Burst-mode Transmission Research Articles

Investigation of real-time 25 Gbps burst mode transmission over 20 km fiber with directly modulated laser, Ge/Si APD receiver and BM-TIA targeting 50G-PON

Investigation of real-time 25 Gbps burst mode transmission over 20 km fiber with directly modulated laser, Ge/Si APD receiver and BM-TIA targeting 50G-PON

Novel Data-Aided Carrier Frequency Offset Compensation Methods Using Asymmetric-Shape Constellations for Burst-Mode Coherent Reception

This paper introduces a novel data-aided carrier frequency offset (CFO) estimation and compensation method for m-array phase shift keying (m-PSK) signals in burst-mode digital coherent reception. Its key advances are as follows; the use of newly designed training symbols (TS) that exhibit asymmetric distributed constellations after differential decoding and a vector summation based feed-forward CFO estimation algorithm. These offer short response time and strong robustness to training symbols (TS) timing detection error with wide CFO estimation range of ±B/2, where B is signal baudrate. We evaluate the feasibility of the proposal by simulations of and experiments on 12.5-Gbaud SP-QPSK signals that target optical budget enhancement of 25-Gbps/λ-class PONs to realize long-reach and high splitting ratio optical access. The 100-km burst-mode transmission experiments confirm the proposal offers high sensitivity detection of better than −43 dBm with much wider CFO range of above ±10 GHz.

Enhanced data‐aided frequency estimation by collaboration in a distributed receiver

In this paper, a communication system with digital burst-mode transmission and distributed reception in the presence of carrier frequency offset and Additive White Gaussian Noise (AWGN) is considered. The distributed receiver consists of distributed nodes and a fusion center. Data-aided frequency estimation at a receiving node can be performed using a preamble. However, accurate frequency estimation may not be achievable at nodes with low signal-to-noise ratio (SNR). The problem can be alleviated by collaboration between nodes. Low-SNR nodes can improve their data-aided frequency estimation by fetching already decoded symbols from the fusion center. This paper investigates deterministic and data dependent criteria for selecting and fetching of additional symbols. The mean-square error (MSE) of frequency estimation errors achieved by different criteria are numerically compared via Monte-Carlo simulations. The Cramer–Rao Lower Bounds (CRLB) for frequency estimation under the considered criteria are presented. The bit-error-rates (BER) of the distributed receiver across different symbol fetching schemes are numerically compared.

Fast band power measurement technique in Wi-Fi systems using spectrum analyzer

Fast band power measurement technique used for measuring band power in wireless fidelity (Wi-Fi) devices. The difficulty during testing the band power is burst mode transmission takes longer time to measure. A test jig or specialized tool required is costly, which allows continuous mode of transmission for power measurement. The delivered average power by a Wi-Fi device depends upon the data rate which can also vary during time. The procedure proposed hereby developed using a spectrum analyzer to measure band power in the burst mode, in order to ensure repeatable results and optimized to enable fast measurements at low cost, less time and above 90% accurate.

Ultrafast optical circuit switching for data centers using integrated soliton microcombs

Due to the slowdown of Moore’s law, it will become increasingly challenging to efficiently scale the network in current data centers utilizing electrical packet switches as data rates grow. Optical circuit switches (OCS) represent an appealing option to overcome this issue by eliminating the need for expensive and power-hungry transceivers and electrical switches in the core of the network. In particular, optical switches based on tunable lasers and arrayed waveguide grating routers are quite promising due to the use of a passive core, which increases fault tolerance and reduces management overhead. Such an OCS-network can offer high bandwidth, low network latency and an energy-efficient and scalable data center network. To support dynamic data center workloads efficiently, however, it is critical to switch between wavelengths at nanosecond (ns) timescales. Here we demonstrate ultrafast OCS based on a microcomb and semiconductor optical amplifiers (SOAs). Using a photonic integrated Si3N4 microcomb, sub-ns (<520 ps) switching along with the 25-Gbps non-return-to-zero (NRZ) and 50-Gbps four-level pulse amplitude modulation (PAM-4) burst mode data transmission is achieved. Further, we use a photonic integrated circuit comprising an Indium phosphide based SOA array and an arrayed waveguide grating to show sub-ns switching (<900 ps) along with 25-Gbps NRZ burst mode transmission providing a path towards a more scalable and energy-efficient wavelength-switched network for data centers in the post Moore’s Law era.

