Nicklas Eiselt

Solutions for 80 km DWDM Systems

We review currently discussed solutions for 80 km DWDM transmission targeting inter data-center connections at 100G and 400G line rates. PDM-64QAM, PAM4 and DMT are investigated, while the focus lies on directly detected solutions.

Demonstration of the First Real-Time End-to-End 40-Gb/s PAM-4 for Next-Generation Access Applications Using 10-Gb/s Transmitter

We demonstrate the first known experiment of a real-time end-to-end 40-Gb/s pulse amplitude modulation (PAM)-4 system for next-generation access applications using 10-Gb/s class transmitters only. Based on the measurement of a real-time 40-Gb/s PAM system, low-cost upstream and downstream link power budgets are estimated. Up to 27 and 25 dB power budgets for 10- and 20-km standard single-mode fiber upstream links using erbium-doped fiber amplifiers (EDFA) preamplifiers are achieved. For downstream links using booster EDFAs and avalanche photodiode receivers, power budgets of 26.5 and 24.5 dB are feasible for 10- and 20-km SMFs, respectively. In addition, we show that colorless 40-Gb/s PAM-4 transmission over 20-km SMF in the C-band is achievable.

First real-time 400G PAM-4 demonstration for inter-data center transmission over 100 km of SSMF at 1550 nm

Real-time transmission of 400G (8×50G DWDM) PAM-4 signals for data center interconnects up to 100 km SSMF is successfully demonstrated. All channels stay well below the 802.3bj KR4 FEC limit, thus allowing error free transmission.

First demonstration of real-time end-to-end 40 Gb/s PAM-4 system using 10-G transmitter for next generation access applications

We demonstrate the first known experiment of a real-time end-to-end 40-Gb/s PAM-4 system for next generation access applications using 10G class transmitters only. Up to 25-dB upstream link budget for 20 km SMF is achieved.

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.

Investigation of PAM-4 for extending reach in data center interconnect applications

Optical four-level pulse amplitude modulation (PAM-4) is being widely studied for various short-reach optical interfaces, motivated by the need to keep cost structure low, and to increase link capacity despite various constraints in component bandwidth. When considering PAM-4 in applications with reach significantly greater than 10 km, such as in extended data center interconnects which require optical amplification, impairments such as chromatic dispersion, optical filtering, and ASE must be controlled. We investigate and report on requirements of PAM-4 for extended-reach, data center interconnect links.

Digital pre-emphasis based system design trade-offs for 64 Gbaud coherent data center interconnects

We report on the role of digital pre-emphasis in facilitating 64 Gbaud DP-64QAM coherent optical systems based on currently available commercial 32 Gbaud transceiver components. In particular, we vary the extent of digital pre-emphasis together with digital-to-analog converter bandwidth and resolution, and show the optical back-to-back performance and transmitter output power trade-offs. Our results suggest that with a minimum required DAC bandwidth and effective number of bits of 25 GHz and 6 bits, respectively (at 1 dB penalty w.r.t best performance), an optimized DPE strength bandwidth of 18 GHz allows for a TX output power of −16 dBm, with an associated maximum OSNR penalty of ∼3 dB, w.r.t. the theoretical bound for 64 Gbaud DP-64QAM.

Practical Solutions for 400Gbit/s Data Center Transmission

We review three solutions for low-cost data center interconnects with a target reach of up to 80 km. Directly detected DMT, PAM-4 and multi-band CAP are promising modulation schemes, enabling 400 Gbit/s by combining eight channels of 56 Gbit/s.