Real-Time Evaluation of 26-GBaud PAM-4 Intensity Modulation and Direct Detection Systems for Data-Center Interconnects

\u3cp\u3eReal-time transmission with 26-GBaud PAM-4 as a promising modulation format for data-center interconnects with operation in C-band is evaluated. For an OSNR penalty below 2 dB a dispersion tolerance of up to 10 km of SSMF is achieved.\u3c/p\u3

56 Gb/s multi-band CAP for data center interconnects up to an 80 km SMF

We present the first (to the best of our knowledge) experimental demonstration of a 56 Gb/s multi-band carrierless amplitude and phase modulation (CAP) signal transmission over an 80-km single-mode fiber link with zero overhead pre-FEC signal recovery and enhanced timing jitter tolerance for optical data center interconnects

200 Gbps/lane IM/DD Technologies for Short Reach Optical Interconnects

Client-side optics are facing an ever-increasing upgrading pace, driven by upcoming 5G related services and datacenter applications. The demand for a single lane data rate is soon approaching 200 Gbps. To meet such high-speed requirement, all segments of traditional intensity modulation direct detection (IM/DD) technologies are being challenged. The characteristics of electrical and optoelectronic components and the performance of modulation, coding, and digital signal processing (DSP) techniques are being stretched to their limits. In this context, we witnessed technological breakthroughs in several aspects, including development of broadband devices, novel modulation formats and coding, and high-performance DSP algorithms for the past few years. A great momentum has been accumulated to overcome the aforementioned challenges. In this article, we focus on IM/DD transmissions, and provide an overview of recent research and development efforts on key enabling technologies for 200 Gbps per lane and beyond. Our recent demonstrations of 200 Gbps short-reach transmissions with 4-level pulse amplitude modulation (PAM) and discrete multitone signals are also presented as examples to show the system requirements in terms of device characteristics and DSP performance. Apart from digital coherent technologies and advanced direct detection systems, such as Stokes–vector and Kramers–Kronig schemes, we expect high-speed IM/DD systems will remain advantageous in terms of system cost, power consumption, and footprint for short reach applications in the short- to mid- term perspective

Evaluation of Real-Time 8 x 56.25 Gb/s (400G) PAM-4 for Inter-Data Center Application Over 80 km of SSMF at 1550 nm

Leveraging client optics based on intensity modulation and direct detection for point-to-point inter-data center interconnect applications is a cost and power efficient solution, but challenging in terms of optical signal-to-noise ratio requirements and chromatic dispersion tolerance. In this paper, real-time 8 x 28.125 GBd dense wavelength division multiplexing four-level pulse amplitude modulation (PAM-4) transmission over up to 80 km standard single mode fiber in the C-Band is demonstrated. Using a combination of optical dispersion compensation and electronic equalization, results below a bit error rate of 1e-6 are achieved and indicate sufficient margin to transmit over even longer distances, if an forward error correction (FEC) threshold of 3.8e-3 is assumed. Moreover, single channel 28.125 GBd PAM4 is evaluated against optical effects such as optical bandwidth limitations, chromatic dispersion tolerance, and optical amplified spontaneous emission noise