Nyquist WDM superchannel using offset-16QAM and receiver-side digital spectral shaping

Xiang, Meng; Fu, Songnian; Tang, Ming; Tang, Hanmei; Shum, Perry Ping; Liu, Deming

doi:10.1364/oe.22.017448

Cited by 25 publications

(10 citation statements)

References 20 publications

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“…A butterfly T/4 spaced finite impulse response (FIR) filters with only 1 tap is adapted to implement the constant modulus algorithm (CMA) for the purpose of polarization de-multiplexing, which is followed by frequency offset compensation (FOC) using the fast Fourier transform (FFT) method. Then, the adaptive equalization is performed by four butterfly 25-tap T/4 spaced FIR filters using modified least-mean-square algorithm (M-LMS) for the sequences after FOC [10]. The carrier phase recovery (CPR) is based on blind phase search (BPS) algorithm with 64 test angles.…”

Section: As Shown Inmentioning

confidence: 99%

Offset-16QAM-based coherent WDM with multi-carrier group detection

Xiang

Tang

et al. 2015

SPIE Proceedings

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Recently, offset-QAM based coherent WDM (CoWDM) has been proposed to build up spectrally-efficient multi-carrier superchannels. Compared with Nyquist wavelength division multiplexing (N-WDM) and orthogonal frequency division multiplexing (OFDM), offset-QAM based CoWDM can relax the stringent transmitter-side requirements for spectrum shaping and achieve significant transmission performance improvement. In order to efficiently utilize the sampling rate of commercially available analog-to-digital converter (ADC) and decrease the receiver-side implementation complexity, multi-carrier group detection scheme is investigated in offset-QAM based CoWDM where multiple carriers are simultaneously detected within single coherent receiver, followed by carrier separation in the digital domain through the 4-point discrete Fourier transform (DFT) method at the baseband. Here, we demonstrate a transmission of five-carrier 100 Gb/s polarization-multiplexed offset-16QAM signal with 12.5 GHz channel spacing. Through 3-carrier group detection, the sampling rate per-carrier is reduced to 1.33 times symbol rate in terms of 50 GS/s ADC and there is only 0.35 dB required OSNR penalty at BER=10 -3 compared with conventional single channel coherent detection. Meanwhile, good tolerance of coherent receiver analog bandwidth is secured and receiver bandwidth is reduced to 8 GHz. Moreover, 0.5 dB required OSNR penalty at BER=10 -3 is obtained given 18 GHz ADC bandwidth. Besides, we find that side carriers suffer from severer performance degradation than the central carrier with limited ADC resolution and only 0.08 dB and 0.2 dB required OSNR penalty at BER=10 -3 are secured with 6 bits ADC resolution for central carrier and side carriers, respectively.

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Section: As Shown Inmentioning

confidence: 99%

Offset-16QAM-based coherent WDM with multi-carrier group detection

Xiang

Tang

et al. 2015

SPIE Proceedings

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“…A matched time-domain FIR filter is firstly employed with identical number of taps as transmitter-side FIR filter anytime. The adaptive equalization and polarization de-multiplexing is then performed by four butterfly T/2-spaced FIR filters with 25 taps based on a modified least-mean-square algorithm for polarization de-multiplexing and ISI mitigation [12]. Then, bit errors are counted.…”

Section: System Configuration and Operation Principlementioning

confidence: 99%

“…11 shows the relationship between required-OSNR at BER=10 -3 and combined laser linewidth. If phase noise is loaded, the receiver-side structure for 16QAM and offset-16QAM can be found in [12] and [21], respectively. When the combined linewidth is zero, the required-OSNR of 16QAM is about 22.2 dB, because of 0.4 dB differential coding penalty which is consistent with the conclusion in [24].…”

Section: Tolerance To Dacs' Constraintsmentioning

confidence: 99%

“…In [12], we point out the RS-DSS can effectively solve the problem. Here, we emphasize that the TS-DSS can achieve the same purpose as well.…”

Section: F Sensitivity To Phase Difference For Offset-16qammentioning

confidence: 99%

“…In [12], we put forward to using offset-QAM modulation and receiver-side digital spectral shaping (RS-DSS) to build up Nyquist WDM superchannel. Owning to the receiver-side post-filtering, robustness to phase difference deviation is greatly enhanced.…”

Section: Introductionmentioning

confidence: 99%

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Performance Comparison of Offset-16QAM and 16QAM for Nyquist WDM Superchannel With Digital Spectral Shaping

