High-speed Optical Fiber Communication Research Articles

Tail Extrapolation in MLSE Receivers Using Nonparametric Channel Model Estimation

This paper presents a method for determining the probability of rare events, in particular for probability density function (pdf) and bit error rate (BER) estimation. The derivation of the method is based on the presumption that the pdf is a member of a family of distributions very often named as the generalized exponential (GE) class of distributions. Based on high reliability estimations obtained in short simulation/measurement times, the low probably events are estimated accurately by extrapolation. The suggested method can be applied to some distributions that are different from GE distributions, such as noncentral chi-square distributions, to extrapolate to low probability events, with some extrapolation error. It can also be applied to BER estimation. The method is in particular helpful for estimating channels suffering from both severe signal distortion causing undesired intersymbol interference (ISI) of several symbols, and from severe noise. Such conditions prevail, for example, in metro and long haul high-speed optical fiber communication systems. So the method may be implemented in particular in maximum-likelihood sequence estimation (MLSE) optical receivers using nonparametric channel model estimation. A special use of the extrapolation method is explained for practical systems using trellis branch metrics derived from the estimated pdf to decode the transmitted sequence of symbols.

Error statistics during the propagation of short optical pulses in a high-speed fibreoptic communication line

Simple analytic expressions are derived to approximate the bit error rate for data transmission through fibreoptic communication lines. The propagation of optical pulses is directly numerically simulated. Analytic estimates are in good agreement with numerical calculations.

Study on the suppression of IFWM in 40 Gb/s WDM systems

The paper analyses the effects of intra-channel four-wave mixing (IFWM) on the high-speed optical fiber communication system. A new code format is developed with double 0 and double π phase separating 1 code; it can decrease the transmission penalty from fiber nonlinearity by counteracting the perturbation terms of IFWM. From the simulation of transmission of two classic code data “11011” and “11100”, we find that our proposed code format has a better suppression effect than the alternative modulation inversion (AMI) or the normal RZ format and supports a wider pulse mode. In a 40 Gbps system, the AMI format is 2 dB less than the RZ format, and our proposed format is 1 dB less than the AMI format when a 1 dB eye open penalty is taken as a metewand. Moreover, it can be realized as easily as the AMI format.

A New Class of Block Turbo Code for High Speed Fiber Optic Communication

A New Class of Block Turbo Code for High Speed Fiber Optic Communication

An alternative method to fabricate the planar-type resonant-cavity light-emitting diodes by using silicon oxide for short-reach communications

In this article, the silicon oxide (SiO x ) planarization technique is presented to fabricate the 650-nm resonant-cavity light-emitting diodes (RCLEDs). The performances of RCLEDs are characterized by forward voltage, light output power, external quantum efficiency, emission spectrum, and dynamic response. As a result, the device with the SiO x -planarized layer exhibits a low operating voltage of 2.3 V at 20 mA, a maximum light output power of 304 μW at 15 mA, and the best external quantum efficiency of 3% at 1.2 mA. In addition, the SiO x -planarized device exhibits temperature insensitivity as compared to the device without it. The RCLED with a 30-μm diameter shows the maximum 3 dB frequency bandwidth of 275 MHz at a driving current of 40 mA. Finally, the RCLED with a SiO x -planarized layer shows a clear eye-opening feature as operating at 100 Mbit/s at 20 mA. These results indicate that such LEDs are excellent candidates for use in high-speed short-reach plastic optical fiber communications.

Ultra high performance planar InGaAs PIN photodiodes for high speed optical fiber communication

This paper reports a front-illuminated planar InGaAs PIN photodiode with very low dark current, very low capacitance and very high responsivity on S-doped InP substrate. The presented device which has a thick absorption layer of 2.92 μm and a photosensitive area 73 μm in diameter exhibited the high performance of a very low capacitance of 0.47 pF, a very low dark current of 0.041 nA, a very high responsivity of 0.99 A/W (79% quantum efficiency) at λ = 1.55 μm, the 3 dB bandwidths of 6.89 GHz (−5 V), 7.48 GHz (−12 V) for bare chips and 4.48 GHz (−5 V), 5.02 GHz (−12 V) for the devices packaged in TO can, respectively. Furthermore, the developed PIN photodiodes possess high breakdown voltage of less than −25 V.

