Parallel Transmission Systems Research Articles

Influence of Fiber Parameters on Stress-Induced Group Delay Variation in Hole-Assisted Fibers

We have studied a specific type of hole-assisted fibers (HAFs) for parallel transmission systems. A fiber ribbon using HAFs will be suitable for parallel transmission systems when used in a small space. Additional skew occurs when a fiber ribbon is used under nonuniform stress environment. We focus on stress-induced group delay variations. Influence of fiber parameters, such as a core diameter 2a and a relative refractive index difference Δ, on stress-induced group delay variations is investigated using a finite-element method. We also study the influence of hole-structure variations.

Stress-Induced Group Delay Variation in Hole-Assisted Fibers

In this paper, we have studied stress-induced group delay variations in hole-assisted fibers (HAFs), experimentally and theoretically for parallel transmission systems. Recently, HAFs having low bending losses have been developed. A fiber ribbon that uses HAFs will be suitable for parallel transmission systems when used in a small space. Additional skew occurs when a fiber ribbon is used under nonuniform stress environment. It is important to know the difference between single-mode fibers (SMFs) and HAFs with respect to stress-induced group delay variations. First, we find out the difference experimentally. Then, we propose a theory to explain the difference. The results calculated by the proposed theory are in good agreement with experimental data. Finally, we discuss the group delay variations, such as the difference between SMFs and HAFs, and the wavelength dependence. We also try to explain the measured group delay variations of five HAFs in a unified way in order to estimate group delay variations of HAFs with various cross-sectional structures.

SDM-WDM Parallel Transmission using a Fiber Ribbon for Ultra High-speed Access Networks

This paper describes a new ultra high-speed access network using a newly proposed SDM-WDM parallel transmission system using a single mode (SM) fiber ribbon. Over 100 Gbit/s of transmission speed for each subscriber is assumed in this paper. The proposed SDM-WDM parallel transmission uses both skew compensations in space division multiplex (SDM) and in wavelength division multiplex (WDM). Considering skew of a fiber ribbon, possible transmission distances are calculated for SDM-parallel transmission. Considering fiber dispersion, possible transmission distances are also calculated for WDM-parallel transmission. Combined with these investigations, we discuss the possibility of the proposed SDM-WDM parallel transmission systems and we show one design example of bi-directional ultra high-speed systems.

Ultra-High-Speed Multichannel Data Transmission Using Hybrid Substrate Integrated Waveguides

Hybrid substrate integrated waveguides (SIWs) are proposed as an alternative low-cost interconnect solution to enable ultra-high-speed signal transmission. The SIW serves as a bandpass data transmission channel providing 15-GHz bandwidth. The hybrid structure utilizes the available low-pass frequency region below the cutoff frequency by adding striplines inside the waveguide. This technique of substrate reuse allows several independent data channels to be transmitted simultaneously through the hybrid structure. Hence, the channel capacity is increased without changing the overall waveguide footprint. Transition structures for routing striplines in the waveguide are designed and optimized through full-wave simulations. A number of test structures are fabricated to investigate data transmission using single and hybrid SIW interconnects. Experiments, as well as system simulations, demonstrate the capability of these interconnects for achieving ultra-high-speed data transmission. The hybrid waveguide system yields 15-Gb/s aggregate data transmission with excellent signal integrity characteristics. The proposed hybrid structure suggests an alternative solution for implementation of parallel data transmission systems with significant increase in the total channel throughput.

Optical Transmitter Using Side-Mode Injection Locking for High-Speed Photonic LANs

This paper discusses an optical transmitter in parallel transmission systems using variable wavelengths. We propose to apply side-mode injection locking using a Fabry-Pe/spl acute/rot laser to realize this transmitter. Important characteristics are the injection power required for single-mode lasing of a slave laser diode (LD) and its dependence on side mode m. This paper measures the required power as a function of m and proposes a new simple theory to explain the measured data. The linewidths of injection-locked LDs were experimentally investigated as a function of m. The relation between the linewidths of master and slave LDs were also measured. Finally, the paper describes fundamental transmission experiments at 1 Gb/s using an injection-locked LD to clarify the side-mode dependence of bit-error rate.

