Experimental demonstration of 110-Gb/s unsynchronized band-multiplexed superchannel coherent optical OFDM/OQAM system
TL;DR: This paper experimentally demonstrates the first 110-Gb/s multi-band superchannel coherent optical orthogonal frequency-division multiplexing based on offset quadrature amplitude modulation (OFDM/OQAM) system and investigates the influence of guard band, finding that very trivial guard band spacing is required without any sensitivity performance or spectral efficiency degradation.
Abstract: In this paper, we experimentally demonstrate the first 110-Gb/s multi-band superchannel coherent optical orthogonal frequency-division multiplexing based on offset quadrature amplitude modulation (OFDM/OQAM) system. Unlike the conventional orthogonal band-multiplexed OFDM system, no timing or frequency synchronization is required for the OFDM/OQAM system. We further investigate the influence of guard band, and find that very trivial guard band spacing (<20MHz) is required without any sensitivity performance or spectral efficiency degradation. Thus, the newly designed scheme would significantly reduce the implementation constrains for the band-multiplexed superchannel coherent optical OFDM system.
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TL;DR: A detailed investigation on the performance of three advanced modulation formats for 100 Gb/s short reach transmission system, PAM-4, CAP-16 and DMT, and a comparison of computational complexity of DSP for the three formats is presented.
Abstract: Advanced modulation formats combined with digital signal processing and direct detection is a promising way to realize high capacity, low cost and power efficient short reach optical transmission system. In this paper, we present a detailed investigation on the performance of three advanced modulation formats for 100 Gb/s short reach transmission system. They are PAM-4, CAP-16 and DMT. The detailed digital signal processing required for each modulation format is presented. Comprehensive simulations are carried out to evaluate the performance of each modulation format in terms of received optical power, transmitter bandwidth, relative intensity noise and thermal noise. The performance of each modulation format is also experimentally studied. To the best of our knowledge, we report the first demonstration of a 112 Gb/s transmission over 10km of SSMF employing single band CAP-16 with EML. Finally, a comparison of computational complexity of DSP for the three formats is presented.
274 citations
TL;DR: In this article, the frequency-domain optical fiber channel transmission model for PDM CO-OFDM/OQAM systems with the IMI effect induced by chromatic dispersion (CD) and polarization mode dispersion(PMD) was systematically analyzed.
Abstract: Intrinsic imaginary interference (IMI) induced by a multiple-path fading channel is an important impairment for orthogonal frequency division multiplexing/offset-quadrature amplitude modulation (OFDM/OQAM) systems. Therefore, the accurate channel estimation is highly desired for such a system. Recently both the simulation studies and the experimental demonstrations for coherent optical OFDM/OQAM (CO-OFDM/OQAM) have been reported. However, there are no theoretical discussions on the IMI effect and the channel estimation method for polarization-division-multiplexed (PDM) CO-OFDM/OQAM systems so far. In this paper, we systematically analyze the frequency-domain optical fiber channel transmission model for PDM CO-OFDM/OQAM systems with the IMI effect induced by chromatic dispersion (CD) and polarization mode dispersion (PMD). The full loaded (FL) and the half loaded (HL) frequency-domain channel estimation methods are discussed to mitigate the IMI effect. The computational complexities and robustness against CD and PMD are also compared for both of the FL and the HL methods. The theoretical analysis is validated by numerical Monte Carlo simulations of PDM CO-OFDM/OQAM systems.
59 citations
Cites methods from "Experimental demonstration of 110-G..."
...The first coherent optical OFDM/OQAM (CO-OFDM/OQAM) experiment has been reported in [14], in which a 9-band 110Gb/s super-channel CO-OFDM/OQAM system demonstrated 15dB higher side lobe suppression ratio than conventional COOFDM with much reduced implementation constrains thanks to the very trivial requirement of guard band spacing....
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TL;DR: In this paper, the authors proposed the time-domain least square (TDLS) channel estimation method for coherent optical OFDM/OQAM (CO-OFDM) systems.