SURFACE QUALITY IN END-FACE LAPPING OF OPTICAL FIBER

The study on high quality surface formation mechanism in lapping of optical fiber end-face has become an important topic about improving performances of optical fiber connectors. With diamond abrasive lapping-films whose grain sizes are from 0.5μm to 6μm used, the optical fiber end-face lapping experiments are processed on optical fiber connector lapping machine, whose style is KE-OFP-12. The experimental results show that there are three material removal modes during lapping optical fiber, namely, brittle fracture mode, semi-brittle semi-ductile mode, and ductile mode. These modes are mainly controlled by abrasive grain size. Brittle-ductile transition's critical point appears when the lapping-films whose abrasive grain size is 3μm are used to lap optical fiber; and they are analyzed theoretically. The surface roughness from ductile lapping mode is much less than that from brittle fracture lapping mode, and the ductile lapping mode is an effective method that improves surface quality of fiber end-faces. The surface roughness Ra 5 nm can be obtained and there are not any scratches and cracks on the fiber end-face when fiber material is removed by ductile mode; it makes insertion loss and return loss of optical fiber connectors meet the requirements of high-speed and broad-brand optical fiber communication.

On new possibilities of increasing transmission capacity of high-speed fiber-optic communication lines

On new possibilities of increasing transmission capacity of high-speed fiber-optic communication lines

Simulation of autosoliton optical pulses in high-speed fibreoptic communication systems

The propagation of a pulse in a fibreoptic communication link with periodically included regenerators — nonlinear optical loop mirrors, is studied. The autosoliton propagation regime of the optical pulse is revealed. It is shown that the inclusion of a ring mirror to the communication link leads to a substantial increase in the transmission distance of the pulse at a small negative average dispersion in the link.

On new possibilities of increasing transmission capacity of high-speed fiber-optic communication lines

In this paper we propose several ways of increasing the information capacity of data transmission based on the combination of the technologies of dispersion control, distributed amplification, spectral channel multiplexing, and optical regeneration of signals. The results of mathematical modelling can be used for upgrading existing lines and designing the next generation of trunk highspeed fiber-optic communication lines.

High-Speed Plastic Optical Fiber and Real-Time Communication with High-Resolution Motion Picture

High-Speed Plastic Optical Fiber and Real-Time Communication with High-Resolution Motion Picture

Coherent Ultrashort Light Pulse CDMA Communication Systems with Multipulse Pulse Position Modulation

We propose coherent ultrashort light pulse code-division multiple-access (CDMA) communication systems with multipulse pulse position modulation (MPPM). Coherent ultrashort light pulse CDMA is an asynchronous multiplexing technique for high-speed fiber-optic communications. MPPM is introduced to outperform both pulse position modulation (PPM) and on-off keying (OOK), when the optical bandwidths for these three modulation methods are the same. We theoretically derive the bit error rate (BER) of the proposed system. The performance characteristics are discussed with respect to a number of system parameters, and are compared with those of PPM and OOK. Our results show that MPPM is able to achieve a lower BER than that of both PPM and OOK when the bit rates for these methods are the same. We also find that there exists the optimum number of pulses in an MPPM signal block, which is inversely proportional to both the bit rate and the total number of multiple access interference (MAI) users.

Impact on the signal degree of polarization due to polarization mode dispersion in optical fibres

Using a compact optical link transmission model, the degradation of signal degre e of polarization (DOP) induced by polarization mode dispersion (PMD), especiall y the second-order PMD, and the input signal state of polarization in high-speed optical fibre communication systems is studied in detail. It is pointed out tha t the signal DOP can be used as the feedback control signal in the optical adapt ive first-order PMD optimal compensation systems compatibly. However, if the sec ond-order PMD is considered, the control algorithm will be complicated, and ther e will be the possibility that the system is trapped in a local optimum which wo uld downgrade compensator the performance.

High-speed digital modulation characteristics of oxide-confined vertical-cavity surface-emitting lasers-numerical simulations consistent with experimental results

The vertical-cavity surface-emitting laser (VCSEL) is a preferred light source for short-distance high-speed fiber-optic communication links. We simulate the digital modulation behavior of typical oxide-confined VCSELs under realistic working conditions with a comprehensive model that includes the detailed geometry when calculating the optical fields and that accurately accounts for the dynamic effects of carrier density and temperature on the modal distributions. The intrinsic output characteristics of single- and multimode VCSELs were studied as functions of bias and modulation depth under a 2/sup 7/-1 pseudorandom bit sequence current modulation at 2 and 10 Gb/s. The data were used to create numerical eye diagrams that show, e.g., the significant impact of the bit pattern history and the noise on the timing jitter in both single- and multimode VCSELs. For the single-mode VCSEL, the choice of the bias current and modulation depth was less critical due to its higher damping of the relaxation oscillations. The simulated VCSELs were fabricated and experimentally evaluated. The measured eye diagrams showed the same characteristic features as those in the simulations.

