Burst-mode Transmission Research Articles

Burst-Mode Clock Recovery Utilizing Relaxation Oscillation in Directly Modulated Lasers

A novel clock recovery scheme utilizing the relaxation oscillation in a directly modulated laser (DML) for burst-mode transmission is proposed for the first time. In this scheme, the DML generates the clock tone along with the transmitted non-return-to-zero data in the optical signal. An injection-locked oscillator (ILO) is employed in the receiver to extract the clock tone and restore the clock. The proposed scheme is investigated systematically and verified by simulations with different laser modulation currents as well as some nonideal characteristics of the system. The simulation results show that the low cost clock recovery method using an ILO in an optical link using a regular DML is highly efficient for burst-mode transmission at 10 Gbps.

Performance analysis of forward error correcting codes in IPTV

In recent years the forward error correction (FEC) schemes at the binary erasure channel have been researched for many applications including DVB-H and IPTV systems. In most cases the packet-level FEC strategies are implemented by either Reed-Solomon (RS) codes at the link layer or Raptor codes at the application layer. Recently an enhanced decoding method for RS codes was presented. The enhanced-decoding scheme is a combination of erasure and error decoding. In this paper we consider the performance comparison of the enhanced-decoding RS code at the link layer and Raptor code at the application layer in the burst mode transmission to give a guidance of FEC scheme for IPTV application. It is noted that the efficient Raptor decoding algorithm makes it possible to broadcast multimedia data more reliable and faster.

A Clock Recovery Scheme utilizing Fiber Dispersion for Burst Mode Transmission

A novel clock recovery scheme for burst mode (BM) transmission is proposed and analyzed. The method utilizes the characteristics of the non-return-to-zero (NRZ) signals propagating through a dispersive single mode optical fiber (SMF) at wavelength around 1550 nm to extract the clock information. The amplified photocurrent carrying the generated clock information by the fiber dispersion is fed directly into the injection locked oscillator (ILO) without perfonning conversions between currents and voltages. The proposed scheme is investigated systematically by simulation and the trade-offs between the transmission reach and the locking time is examined. It is shown that the clock recovery method is highly effective for burst mode transmission reach of 17 -38 km at 10 Gbit/s, which is typical of access networks.

Burst-mode optical transmitter with DC-coupled burst-enable signal for 2.5-Gb/s GPON system

In this paper, first burst-mode transmitter for 2.5-Gb/s gigabit-capable passive optical networks (GPON) system is evaluated. Small form factor (SFF) type optical network unit (ONU) generates 2.5-Gb/s optical eyes with commercial distributed feedback-laser diode (DFB-LD). For the fast burst signal access, burst enable (BEN) connection on the evaluation board utilizes DC-coupling configuration. Resultant optical output waveform shows 16.30dB extinction ratio with wide eye opening for GPON mask test. No significant eye degradation is detected in high temperature operation and after 10km distance transmission. Proposed GPON ONU successfully shows fast timing characteristics of 2.17nsec for Tx enable stage and 1.17ns for Tx disable stage.

OBT: Optical Burst Transport in Metro Area Networks

For the past few years, the evolution of electro-optical technology has driven change in optical networks in the access and backbone areas. Optical bypassing and traffic aggregation mitigate the scalability problem in backbone networks, and burst mode transmission can provide a cost-efficient solution for access networks. Using those technologies, a new solution can be found for metro area networks, which interconnect access and backbone networks. In this article, we introduce a new solution for metro area networks, called optical burst transport (OBT). OBT is designed to use the promising technologies of backbone and access networks so that it provides all benefits, such as dynamic bandwidth provisioning, scalability, and robustness for unbalanced traffic. The performance evaluation of OBT also is verified by means of a testbed implementation.

