Cristian Prodaniuc

Bio: Cristian Prodaniuc is an academic researcher from Huawei. The author has contributed to research in topics: Pulse-amplitude modulation & Bit error rate. The author has an hindex of 13, co-authored 36 publications receiving 446 citations. Previous affiliations of Cristian Prodaniuc include Polytechnic University of Valencia.

Volterra and Wiener Equalizers for Short-Reach 100G PAM-4 Applications

Abstract: Unlike ultralong coherent optical systems that seriously suffer from fiber nonlinearities, short-reach noncoherent systems such as data center interconnections, which utilize small, cheap, and low-bandwidth components, are sensitive to nonlinearities that are mainly produced by devices responsible for electrical signal amplification, modulation, and demodulation. One of the most promising schemes for these applications is the four-level pulse amplitude modulation format combined with intensity modulation and direct detection; however, it can be significantly degraded by linear and nonlinear intersymbol interference. Linear and nonlinear signal degradation can efficiently be handled by different types of equalizers. In many cases, the straightforward linear equalizer cannot lower the error rate at the acceptable level. Therefore, much stronger equalizers based on nonlinear models such as the Volterra series are proposed. Volterra filter that can also be orthogonalized by the Wiener model is well described in the existing literature, and, in this paper, we investigate the most critical points related to high-speed Volterra filter design and implementation. Several experiments are carried out in order to indicate filter requirements/complexity, acquisition, and stability. We also provide a simple guidance for filter complexity reduction and useful hints for channel acquisition.

Directly PAM-4 Modulated 1530-nm VCSEL Enabling 56 Gb/s/ $\lambda $ Data-Center Interconnects

Abstract: We demonstrate a 56 Gb/s four-level pulse-amplitude modulation (PAM-4) transmission using direct detection and a long-wavelength 18-GHz bandwidth vertical-cavity surface-emitting laser as directly modulated light source for short-reach inter- and intra-connects in datacenters and short-reach networks. Error-free transmission over 2 km at 7% hard-decision forward-error correction threshold is achieved by applying powerful equalization schemes at the receiver side. Three equalization schemes, i.e., a maximum likelihood estimation (MLSE), a feed-forward equalizer (FFE), and a combination of the FFE and the MLSE are thoroughly investigated, and the performance comparison between them is carried out.

Transmission of single lane 128 Gbit/s PAM-4 signals over an 80 km SSMF link, enabled by DDMZM aided dispersion pre-compensation.

Abstract: Direct detection systems with advanced modulation schemes are of great importance in metropolitan networks, because of their low cost and low power requirements. In particular, PAM-4 has attracted considerable attention, but has significant transmission distance limitations in the C-band. To extend its reach, we used a dual drive Mach-Zehnder modulator to generate a chromatic dispersion (CD) pre-compensated signal with an extra (j-1) multiplication to align the optical carrier and the modulated optical signal; by doing so, we achieved successful 128 Gbit/s transmission over an 80 km SSMF link, the longest reported reach of single lane 100 Gbit/s PAM-4 signals over DCF-free links. Synchronized bandwidth pre-compensation was also used, to reduce the influence of bandwidth-limitations.

Single-lane 180 Gbit/s PAM-4 signal transmission over 2 km SSMF for short-reach applications.

Abstract: We experimentally demonstrate the generation and transmission of a single-lane 180 Gbit/s (90 GBaud) four-level pulse-amplitude modulation (PAM-4) signal in an intensity-modulation direct-detection system with a 7.5 GHz 3 dB bandwidth. The generated signal is transmitted over a 2 km standard single-mode fiber with, to the best of our knowledge, the highest reported net data rate in the C-band: 150 Gbit/s. A net data rate of 168 Gbit/s is also reachable with 1 km reach. The PAM-4 and duobinary (DB) PAM-4 modulation schemes are compared; the obtained results show that DB-PAM-4 significantly outperforms PAM-4 in the considered strong bandwidth-constrained system. Both a feed-forward equalizer and a maximum-likelihood sequence estimator are investigated for data recovery.

210/225 Gbit/s PAM-6 Transmission with BER Below KP4-FEC/EFEC and at Least 14 dB Link Budget

Abstract: We experimentally demonstrate Tx DSP-free 210/225 Gbit/s duobinary PAM-6 B2B transmission at 1550 nm using commercially available devices. Excellent performance is achieved by using Volterra filter, noise cancellation algorithm, and MLSE.

Digital Signal Processing for Short-Reach Optical Communications: A Review of Current Technologies and Future Trends

Abstract: Driven primarily by cloud service and data-center applications, short-reach optical communication has become a key market segment and growing research area in recent years. Short-reach systems are characterized by direct detection-based receiver configurations and other low-cost and small form factor components that induce transmission impairments unforeseen in their coherent counterparts. Innovative signaling and digital signal processing (DSP) play a pivotal role in enabling these components to realize their ultimate potentials and meet data rate requirements in cost-effective manners. This paper presents an overview of recent DSP developments for short-reach communications systems and discusses future trends.

Artificial Intelligence (AI) Methods in Optical Networks: A Comprehensive Survey

Abstract: Artificial intelligence (AI) is an extensive scientific discipline which enables computer systems to solve problems by emulating complex biological processes such as learning, reasoning and self-correction. This paper presents a comprehensive review of the application of AI techniques for improving performance of optical communication systems and networks. The use of AI-based techniques is first studied in applications related to optical transmission, ranging from the characterization and operation of network components to performance monitoring, mitigation of nonlinearities, and quality of transmission estimation. Then, applications related to optical network control and management are also reviewed, including topics like optical network planning and operation in both transport and access networks. Finally, the paper also presents a summary of opportunities and challenges in optical networking where AI is expected to play a key role in the near future.

Performance limits in optical communications due to fiber nonlinearity

Abstract: In this paper, we review the historical evolution of predictions of the performance of optical communication systems. We will describe how such predictions were made from the outset of research in laser based optical communications and how they have evolved to their present form, accurately predicting the performance of coherently detected communication systems.

Volterra and Wiener Equalizers for Short-Reach 100G PAM-4 Applications

Abstract: Unlike ultralong coherent optical systems that seriously suffer from fiber nonlinearities, short-reach noncoherent systems such as data center interconnections, which utilize small, cheap, and low-bandwidth components, are sensitive to nonlinearities that are mainly produced by devices responsible for electrical signal amplification, modulation, and demodulation. One of the most promising schemes for these applications is the four-level pulse amplitude modulation format combined with intensity modulation and direct detection; however, it can be significantly degraded by linear and nonlinear intersymbol interference. Linear and nonlinear signal degradation can efficiently be handled by different types of equalizers. In many cases, the straightforward linear equalizer cannot lower the error rate at the acceptable level. Therefore, much stronger equalizers based on nonlinear models such as the Volterra series are proposed. Volterra filter that can also be orthogonalized by the Wiener model is well described in the existing literature, and, in this paper, we investigate the most critical points related to high-speed Volterra filter design and implementation. Several experiments are carried out in order to indicate filter requirements/complexity, acquisition, and stability. We also provide a simple guidance for filter complexity reduction and useful hints for channel acquisition.