAM), 16QAM, and 64QAM signals according to envelope flatnesses R 1 , R 2 , and R 3 of signals in different amplitude ranges. The feasibility of the proposed MFI scheme is first verified via numerical simulations with 28 GBaud PDM-QPSK/-8QAM/-16QAM/-64QAM signals. Only by using 4000 symbols can the proposed MFI scheme achieve a 100% correct identification rate for the four modulation formats over a wide optical signal-to-noise ratio (OSNR) range. Proof-of-concept experiments among 28 GBaud PDM-QPSK/-8QAM/-16QAM systems under back-to-back and long-haul fiber transmission links are implemented to further demonstrate the effectiveness of the proposed MFI scheme. The experimental results show that the proposed MFI scheme can obtain a 100% correct identification rate when the OSNR value of each modulation format is higher than the threshold corresponding to 7% FEC and is resilient towards fiber nonlinearities. More importantly, the proposed MFI scheme can significantly reduce computational complexity.

Modulation Format Identification Based on Multi-Dimensional Amplitude Features for Elastic Optical Networks

“…In elastic optical networks (EONs), according to different channel characteristics and various data services, the involved transceivers can dynamically adjust the modulation formats utilized for encoding the optical signals, which raises new demands on digital coherent receivers. Therefore, the MFI module embedded in a digital coherent receiver, which can identify the modulation format of incoming signals on-the-fly, is of great importance [4]. MFI provides a foundation for optimizing the performance of subsequent modulation format-dependent algorithms in the digital signal processing (DSP) chain; as such, MFI is a critical technology to ensure the flexibility and reliability of the EON.…”

Cascaded modulation format identification and optical signal-to-noise ratio estimation method for optical communication system

“…In long-haul transmission, optical signals suffer from various impairments, including chromatic dispersion (CD), nonlinear effect, frequency offset, self-phase modulation effect, polarization-dependent loss effect, polarizationmode dispersion (PMD), and laser phase noise. 3 At the receiver, the digital signal processing (DSP) module can compensate for and mitigate these impairments. Several algorithms have been adopted for the DSP module, which can be divided into two categories: 4 the first is MF-independent algorithms; for example, the CD compensation algorithm, timing recovery, resampling and IQ orthogonalization, and constant modulus equalization algorithms (CMA).…”

“…Flexible transmitters are deployed in elastic optical networks, which can dynamically adjust the modulation format (MF) to improve transmission and scheduling efficiency. In long-haul transmission, optical signals suffer from various impairments, including chromatic dispersion (CD), nonlinear effect, frequency offset, self-phase modulation effect, polarization-dependent loss effect, polarization-mode dispersion (PMD), and laser phase noise 3 . At the receiver, the digital signal processing (DSP) module can compensate for and mitigate these impairments.…”