Impairments Due to Burst-Mode Transmission in a Raman-Based Long-Reach PON Link

A recently proposed passive-optical-network (PON) link based on distributed Raman amplification is tested with disturbing burst-mode traffic. The resulting impairments are quantified through penalty measurements on a single surviving data channel as a function of the disturbing channel power. When the disturbing channels co- or counter propagate with the data channel, penalties of less than 1 dB are found for disturbing input powers up to 7 and 11 dBm, respectively. The penalty is further reduced when a moderate amount of continuous-wave light is used to clamp the gain. The results indicate that the highly linear PON link is a promising candidate for long-reach feeder links in future, high-capacity PON systems with burst-mode traffic.

Estimation techniques for GMSK using linear detectors in satellite communications

This paper describes data-aided signal level and noise variance estimators for Gaussian minimum shift keying (GMSK) when the observations are limited to the output of a filter matched to the first pulse-amplitude modulation (PAM) pulse in the equivalent PAM representation. The estimators are based on the maximum likelihood (ML) principle and assume burst-mode transmission with known timing and a block of L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> known bits. While it is well known that ML estimators are asymptotically unbiased and efficient, the analysis quantifies the rate at which the estimators approach these asymptotic properties. It is shown that the carrier phase, amplitude, and noise variance estimators are unbiased and can achieve their corresponding Cramer-Rao bounds with modest combinations of signal-to-noise ratio and observation length. The estimates are used to estimate the signal-to-noise ratio. It is shown that the mean squared error performance of the ratio increases with signal-to-noise ratio while the mean squared error performance of the ratio in decibels decreases with signal-to-noise ratio. Simulation results are provided to confirm the accuracy of the analytic results.

Optical Burst Transport: A Technology for the WDM Metro Ring Networks

We propose a sublambda traffic-grooming scheme on wavelength-division-multiplexing ring networks, named optical burst transport. The network protocol and architecture are designed to support dynamic bandwidth allocation, which is more reasonable for bursty data traffic. To verify our network protocol and architecture, we build a testbed which supports burst-mode transmission. Also, we transmit streaming video over Ethernet as an application

1.25-Gb/s burst-mode receiver ICs with quick response for PON systems

This paper describes burst-mode receiver ICs with quick response for 1.25-Gb/s optical access networks. In a point-to-multipoint fiber access system, such as a passive optical network (PON) system, the receiver should be able to handle burst-data packets with different amplitudes. In burst-mode transmission, a receiver with a quick response is desired for high efficiency in data transmission. In addition, high sensitivity is also required for such a shared access system. To achieve a quick response and high sensitivity at the same time, a transimpedance amplifier (TIA) with three gain modes has been designed. The use of a hysteresis comparator enables fast gain mode switching. A limiting amplifier with feed-forward auto-offset compensation (AOC) is also used for quick response to burst data. These circuit techniques require no external adjustment. Using these design techniques, optical receiver ICs were fabricated in SiGe-BiCMOS technology. The optical receiver built with the ICs exhibits a settling time of under 20 bits and a sensitivity of -30 dBm with wide dynamic range of over 26 dB using a p-i-n photodiode (PD) for burst-mode optical input at 1.25 Gb/s. These fast-response receiver chips improve the data transmission efficiency. The use of a conventional p-i-n PD and the freedom from external adjustment make it possible to build an inexpensive receiver.

A CMOS burst-mode optical transmitter for 1.25-Gb/s ethernet PON applications

This brief presents a CMOS burst-mode optical transmitter suitable for use in 1.25-Gb/s Ethernet passive optical network applications. Based on feedback from the monitoring photodiode, in order to control consecutive burst data the proposed transmitter in this brief uses a reset mechanism, which allows fast responses from the beginning of a high-speed input burst. The chip is fabricated in mixed-mode 0.18-/spl mu/m CMOS technology and measurements are implemented in a chip-on-board configuration using a pig-tailed type Fabry-Perot laser. Under burst-mode operation of 1.25-Gb/s pseudorandom binary sequences, measurements show about 1-dBm averaged transmitted optical power with an over 12-dB extinction ratio over a wide temperature range.