Asynchronous Demodulation Method for Four SS Barranged on Frequency Axis in Mobile Radio Path using Hilbert Transform

In this paper, an asynchronous demodulation method for a four-single sideband (SSB) signal arranged on the frequency axis is developed to support burst mode transmission in a mobile radio path and to achieve greater data throughputs. When a reduced pilot carrier is placed at the center of the 4-SSB signal, it is guarded by lower and upper sidebands, that is, this scheme is classified into a tone-in-band (TIB) system. Digital signal processing (DSP) processors are useful for implementing a Hilbert transform. However, we have for a long time neglected introducing it into the demodulation process of SSB signals.

A Robust Timing and Phase Offset Estimation Technique for CPM-DSSS-Based Secured Communication Link

Continuous Phase Modulation–Direct Sequence Spread Spectrum (CPM-DSSS) is a promising scheme for a secured Point-to-Point (P2P) communication system having Anti-Jamming (AJ) capabilities. However, like other communication systems, synchronization of CPM-DSSS based systems is required for reliable detection of data. This paper presents a novel algorithm for estimating the timing and phase offset for binary full-response CPM-DSSS based systems. A burst mode transmission is considered here, and within each burst, a training sequence is embedded along with data. Firstly, the entire burst is spread using DSSS and then modulated with CPM, which is later upconverted and passed on to the channel. After down-conversion at the receiver, the proposed algorithm estimates timing and phase offset from the received spread training sequence. Then estimation accuracy of the proposed algorithm is compared with the state-of-the-art. The results indicate that the proposed joint estimator is superior by 9 dB and 10 dB for the estimation of timing and phase offset, respectively, as compared to the existing algorithm. Furthermore, the estimator’s variance for three different frequency pulses is compared with Modified Cramer-Rao Bound (MCRB). The results suggest that the phase offset estimator’s variance approaches MCRB for all Signal-to-Noise Ratios (SNRs). The effectiveness of the proposed algorithm in the multipath fading channel is also demonstrated.

A novel DSP scheme for eliminating the interaction between dispersion and transient frequency offset in optical burst-mode coherent systems

Optical coherent burst-mode transmission can offer not only flexibility but also efficiency of the network resource utilization in elastic optical networks. We propose a new digital signal processing (DSP) scheme of coherent burst reception with a training sequence (TS) to solve the convergence problem of equalization caused by the interaction between fast-changing transient frequency offset (TFO) and fiber chromatic dispersion (CD) compensation in optical burst (OB)-mode systems. The DSP scheme is demonstrated to perform well by the simulation and experimentation on 128 Gbps polarization multiplexing quadrature phase-shift keying (PM-QPSK) coherent systems. Thanks to the DSP scheme, a guard interval between two OBs is no longer needed, and the valid payload can be transmitted during TFO changing from wavelength tuning. The proposed DSP scheme can reduce the overhead by ∼73% for wavelength-tunable OB-mode coherent systems compared with using guard intervals, which significantly improves the spectral efficiency of burst-mode systems.

Redesigned TDM-PON System Architecture Based on Point-to-Point Ethernet Transmission and Software Processing With General-Purpose Hardware

This article proposes a novel architecture of a time division multiplexing passive optical network (TDM-PON) system with general-purpose hardware. The system operates with the point-to-point (P2P) Ethernet protocol and software processing. The architecture is redesigned from the ground up, differing from conventional PON system architectures. In recent years, researchers have attempted to softwarize a number of PON functions such as media access control (MAC) and physical functions, which run on a general-purpose central processing unit (CPU). On the other hand, these existing systems still required PON-dedicated or programmable hardware for processing the PON specific protocol. This paper proposes a TDM-PON system that requires only general-purpose hardware; a network interface card with the use of the P2P Ethernet protocol and a general-purpose server with the use of software processing. To operate the proposed system, we newly developed burst-mode operation and multipoint MAC control schemes, while taking Link Fault Signaling and CPU processing jitter into account. We quantitatively evaluated the burst-mode transmission with P2P generic Ethernet TRx as a preliminary experiment, which showed that T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> and T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</sub> were 75 μs and less than 1 μs, respectively. Then, we measured our developed prototype system's performance for verifying the feasibility of our proposal. In specific, it achieved a 5.2 Gbps PON system consisting of an optical line terminal (OLT) server and two optical network unit (ONU) servers under the condition of a 500-ms grant cycle including a 100-ms discovery window.