An embedded transmission scheme using ppm signaling with symmetric error-correcting codes for optical CDMA

An embedded transmission (ET) scheme is proposed to easily apply error-correcting codes into optical code-division multiple-access (CDMA) systems for immunity from multiple-access interference (MAI). The ET scheme offers high transmission capability over the traditional scheme using pulse position modulation (PPM) signaling, because a 2/sup J/-ary symbol of each user is embedded in the signature sequence with 2/sup J/ weighted positions. Furthermore, the ET scheme with 2/sup J/-ary PPM signaling makes the optical CDMA system J parallel transmission systems, because J bits consisting of 2/sup J/-ary symbol are separately decided. Since such a separate decision is a comparison decision, the effect of MAI added in the optical channel is converted to symmetric errors in the individual parallel transmission systems. Using the symmetric error-correcting (SEC) code immunizes the individual parallel transmission systems against MAI more easily than the embedded-modulation scheme described in because the ET scheme avoids using the asymmetric error correcting code, which is difficult to implement. We analyze the bit error rate under Poisson photon counting channel and show that the ET scheme has an advantage of good energy efficiency over the traditional scheme in applying SEC codes.

Accurate Fiber Skew Measurements by a Phase Method

Recently, an optical parallel transmission using fiber ribbons has been investigated. The important parameter for optical parallel transmission systems is skew and recent fiber ribbon manufacturing technologies make the skew value low. Therefore, the accurate skew measurements for these low skew fiber ribbons become very important. In this paper, we discuss the accurate skew measurements by the phase method. Phase fluctuations are measured for two types of lasers, a DFB-LD and a FP-LD, to clarify the light source dependence. Phase fluctuations are also investigated theoretically, based on the lasing mode fluctuations (mode partition). Fluctuations using an ordinary single mode fiber and a dispersion shift fiber (DSF) are measured and the measured results are in good agreement with the theoretical ones.

Investigation of Fiber Skew for Economical High-speed Parallel Transmission Systems

Economical parallel transmission systems are investigated by using fiber ribbons with several fiber parameters. For this purpose, skews are measured for single-mode fiber ribbons with same fiber parameters and the fiber length difference in a fiber ribbon is evaluated. This value is used to clarify the influence of fiber parameter specifications and fiber length difference on skew for several cases by simulations. The simulations reveal a production yield of fiber ribbons for a required skew value. Acceptable fiber specifications are discussed from the view point of fiber skew compensation. Although the acceptable fiber specifications depend on system parameters, it seems to be possible to use a fiber ribbon with several fiber parameters to construct economical parallel transmission systems with the aid of skew compensation.

Design and analysis of single-mode oxidized VCSELs for high-speed optical interconnects

Oxide-confined vertical-cavity surface-emitting laser diodes (VCSELs) are fabricated for applications in high-performance optical interconnects. Both 980-nm as well as 850-nm wavelength devices in one- and two-dimensional arrays are investigated. Noise properties of single- and multimode devices under different operation conditions are relative intensity noise of single-mode devices can be as low as -150 dB/Hz at output powers of about 1 mW and feedback levels up to -30 dB. Data rates up to 12.5 Gb/s with bit error rates below 10/sup -11/ are achieved with VCSELs showing stable single-mode emission at large-signal modulation, combined with modulation bandwidths exceeding 10 GHz. Arrays with 4/spl times/8 elements flip-chip mounted on Si CMOS driver chips ready for use in parallel data transmission systems are presented.

Skew-free parallel optical transmission systems

This paper proposes two kinds of parallel line codes based on multiplexing and nonmultiplexing, and a method of automatic skew suppression based on bit synchronization and frame synchronization. This achieves parallel high-speed optical transmission to overcome bottlenecks in parallel electronic transmission and to increase the distance of high-throughput interconnections. We have developed GaAs coder/decoder large-scale integrations (LSIs) for the coding algorithm and skew suppression, and analog LSIs for compact, low-power, highspeed parallel optical links. Experimental results show that our proposed parallel transmission methods and fabricated LSIs can play a key role in realizing high-speed, long-distance parallel transmission and in reducing the size and power consumption of high-throughput parallel optical links.

Analysis of a High Density Two-Dimensional Vertical-Cavity Surface Emitting Laser Array

A two-dimensional vertical-cavity surface emitting laser array is expected to be a key device for parallel lightwave transmission and optical interconnection systems. This paper analyzes the number of channels in a two-dimensional vertical-cavity surface emitting laser array, from the viewpoint of the electric power consumption and the light-output. Dependence of the number of channels on several parameters is examined. It was found that high slope efficiency and low electrical resistance lead to a large number of channels, and the contribution of threshold reduction is small if the threshold current is of the order of 100 µ A or less. It is also shown that if each channel is composed of plural elements, the number of channels increases.