Abstract: Suppressing the intrinsic imaginary interference (IMI) effect induced by the multiple-path fading channel is the key technology for maintaining the good performance of the orthogonal frequency-division multiplexing offset-quadrature amplitude modulation (OFDM/OQAM) systems. Recently, the first theoretical discussion on the IMI effect and the corresponding frequency-domain channel estimation method for polarization-division-multiplexed (PDM) coherent optical OFDM/OQAM (CO-OFDM/OQAM) system has been studied. The full-loaded and the half-loaded channel estimation methods have been proposed to mitigate the IMI effect. However, for these frequency-domain methods, the condition that the symbol interval is much longer than the maximum channel delay spread has to be satisfied. When the transmission distance is long, the frequency-domain residual errors induced by the chromatic dispersion (CD) and polarization mode dispersion (PMD) reduce the channel estimation accuracy evidently. In this paper, we systematically discuss the time-domain channel transmission model for PDM CO-OFDM/OQAM systems. With the analysis of the distribution of the received additive noise, we propose the time-domain least square (TDLS) channel estimation method for PDM CO-OFDM/OQAM systems. Compared with the frequency-domain methods, the TDLS method promotes the system robustness against both the IMI effect and the additive noise significantly. The computational complexities and the transmission performance have been compared for both the TDLS and the frequency-domain full-loaded methods. The theoretical analysis is validated by numerical Monte Carlo simulations of the PDM CO-OFDM/OQAM system.
45 citations
Cites methods from "Experimental demonstration of 110-G..."
...The first optical OFDM/OQAM experiments have been reported in [19]....
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TL;DR: A novel approach to simultaneously receive multi-band 100-Gb/s direct-detection optical signal with only one polarization and one conventional 40-GHz photodiode is proposed.
Abstract: In this paper, we propose a novel approach to simultaneously receive multi-band 100-Gb/s direct-detection optical signal with only one polarization and one conventional 40-GHz photodiode. The modulation format of orthogonal frequency-division multiplexing based on offset quadrature amplitude modulation (OFDM/OQAM) is selected to provide signal spectrum with high side-lobe suppression ratio, which can effectively reduce the electrical sub-band frequency interference. The whole 100-Gb/s OFDM/OQAM signal is comprised of 6 sub-bands with 16- and 32-QAM formats loading. Only one guard band is required to accommodate the overlapped 6-band signal-to-signal beat interference (SSBI). The receiver bandwidth is mainly limited by the digital storage oscilloscope (DSO) of 33 GHz. The transmission distance over standard single mode fiber (SSMF) is up to 320 km.
42 citations
TL;DR: To enhance the communication performance, the orthogonal frequency-division multiplexing in conjunction with offset quadrature amplitude modulation (OFDM-OQAM) is applied, and its performance is compared against the traditional dc-biased optical OFDM.
Abstract: An organic light emitting diode (OLED) shows characteristics different from a traditional semiconductor LED when both are applied to visible light communication (VLC). This paper first experimentally characterizes its static and dynamic communication properties with varying input signals. This band-limited and power-limited light source leads to unique communication channel and noise models. Accordingly, the orthogonal frequency-division multiplexing in conjunction with offset quadrature amplitude modulation (OFDM-OQAM) is applied, and its performance is compared against the traditional dc-biased optical OFDM. To further enhance the communication performance, a bit and power loading algorithm and a proper equalization algorithm are jointly implemented to combat the channel frequency selectivity and increase the data rate. A bit-rate of 51.6 Mb/s based on a monochromic OLED is experimentally achieved through the proposed design. The rate is comparable to the multicolor OLEDs-based VLC link in the literature.
38 citations
References
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TL;DR: This work reviews detection methods, including noncoherent, differentially coherent, and coherent detection, as well as a hybrid method, and compares modulation methods encoding information in various degrees of freedom (DOF).
Abstract: The drive for higher performance in optical fiber systems has renewed interest in coherent detection. We review detection methods, including noncoherent, differentially coherent, and coherent detection, as well as a hybrid method. We compare modulation methods encoding information in various degrees of freedom (DOF). Polarization-multiplexed quadrature-amplitude modulation maximizes spectral efficiency and power efficiency, by utilizing all four available DOF, the two field quadratures in the two polarizations. Dual-polarization homodyne or heterodyne downconversion are linear processes that can fully recover the received signal field in these four DOF. When downconverted signals are sampled at the Nyquist rate, compensation of transmission impairments can be performed using digital signal processing (DSP). Linear impairments, including chromatic dispersion and polarization-mode dispersion, can be compensated quasi-exactly using finite impulse response filters. Some nonlinear impairments, such as intra-channel four-wave mixing and nonlinear phase noise, can be compensated partially. Carrier phase recovery can be performed using feedforward methods, even when phase-locked loops may fail due to delay constraints. DSP-based compensation enables a receiver to adapt to time-varying impairments, and facilitates use of advanced forward-error-correction codes. We discuss both single- and multi-carrier system implementations. For a given modulation format, using coherent detection, they offer fundamentally the same spectral efficiency and power efficiency, but may differ in practice, because of different impairments and implementation details. With anticipated advances in analog-to-digital converters and integrated circuit technology, DSP-based coherent receivers at bit rates up to 100 Gbit/s should become practical within the next few years.