A 1.25-Gb/s CMOS burst-mode optical transceiver for ethernet PON system

A 1.25-Gb/s burst-mode optical transceiver for an Ethernet Passive Optical Network (EPON) system has been developed using a 0.25-/spl mu/m CMOS technology. With the new automatic gain control (AGC) technique and reference-voltage generator (RVG), the optical receiver achieved wide dynamic range of 26.8 dB with sensitivity of -29.0 dBm and overload of -2.2 dBm at a 1.25-Gb/s burst-mode transmission. Moreover, coming up with the novel automatic optical output power and extinction ratio control (APC) system, the optical transmitter successfully suppressed their variations within /spl plusmn/0.4 dBm and /spl plusmn/0.6 dB, respectively in wide temperature range from -40 to 100/spl deg/C. This is the first CMOS optical transceiver that meets the specifications of IEEE802.3ah PX20 standard.

DC-coupled burst-mode transmitter for 1.25 Gbit/s upstream PON

An innovative DC-coupled burst-mode optical transmitter is presented for gigabit PON upstream transmission at 1.25 Gbit/s. Experimental results show that this burst-mode transmitter meets the specifications of the recently approved ITU-T Recommendation G.984.2. The chip can stabilise and control the launched optical power level with accuracy better than 1 dB over a wide temperature range.

Symbol Synchronization Technique in COFDM Systems

In this paper we focus our research on the symbol timing synchronization technique in COFDM systems. A new method utilizing pilots to do coarse symbol timing is proposed. It overcomes the problem of fluctuation of the estimated symbol start position with cyclic prefix correlation method. The symbol timing error with the proposed method is within only /spl plusmn/10 samples. Different from previous algorithms in , we utilize the known pilot information to estimate the residual symbol timing offset with low system complexity. This paper also proposes a new control model for the sampling clock adjustment, different from the phase-locked loop (PLL), or delay-locked loop (DLL) method. The simulation and correspondent Field Programmable Gate Array (FPGA) circuit through test in HDTV prototype in Team of Engineering Expert Group (TEEG) proves its feasibility and availability. The proposed method is also suitable for burst mode transmission systems such as Wireless Local Area Network (WLAN) and Fixed-Broadband Wireless Access (F-BWA).

Frequency offset estimation for OFDM in wireless communications

Timing jitter, frequency offset, carrier phase jitter and sampling clock frequency offset are the main synchronization errors encountered by OFDM systems. As many literatures have proved, OFDM systems are very sensitive to frequency errors. In this paper, three new methods to estimate the integer part of frequency offset are proposed, simulation results show its robustness to mitigate the multi-path effect and its enlarged estimation range for frequency offset. The correspondent field programmable gate array (FPGA) circuit through test in HDTV prototype in Team of Engineering Expert Group (TEEG) proves its feasibility and availability. The proposed method is also suitable for burst mode transmission systems such as wireless local area network (WLAN) and fixed-broadband wireless access (F-BWA).

Fast coarse frequency offset estimation for OFDM systems by using differentially modulated subcarriers

In this paper, we propose a fast coarse estimation method of carrier frequency offset for orthogonal frequency division multiplexing (OFDM) systems using a burst mode transmission. In the proposed method, we use two OFDM symbols for a training sequence, where the subcarriers of each training symbol are differentially modulated in phase. By exploiting the phase difference between two adjacent subcarriers of the received signal, which is proportional to the frequency offset, we estimate the even integer part of relative frequency offset (RFO). The proposed scheme has much lower computational load compared to the conventional crosscorrelation-based methods. Simulation results show that the failure rate of the proposed coarse estimator is sufficiently low and the total estimator combined with a fine estimator reveals similar estimation performance to the case of a conventional cross-correlation-based method for practical range of signal-to-noise ratio (SNR).

