Time Division Multiplexing System Research Articles

All-optical TDM data demultiplexing at 80 Gb/s with significant timing jitter tolerance using a fiber Bragg grating based rectangular pulse switching technology

We demonstrate the use of fiber Bragg grating based pulse-shaping technology to provide timing jitter tolerant data demultiplexing in an 80 Gb/s all-optical time division multiplexing (OTDM) system. Error-free demultiplexing operation is achieved with /spl sim/6 ps timing jitter tolerance using superstructured fiber Bragg grating based 1.7 ps soliton to 10 ps rectangular pulse conversion at the switching pulse input to a nonlinear optical loop mirror (NOLM) demultiplexer comprising highly nonlinear dispersion shifted fiber (HNLF). A 2-dB power-penalty improvement is obtained compared to demultiplexing without the pulse-shaping grating.

A SiGe HBT IC CHIPSET for40-Gb/s OPTICAL TRANSMISSION SYSTEMS

Using a 0.2-μm self-aligned epitaxial-growth silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) technology, we have developed a chipset for 40-Gb/s time-division multiplexing optical transmission systems. In this paper, we describe seven analog and digital ICs: a 45-GHz bandwidth transimpedance amplifier, a 48.7-GHz bandwidth automatic-gain-controllable amplifier, a 40-Gb/s decision circuit, a 40-Gb/s full-wave rectifier, a 40-Gb/s limiting amplifier with a 32-dB gain, a 45-Gb/s 1:4 demultiplexer, and a 45-Gb/s 4:1 multiplexer. To increase bandwidth of the transimpedance amplifier, a common-base input stage is introduced. In order to have high gain and wide bandwidth simultaneously, active load circuits composed of a differential transimpedance amplifier are used for the AGC amplifier, the limiting amplifier, and the decision circuit. Full-rate clocking is employed to reduce the influence caused by clock-duty variation in digital circuits such as the decision circuit, the demultiplexer, and the multiplexer. All ICs were characterized by using on-wafer probes, and some of them were built in brass-packages for bit-error rate measurement.

Pedestal-free 10-GHz pulse compression using comb-like dispersion profiled fibers and its application in 40-Gb/s OTDM systems

A phase shift increasing method (PSIM) is proposed to construct a comb-like dispersion profiled fiber (CDPF) with an optimum-designed dispersion map. Using this CDPF, a 10-GHz, 12-ps pulse generated from an actively mode-locked Er 3 + -doped fiber ring laser (AML-EDFL) is compressed to 2 ps without a pedestal. The compressed optical pulse source is used in a 40-Gb/s 247-Km optical time-division multiplexing (OTDM) system with a transmission power penalty of 0.42 dB.

Impact of fiber chromatic dispersion in high-speed TDM transmission systems

General guidelines for high-speed time-division multiplexing (TDM) data-rate transmission are essential for the increase of the overall transmission capacity. In this paper, general theoretical investigations concerning fiber chromatic dispersion in optical TDM systems are performed. Recent experiments that confirm the theoretical predictions are presented. Nonzero dispersion-shifted fiber and standard single-mode fiber are recommended for 40 and 160 Gb/s, respectively, independent of the chromatic dispersion compensation scheme.

Interferometric noise in optical time division multiplexing transmission system

A theoretical assessment of the interferometric noise in the optical time division multiplexing (OTDM) transmission system is presented. The impact of such noise on the system performance were investigated in detail. The corresponding system requirements were also revealed by the calculation results. Recommendations on the use of prechirping to reduce the interferometric noise in the OTDM system are given.

Effects of fourth-order dispersion in very high-speed optical time-division multiplexed transmission

We present a closed-form expression for computation of the output pulse's rms time width in an optical fiber link with up to fourth-order dispersion (FOD) by use of an optical source with arbitrary linewidth and chirp parameters. We then specialize the expression to analyze the effect of FOD on the transmission of very high-speed linear optical time-division multiplexing systems. By suitable source chirping, FOD can be compensated for to an upper link-length limit above which other techniques must be employed. Finally, a design formula to estimate the maximum attainable bit rate limited by FOD as a function of the link length is also presented.

