The reduction of Soliton-soliton interaction to stabilize the soliton pulse propagation in the periodic dispersion-compensated standard fiber system using optical bandpass filter has been investigated by numerical simulation, and experimentally 10 Gbit/s soliton transmission was realized without fine tuning dispersion management over 5700 km, using appropriate optical bandpass filters and polarization scrambler.

Different-wavelength distributed feedback laser diodes with integrated modulators (DFB/MODs) are fabricated on a single wafer operate at wavelengths from 1. 52 µm to 1. 59 µm, a range comparable to the expanded Er-doped fiber amplifier gain band. A newly developed field-size-variation electron-beam lithography enables grating pitch to be controlled to within 0. 0012 nm, and narrow-stripe selective metal-organic vapor-phase epitaxy is used to control the bandgap wavelength of laser active layers and modulator absorption layers for each channel. The channel spacing of fabricated 40-channel DFB/MODs is 214 GHz in average with a standard deviation of 0. 39 nm. Very uniform lasing and modulating performances are achieved, such as threshold currents about 10 mA and extinction ratios about 20 dB at -2 V in average. These devices have been used to demonstrate 2. 5-Gb/s transmission over 600 km of a normal fiber with a power penalty of less than 1 dB.

The three dimensional (3D) packing problem is to arrange given rectangular boxes in a rectangular box of the minimum volume without overlapping each other. As an approach, this paper introduces the system of three sequences of the box labels, the sequence-triple, to encode the topology of the 3D-packing. The topology is the system of relative relations in pairs of boxes such as right-of, above, front-of, etc. It will be proved that the sequence-triple represents the topology of the tractable 3D-packings which is a 3D-packing such that there is an order of the boxes along which all the boxes are extracted one by one in a certain fixed direction without disturbing other remaining boxes. The idea is extended to the system of five ordered sequences, the sequence-quintuple. A decoding rule is given by which any 3D-packing is represented. These coding systems are applied to design heuristic algorithms by simulated annealing which search the codes for better 3D-packings. Experimental results were very convincing its usefulness as automated packing algorithms.

We propose a device called the Waveguide width abruptly EXpanded Spot-Size-Converter integrated Laser Diode (WEX-SSC-LD) that has been designed to improve lasing characteristics by achieving a steep photoluminescence wavelength change along the cavity. The waveguide parameter was optimized by a three-dimensional beam propagation method to reduce mode conversion and absorption losses. The WEX-SSC-LD's showed superior lasing characteristics such as threshold currents of 5.8 mA at 25C and 19 mA at 85C and operation current of 57.5 mA at an output power of 10 mW for 85C. These excellent lasing characteristics were achieved due to the steeper bandgap-energy shift in the SSC section near the LD section side by introducing the WEX-SSC structure as well as the high-quality MQW active layer grown by selective MOVPE and the precisely controlled pn-pn current blocking structure. The coupling loss to normal single-mode fiber was as low as 1.8 dB while maintaining a large coupling tolerance of 1.8 µm. These excellent coupling characteristics are very promising for passively aligned optical modules.

We have proposed a tunable laser with silica-waveguide ring resonators. In this tunable laser, a semiconductor optical amplifier was passively aligned and mounted onto a silica-waveguide substrate. The ring resonators can be tuned by controlling their temperatures using the thermo optic heaters formed on them, and there are no mechanically moving parts. Thus, they are sufficiently stable and reliable for practical use. Our tunable laser exhibits a high fiber-output power of more than 15 dBm and a wide tunable range of 60 nm (L-band, 50 GHz spacing, 147 channels). Moreover, a tunable laser with a much wider tunable range of 96 nm using 100-GHz-FSR ring resonators is also reported.