Demonstration of a low-power, local-oscillator-less, and DSP-free coherent receiver for data center interconnects

Kamran, Rashmi; Nambath, Nandakumar; Manikandan, Sarath; Ashok, Rakesh; Jain, Rachit; Thaker, Nandish Bharat; Gupta, Shalabh

doi:10.1364/ao.383185

Cited by 7 publications

(2 citation statements)

References 22 publications

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“…Another element which can be compensated in analogue domain is timing recovery. This is not a feature of the OIPLL, but it could be implemented together with the latter [19], removing the need for any DSP if the link budget was to be strong enough as to remove the need for FEC. The power consumption of a satellite optical coherent receiver is of great importance in the power budget.…”

Section: Discussionmentioning

confidence: 99%

Low-power-consumption coherent receiver architecture for satellite optical links

Bernini

Fice

Bałakier

2022

2022 IEEE International Conference on Space Optical Systems and Applications (ICSOS)

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As the demand for satellite data transmission increases, higher capacity optical links need to be developed to allow satellites to be connected directly to ground stations (GST). The advantages of Low Earth Orbit (LEO) direct-to-Earth links are smaller latency when compared to relay systems using Geostationary Orbit (GEO) satellites, i.e. LEO-to-GEO and GEO-to-GST, and an increased available bandwidth offered by the optical spectrum with respect to radio frequency (RF) which allows for much higher link capacity. The increase in data rate of optical satellite to ground links towards 100 Gbps will require implementing optical coherent transceivers with capability to compensate for Doppler shift and atmospheric channel impairments. An important figure of merit which needs to be carefully considered in a satellite system is the equipment power consumption. The power consumption of coherent receivers used for terrestrial applications is closely related to the bit rate, with a receiver back-end digital signal processing being responsible for the vast majority of the power consumed.In this paper we propose a hybrid approach to signal processing consisting of simplified digital and analogue elements allowing for significant power reduction. Moreover, one of the attractive aspects of the proposed approach is that it does not require an increased complexity for an increase in baud rate. It will be discussed that the analogue approach to the frequency and phase recovery would allow a saving of approximately 40% to 50% of power on the overall DSP block at baud rates between 10 Gbaud and 100 Gbaud.

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Section: Discussionmentioning

confidence: 99%

Low-power-consumption coherent receiver architecture for satellite optical links

Bernini

Fice

Bałakier

2022

2022 IEEE International Conference on Space Optical Systems and Applications (ICSOS)

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“…The constellation shaping scheme, both probabilistic shaping (PS) and geometric shaping (GS), are broadly applied to reduce the gap of channel capacity to Shannon limit, which also require specified DSP scheme to optimize the performance [28,29]. These increasing demands of DSP costs have led researchers to pay more attention to the DSP-free coherent receivers [30][31][32][33]. On the other hand, the terabit optical Ethernet technologies will be affected by security issues, and to solve such problem, the properly designed fiber Bragg gratings (FBGs) application in impulse responses derived from mutually orthogonal Slepian sequences has been advocated in [1] to enable positive rate to convert optical communications [2,3].…”

Section: Introductionmentioning

confidence: 99%

Two-Dimensional Transmission of Four-Dimensional LDPC-Coded Modulation with Slepian Sequences for DSP-Free 40 km Metro Network Applications

Han

Djordjević

2022

Sensors

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The growing data demands are pushing researchers to pay more attention to spectrally efficient modulation formats. The four-dimensional (4D) signal constellation modulation format has been investigated for metro networks’ applications to achieve better power efficiency. To cope with such modulation formats, the requirement of better digital signal processing (DSP) is also increasing rapidly. More complicated DSPs bring us extra costs; thus, the DSP-free coherent receivers are also investigated because of the high-power consumption of conventional DSP-based receivers, but the transceivers upgrading also results in extra costs. In this invited paper we implement a 4-dimentional modulation format based on Slepian sequences. We applied LDPC coding and experimentally investigated the BER performance in a two-dimensional (2D) 40 km fiber link transmission and demonstrate that being error free is possible without employing the complicated DSP. We compared our proposed modulation scheme with regular 16QAM and found it outperforms 16QAM with DSP over back-to-back transmission by 3.8 dB improvement in OSNR when BER = 10−5, while over 40 km metro network communication link our proposed 4D modulation signals are still successfully transmitted, and the LDPC-coding still works properly with such a new transmission strategy. On the other hand, DSP-free transmission of LDPC-coded 16-QAM exhibits an early error floor phenomenon.

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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 of a low-power, local-oscillator-less, and DSP-free coherent receiver for data center interconnects

Cited by 7 publications

References 22 publications

Low-power-consumption coherent receiver architecture for satellite optical links

Low-power-consumption coherent receiver architecture for satellite optical links

Two-Dimensional Transmission of Four-Dimensional LDPC-Coded Modulation with Slepian Sequences for DSP-Free 40 km Metro Network Applications

All-Analog Adaptive Equalizer for Coherent Data Center Interconnects

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