Author
Jiahao Huo
Other affiliations: Hong Kong Polytechnic University
Bio: Jiahao Huo is an academic researcher from University of Science and Technology Beijing. The author has contributed to research in topics: Transmission (telecommunications) & Computer science. The author has an hindex of 7, co-authored 47 publications receiving 335 citations. Previous affiliations of Jiahao Huo include Hong Kong Polytechnic University.
Papers
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TL;DR: An overview of recent DSP developments for short-reach communications systems is presented and future trends are discussed.
Abstract: Driven primarily by cloud service and data-center applications, short-reach optical communication has become a key market segment and growing research area in recent years. Short-reach systems are characterized by direct detection-based receiver configurations and other low-cost and small form factor components that induce transmission impairments unforeseen in their coherent counterparts. Innovative signaling and digital signal processing (DSP) play a pivotal role in enabling these components to realize their ultimate potentials and meet data rate requirements in cost-effective manners. This paper presents an overview of recent DSP developments for short-reach communications systems and discusses future trends.
319 citations
TL;DR: The receiver computational complexity can be effectively reduced by employing appropriate ETC and Pre-EQ in the transmitter, and a joint equalization and error table generation (JEEG) module is proposed.
Abstract: The transmission performance of 112 Gbit/s PAM-4 signal with commercial 25 G-class EML and APD is experimentally studied by using advanced digital signal processing (DSP) algorithms, i.e. pre-equalization (Pre-EQ), error-table based pre-correction (ETC), least-mean square (LMS) based equalization, direct detection faster than Nyquist (DD-FTN) algorithm. Among them, Pre-EQ and ETC are implemented at the transmitter, and ETC is a symbol-pattern-dependent pre-compensation algorithm based on the look-up-table approach. In order to obtain these pre-compensated parameters readily, a joint equalization and error table generation (JEEG) module is proposed. Employing the combination of ETC, LMS, and DD-FTN, a single line 112 Gbit/s PAM-4 40 km amplifier-less transmission with a record receiver sensitivity of -16.6 dBm (at 7% HD-FEC threshold) is experimentally demonstrated. In addition, the computational complexities of different DSP schemes are analyzed and discussed in detail. The receiver computational complexity can be effectively reduced by employing appropriate ETC and Pre-EQ in the transmitter.
29 citations
TL;DR: In this paper, the influence of phase noise on the performance of self-homodyne coherent (SHC) systems is thoroughly analyzed by studying the PN probability distribution characteristic and bit error rate performance in theory.
Abstract: The intra- and inter- data center links face continuously increasing pressure on the transmission capacity while having to meet strict constraints in cost and power consumption. For such cost-sensitive data center applications, self-homodyne coherent (SHC) system as a promising solution has attracted increasing attention. In this article, the influence of phase noise (PN) for the SHC system is thoroughly analyzed by studying the PN probability distribution characteristic and bit-error rate (BER) performance in theory. The correctness of the theorical PN analysis is also verified by simulation. Further, the PN characteristics in SHC systems are investigated and discussed with and without the implementation of carrier phase recovery (CPR). A unique property is found for SHC systems that the system performance is only related to the product of linewidth and mismatch length, independent of the symbol rate in the absence of CPR. For SHC-16QAM systems, in order to limit the OSNR penalty to below 1-dB, the product of laser linewidth and delay mismatch should be kept below 0.18 ${\bf{MHz}} \cdot {\bf{m}}$ . Under such a conduciton, no CPR algorithm is reuiqred. Alternatively, in presence of CPR, the phase noise tolerance of SHC and conventional coherent systems are similar.
26 citations
TL;DR: Based on the proposed algorithms, 112 Gb/s PDM-PAM4 transmission over 80 km standard single mode fiber in C-band for a bit error rate below 3.8e-3 is successfully demonstrated without optical amplifier, chromatic dispersion (CD) pre-compensation and extra carrier recovery operations.
Abstract: Polarization-division-multiplexed (PDM) four-level pulse amplitude modulation (PAM4) with coherent detection is a promising low cost solution for 80 km inter-datacenter transmissions at 100 Gb/s and beyond. In this paper, three modified adaptive equalization algorithms for the PDM-PAM4 optical coherent systems, i.e. signal-phase aid least-mean-square (SP-LMS) algorithm, training multi-modulus algorithm (TMMA) and cascaded four-modulus algorithm (CMMA-4), are proposed and compared. Based on the proposed algorithms, 112 Gb/s PDM-PAM4 transmission over 80 km standard single mode fiber (SSMF) in C-band for a bit error rate (BER) below 3.8e-3 is successfully demonstrated without optical amplifier, chromatic dispersion (CD) pre-compensation and extra carrier recovery operations.