Effects of pulse chirp on supercontinuum produced in dispersion decreasing fibre

The supercontinuum (SC) source plays a key role in wavelength division multiplexing over the optical time division multiplexing (WDM/OTDM) transmission system. The SC produced in dispersion decreasing fibre (DDF) is wider and flatter than that produced in dispersion shifted fibre (DSF). In this paper, a SC producing process in DDF is numerically simulated, the effects of pump pulse chirp on the SC width and flatness are initially studied and the corresponding theoretical explanations are given. Particularly, we have analysed and compared the evolutions of the SC along DDF pumped by different chirp pulses. Several valuable conclusions are obtained.

Comparison of interferometric all-optical switches for demultiplexing applications in high-speed OTDM systems

We have investigated three interferometric all-optical switches based on cross-phase modulation (XPM) in semiconductor optical amplifiers (SOAs), the semiconductor laser amplifier in a loop mirror (SLALOM) switch, the Mach-Zehnder interferometer (MZI) switch, and the ultrafast nonlinear interferometer (UNI) switch. Switching windows with different widths are measured under similar conditions for all three switching configurations. We introduce the integrated contrast ratio (ICR) as a measure to evaluate the performance of a switch from switching windows. Using the ICR, the switches are compared and their application is discussed as demultiplexer in optical time division multiplexing (OTDM) systems for data rates of 40, 80, and 160 Gb/s.

Prescaled clock recovery based on small timing misalignment of data pulses

A simple and robust prescaled clock recovery technique is analyzed and demonstrated. An electrical clock is extracted from an ultra-high-speed time-division multiplexed (TDM) RZ signal using a classic approach to clock recovery with a detector and a bandpass filter (BPF). A subharmonic tone at the base rate frequency is generated by inducing a small misalignment between adjacent pulses in the transmitted data. The subharmonic tone is recovered as a clock signal at the receiver. Numerical calculations clarify the effect of filter bandwidth, word length, and strength of timing shift on the received timing jitter. Furthermore, it is found numerically that correlated TDM channels will decrease the jitter of the recovered clock considerably. A clock recovery circuit is implemented into an experimental 40 Gb/s and 80 Gb/s optical TDM (O-TDM) system without any observed penalty. Measurements of the timing jitter of the recovered prescaled clock have been performed to verify the numerical results. A 10 GHz clock signal with subpicosecond root-mean-square timing jitter is recovered from a 40-Gb/s O-TDM sequence without a phase-locked loop (PLL) configuration. By using a PLL-configuration, the timing jitter is reduced further by 50%. A discussion on the influence on transmission capacity is performed in general and for nonlinear optical communication systems in particular.

Bit error rate analysis of OTDM system based on moment generation function

The performance of optical time division multiplexing (OTDM) system is limited by a complex combination of noise. In this paper we present a theoretical framework for the optical receiver in OTDM system based on the moment generation function. The proposed receiver model is showed to be more accurate in predicting the bit error rate (BER) performance than the former ones. Its validity is also verified by the experimental results.

Receiver performance analysis and basic design for optical time‐division multiplexed transmission systems

The characteristics of the receiver used for an optical time-division multiplex transmission system are studied from the signal-to-noise ratio point of view. The receiver, which is characterized by having an optical time-division demultiplexing circuit, has so far been the subject of experimental and analytical discussion only regarding the characteristics of the optical demultiplexing circuit. Taking into account the signal pulse width of the received signal and the frequency bandwidth of the baseband circuit in addition to the optical demultiplexing circuit, we derive the expression of the signal-to-noise ratio, resulting in a systematic analysis of the receiver, which has never before been attempted. For the receiver with an optical time-division demultiplexing circuit, the optimum and allowable baseband bandwidth are quantitatively presented in terms of the signal pulse width and the optical noise power. This provides basic guidelines of receiver design. For instance, when a 20 Gbit/s signal with a 20-ps pulse width is optically demultiplexed into 10 Gbit/s, with a rectangular optical gate, the optimum baseband width is 6.3 GHz. Even for different pulse widths, this bandwidth exhibits signal-to-noise ratio degradation of 1 dB or less in comparison to the receiver with an optimized bandwidth. Furthermore, the requirements for the modulation depth and the width of the optical gate, as well as the phase difference between the optical gate and the signal pulse are discussed. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 83(4): 93–104, 2000

