Kiichi Yoshiara

Tunable dispersion slope compensator with a chirped fiber grating and a divided thin-film heater for 160-Gb/s RZ transmissions

We have developed the tunable dispersion slope compensator with a chirped fiber grating and a divided thin-film heater composed of 32 thin-film heaters for single-channel 160-Gb/s return-to-zero (RZ) transmission. We successfully demonstrated the dispersion slope change between -20 and +20 ps/nm/sup 2/ and ability of this dispersion slope compensation in 160-Gb/s RZ transmission by the simulations.

Design and Characteristics of Guardring-Free Planar AlInAs Avalanche Photodiodes

This paper reports a guardring-free planar AlInAs avalanche photodiode (APD) for optical fiber communications. AlInAs APDs can achieve a larger gain-bandwidth product (GBP) with lower excess noise than commercial InP APDs, and the guardring-free planar structure enables these superior AlInAs APDs to have both a low dark current and high reliability for practical use. We present the structure, fabrication, designs, APD characteristics, and receiver sensitivity, systematically. The guardring-free planar structure and its peculiarities are described, and we show APD designs for 2.5-Gb/s and 10-Gb/s applications and their characteristics. A 0.2-mum -thick AlInAs multiplication layer achieves a GBP of 120 GHz and an excess noise factor of 2.9 at a multiplication factor of 10. Their dark currents are less than 20 nA and their lifetime is evaluated to be 25 million hours at 85degC. Lastly, we demonstrate that the guardring-free planar AlInAs APDs with a transimpedance amplifier achieve the remarkable sensitivity of -37.0 dBm at a bit error rate of 10-10 for 2.5-Gb/s signals and of -29.9 dBm at a bit error rate of 10-12 for 10-Gb/s signals. This performance indicates that the guardring-free planar AlInAs APDs have made great advances against commercial InP APDs and other AlInAs APDs.

Tunable dispersion equalizer with a divided thin film heater

We developed tunable dispersion equalizer with a chirped fiber grating and a divided thin film heater composed thirty-two thin film heaters. The divided thin film heater took an important role in the control of dispersion and dispersion slope, moreover the correction of group delay ripples. We successfully demonstrated the dispersion change from -304 ps/nm to -196 ps/nm and the dispersion slope change from +100 ps/nm/sup 2/ to -300 ps/nm/sup 2/.

Automatically tracked dispersion compensation with penalty-free tunable dispersion equalizer for 40 Gbit/s systems

The automatic control of a tunable dispersion equalizer by means of a bit error monitor was demonstrated. The tunable dispersion equalizer developed consists of a chirped fiber grating and divided thin film heaters. From the tests of the step response and the automatic DEQ control, we confirmed that the tunable dispersion equalizer based on the grating and heaters is suitable for adaptive dispersion compensation of dispersion variations caused by slowly varying environmental conditions with a fluctuation rate of several minutes or more.

Highly External Optical Feedback-Tolerant 1.49-

A 1490 nm InGaAsP single-mode laser diode, with high endurance against external optical feedback, was realized utilizing an optimized partially corrugated grating and a window-mirror-structure. The gratingpsilas length and the coupling coefficient were designed to enable moderate output power, low feedback sensitivity and a SMSR of 40 dB simultaneously. The relative intensity noise (RIN) was maintained less than -120 dB/Hz under strong external optical feedback as high as -10 dB.

\mu

We have developed new tunable dispersion compensators with twin chirped fiber gratings for polarization mode dispersion (PMD) and chromatic dispersion (CD), simultaneously, and successfully demonstrated their ability to change differential group delay (DGD) and chromatic dispersion, independently. The tuning range for the DGD and CD are 150 ps and 200 ps/nm, respectively. The validity of this device for ultra high speed optical communication was confirmed by the simulations of 43 Gbit/s CS-RZ optical transmission.

m Single-Mode Lasers With Partially Corrugated Gratings

We have developed tunable polarization mode dispersion (PMD) compensators and successfully demonstrated to change differential group delay (DGD) from several ps to 90 ps and to compensate DGD in 43 Gbit/s RZ optical transmission experiment.

Tunable dispersion compensator with twin chirped fiber gratings for polarization mode dispersion and chromatic dispersion

We have developed the tunable dispersion slope compensator with a chirped fiber grating for 160-Gb/s transmissions. We successfully demonstrated the dispersion slope change from -20 ps/nm/sup 2/ to +20 ps/nm/sup 2/ and ability of this dispersion slope compensation in 160-Gb/s RZ transmissions.

Tunable polarization mode dispersion compensator with chirped fiber Bragg gratings

The InAlAs avalanche photodiodes that employ a guardring-free structure demonstrate record high reliability of over 10000 hours at a high temperature of 200degC with no degradation in the surfaced pn-junction.

Tunable dispersion slope compensator with a chirped fiber grating for 160-Gb/s RZ transmissions

Three-electrode-type self-pulsating (SP) distributed feedback (DFB) laser diodes (LDs) were fabricated. Lasing mode selectivity and pulsating frequency of SP-DFB LDs were investigated experimentally and device parameter dependences were well explained by numerical simulations.