907 citations
TL;DR: In this article, a coherent optical orthogonal frequency division multiplexing (OFDM) was proposed to combat dispersion in optical media, and it was shown that optical-signal-to-noise ratio penalty at 10 Gbit/s is maintained below 2 dB for 3000 km transmission of standard-singlemode fiber without dispersion compensation.
Abstract: Coherent optical orthogonal frequency division multiplexing is proposed to combat dispersion in optical media. It is shown that optical-signal-to-noise ratio penalty at 10 Gbit/s is maintained below 2 dB for 3000 km transmission of standard-singlemode fibre without dispersion compensation.
629 citations
TL;DR: The performance of OFDM is discussed, and filterbanks for multicarrier communication and spectral analysis in a CR setting are introduced, and the multitaper method has been proposed as an effective method for spectrum analysis.
Abstract: In this tutorial article we review different multicarrier communication methods for the physical layer of cognitive radio systems. There, secondary users need to dynamically and reliably determine spectral holes, and transmit data in these resources without interfering with other parts of the frequency band. To satisfy the first, each SU has to be equipped with a spectrum analyzer. To satisfy the second, it is widely accepted that a multicarrier modulation technique should be adopted. Moreover, to maximize efficiency, it has been recognized that the side-lobes of each subcarrier band must be minimized. Much of the attention in the present literature emphasizes on the use of conventional OFDM, exploiting the fact that fast Fourier transform (FFT) as part of the OFDM modulator can also be used for channel sensing. Herein, we discuss the performance of OFDM, and also introduce filterbanks for multicarrier communication and spectral analysis in a CR setting. Moreover, the multitaper method has been proposed as an effective method for spectrum analysis. Our article provides an insight into the pros and cons of these technologies.
362 citations
TL;DR: In this paper, a coherent optical orthogonal frequency-division multiplexing (CO-OFDM) scheme with reduced guard interval (RGI) was proposed for high-speed high-spectral-efficiency long-haul optical transmission.
Abstract: We propose a novel coherent optical orthogonal frequency-division multiplexing (CO-OFDM) scheme with reduced guard interval (RGI) for high-speed high-spectral-efficiency long-haul optical transmission. In this scheme, fiber chromatic dispersion is compensated for within the receiver rather than being accommodated by the guard interval (GI) as in conventional CO-OFDM, thereby reducing the needed GI, especially when fiber dispersion is large. We demonstrate the generation of a 448-Gb/s RGI-CO-OFDM signal with 16-QAM subcarrier modulation through orthogonal band multiplexing. This signal occupies an optical bandwidth of 60 GHz, and is transmitted over 2000 km of ultra-large-area fiber (ULAF) with five passes through an 80-GHz-grid wavelength-selective switch. Banded digital coherent detection with two detection bands is used to receive this 448-Gb/s signal. Wavelength-division multiplexed transmission of three 80-GHz spaced 448-Gb/s RGI-CO-OFDM channels is also demonstrated, achieving a net system spectral efficiency of 5.2 b/s/Hz and a transmission distance of 1600 km of ULAF.
178 citations
TL;DR: In this article, a weighted sum of near-adjacent IFT filters is used to realize the individual channel-bank filters, with constraints added that results in significantly improved stopband performance while still achieving small reconstruction errors.
Abstract: An approach for realizing filter banks having improved side-lobe performance compared to approaches such as those based on inverse Fourier transforms (IFTs), especially for greater frequency differences from the passband frequencies, is presented. The approach is based on using a weighted-sum of near-adjacent IFT filters to realize the individual channel-bank filters, but with constraints added that results in significantly improved stopband performance while still achieving small reconstruction errors. The proposed channel banks are suitable for realizing multitone digital data communication systems, such as Asymmetric Digital Subscriber Line (ADSL) systems, where stopband performance is critical. Under the conditions of maximal decimation, the reconstruction is not perfect, but aliasing errors are small enough to be negligible in practical communication systems. For some cases, the filter coefficients can be determined exactly without using optimization. Given the frequency-weighting coefficients reported herein, near-optimal multirate filter banks may be designed exactly without optimization for all even n.
105 citations