Skew evaluation using two-dimensional refractive-index profile in single-mode fiber ribbons

The skew of fiber ribbons must be small for high bit rate parallel optical transmission systems. Accurate skew evaluation using fiber parameters is important for this purpose. A simple method, based on the calculus of variations, is proposed for evaluating the skews of fiber ribbons. This method employs only one mode field (LP/sub 01/ mode) of an ideal step-index fiber as a trial function and a two-dimensional (2-D) refractive index profile. The measured skews of a 16-fiber ribbon composed of fibers with different parameters are compared with calculated values and are found to be in good agreement. The influence on the skew of several refractive index profile deviations (including asymmetric profile deviations) are evaluated using the proposed method. It is found that the asymmetric core profile has a large influence on skew whereas that of the asymmetric core-cladding boundary is relatively small.

Compressively strained 1.3 mu m InAsP/InP and GaInAsP/InP multiple quantum well lasers for high-speed parallel data transmission systems

Turn-on delay times in the pulse response of compressively strained InAsP/InP double-quantum-well (DOW) lasers and GaInAsP/InP multiple-quantum-well (MQW) lasers emitting at 1.3 mu m were investigated. DQW lasers with 200- mu m cavity length and high-reflection coating achieved both a very low threshold current (1.8 mA) and a small turn-on delay time (200 ps), even under a biasless 30-mA pulse current. Compressively strained or lattice-matched GaInAsP MQW lasers and GaInAsP double-heterostructure (DH) lasers were also fabricated and compared. It was observed that the carrier lifetime was enhanced for InAsP DQW lasers and strained GaInAsP MQW lasers compared to the lattice-matched GaInAsP MQW lasers and conventional double-heterostructure lasers. To explain this increase in the carrier lifetime, the effect of the carrier transport on the carrier lifetime was studied. The additional power penalty due to the laser turn-on delay was simulated and is discussed. >

Characteristics of 4×4 photonic switch array with gain and high contrast

A two-dimensional semiconductor photonic switch array with a new operating principle based on the change of the gain coefficient in the GaAs crystal is reported. This switch realizes direct amplification and absorption of the optical signal and features optical gain of 4 dB, contrast of 9.6 dB, applied voltage of 2.2 V, and a simple planar structure. This array is applicable to photonic parallel data transmission systems.

4548101 Transmission mechanism with parallel transmission systems including torque converter in the first speed one only : Teruo Akashi, Hiroshi Ito, Shigemichi Yamada, Toyota, Japan assigned to Toyota Jidosha Kabushiki Kaisha

4548101 Transmission mechanism with parallel transmission systems including torque converter in the first speed one only : Teruo Akashi, Hiroshi Ito, Shigemichi Yamada, Toyota, Japan assigned to Toyota Jidosha Kabushiki Kaisha

Stabilizing control of parallel AC‐DC power transmission systems by approximate switching curve

A method to improve the transient stability of bulk power transmission system is presented. The method stabilizes the control of parallel ac-dc transmission systems using an approximate switching curve. The optimal switching curve is approximated by a power series and the resulting switching curve is determined independent of type and duration of faults that occur to the system. In addition, coefficients of the switching curve can be calculated on a off-line basis which allows use of simple on-line algebraic calculations in emergency conditions.

A nonrecursive digital filter for data transmission

High-speed digital data transmission systems often require special filter functions for spectral shaping with prescribed phase characteristics. One such filter is the cosine roll-off filter, which has applications in both serial and parallel data transmission systems. This filter is of special interest, because in such applications it is common to utilize two identical cosine roll-off filters in a cascade connection, i.e., one in the transmitter and one in the receiver. The composite response of the cascade connection has the raised-cosine roll-off characteristic, which yields low intersymbol interference. Because a linear phase characteristic is further required, the digital filter type chosen for this application is nonrecursive. The difference equation coefficients are determined from the coefficients of a Fourier series expansion of the magnitude-frequency characteristic in the form of a cosine series. The linear phase characteristic is the direct result of setting the sine terms of the Fourier series to zero. Two criteria have been selected as a measure of the digital filter performance: minimum stop-band attenuation and an RMS measure of intersymbol interference. Performance was calculated as a function of the number of terms in the cosine series used to approximate the desired function. Performance graphs, which summarize the results of this investigation, are included. The application of digital filtering techniques in the field of data transmission systems is shown to have practical value.