US9270513B2 - Method and apparatus for algorithm on flexible square-QAM coherent detection - Google Patents
Method and apparatus for algorithm on flexible square-QAM coherent detection Download PDFInfo
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- H—ELECTRICITY
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- H04L27/00—Modulated-carrier systems
- H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
- H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
- H04L27/38—Demodulator circuits; Receiver circuits
- H04L27/3818—Demodulator circuits; Receiver circuits using coherent demodulation, i.e. using one or more nominally phase synchronous carriers
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L25/03012—Arrangements for removing intersymbol interference operating in the time domain
- H04L25/03019—Arrangements for removing intersymbol interference operating in the time domain adaptive, i.e. capable of adjustment during data reception
- H04L25/03038—Arrangements for removing intersymbol interference operating in the time domain adaptive, i.e. capable of adjustment during data reception with a non-recursive structure
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L2025/03592—Adaptation methods
- H04L2025/03598—Algorithms
- H04L2025/03611—Iterative algorithms
- H04L2025/03617—Time recursive algorithms
Definitions
- Polarization multiplexing 16-ary quadrature amplitude modulation (PM-16QAM) [6] and higher-level QAM (e.g., 36QAM) [7], [8] are proposed for beyond 100-Gb/s optical transmission system. Therefore, it is quite important to discuss the DSP compatibility for the mQAM signal especially for QPSK and 16QAM in the future elastic optical networks.
- the static filter is used for chromatic dispersion (CD) compensation [9].
- the filter parameters are dependent on the residual CD and have no relation with modulation format.
- the constant modulus algorithm (CMA) is well accepted to separate the two polarization components. It is proved efficient to adapt the finite impulse response (FIR) tap weights for the QPSK and m-ary phase shift keying (mPSK) signal which has constant modulus.
- FIR finite impulse response
- mPSK m-ary phase shift keying
- RDE radius directed equalization
- Viterbi and Viterbi algorithm are useful to QPSK signal [11], while feed forward estimation is more hardware efficient for mQAM signal [12].
- the common problem is that the algorithm needs re-configuration and re-initialization so they are not flexible for the dynamic modulation format deployment.
- DD-LRD decision-directed least radius distance
- DD-LMS phase independent decision-directed least mean square
- DD-MLMS decision-directed modified least mean square
- FIG. 1 illustrates a DD-MLMS based adaptive FIR equalizer
- FIG. 2 illustrates cascaded adaptive equalizers with DD-MLMS
- FIG. 3 is a chart showing Q value versus product of laser linewidth and symbol duration ⁇ T s .
- Inset is the 16QAM constellations of received signal and processed signal based on proposed algorithm;
- FIG. 4 illustrates an experimental setup where CW: continuous wave, I/Q mod.: I/Q modulator, ATT: attenuator, OBPF: optical band-pass filter, LO: local oscillator;
- FIG. 5 illustrates measured BER as a function of OSNR (0.1 nm). Inset is the QPSK constellations of recovered signal based on different methods which is measured at an OSNR of 15 dB;
- FIG. 6 illustrates measured BER as a function of OSNR (0.1 nm). Inset is the 16QAM constellations of recovered signal based on different methods which is measured at an OSNR of 25 dB; and
- FIG. 7 illustrates measured BER as a function of transmission length for 16QAM signal.
- [ z x z y ] h cd ⁇ [ cos ⁇ ⁇ ⁇ e - j ⁇ ⁇ ⁇ ⁇ sin ⁇ ⁇ ⁇ - e j ⁇ ⁇ ⁇ sin ⁇ ⁇ ⁇ cos ⁇ ⁇ ⁇ ] ⁇ [ e j ⁇ ⁇ ⁇ x 0 0 e j ⁇ ⁇ ⁇ y ] ⁇ [ s x s y ] ( 1 )
- h cd is the fiber transfer function under dispersion. 2 ⁇ and ⁇ are the azimuth and elevation rotation angles, respectively.
- ⁇ x and ⁇ y are the carrier phase offset.
- FIG. 1 illustrates our proposed novel FIR blind equalizer with DD-MLMS algorithm to adapt the filter tap coefficients.
- x(n) is the received signal data.
- w(n) [a 1 , a 2 , . . . a i ] is the tap coefficients vector.
- y(n) w(n) T x(n), where superscript T stands for the transposition of a vector.
- the decision symbol is ⁇ circumflex over (d) ⁇ (n) decided by the shortest distance away from mQAM constellation point.
- DD-MLMS algorithm is proposed for the adaptive equalizer to minimize the mean square error. Since the mQAM signal constellation is square like, multi-modulus cost functions on both real axis and imaginary axis are considered. Meanwhile we want to reserve not only the amplitude error information but also the phase error information. Thus, the error function is divided into two parts. The errors of real part and imaginary part are calculated separately.