21 citations
21 Sep 2017
TL;DR: For the first time, an amplifier-less transmission of a single lane 112Gbit/s PAM4 signal over 40km using 25G EML and APD at O band with a record receiver sensitivity of −14.8dBm is demonstrated.
Abstract: For the first time, we experimentally demonstrated an amplifier-less transmission of a single lane 112Gbit/s PAM4 signal over 40km using 25G EML and APD at O band with a record receiver sensitivity of −14.8dBm.
19 citations
Cited by
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TL;DR: An overview of recent DSP developments for short-reach communications systems is presented and future trends are discussed.
Abstract: Driven primarily by cloud service and data-center applications, short-reach optical communication has become a key market segment and growing research area in recent years. Short-reach systems are characterized by direct detection-based receiver configurations and other low-cost and small form factor components that induce transmission impairments unforeseen in their coherent counterparts. Innovative signaling and digital signal processing (DSP) play a pivotal role in enabling these components to realize their ultimate potentials and meet data rate requirements in cost-effective manners. This paper presents an overview of recent DSP developments for short-reach communications systems and discusses future trends.
319 citations
TL;DR: How predictions were made from the outset of research in laser based optical communications and how they have evolved to their present form, accurately predicting the performance of coherently detected communication systems are described.
Abstract: In this paper, we review the historical evolution of predictions of the performance of optical communication systems. We will describe how such predictions were made from the outset of research in laser based optical communications and how they have evolved to their present form, accurately predicting the performance of coherently detected communication systems.
149 citations
TL;DR: An overview of the recent developments in UWOC systems, covering aspects about the system transmitters and receivers, advanced modulation formats and underwater channels and some key technologies to improve transmission capacity are classified and summarized to provide guidance for system design.
109 citations
15 Jan 2020
TL;DR: This article focuses on IM/DD transmissions, and provides an overview of recent research and development efforts on key enabling technologies for 200 Gbps per lane and beyond, and expects high-speed IM/ DD systems will remain advantageous in terms of system cost, power consumption, and footprint for short reach applications in the short- to mid- term perspective.
Abstract: Client-side optics are facing an ever-increasing upgrading pace, driven by upcoming 5G related services and datacenter applications. The demand for a single lane data rate is soon approaching 200 Gbps. To meet such high-speed requirement, all segments of traditional intensity modulation direct detection (IM/DD) technologies are being challenged. The characteristics of electrical and optoelectronic components and the performance of modulation, coding, and digital signal processing (DSP) techniques are being stretched to their limits. In this context, we witnessed technological breakthroughs in several aspects, including development of broadband devices, novel modulation formats and coding, and high-performance DSP algorithms for the past few years. A great momentum has been accumulated to overcome the aforementioned challenges. In this article, we focus on IM/DD transmissions, and provide an overview of recent research and development efforts on key enabling technologies for 200 Gbps per lane and beyond. Our recent demonstrations of 200 Gbps short-reach transmissions with 4-level pulse amplitude modulation (PAM) and discrete multitone signals are also presented as examples to show the system requirements in terms of device characteristics and DSP performance. Apart from digital coherent technologies and advanced direct detection systems, such as Stokes–vector and Kramers–Kronig schemes, we expect high-speed IM/DD systems will remain advantageous in terms of system cost, power consumption, and footprint for short reach applications in the short- to mid- term perspective.
99 citations
TL;DR: In this article, the Schottky-barrier diode (SBD) was used as a nonlinear element and generalized the theory of KK processing to account for the non-quadratic characteristics of this device.
Abstract: High-speed communication systems rely on spectrally efficient modulation formats that encode information both on the amplitude and on the phase of an electromagnetic carrier. Coherent detection of such signals typically uses rather complex receiver schemes, requiring a continuous-wave (c.w.) local oscillator (LO) as a phase reference and a mixer circuit for spectral down-conversion. In optical communications, the so-called Kramers-Kronig (KK) scheme has been demonstrated to greatly simplify the receiver, reducing the hardware to a single photodiode. In this approach, an LO tone is transmitted along with the signal, and the amplitude and phase of the complex signal envelope are reconstructed from the photocurrent by digital signal processing. This reconstruction exploits the fact that the real and the imaginary part, or, equivalently, the amplitude and the phase of an analytic signal are connected by a KK-type relation. Here, we transfer the KK scheme to high-speed wireless communications at THz carrier frequencies. We use a Schottky-barrier diode (SBD) as a nonlinear element and generalize the theory of KK processing to account for the non-quadratic characteristics of this device. Using 16-state quadrature amplitude modulation (16QAM), we transmit a net data rate of 115 Gbit/s at a carrier frequency of 0.3 THz over a distance of 110 m.
80 citations