High-Capacity Super-Channel-Enabled Multi-Core Fiber Optical Switching System for Converged Inter/Intra Data Center and Edge Optical Networks

The introduction of the space domain in optical communications, collectively referred as space division multiplexing (SDM), have recently gained a lot of research attention motivated by the capacity exhaustion of conventional wavelength division multiplexing (WDM) systems. SDM not only increases the capacity, but also introduces new challenges and opportunities owing to the properties of the spatial channels in the form of fiber cores, modes or a combination of both. One promising application of SDM systems could be in future edge optical networks, where multi-core fibers (MCFs) with low inter-core crosstalk may be used with packet spatial super-channels (pSSCs) and core-joint SDM optical switches in a time-slotted network. We first briefly review the state-of-the-art of SDM transmission systems and other important technologies for edge networks such as burst-mode transmission. Finally, we focus on two recent experimental demonstration of such a switching system, achieving a capacity of 53.3 Tb/s for 7 spatial channels and QPSK modulation formant and an upgraded version with 8 spatial channels and 8PSK modulation format that achieves 83.33 Tb/s.

A New CMOS Implementation for Miniaturized Active RFID Insect Tag and VHF Insect Tracking

This paper proposes a new circuit design for Very High Frequency (VHF) radio telemetry, in order to miniaturize active RFID tags for tracking small insects and bees. It presents a CMOS insect-tag implementation for generating 150 MHz burst-mode signaling scheme by employing digital approach which was not reported before. This design is vastly different from many presently available VHF tags which employs analog signal generation and discrete components. The new telemeter circuit employs a 150MHz voltage-controlled ring oscillator (VCRO) feeding into a cascade of frequency-dividers whose outputs are combined to generate an extremely low duty-cycle (LDC) burst-mode transmission signal to conserve power. In addition, it also incorporates digital-code for insect-tag identification, compared to analog methods which employs small frequency shifts from a reference f (~150MHz) to $\text{f}+{\boldsymbol{\Delta }}\text{f}$ MHz for individual tag identification. In the proposed design the strength of the modulated carrier signal is employed to track the tagged insect location through the triangulation technique. A design-rule-check (DRC) and pattern-density clean chip-tag was designed for an 8-bit identification code at a throughput of 576b/s, on a 28-nm CMOS process. It occupies an active layout area of 1600- $\mu \text{m}^{2}$ and consumes 8.2- $\mu \text{W}$ . The core transmitter employs supply-voltage of 0.6V to conserve power while the output drivers uses 1.2V for high transmitted signal strength. In addition, the new LDC burst-mode signal generation method was verified on silicon through measurements on a fabricated test chip using a 130nm CMOS process. This test circuit consumed a measured average power of only 7.07- $\mu \text{W}$ . This novel design enables the smallest tag-size (5mm $\times$ 5mm $\times$ 2.5 mm) and tag-weight (< 95mg) compared to many recent VHF tags.

Burst-Mode Synchronization for SOQPSK

We consider a comprehensive synchronization strategy for burst-mode transmission of shaped-offset quadrature phase-shift keying (SOQPSK) signals over the additive white Gaussian noise channel. Due to the similarities between SOQPSK and continuous phase modulation (CPM), we make use of recent results for synchronization of burst-mode CPMs. We first derive a training sequence that is optimal in the sense that it jointly minimizes the Cramer–Rao bounds (CRBs) for frequency offset, phase offset, and timing offset estimation. Additionally, we develop a maximum likelihood data-aided algorithm for joint estimation of the synchronization parameters for SOQPSK signals. We show that the proposed algorithm for the optimal training sequence can be adapted to work with the suboptimal training sequence that is being considered for use in burst-mode integrated network enhanced telemetry. This demonstrates an immediate practical application for our approach. We present numerical results on the mean-squared error performance of the proposed algorithm for both training sequences and for different versions of SOQPSK. The numerical results show that our joint estimation algorithm yields performance that is very close to the CRBs for all three synchronization variables. Finally, we compare the overall performance of our proposed training sequence and synchronization algorithm for different sequence lengths by simulating a burst-mode SOQPSK receiver. This allows us to employ the right training sequence length based on the desired complexity and bit error rate performance.

