Demonstration and Performance Analysis of 4 Tb/s DWDM Metro-DCI System with 100G PAM4 QSFP28 Modules

Filer, Mark; Searcy, Steven; Fu, Yang; Nagarajan, Radhakrishnan; Tibuleac, Sorin

doi:10.1364/ofc.2017.w4d.4

Cited by 33 publications

(13 citation statements)

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“…Sci. 2019, 9, 2342 5 of 22 CD in terms of the optical signal-to-noise ratio (OSNR) for PAM4 is shown in Figure 3, where the OSNR penalty is about 1 dB for dispersion within ±100 ps/nm [62]. Meanwhile, the eye diagrams for 56 Gbps PAM4 signal after 0 km and 20 km transmission are shown in Figure 3b,c, respectively.…”

Section: Linear Impairments: Limited Bandwidth and Chromatic Dispersionmentioning

confidence: 99%

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Recent Advances in Equalization Technologies for Short-Reach Optical Links Based on PAM4 Modulation: A Review

Zhou

Liu

et al. 2019

Applied Sciences

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In recent years, short-reach optical links have attracted much more attention and have come to constitute a key market segment due to the rapid development of data-center applications and cloud services. Four-level pulse amplitude modulation (PAM4) is a promising modulation format to provide both a high data rate and relatively low cost for short-reach optical links. However, the direct detector and low-cost components also pose immense challenges, which are unforeseen in coherent transmission. To compensate for the impairments and to truly meet data rate requirements in a cost-effective manner, various digital signal processing (DSP) technologies have been proposed and investigated for short-reach PAM4 optical links. In this paper, an overview of the latest progress on DSP equalization technologies is provided for short-reach optical links based on PAM4 modulation. We not only introduce the configuration and challenges of the transmission system, but also cover the principles and performance of different equalizers and some improved methods. Moreover, machine learning algorithms are discussed as well to mitigate the nonlinear distortion for next-generation short-reach PAM4 links. Finally, a summary of various equalization technologies is illustrated and our perspective for the future trend is given. Appl. Sci. 2019, 9, 2342 2 of 22 multi-tone (DMT), and quadrature amplitude modulation (QAM) based on Kramers-Kronig (KK) receiver [18]. Considering the power consumption and implementation complexity, the most attractive format in short-reach optical links is PAM4, which is believed as a highly promising candidate for the next-generation passive optical network (NG-PON) and has been ratified by IEEE 802.3 bs for 400 Gbps Ethernet transmission [19][20][21][22][23][24][25].However, the low-pass filtering effects induced by the limited bandwidth of transmitter and receiver can cause severely inter-symbol interference (ISI). Low-cost devices such as lasers, modulators, photodiodes (PD) and trans-impedance amplifiers (TIA) also produce nonlinear distortions like level-dependent skew and level-dependent noise. Furthermore, the interaction between chromatic dispersion (CD) and direct detection will lead to a power-fading effect, where the detected signal may contain frequency notches after several kilometers transmission at a high symbol rate. Therefore, various equalization technologies based on digital signal processing (DSP) have been investigated for short-reach links over the years . Conventional equalizers, such as the feed-forward equalizer (FFE) or decision feedback equalizer (DFE), are employed to compensate for the linear impairments induced by limited bandwidth and CD [26][27][28], while the equalizer based on the Volterra series is utilized to mitigate nonlinear distortion [29][30][31][32]. Some new equalization techniques, such as direct detection-faster than Nyquist (DD-FTN) algorithm [33][34][35], intensity directed FFE/DFE (ID-FFE/ID-DFE) algorithm [36,37] and joint clock recovery and FFE (CR-FFE) algorithm...

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Section: Linear Impairments: Limited Bandwidth and Chromatic Dispersionmentioning

confidence: 99%

“…(a) Four-level pulse amplitude modulation (PAM4) signaling tolerance on dispersion in terms of optical signal-to-noise ratio (OSNR) penalty (reprinted from[62] with permission from authors). Eye diagrams for 56 Gbps PAM4 signal after (b) 0 km and (c) 20 km transmission.…”

mentioning

confidence: 99%

Recent Advances in Equalization Technologies for Short-Reach Optical Links Based on PAM4 Modulation: A Review