A 49-GHz preamplifier with a transimpedance gain of 52 dBΩ using InP HEMTs

This paper describes a new preamplifier IC with 0,15-/spl mu/m gate InP-based high electron mobility transistors (HEMTs) for a high-speed fiber optic communication system. The preamplifier consists of a lumped-element transimpedance amplifier (TIA) for the input stage and a highly stabilized distributed amplifier with cascode-configured unit cells for the gain stage. A gain-peaking technique for a distributed amplifier was employed to enhance the bandwidth and gain flatness of the preamplifier. This gain peaking profile compensates for a lack of bandwidth of a TIA. As a result, we achieved a flat transimpedance gain of 52 dB/spl Omega/ and a bandwidth of 49 GHz.

Free-space optical cross-connect switch by use of electroholography

An electrically controlled holographic switch is proposed as a building block for a free-space optical interconnection network. The switch is based on the voltage-controlled photorefractive effect in KLTN crystals at the paraelectric phase. It is built of electrically controlled Bragg gratings stored in the volume of the crystal. A compact switch that connects four high-speed fiber-optic communication channels with high efficiency is demonstrated experimentally. The switch performance is investigated and optimized. This switch is extremely attractive for cascaded switching arrays such as those found in multistage interconnect networks.

Interface Reactions in LiNbO3 Based Optoelectronics Devices

AbstractWe present secondary ion mass spectrometry (SIMS) study results on interfaces of LiNbO3 based optoelectronic devices, which have been performed in order to examine the cause of device failures. The devices are widely used in current high-speed optical fiber communication systems, and such investigation from a materials-viewpoint is important to improve the device quality. Especially, the device long-term stability is strongly affected by alkali-contaminants diffused into the SiO2 buffer layer of device, and here we confirmed that an adoption of common Si3N4 passivation is effective in preventing the process-induced contamination without any influence to device performance.

High-speed avionic optical fiber CDMA networks

With applications of systems integration technology to advanced aircrafts, high-speed and high-capacity optical fiber communication networks should be employed to support airborne broadband communication services. To guarantee real-time multiuser communications over a network, the selection of medium-access schemes is critical for avionics applications. In this paper, we briefly discuss the issues on high-speed multiple-access techniques and their applicability. Then we focus on the design and operation aspects of avionic optical fiber code-division multiple access (CDMA) networks. Some practical considerations on implementing such a CDMA network are also addressed and further improvement is pointed out. It is shown that avionic optical fiber CDMA networks can find a use in real-time avionic sensor data distribution, data exchange, and computer interconnects.

High Speed Receiver Circuit Designs for Fiber Optic Communications

In this paper, the evolution of receiver designs used in high speed fiber optic communication systems is presented. The basic guidelines of the design with associated constraints are also given. Some recent receiver designs are illustrated, alongwith the future trend.

Timing jitter of ultrashort solitons in high-speed communication systemsII Control of jitter by periodic optical phase conjugation

We consider the use of periodic optical phase conjugation for reducing the timing jitter in high-speed fiber-optic communication systems employing ultrashort solitons (width <10 ps) in dispersion-decreasing fibers. Using adiabatic perturbation theory, we derive analytically an expression for the trajectory of a periodically conjugated ultrashort soliton in a communication link after including the effect of amplifier noise and use it to derive the timing jitter in the soliton arrival time at the end of a transmission line. The analysis takes into account not only the group-velocity dispersion but also the Raman effect and the third-order dispersion. We show that the timing jitter can be minimized by using an optimized amplifier spacing (∼65–80 km) for a specific value of average fiber dispersion. The use of shorter amplifier spacings increases timing jitter because of third-order dispersion while for larger amplifier spacings the increased jitter originates from the Raman effect. For high-bit rate systems considered in this paper the Gordon–Haus contribution to the timing jitter is negligible. Under optimized conditions, nearly error-free transmission can be realized at a bit rate of ∼100 Gb/s over a distance of 1200 km even in the absence of optical filters. We discuss the role of optical filters for improving system performance and the impact of fiber-dispersion fluctuations on the periodic filtering of ultrashort solitons.