Over 10 Gb/s regenerators using monolithic ICs for lightwavecommunication systems

The design and performance of repeater circuits based on Si and GaAs MESFET process technologies are described. Repeater circuits were designed and fabricated for around 10 Gb/s repeater systems using Si and GaAs IC processes. The Si ICs operated up to 9 Gb/s, and the GaAs ICs exceeded 10 Gb/s. It was verified that regenerative repeater systems using these ICs and optical amplifiers exhibit a stable operation at 10 Gb/s. The performance of the 10 Gb/s repeater using these monolithic ICs and photonic circuits is discussed     

High-speed lightwave communication ICs based on III-V compoundsemiconductors

Ultra-high-speed ICs are one of the keys to achieving large-capacity lightwave communications systems. This article reviews advances in lightwave communication ICs based on III-V compound semiconductors developed to obtain next-generation 40-Gb/s/wavelength channel systems     

Principles for electronic equalization of polarization-mode dispersion

System performance of optical fiber transmission in the presence of polarization-mode dispersion (PMD) can be improved by various types of electronic equalizers, which will be discussed in this paper. After a brief review of equalization and detection theory, equalizer concepts are adapted to the nonlinear optical channel and the architecture is optimized for high bit rate applications. Simulation results accounting for implementation losses in state-of-the-art technologies and realistic transmission conditions indicate that these concepts provide adequate solutions for equalization in lightwave transmission systems.     

Long-wavelength optical fiber communication

Recent research on long-wavelength lightwave communication utilizing the wavelength region between 1.3 and 1.6 µm is reviewed with an eye toward future system development. The attraction of the long-wavelength region is the availability of the ultimately low-loss and wide-band features of the silica fiber, where minimum loss is 0.27 dB/km at a wavelength of 1.3 µm and 0.16 dB/km at 1.55 µm. The single-mode fiber has found its first significant applications in long-wavelength systems. The specific characteristics of lightwave components are discussed with focus on physical fundamentals. The practical performance of fibers and lightwave devices is surveyed. The dynamic properties of long-wavelength laser diodes are discussed in relation to fiber characteristics. The noise characteristics of long-wavelength detectors are considered for the purpose of specifying the repeater spacing. Some system studies are reviewed, for example, 1.3-µm-wavelength lightwave systems, which have demonstrated bandwidth-distance products of about 40 GHz ċ km. Various approaches to extend the capacity of long-wavelength lightwave transmission are given. In the future, the 1.5-µm wavelength system could operate at the lowest loss wavelength region extending from 1.5 to 1.65 µm. Much higher performance, for example, bandwidth-distance products of 185 GHz ċ km, achieved by further continuation of research and development on lightwave sources as well as fibers. Because of the author's familiarity with work in Japan, that work is emphasized and most frequently cited.     

Recent progress in amplified undersea systems

The advent of the optical amplifiers has removed the loss limitation of the fiber in the conventional undersea systems using 3R (retiming, reshaping, regenerating) repeaters, and it has introduced new design criteria for the undersea lightwave systems. The accumulation of the small impairment factors that was negligible in the conventional system becomes significant to determine the transmission performances of the amplified system. The fiber nonlinearity is a distinctive limitation factor that dominates the transmission performance of the amplified system, although it was not a limitation factor in the conventional system. This paper describes the recent progress of the undersea lightwave cable systems employing optical amplifier repeaters. The limitation factors and the polarization dependent characteristics of the amplified system are described. The system demonstrations with conventional IM-DD technology are presented using both recirculating loop and straight fiber transmission line. The system maintenance method is also explained briefly. Future technologies adopting the WDM or the optical solitons are also discussed     

Performance of directly modulated DFB lasers in 10-Gb/s ASK, FSK,and DPSK lightwave systems

A comparison is presented of the performance of amplitude-shift-keying (ASK), frequency-shift keying (FSK), and differential-phase-shift-keying (DPSK) lightwave systems which operate at 10 Gb/s with directly modulated 1550-nm distributed feedback (DFB) laser transmitters and conventional 1310-nm dispersion-optimized fiber. Computer modeling techniques were used to accurately simulate the amplitude modulation response and the frequency modulation response of DBF lasers. The system performance is evaluated from simulated eye patterns for both direct and heterodyne detection. With the narrow-optical spectral widths of these signal formats, fiber chromatic dispersion limits up to 70 km were obtained for transmission at 1550-nm using conventional 1310-nm optimized fiber     