- 2 ) ⁇ sgn[ y r ( n )] (2) e i ( n ) (
- the error functions of real part and imaginary part are then combined together, which is expressed as a complex error vector as shown in (4).
- w ( n ) w ( n ⁇ 1)+ ⁇ e ( n ) ⁇ ( n )* (5)
- w(n) is the adaptive FIR filter
- ⁇ is the convergence parameter. [ ⁇ ]* stands for conjugation operation.
- the DD-MLMS algorithm tries to force the equalized signal to reside on the decision point.
- the error function includes both amplitude and phase information of the equalized signal.
- carrier phase offset is also blindly compensated.
- FIG. 2 shows the DSP of this blind equalization.
- the cascaded adaptive blind equalizers consist of four butterfly FIR filters (h xx , h xy , h yx , h yy ) for polarization separation and two FIR filters (g x , g y ) for carrier phase recovery. All of the filters are adaptively updated by DD-MLMS. It should be pointed out that all the signal processing is modulation format independent for square-QAM signal except for symbol final decision. Nevertheless, symbol decision must be required in any situation and format dependence is inevitable for the final decision.
- FIG. 4 shows the experimental setup of 28 Gbaud PM-QPSK and PM-16QAM back-to-back transmission.
- the bit sequence with a pseudo-random binary sequence (PRBS) length of 212 is coded by applying Gray-mapping for QPSK and 16QAM.
- the 28 Gbaud electrical signals are generated with two digital-to-analog converters (DACs) with a bandwidth of 16 GHz for in-phase (I) and quadrature (Q) branches.
- An external cavity laser (ECL) is used as the continuous wave (CW) source and modulated by an I/Q modulator biased at null point.
- the modulation format of QPSK or 16QAM can be defined by the software.
- the signal is polarization multiplexed with a differential delay of 150 symbols between two polarizations. Therefore, the bit-rate is 112 Gb/s when QPSK is deployed and 224 Gb/s when 16QAM is deployed.
- a variable attenuator and an Erbium Doped Fiber Amplifier (EDFA) are used to control the optical signal-to-noise ratio (OSNR) of the received signal.
- EDFA Erbium Doped Fiber Amplifier
- OBPF optical band-pass filter
- OBPF optical band-pass filter
- Polarization diversity homodyne detection is utilized at the receiver.
- the linewidth of ECLs at the transmitter and for LO at the receiver are both smaller than 100 kHz.
- ADCs analog-to-digital converters
- the received signal is resampled to 2 times of the symbol rate by cubic interpolation with square timing method [15].
- cascaded FIR equalizers are used to blindly recover the signal.
- Four 9-tap T/2-spaced adaptive butterfly FIR filters are applied for polarization demultiplexing.
- two 9-tap T-spaced adaptive FIR filters are applied for carrier recovery.
- the filters' weights are first updated by CMA for pre-convergence.
- the final adaptation is switched to DD-MLMS for precise feedback control. Frequency offset is compensated based on the fast Fourier transform (FFT) method [16] which is also modulation format independent.
- FFT fast Fourier transform
- the signal is detected for data bit error ratio (BER) measurement.
- BER data bit error ratio
- DD-LRD scheme together with general carrier phase estimation (CPE) (Viterbi-and-Viterbi algorithm for QPSK signal and feed forward estimation algorithm for 16QAM signal) is also evaluated.
- CPE general carrier phase
- the measured BERs of QPSK and 16QAM signals as a function of OSNR are shown in FIG. 5 and FIG. 6 , respectively.
- the OSNR is measured in a 0.1-nm noise bandwidth.
- the OSNR penalty is less than 0.5 dB for QPSK and 16QAM signals.
- the proposed algorithm works well enough and comparably with conventional algorithm but the complexity is reduced and compatible with both QPSK and 16QAM formats in our experiment.
- the DSP is compatible with square-QAM signal. So it could be deployed in the flexible mQAM modulation format coherent optical systems.
- the 8 channel WDM 240 Gb/s/ch PM-16QAM signal transmission with different fiber length is demonstrated. The transmission length can achieve 1200 km with a BER less than 2 ⁇ 10 ⁇ 2 based on the proposed blind equalization.
