High brightness and reliable AlGaInP-based light-emitting diode for POF data links

High brightness and reliability operation ring light-emitting diode (LED) is fabricated for plastic optical fiber (POF) link using the distributed Bragg reflector (DBR) mirror and antireflection (AR) coating. The ring LED exhibited optical output as high as 3.5 mW at the bias current of 100 mA. Furthermore, the projection lifetime is also estimated to be 1/spl times/10/sup 6/ h at a 35-mA data-link operating current and ambient temperature of 60/spl deg/C.     

A Trial Thermal Rectifier

We have prepared a trial oxide thermal rectifier made of two cobalt oxides with different thermal conductivities based on a theoretical design. We created an experimental system to measure the thermal rectification and found that the rectifying coefficient defined by the ratio of heat current in a forward direction to that in the opposite direction was 1.43. We verified the thermal rectification by analyzing it quantitatively.     

1 Tbit/s (111 Gbit/s/ch X 10 ch) no-guard-interval CO-OFDM transmission over 2100 km DSF

Spectrally efficient (2bit/s/Hz) 1 Tbit/s DWDM transmission of 111 Gbit/s no-guard-interval PDM CO-OFDM signals with 50 GHz spacing over DSF is demonstrated. The record transmission distance of 2100 km was achieved for a 100 Gbit/s-data-rate CO-OFDM system.     

Fiber fuse phenomenon in step-index single-mode optical fibers

The unsteady-state thermal conduction process in step-index single-mode (SM) optical fiber was studied theoretically with the explicit finite-difference method. We considered a high-temperature loss-increase mechanism, which includes two factors that bring about an increase in the absorption coefficients: 1) electronic conductivity due to the thermal ionization of a Ge-doped silica core and 2) thermochemical SiO production in silica glass. The core-center temperature changed suddenly and reached over 4/spl times/10/sup 5/ K when a 1.064-/spl mu/m laser power of 2 W was input into the core layer heated at 2723 K. This rapid heating of the core initiated the "fiber fuse" phenomenon. The high-temperature core areas were enlarged and propagated toward the light source. The propagation rates of the fiber fuse, estimated at 1.064 and 1.48 /spl mu/m, were in fair agreement with the experimentally determined values. We found that the threshold power for initiating the fiber fuse increases from 0.98 to 1.26 W when the input laser wavelength is increased from 1.06 to 1.55 /spl mu/m.     

Electron-microscopic imaging of single-walled carbon nanotubes grown on silicon and silicon oxide substrates

Direct imaging of single-walled carbon nanotubes (SWNTs) suspended on pillar-patterned Si or SiO2 substrates is investigated using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The suspended nanotubes are successfully observed by direct TEM imaging and it is seen that they have either individual or bundles of SWNTs. Low energy (< or =2 keV) SEM produces high contrast images of suspended SWNTs. On the contrary, when SWNTs contact a SiO2 substrate, they are imaged using electron-beam induced current. The image brightness depends on the length of SWNTs.     

All-optical discrimination based on nonlinear transmittance of MQWsemiconductor optical gates

This paper proposes an all-optical regenerator utilizing a novel all-optical discriminator. The impacts of nonlinearity of optical gates on discrimination performance are estimated. The evaluation of discrimination performance shows that amplified spontaneous emission noise and wave form distortion in optical signals can be effectively suppressed. We experimentally demonstrate the suppression using a low-temperature-grown optical switch up to 10 Gb/s     

Partial-response coding, maximum-likelihood decoding: capitalizing on the analogy between communication and recording - [History of communications]

Signal processing and coding technology for digital magnetic recording is the core technology of the channel electronics module in a hard disk drive (HDD) that processes signals read from magnetic media. In this historical review I focus on what is now widely known as partial-response, maximum-likelihood (PRML) technology, which takes advantage of the inherent redundancy that exists in signals read out of magnetic media; its theoretical foundation goes back to 1970, and it capitalizes on the analogy between high-speed data transmission and high-density digital recording, and that between a convolutional code and a partial-response signal. The first PRML-based product was introduced by IBM in 1990, and PRML technology soon became the industry standard for all digital magnetic recording products, ranging from computers' HDDs and tape drives to micro hard discs used in PCs, mobile phones, and MP3 players; use of the PRML principle has recently been extended to optical recording products such as CDs and DVDs. Its improved version, called NPML (noise-predictive, maximum-likelihood), and variants have been adopted by the HDD industry since 2000. Today, a large number of communication and information theory researchers are investigating use of advanced techniques such as turbo coding/decoding to further improve the density and reliability of both magnetic and optical recording systems.     

Repeater Fault Location for a Submarine Optical Fiber Cable Transmission System

This paper introduces a repeater fault location system for a repeated submarine optical fiber transmission system of 400 Mbits/ s at 1.3μm. The repeater fault location system is used in an out-of-service test. The fault locator transmits a test signal via a main optical fiber line, in order to make a loop-back path in one of the repeaters for returning the test signals via another main optical fiber line and to measure the bit error rate (BER) of the interrogated repeater. The test signal is a kind of pseudorandom signal that includes a low frequency component, which is assigned to the repeater as a supervisory frequency tone (SVT) signal. The BER is measured by counting the number of low frequency signal phase inversions in a time. This paper first describes the test signal generating method, SVT frequency allocation, and the filter design installed in a repeater. Next, there is a discussion of how the capability of the repeater fault locator has been experimentally verified by using two submarine repeaters, including four regenerative repeater units and three submarine optical fiber cables. As a result, a BER of less than5 times 10^{-6}is accurately measured.     

Atomistic origin of high-quality “novel SiON gate dielectrics”

We have investigated the effect of the oxygen incorporation into SiN films by the first principles calculations. The calculated results show that the oxygen incorporation tends to generate defect states in SiN band gap by forming dangling bonds and floating bonds of Si. Based on the calculated results, it is also indicated that the high quality SiON film can be fabricated by suppressing the incorporation of O atoms into the SiN film, reproducing the reported experiments.     

PMD compensation in optical coherent single carrier transmission using frequency-domain equalisation

The transmission performance of optical single-carrier (SC) transmission using frequency-domain equalisation (FDE) to counter polarisation mode dispersion (PMD) is evaluated. 25 Gbit/s coherent optical SC transmission using FDE (CO-SC-FDE) is demonstrated in the presence of a significant amount of differential group delay (DGD). The results show that CO-SC-FDE compensates for the influence of the 125 ps DGD; the OSNR penalty is 0.81 dB.