Fully electrical 40-Gb/s TDM system prototype based on InP HEMT digital IC technologies

This paper presents a fully electrical 40-Gb/s time-division-multiplexing (TDM) system prototype transmitter and receiver. The input and output interface of the prototype are four-channel 10-Gb/s signals. The prototype can be mounted on a 300-mm-height rack and offers stable 40-Gb/s operation with a single power supply voltage. InP high-electron mobility transistor (HEMT) digital IC's perform 40-Gb/s multiplexing/demultiplexing and regeneration. In the receiver prototype, unitraveling-carrier photodiode (UTC-PD) generates 1 V/sub pp/ output and directly drives the InP HEMT decision circuit (DEC) without any need for an electronic amplifier. A clock recovery circuit recovers a 40-GHz clock with jitter of 220 fs/sub pp/ from a 40-Gb/s nonreturn-to-zero (NRZ) optical input. The tolerable dispersion range of the prototype within a 1-dB penalty from the receiver sensitivity at zero-dispersion is as wide as 95 ps/nm, and the clock phase margin is wider than 70/spl deg/ over almost all the tolerable dispersion range. A 100-km-long transmission experiment was performed using the prototype. A high receiver sensitivity [-25.1 dBm for NRZ (2/sup 7/-1) pseudorandom binary sequence (PRBS)] was obtained after the transmission. The 40-Gb/s regeneration of the InP DEC suppressed the deviation in sensitivity among output channels to only 0.3 dB. In addition, four-channel 40-Gb/s wavelength-division-multiplexing (WDM) transmission was successfully performed.

Network resource advantages of bidirectional wavelength-path switched ring

Wavelength-division-multiplexing (WDM) transport ring-network architectures analogous to conventional time-division multiplexing systems are disadvantageous in that they require either an increase in the necessary number of wavelengths, or long optical-transmission brought about by loop-back, thus raising costs. We have studied a transport WDM ring network in which the switching unit is wavelength and the standby resources are shared. Its advantages are confirmed by evaluation of the necessary number of wavelengths, the maximum circumference for a transparent ring, and the number of 3R-regenerators (3R: reshaping, regeneration, and retiming) for a large-sized opaque ring network.

Technology of InP-based 1.55-μm ultrafast OEMMICs: 40-Gbit/s broad-band and 38/60-GHz narrow-band photoreceivers

For future long-haul communication systems operating at bitrates of 40 Gbit/s and for broad-band mobile access systems using 38- or 60-GHz carrier frequencies, ultrafast photoreceivers have to be provided. Therefore, an integration concept for InP-based optoelectronic microwave monolithic integrated circuits for the 1.55-/spl mu/m wavelength regime is demonstrated, which allows independent optimization of the constituting devices. Two different types of photodetectors (PDs), a waveguide-integrated PIN photodiode (PD) and a top-illuminated metal-semiconductor-metal PD, both having bandwidths of up to 70 GHz, have been developed. These are fabricated together with different amplifier designs employing high electron mobility transistors which exhibit transit frequencies of up to 90 GHz. The application to a 40-Gbit/s broadband photoreceiver for high-bit-rate time-division multiplexing systems is reported, as well as the application to 38- and 60-GHz narrow-band photoreceivers for use as optic/millimeterwave converters in mobile communication systems.

Photonic Technologies for Ultra-High-Speed Information Highways I. 40 Gbit/s TDM Components and Subsystems

The ACTS project HIGHWAY (AC067) addresses promising ultra-high speed optoelectronic components and system technologies for 40 Gbit/s time-division-multiplexed (TDM) transport systems. Advanced 40 Gbit/s TDM system lab demonstrators are to be realized and tested over installed field fiber testbeds. This paper reviews the current status of 40 Gbit/s TDM components and subsystem technologies achieved in HIGHWAY. The results of HIGHWAY 40 Gbit/s TDM systems and field tests will be reported in a subsequent paper.