A Low Duty Cycle Burst-Mode Telemeter Signal Generation Technique for VHF Insect Tracking and Its CMOS Implementation

This brief presents a new circuit design for very high-frequency (VHF) radio telemetry, to miniaturize active RFID tags for tracking small insects and bees. It reports the first CMOS insect tag implementation for generating 150-MHz burst-mode telemeter signals using employing digital approach. This design is vastly different from the present PCB-based analog VHF tag which uses bipolar transistors and large passive components. The new telemeter circuit uses a 150-MHz voltage-controlled ring-oscillator (VCRO) feeding into a cascade of frequency dividers whose outputs are combined (without requiring control logic) to generate extremely low duty cycle burst-mode transmission signal to save power. In addition, it is the first advancement of the VHF telemeter that incorporates digital code for insect tag identification, compared with the present state-of-the-art analog methods which use small frequency shifts from a reference $f_{o}$ (~150 MHz) to $f_{o}+\Delta f$ MHz for individual tag identification. In the proposed design, the strength of the modulated carrier signal is used to track the tagged insect location through the triangulation technique. A DRC and pattern-density clean chip-tag was designed for an 8-bit code at a throughput of 576 b/s, on a 28-nm CMOS process. It occupies an active layout area of $1600~\mu \text{m}^{2}$ and consumes $8.2~\mu \text{W}$ .

First Ever Lowest Duty Cycle for Periodic Burst Mode Signals for Insect Telemeter Package Design

An extremely low duty cycle (LDC) generation digital circuit, for very high-frequency (VHF) radio telemetry application, is described in this article. This is done to miniaturize the package size for active radio frequency identification (RFID) tags, for tracking small insects and bees. This design is built on a silicon chip to prove the manufacturability of these LDC tags in high-volume manufacturing environments in a tiny package. The study was done to determine the total weight of this LDC tag, and it was estimated to be less than 15 mg, without battery and 95 mg with battery. This is much less compared to the existing tags that use many passive components for insect telemeter design. This kind of digital circuit is being built for the first time, where no passive components are used. Here, CMOS technology was used for generating a 132-MHz radio frequency signal at 0.0078 or less duty cycle, for saving power. The lowest duty cycle we found was close to $6.1 \times 10^{-5}$ at 132-MHz frequency. This signal comes in burst mode for about 485 ns and then remains silent until about $62.3~\mu \text{s}$ . In the new approach, for the first time, digital binary division and multiplication circuits are used for getting the lowest duty cycles. This design is different than the present printed circuit board (PCB)-based, analog VHF tags. These tags use bipolar transistors circuit and passive components. The new telemeter circuit generates about 3.2 MHz/132 MHz frequency, using a voltage-controlled ring oscillator, which then passes through multiple cascaded frequency dividers. The outputs of those frequency dividers are combined to form an LDC burst-mode transmission signal for saving the battery-operated tags, in order for the battery to last longer in the field. The chip designed in 130-nm CMOS technology was fabricated and tested using quad flat no-lead (QFN) package. It requires 0.028-mm2 active die area and consumes about 7.07- $\mu \text{W}$ power at 0.6-V power supply voltage while operating at 132 MHz.

Joint Symbol Timing and Channel Estimation for FBMC-OQAM Systems

Filter bank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) can achieve very low out-of-band radiation and is considered to be an important candidate waveform for future communication networks. However, the synchronization sequence design and channel estimation issues are complicated in FBMC-OQAM systems owing to the pulses overlap and the intrinsic interference. In this paper, we propose a new training sequence pattern with a high bandwidth efficiency. A pilot symbol and two auxiliary data symbols are used to generate a conjugate symmetric sequence in the time domain while protecting the pilots from the intrinsic interference. Thus, channel estimation can be performed directly by the pilots, and an auto-correlation symbol timing algorithm is introduced by exploiting the conjugate symmetry property. In addition, a pulse tail truncation method is proposed to improve the bandwidth efficiency for burst-mode transmission. Finally, some numerical simulation results are presented to validate the proposed symbol timing, channel estimation, and truncation methods in various scenarios.

Cold-start of coherent optical receivers with decision-aided maximum likelihood phase estimation scheme

Abstract In coherent optical communication systems adopting decision-aided maximum likelihood (DA-ML) phase estimation, receiver initialization requires transmission of a training sequence followed by data symbols. However, such a start-up scheme is infeasible under the scenarios like burst-mode transmission and multi-receiver scheme. We propose a novel cold-start concept for DA-ML receiver without using a training sequence. By adopting the M th-power scheme, initial data symbols are estimated and further utilized to start up the DA-ML receiver effectively. Extensive numerical simulations are conducted under different situations for comparison. Results verify the feasibility of the proposed cold-start scheme. Based on conventional DA-ML, adopting cold-start can effectively start up the DA-ML receiver as well as achieve comparative bit error rate (BER) performance under burst-mode transmission and multi-receiver scenarios, with good robustness and nearly the same system complexity.