A TDMA satellite communication system for ISDN services

The authors propose a TDMA (time-division multiple-access) satellite communication system suitable for both basic and primary ISDN services in addition to B-channel transmission lines among ISDN switches. To provide these services economically and efficiently, the proposed system uses an offset quadrature phase-shift keying (QPSK) burst model coupled with high-coding gain and rate-forward-error correction, demand assignment technology for each data burst, and a transmission and reception transponder (carrier) hopping scheme. To realize cost-effective transmission and subscriber lines and to increase the reliability of TDMA terminals, the major functions of TDMA terminals have been implemented in large-scale integrated circuits (LSICs), monolithic ICs (MICs) and hybrid ICs (HICs). The experimental results show narrow spectrum transmission with little bit error probability degradation for the offset QPSK burst modem and perfect operation of demand assignment and carrier hopping capability of the system     

多路FM－SCM光波系统研制

介绍我们研制的多路ＦＭ－ＳＣＭ（调频副载波复用）光波系统及其性能，讨论了ＳＣＭ光波系统的噪声。该系统主要可用于多路ＣＡＴＶ光纤传输。采用Ｆ－Ｐ腔ＬＤ和ＰＩＮ－ＦＥＴ接收组件，通过系统优化，实现了接收端输出电视图象信号ＳＮＲ＞５５ｄＢ。     

Performance limitations imposed on all-optical ultralong lightwavesystems at the zero-dispersion wavelength

The performance limitations imposed on all-optical transoceanic lightwave systems are discussed. Specifically, the performance of a 8910-km-long 5-Gb/s communication system with in-line optical amplifiers is evaluated. The analysis, which is performed both analytically and with the aid of computer simulations, considers the impact of the transmission impairments on the system performance. In particular, the impairments due to the accumulated amplified spontaneous emission noise, the fiber dispersion, the fiber nonlinearity and polarization effects are analyzed, and improvement methods are suggested     

CMOS 2.4 μm chaotic oscillator: experimental verification ofchaotic encryption of audio

The authors report the first experimental verification of chaotic encryption of audio using custom monolithic chaotic oscillators. We use G_m-C techniques to realise a chaotic modulator/demodulator IC that implements a 3rd-order nonlinear differential equation. This has been fabricated in 2.4 μm double-poly technology and includes on-chip tuning circuitry based on amplitude detection. Measurements demonstrate how to exploit the synchronisation between two of these ICs for encrypted transmission     

Lightwave systems with optical amplifiers

Fiber-optic communication systems using semiconductor laser amplifiers are investigated theoretically and experimentally. The noise and bit-error-rate characteristics of lightwave systems with optical amplifiers are calculated and the dependence of system performance on amplifier characteristics such as optical bandwidth, noise figure, gain, etc., is shown. Experimental results for both a 4-Gb/s optical preamplifier as well as coherent and direct detection systems with four inline amplifiers are presented     

Theory of signal degradation in semiconductor laser amplifiers indirect detection systems

Theoretical studies are carried out on long haul direct detection optical fiber communication systems, with inline optical semiconductor amplifier repeaters. Calculations are made of the noise, eye diagrams, and bit-error-rate characteristics of lightwave systems with optical amplifiers. Indications are given of the effect of amplifier characteristics such as spontaneous noise and signal distortion due to gain saturation on the system performance. The nonlinear process within semiconductor laser amplifiers leads generally to pulse amplitude-temporal distortions due to gain saturation. This theoretical study demonstrates that the system penalty caused by these nonlinear effects appears progressively as the optical input power at each amplifier is increased. For example, nonregenerated fiber transmission using traveling wave semiconductor laser amplifiers was simulated, and results obtained at 0.5 and 2.5 Gb/s are presented. In order to improve the system performance, the influence of structure and bulk dimensions of the amplifier cavity is also considered     

The effect of chirping-induced pulse shaping on the performance of11 Gbit/s lightwave systems

The influence of laser chirping, fiber chromatic dispersion, and receiver filtering on the shape of the pulses in 11 Gb/s lightwave transmission systems is discussed. Both the NRZ and RZ encoding formats are considered as well as positive and negative dispersion. The results quantify the sensitivity of the system performance to the receiver decision time, the maximum permissible deviation of the laser wavelength from the fiber zero dispersion wavelength, and the improvement in transmission performance offered by pulse compression arising from negative dispersion     