Xiang

Tang

et al. 2015

J. Lightwave Technol.

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We investigate 5-channel polarization division multiplexed (PDM) Nyquist WDM superchannel using offset-16QAM and 16QAM modulation format, under the condition of transmitter-side digital spectral shaping (TS-DSS) technique, respectively. The offset-16QAM scheme can greatly relax the implementation complexity, because the tap number of 35 is sufficient for the required finite impulse response (FIR) filter, compared with 81-tap FIR filter of the 16QAM scheme. About 1.3 dB back-to-back sensitivity improvement is obtained for the offset-16QAM scheme. In particular, the offset-16QAM scheme has better tolerance of DACs' constraints, including the untracked jitter, sampling rate, and resolution. Finally, practical implementation of offset-16QAM based Nyquist WDM superchannel with TS-DSS is evaluated, by taking the phase difference deviation among wavelength channels and phase noise into account. No more than 1.3 dB required-OSNR penalty can be obtained, in case the phase difference is varied from 0 to 360 degree. When the laser with a linewidth of 100 kHz is used, there still exists about 1 dB overall performance improvement, compared with the 16QAM scheme.Index Terms-Nyquist WDM, offset-QAM modulation, finite impulse response filter, digital to analog converter.

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Independent and mixed transmission of 166.5 Gb/s PM‐8QAM and 222 Gb/s PM‐16QAM Nyquist‐wavelength division multiplexed superchannel for long‐haul metro network

Sachan

Sharma

Prajapati

et al. 2021

Int J Communication

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Summary This paper investigates the Nyquist‐wavelength division multiplexed (Nyquist‐WDM) terabit superchannel by employing independent and mixed line rate (MLR) transmission of different polarization‐multiplexed quadrature amplitude modulation (PM‐QAM) subcarriers. Here, terabit superchannel transmission including forward error correction overhead is successfully achieved by employing either 7 × 166.5 Gb/s PM‐8QAM or 5 × 222 Gb/s PM‐16QAM or both 2 × 166.5 Gb/s PM‐8QAM and 3 × 222 Gb/s PM‐16QAM simultaneous transmission. Considering linear filtering penalties and nonlinear propagation effects, the proposed superchannel is transmitted over standard single‐mode fiber (SSMF) and pure silica core fiber (PSCF) along with erbium‐doped fiber amplifier (EDFA) at 19.8‐ and 15.12‐dB span loss for SSMF and PSCF, respectively. The performance of both terabit superchannels is analyzed in terms of maximum reach, good spectral efficiency, highest transmission capacity, and optimum launch power with variation in channel spacing from 50‐GHz fixed ITU‐T grid to 29 GHz, at an acceptable bit error rate (BER). To achieve BER 4 × 10−3, MLR‐based 166.5 Gb/s PM‐8QAM and 222 Gb/s PM‐16QAM suffer a penalty of 5.5‐ and 9.2‐dB OSNR over Nyquist‐only 7 × 166.5 Gb/s PM‐8QAM and 5 × 222 Gb/s PM‐16QAM transmission at the advent of a flexible multi‐flow transponder. It is observed that at 33.33‐GHz Nyquist spacing over PSCF, 5 × 222 Gb/s PM‐16QAM and 7 × 166.5 Gb/s PM‐8QAM superchannels deliver a reach up to 1800 and 2970 km, while MLR approach results in extreme reach of 2250 and 3600 km over PSCF as per MLR PM‐16QAM and PM‐8QAM subcarriers, respectively. Hence, an appreciable spectral efficiency–distance product (SEDP) is achieved due to PSCF at Nyquist spacing of 33.33 GHz with 5.25 bit/s/Hz spectral efficiency. A good link power budget is also calculated for the proposed MLR‐based Nyquist‐WDM superchannel. MLR‐based PM‐16QAM and PM‐8QAM subcarriers deliver excellent SEDP of 11,812 and 18,900 bit/s/Hz·km, respectively, which is, to the best of author's knowledge, better on comparing with the other existing literature for single‐core channel explorations.

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Nyquist WDM superchannel using offset-16QAM and receiver-side digital spectral shaping

Cited by 25 publications

References 20 publications

Offset-16QAM-based coherent WDM with multi-carrier group detection

Offset-16QAM-based coherent WDM with multi-carrier group detection

Performance Comparison of Offset-16QAM and 16QAM for Nyquist WDM Superchannel With Digital Spectral Shaping

Independent and mixed transmission of 166.5 Gb/s PM‐8QAM and 222 Gb/s PM‐16QAM Nyquist‐wavelength division multiplexed superchannel for long‐haul metro network

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