SiGe driver circuit with high output amplitude operating up to 23 Gb/s

A high-speed driver circuit is presented with special regard to layout aspects. The IC, which was fabricated in an advanced SiGe bipolar technology, was developed for driving external modulators in a 20 Gb/s fiber-optic time division multiplex transmission system but can also be used as an output stage of multipurpose pulse generators. Measurements on mounted chips show clear eye diagrams up to 23 Gb/s data rate and high single-ended and differential output swings of 3.5 and 7 V/sub p-p/, respectively, at 50 /spl Omega/ external load. To the best of the authors' knowledge, this is the highest voltage swing reported so far for a silicon-based driver circuit at comparable operating speed.

Towards multi-patient leadless and wireless cardiotocography via RF telemetry

During labour the condition of the fetus is monitored by a cardiotocograph which displays fetal heart rate and a measure of uterine contractions. Ultrasound and tocodynamometer transducers are placed on the mother's abdomen and connected to a bedside monitor and display unit via a cable. This paper describes a prototype wireless system aimed at demonstrating the potential elimination of the cable which is undesirable in a number of respects. The radio link utilised operates at a frequency of 418 MHz with data compression and time division multiplexing (TDM) employed to allow up to 10 units to operate simultaneously on the same frequency in the same area. Data compression is achieved by extracting the Doppler ultrasound signal envelope and representing the frequency content of the signal using a zero crossing counting technique. Two Medium Access Control (MAC) protocols were considered, with a synchronised time division multiplexing system shown to offer greater throughput and resistance to interference than Carrier Sense Multiple Access (CSMA). This wireless RF telemetry system could be readily adapted for other multi-patient monitoring applications.

Recent progress of integrated optics planar lightwave circuits

Planar lightwave circuits (PLCs) are waveguide devices that integrate fiber-matched optical waveguides on silicon or glass substrate to provide an efficient means of interaction for the guided-wave optical signals. PLCs provide various important and functional devices for optical wavelength division multiplexing (WDM), time division multiplexing (TDM) systems and subscriber networks. This paper reviews the recent progress and future prospects of PLC technologies including arrayed-waveguide grating multiplexers, optical add/drop multiplexers, programmable dispersion equalizers and hybrid optoelectronics integration technologies.

State-of-the-Art and Future Perspectives of Time Division Multiplexing (TDM) High Bit Rate Optical Transmission.

This paper reviews state-of-the-art technologies that will play important roles in high bit rate transmissionsystems. To take full advantage of fiber capacity, combined multiplexing of WDM (Wavelength Division Multiplexing) and TDM (Time Division Multiplexing) technologies is recommended. Not only device technologies, but also system-side viewpoints are emphasized in order to clarify the differences between TDM and WDM systems. Linear transmission and nonlinear ones, which includes optical soliton systems are comparedfrom such a viewpoint. Short light pulse sources, electrical and optical time-division multiplexing/demultiplexing, timing extraction, dispersion tolerant coding, equalization for second- and third-order dispersionof dispersion-shifted fiber, and optical soliton transmission technologies are described. This paper predictsthat pursuing increased transmission capacity will result in more combined designs of detailed fiberdispersion and transmitted optical signal parameters.

Considerations on adaptive techniques for time-division multiplexing radio systems

This paper addresses the problem of providing a fair comparison among the performance of the different techniques that adapt the transmission parameters, such as the modulation, power, and bit rate, to the channel characteristics. A coordinated time-division multiplexing (TDM) scheme is adopted. Both an isolated cell scenario and a cellular system scenario are taken into consideration. In the single-cell case, closed-form expressions of the optimum power and modulation adaptation law are found. It is shown that the examined techniques offer a similar performance in most cases, although modulation adaptation is somewhat superior to power control in the cellular case. It is made clear that the improvement obtained by adopting an adaptive technique should not be evaluated without specifying the acceptable consequences on service distribution because it is the service distribution that determines the achievable gain ultimately. Previously, a new wireless access system, called Infostations, has been proposed which provides isolated pockets of high-bandwidth connectivity for future data and messaging services. Although the main considerations hold in general, they are particularly useful for defining a time multiplexing scheme for Infostations.