Adaptive nonlinear cancellation for high-speed fiber-optic systems

The authors propose techniques for adaptive nonlinear cancellation of intersymbol interference (ISI) in the electrical signal at the receiver in Gb/s lightwave systems and describe several demonstrations of these techniques. Techniques for adjustable nonlinear cancellations are discussed and demonstrations of these techniques using commercially available integrated circuits (ICs) at data rates as high as 1.7 Gb/s are described. Techniques for automatic adjustment are discussed, and a demonstration of adaptive nonlinear cancellation at 450 Mb/s is described. The authors discuss how these techniques can be integrated onto the detector IC for operations at 2.5 Gb/s and higher data rates. These techniques allow a single IC detector with adaptive nonlinear cancellation to be used in long-haul and undersea lightwave systems to optimize the detector threshold and compensate for the ISI     

A WDM-PON with DPSK modulated downstream and OOK modulated upstream signals based on symmetric 10 Gbit/s wavelength reused bidirectional reflective SOA

We investigate a wavelength-division-multiplexing passive optical network (WDM-PON) with centralized lightwave and direct detection. The system is demonstrated for symmetric 10 Gbit/s differential phase-shift keying (DPSK) downstream signals and on-off keying (OOK) upstream signals, respectively. A wavelength reused scheme is employed to carry the upstream data by using a reflective semiconductor optical amplifier (RSOA) as an intensity modulator at the optical network unit (ONU). The constant-intensity property of the DPSK modulation format can keep high extinction ratio (ER) of downstream signal and reduce the crosstalk to the upstream signal. The bit error rate (BER) performance of our scheme shows that the proposed 10 Gbit/s symmetric WDM-PON can achieve error free transmission over 25-km-long fiber transmission with low power penalty.     

Performance characteristics and applications of hybrid multichannelANI-VSB/M-QAM video lightwave transmission systems

The performance characteristics and applications of hybrid multichannel amplitude modulation vestigal sideband (AM-VSB)/M-quadrature amplitude modulation (QAM) video lightwave transmission systems operating at either 1310 or 1550 nm are reviewed. These systems can transport up to 80 AM-VSB video channels and more than 30 64/256-QAM digital video channels over a standard single-mode fiber (SMF) using a single laser transmitter. Five main transmission impairment mechanisms for these systems are reviewed as follows: (a) clipping-induced impulse noise, (b) bursty nonlinear distortions, (c) multiple optical reflections, (d) stimulated Brillouin scattering, and (e) self-phase modulation. For AM-QAM video lightwave trunking applications, the in-line erbium-doped fiber amplifier (EDFA) selection is discussed using a frequency-domain simulation model. Such lightwave trunking systems can provide an AM carrier-to-noise ratio (CNR) greater than 50 dB with composite second order (CSO) and composite-triple-beat (CTB) distortions less than -65 dBc, and nearly error-free transmission (BER⩽10^-9) for the 64-QAM channels with signal-to-noise ratio (SNR) of 30-dB or better. Comparison between 64-QAM and 256-QAM video channel transmission and the effect of the QAM channels on the AM-VSB channels are also presented. The implications of these results and others in hybrid multichannel AM-QAM video lightwave trunking systems are discussed     

8 Gb/s 8:1 multiplexer and 1:8 demultiplexer IC's using GaAs DCFLcircuit

High-speed 8:1 multiplexer and 1:8 demultiplexer ICs composed of GaAs direct-coupled FET logic (DCFL) have been designed and fabricated. The ICs were designed with a tree-type architecture and using memory-cell-type flip-flops (MCFFs). Self-aligned GaAs MESFETs with a gate length of 0.5 μm were used in these ICs. The propagation delay time of the DCFL inverter was 19.0 ps/gate. Both ICs operated up to 8 Gb/s with power dissipations of 1.5 W for the multiplexer and 1.9 W for the demultiplexer at a single power supply voltage of 2.0 V. These ICs are applicable for multigigabit lightwave communication systems     

Operation trial of 400 Mbit/s submarine optical transmission system

The letter reports the 8000 m deep-sea trial of a 400 Mbit/s submarine optical system, FS-400M, which was carried out in the Ogasawara trench in November 1984. Two repeaters fully integrated by six monolithic ICs, and 28 km-long submarine cables were used. In addition to transmission experiments for repeater spacing of 40 km, repair operation was simulated to confirm operational feasibility of the FS-400M.