Zhou

Liu

et al. 2019

Applied Sciences

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“…Average symbol energy E s for the standard (uniformly spaced) 16-QAM can be calculated as: Resulting expression for BER PMC-SH 16-QAM by considering general expressions as in (6) and (7) for the case of thermal noise limited receiver is derived as:…”

Section: Pmc-sh-16 Qam Linksmentioning

confidence: 99%

High-Capacity Coherent DCIs Using Pol-Muxed Carrier and LO-Less Receiver

Kamran

Naaz

Goyal

et al. 2020

J. Lightwave Technol.

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A PAM 4 based direct detection system has been standardized for short-distance data center interconnects because of its simple architecture. Performance of the PAM 4 systems is limited for high dispersion values or demands complicated signal processing for further increase in data rates. A polarization multiplexed carrier based self-homodyne (PMC-SH) link with adaptive polarization control is a practical approach with an laser oscillator (LO)-less and carrier phase recovery (CPR)-free coherent receiver that can replace PAM 4 links for achieving high data rates. We analytically find that PMC-SH scheme results in a significantly better BER for a given transmission rate or can achieve doubling of the data rate for given bandwidth of electronics and laser power (when compared with PAM 4). Practical implementation of the proposed system with adaptive polarization control is also discussed. Presented theoretical frame work highlights the advantages of such self-homodyne systems over PAM 4 based systems in terms of SNR requirements and capacity.Index Terms-PAM 4 links, data center interconnects, selfhomodyne system, polarization multiplexed carrier.

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“…8. The high gain amplifier of the integrator is a modified version of the basic folded cascode amplifier discussed in [32][33][34] and the G m stage of the amplifier is designed with bipolar transistors as 4 10/0.28 suggested in [35]. To obtain a very low-frequency pole without affecting the high gain, the output resistance of the circuit has to be maximized.…”

Section: A Issues Of Delay Mismatch and Signal Swingmentioning

confidence: 99%

“…To support the increased traffic, DCI interface speeds are projected to cross 1.6 Tb/s in the near future [3]. To meet the current needs, 4-level pulse amplitude modulation (PAM-4) format based intensity modulation-direct detection (IMDD) transceivers with electronics operating at 56 GBd rate are being standardized [3,4]. However, IMDD techniques are anticipated to give way to the transmission of more spectrally efficient modulation formats through singlemode fiber (SMF) in short-reach links [5,6], mainly due to N. Nambath is with the School of Electrical Sciences, Indian Institute of Technology Goa, Ponda -403401, India (e-mail: npnandaku-mar@iitgoa.ac.in).…”

Section: Introductionmentioning

confidence: 99%

All-Analog Adaptive Equalizer for Coherent Data Center Interconnects

Nambath

Ashok

Manikandan

et al. 2020

J. Lightwave Technol.

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We present the detailed architecture of an allanalog adaptive equalizer for low-power analog signal processing based coherent optical dual-polarization quadrature phase-shift keying transceivers. The proof of concept equalizer uses the constant modulus algorithm for weight coefficient update. The equalizer, implemented in a 130 nm SiGe BiCMOS technology for 100 Gb/s operation, occupies ∼1.4 mm × 1.35 mm area and draws 1 A current from a 2.5 V supply. Its functionality is validated experimentally for data rates up to 40 Gb/s and by using postlayout circuit simulations for data rates up to 100 Gb/s. The equalizer output after processing with a behavioral Costas loopbased carrier phase recovery and compensation module shows bit error rates well within the hard-decision forward error correction limit for 40 Gb/s single-mode fiber links of length up to 10 km. Performance and power consumption of the equalizer are expected to improve when implemented in advanced CMOS or FinFET technologies. The simple architecture of the analog domain equalizer makes it suitable for analog coherent shortreach interconnects with length less than 10 km and carrier wavelengths of either 1310 nm or 1550 nm.

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Demonstration and Performance Analysis of 4 Tb/s DWDM Metro-DCI System with 100G PAM4 QSFP28 Modules

Cited by 33 publications

References 1 publication

Recent Advances in Equalization Technologies for Short-Reach Optical Links Based on PAM4 Modulation: A Review

Recent Advances in Equalization Technologies for Short-Reach Optical Links Based on PAM4 Modulation: A Review

High-Capacity Coherent DCIs Using Pol-Muxed Carrier and LO-Less Receiver

All-Analog Adaptive Equalizer for Coherent Data Center Interconnects

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