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Abstract
Description
where hcd is the fiber transfer function under dispersion. 2θ and ø are the azimuth and elevation rotation angles, respectively. φx and φy are the carrier phase offset. With respect to (1), we can recover the signal with the digital FIR equalizer.
e r(n)=(|{circumflex over (d)} r(n)|2 −|y r(n)|2)×sgn[y r(n)] (2)
e i(n)=(|{circumflex over (d)} i(n)|2 −|y i(n)|2×sgn(y i(n)) (3)
e(n)=e r(n)+j·e i(n) (4)
where the signum function is defined as sgn(x)=x/|x|. The error functions of real part and imaginary part are then combined together, which is expressed as a complex error vector as shown in (4).
w(n)=w(n−1)+μe(n)×(n)* (5)
where w(n) is the adaptive FIR filter, and μ is the convergence parameter. [·]* stands for conjugation operation.
- [1] O. Gerstel, M. Jinno, A. Lord, and S. J. B. Yoo, “Elastic optical networking: a new dawn for the optical layer?” IEEE Commun. Mag., vol. 50, no. 2, pp. s12-s20, February 2012.
- [2] H. Y. Choi, T. Tsuritani, and I. Morita, “BER-adaptive flexible-format transmitter for elastic optical networks,” Opt. Express, vol. 20, no. 17, pp. 18652-18658, August 2012.
- [3] R. Borkowski, et al., “Experimental study on OSNR requirements for spectrum-flexible optical networks,” J. Opt. Commun. Netw., vol. 4, no. 11, pp. B85-B93, November 2012.
- [4] Y.-K. Huang, et al., “High-capacity fiber field trial using terabit/s all-optical OFDM superchannels with DP-QPSK and DP-8QAM/DP-QPSK modulation,” J. Lightw. Technol., vol. 31, no. 4, pp. 546-553, February 2013.
- [5] K. Roberts, M. O'Sullivan, K.-T. Wu, H. Sun, A. Awadalla, D. J. Krause, and C. Laperle, “Performance of dual-polarization QPSK for optical transport systems,” J. Lightw. Technol., vol. 27, no. 16, pp. 3546-3559 May 2009.
- [6] P. J. Winzer, A. H. Gnauck, S. Chandrasekhar, S. Draving, J. Evangelista, and B. Zhu, “Generation and 1,200-km transmission of 448-Gb/s ETDM 56-Gbaud PDM 16-QAM using a single I/Q modulator,” in Proceedings of ECOC2010, Torino, Italy, Paper PDP 2.2.
- [7] X. Zhou, et al., “64-Tb/s, 8 b/s/Hz, PDM-36QAM transmission over 320 km using both pre- and post-transmission digital signal processing,” J. Lightw. Technol., vol. 29, no. 4, pp. 571-577, February 2011.
- [8] J. Yu, Z. Dong, H.-C. Chien, Y. Shao, and N. Chi, “7-Tb/s (7×1.284 Tb/s/ch) signal transmission over 320 km using PDM-64QAM modulation,” IEEE Photon. Technol. Lett., vol. 24, no. 4, pp. 264-266, February 2012.
- [9] S. J. Savory, “Digital filters for coherent optical receivers,” Opt. Express, vol. 16, no. 2, pp. 804-817, January 2008.
- [10] I. Fatadin, D. Ives, and S. J. Savory, “Blind equalization and carrier phase recovery in a 16-QAM optical coherent system,” J Lightw. Technol., vol. 27, no. 15, pp. 3042-3049, August 2009.
- [11] A. J. Viterbi and A. M. Viterbi, “Nonlinear estimation of PSK-Modulated carrier phase with application to burst digital transmission,” IEEE Trans. Inf. Theory, vol. 29, no. 4, pp. 543-551, July 1983.
- [12] T. Pfau, S. Hoffmann, and R. Noe, “Hardware-efficient coherent digital receiver concept with feedforward carrier recovery for M-QAM constellations,” J. Lightw. Technol., vol. 27, no. 8, pp. 989-999, April 2009.
- [13] X. Xu, B. Chatelain, and D. V. Plant, “Decision directed least radius distance algorithm for blind equalization in a dual-polarization 16-QAM system,” in Proceedings of OFC2012, L. A., Paper OM2H.
- [14] P. J. Winzer, A. H. Gnauck, C. R. Doerr, M. Magarini, and L. L. Buhl, “Spectrally efficient long-haul optical networking using 112-Gb/s polarization-multiplexed 16-QAM,” J. Lightw. Technol., vol. 28, no. 4, pp. 547-556, February 2010.
- [15] M. Oderder, and H. Meyr, “Digital filter and square timing recovery,” IEEE Transac. Commun., vol. 36, no. 5, pp. 605-612, May 1988.
- [16] M. Selmi, Y. Jaouen, P. Ciblat, “Accurate digital frequency offset estimator for coherent PolMux QAM transmission systems,” in Proceedings of ECOC2009, Vienna, Austria, Paper P3.08.
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US20160285657A1 (en) * | 2013-11-04 | 2016-09-29 | Zte Corporation | Adaptive pre-equalization in optical communications |
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