Showing papers by "Koichi Asatani published in 1978"

High-speed optical pulse transmission at 1.29-µm wavelength using low-loss single-mode fibers

Abstract: Optical-fiber transmission experiments in the 1.3-μm wavelength region are reported. GaInAsP/InP double-heterostructure semiconductor laser emitting at 1.293 μm is modulated directly in nonreturn-to-zero (NRZ) codes at digit rates tanging from 100 Mbit/s to 1.2 Gbit/s. Its output is transmitted through low-loss GeO 2 -doped single-mode silica fibers in 11-km lengths. Transmitted optical signals are detected by a high-speed Ge avalanche photodiode. Overall loss of the 11-km optical fibers, including 11 splices, is 15.5 dB at 1.3 μm. Average received optical power levels necessary for 10-9error rate are -39.9 dBm at 100 Mbit/s and -29.1 dBm at 1.2 Gbit/s. In the present system configuration, the repeater spacing is limited by loss rather than dispersion. It seems feasible that a more than 30 km repeater spacing at 100 Mbit/s and a more than 20 km even at 1.2 Gbit/s can be realized with low-loss silica fiber cables, whose loss is less than 1 dB/km. Distinctive features and problems associated with this experimental system and constituent devices are discussed.

Linearization of LED Nonlinearity by Predistortions

Abstract: Light-emitting diode (LED) nonlinear differential gain (DG) and differential phase (DP) were measured, since they are important performance factors in video signal transmission. Typical, experimentally measured temperature dependence of DG and DP is also presented. A linearizing method for minimizing LED DG and DP distortions, using predistortion, is proposed and experimentally examined. With this technique, and with precise adjustment of the predistortion circuits, the DG of a typical LED was improved from 12.5 percent to less than 1 percent, and the DP from 2.8/spl deg/ to 1/spl deg/.This corresponds to an improvement in second and third-order harmonic distortions of 19 dB and 21 dB, respectively. DG and DP were measured with respect to the 3.58-MHz color subcarrier frequency superimposed on the 15.75-kHz horizontal scanning sawtooth wave. The linearization stability with regard to temperature variation was lowered to be less than 1-percent DG and 1/spl deg/ DP in the temperature range from 15 to 45/spl deg/C.

Analyses of LED nonlinear distortions

Abstract: This paper treats LED nonlinear distortions of differential gain (DG) and differential phase (DP) theoretically. Possible origins and numerical analyses are presented for Al x Ga 1-x As LED's, considering various junction structures; double-heterostructure, single-heterostructure, and homostructure. It is shown that homostructure is superior to the others in linearity. The double-heterostructure is superior in optical power generation and in high-speed modulation, if the same structure parameters are adopted. The effects on linearity of doping concentrations, thermal resistance, and carrier confinement breakdown due to insufficient heterointerface barrier height are analyzed. An experimental result is shown to confirm the analyses. The results obtained will contribute to linear LED design.

Linearization of LED nonlinearity by predistortions

Abstract: Light-emitting diode (LED) nonlinear differential gain (DG) and differential phase (DP) were measured, since they are important performance factors in video signal transmission. Typical, experimentally measured temperature dependence of DG and DP is also presented. A linearizing method for minimizing LED DG and DP distortions, using predistortion, is proposed and experimentally examined. With this technique, and with precise adjustment of the predistortion circuits, the DG of a typical LED was improved from 12.5 percent to less than 1 percent, and the DP from 2.8° to 1°. This corresponds to an improvement in second and third-order harmonic distortions of 19 dB and 21 dB, respectively. DG and DP were measured with respect to the 3.58-MHz color subcarrier frequency superimposed on the 15.75-kHz horizontal scanning sawtooth wave. The linearization stability with regard to temperature variation was lowered to be less than 1-percent DG and 1° DP in the temperature range from 15 to 45°C.

Pulse broadening in long-span single-mode fibers around a material-dispersion-free wavelength

Abstract: Broadening of short optical pulses propagated along 10.4- and 6-km-long single-mode fibers was measured at a wavelength of 1.293 μm. The fiber core was made of germanium-doped silica glass, and the cladding was pure silica glass. The average loss was 1.33 dB/km on ten pieces about 1 km long. Measured dispersion was 3.9 psec/km/nm for 10.4-km-long fibers, which is in good agreement with the theoretical result obtained by taking the waveguide as well as material dispersion into account. The present experiment confirms that it is beneficial to use the 1.3-μm wavelength region for large-capacity digital transmission.

Low loss fibre transmission of high speed pulse signals at 1.29 μm wavelength

Abstract: Using InGaAsP semiconductors laser emitting at 1.29 μm wavelength as optical sources, and low-loss germanium-doped single-mode silica fibres with 11 km lengths, optical transmission experiments were carried out at 400 and 800 Mb/s bit rates.

Analyses of LED Nonlinear Distortions

Abstract: This paper treats LED nonlinear distortions of differential gain (DG) and differential phase (DP) theoretically. Possible origins and numerical analyses are presented for Al/sub x/ Ga/sub 1-x/As LED's, considering various junction structure; double-heterostructure, single-heterostructure, and homostructure. It is shown that homostructure is superior to the others in linearity. The double-heterostructure is superior in optical power generation and in high-speed modulation, if the same structure parameters are adopted. The effects on linearity of doping concentrations, thermal resistance, and carrier confinement breakdown due to insufficient heterointerface barrier height are analyzed. An experimental result is shown to confirm the analyses. The results obtained will contribute to linear LED design.

High Sensitivity Optical Receivers Fiber-optic Syste

Abstract: The performance of high-speed, highquantumefficiency GaAlAsSb avalanche photodetectors suitable for a 1 .O-1.4 pm high-per- formance fiber-optical communication system is described. The incor- poration of these APD's with state-of-the-art GaAs FET electronics can lead to hybrid integrated optical receivers with 10-20 times better sensitivity at a 100-MHz bandwidth than is available with germanium APD's.