Reverse Bias Voltage Controlled Burst-Mode Booster SOA in λ-Tunable ONU Transmitter for High-Split-Number TWDM-PON

This paper presents a λ-tunable optical network unit (ONU) burst-mode transmitter (B-Tx) with high output power and low burst-off-level power for high-splitnumber time and wavelength division multiplexing passive optical networks (TWDM-PONs). The proposed ONU B-Tx utilizes a burst-mode booster semiconductor optical amplifier (SOA) with a control technique for reverse bias voltage that creates an optical power absorption effect in the burstoff- level state. This paper introduces the design of the biasvoltage- state control circuit, simulations of control-circuit operation, evaluations of the static optical power-absorption effect, and burst-mode operation performance in the booster SOA operated by reverse bias voltage. High output power of over +7.4 dBm and low burst-off-level power of under −73.4 dBm∕15 GHz are successfully achieved in all upstream channels. Crosstalk penalty measurements confirm a very low penalty of under 0.1 dB, which leads to a 256 splitnumber TWDM-PON.

Burst-Mode FPGA Implementation and Error Location Analysis of Forward Error Correction for Passive Optical Networks

Forward error correction (FEC) based on Reed–Solomon coding for the burst-mode upstream traffic of passive optical networks (PONs) is analyzed in detail using flexible field-programmable gate arrays (FPGAs). In order to achieve true burst-mode transmission using FPGAs, specific architectural solutions are required. In particular, a burst-mode frame synchronizer and a burstmode Reed–Solomon decoder are described in detail and analyzed experimentally within a state-of-the-art longreach PON test-bed. During this analysis, the upstream FEC performance is impaired by introducing strongly correlated and localized errors within the burst through the reduction of the burst preamble duration. The observed FEC degradation is exhaustively analyzed by implementing on the FPGAs a tool for error location analysis and frame loss measurements. This investigation demonstrates the importance of understanding the error distribution within the burst in order to correctly estimate the FEC performance in PON upstream links.

Efficient polling cycle adaptive passive optical network for low-latency 5G fronthaul

Under the large and ubiquitous bandwidth requirements of the upcoming 5G era, new common public radio interface (CPRI) solutions (such as eCPRI) characterized by scale flexible, packet-based bandwidth reduction are receiving extensive attention. In this context, applying a passive optical network (PON) into the mobile fronthaul (MFH) has good prospects due to the features of low cost and wide coverage. However, the millisecond-level latency of the dynamic bandwidth allocation (DBA) procedure exceeds the harsh latency constraints of 5G MFH, and the uneven distribution of traffic caused by user mobility brings waste or congestion of MFH bandwidth resources. To meet the latency constraint and simultaneously improve bandwidth utilization, we propose a flexible time- and wavelength-division multiplexed passive optical network (TWDM-PON)-based MFH architecture, in which optical network units (ONUs) can be dynamically grouped to support efficient use of the bandwidth and adaptive polling cycle. Based on this architecture, the influence of the propagation time on latency is analyzed, and a joint bandwidth and latency constraint (JBL) grouping algorithm is proposed to obtain the appropriate ONU group for different network slice scenarios. The simulation results indicate that, in the case satisfying the latency constraint, the bandwidth utilization reaches 94% and above (maximum 99.5%). Simultaneously, within different slicing scenarios, the polling cycle can be increased by 98% on average (maximum 122%) or decreased by a maximum of 36μs. Compared with the non-grouping situation, the adaptive polling cycle lowers the performance requirement of the hardware device (such as a burst mode transmitter), expands the MFH coverage, and improves the channel utilization.

Comparison of NRZ and duo-binary format in adaptive equalization assisted 10G-optics based 25G-EPON

We investigate and compare the requirements of FFE/DFE based adaptive equalization techniques for NRZ and Duo-binary based 25-Gb/s transmission, which are two of the most promising schemes for 25G-EPON. A 25-Gb/s transmission system based on 10G optical transceivers is demonstrated and the performance of only FFE and combination of FFE and DFE with different number of taps are compared with two modulation formats. The FFE/DFE based Duo-binary receiver shows better performance than NRZ receiver. For Duo-binary receiver, only 13-tap FFE is needed for BtB case and the combination of 17-tap FFE and 5-tap DFE can achieve a sensitivity of −23.45 dBm in 25 km transmission case, which is ∼0.6 dB better than the best performance of NRZ equalization. In addition, the requirements of training sequence length for FFE/DFE based adaptive equalization is verified. Experimental results show that 400 symbols training length is optimal for the two modulations, which shows a small packet preamble in up-stream burst-mode transmission.