A simple interpolation technique for the dft for joint system parameters estimation in burst mpsk transmissions

In this paper, we propose a simple frequency-domain interpolation technique for the discrete Fourier transform (DFT). This interpolation technique can significantly improve the frequency and phase resolution capabilities of the DFT without increasing the size of the DFT (the number of points used for the DFT). This new technique employs a dividing point in the amplitude and phase spectra. Suitable areas of application include joint estimation of fine frequency and phase offsets in burst-mode digital transmission.

Blind adaptive multiple-input decision-feedback equalizer with a self-optimized configuration

This paper introduces a novel blind adaptive multiple-input decision-feedback equalizer (MI-DFE) which is basically characterized by its ability to self-optimize its configuration, in terms of both structure and criteria, according to the severity of the transmission medium. In the first running mode, the novel equalizer is recursive, linear and "blindly" adapted by criteria leading to a solution closely related to the minimum MSE solution. In the second running mode, it becomes the conventional MI-DFE. From the viewpoints of both robustness and spectral efficiency, this equalizer proves to be very attractive since it avoids pathological behaviors, often encountered with the conventional trained MI-DFE, while requiring no training sequence. Furthermore, its very high speed of convergence renders it competitive in various standard applications, even in the case of burst mode transmission systems. Finally, the novel blind MI-DFE has been successfully tested on underwater acoustic communications signals, in a very severe context. The results are clearly convincing.

Blind channel estimation exploiting transmission filter knowledge

This contribution elaborates on the concept of blind identification of multiple FIR channels with transmission filter knowledge (WTXFK). This prior knowledge could, in fact, include not only the transmitter (TX) (pulse shaping) filter but also the receiver (RX) filter present in digital communication systems. Exploitation of this side information allows the estimation to concentrate on the impulse response of the actual propagation channel itself. Hence this estimation can be done more accurately. Since the prior information is expressed in terms of the channel impulse response, we review a number of blind channel estimation methods that are parameterized directly by the channel and consider their extension to incorporate the prior knowledge. These methods include essentially subchannel response matching (SRM), subspace fitting and maximum likelihood (ML) techniques. All these methods are formulated for burst mode transmission. We also discuss performance limits in the form of Cramer–Rao bounds (CRBs). Both the methods and the CRBs are discussed in a deterministic and a Gaussian context for the unknown transmitted symbols. Simulation results indicate that the exploitation of the prior knowledge can lead to significant improvements, a capability of the extended method to identify ill-conditioned channels, that one particular version SRM WTXFK often outperforms another one, and that ML methods can still further improve performance.

On the diversity, bandwidth, and performance of digital transmission over frequency-selective slow fading channels

The issues of diversity reception, bandwidth utilization, and performance evaluation of digital transmission over slowly time-varying frequency-selective fading channels are investigated, with a transmit pulse design that is more general than previously considered. In particular, the tradeoffs among performance, bandwidth, and complexity are addressed. Three types of transmit pulses are considered and compared, including the raised cosine (RC), square-root RC (SRRC), and Gaussian pulses. Union bounds on the symbol and burst error rate are derived for maximum likelihood sequence estimation (MLSE) based on exact pairwise error probabilities for burst-mode transmission. Explicit and implicit diversity are employed to improve the system performance. The results show that the implicit diversity is flexible and easy to exploit and is a good complement to the space or other explicit diversity to further improve the system performance.

Feedforward LF compensation for laser fibre optic transmitter

Direct intensity modulation of laser optical power is probably the one most often used in practice. Classical circuits for semiconductor laser driving are not suitable for operation with unbalanced codes or data transmitted in the form of bursts. The reason for this is a low-frequency (LF) cut-off caused by the laser stabilising circuit. In the paper a concept is presented, along with practical realisation of the laser driving and stabilising circuit for unbalanced codes or burst-mode transmission. A developed circuit allows modulation of the laser diode from DC up to the maximum modulation frequency of the laser. Experimental data including pulse tests, eye pattern test and thermal properties of proposed solutions are presented.