A 161 km non-repeatered transmission and a 216 km transmission with a linear repeater have been achieved at 10 Gbit/s using Er3+-doped fiber amplifiers. It is also verified that GaAs-IC technology is applicable to 10 Gbit/s optical transmission systems.

In this letter, we describe the conditions for measuring the nonlinear refractive index n2 when using the self-phase modulation-based cw dual-frequency method. We clarify the appropriate measurement conditions for dispersion-shifted and conventional single-mode fibers both numerically and experimentally. We also show experimentally that the evaluated n2 values for conventional single-mode fiber depend on the signal wavelength separation.

This paper presents a design procedure of multilayer single-input/single-output dual-band filters of small size fabricated in high-permittivity LTCC (Low Temperature Co-fired Ceramic) substrates. The present dual-band filter, with pass bands of 950 MHz and 1.9 GHz, consists of two single-band filters each one of which has a matching circuit for controlling the input impedance in the pass band of the counterpart. Discussed first in this paper is a dual-band filter that has the matching circuit connected to the single-band filters externally. Then, a dual-band filter with the matching circuit embedded in its body is investigated together with metallization patterns of the matching elements. Presented finally is a very small single-input/single-output dual-band filter suitable for dual-band wireless communication systems.

A low-loss dispersion-modified single-mode fiber with low dispersion in the 1.5µm wavelength region has been designed and fabricated by using VAD method. A minimum loss of 0.23 dB/km at 1.55 µm and a small dispersion slope less than 0.023 ps/km/nm2 have been achieved around the zero-dispersion wavelength. Moreover, for the fist time, the tolerance of the core radius has been estimated by waveguide dispersion measurement.

The design of multi-branch optical waveguides having 3 or more output ports is not so easy as that of 2-output branches because some innovative geometry is required to realize equal power splitting. All previous studies take the same approach in which they first introduce innovative geometries and then adjust the structural parameters for equal splitting. On the other hand, we propose quite a different method where distribution of refractive index is calculated from an ideal field distribution which is synthesized artificially. The method is extended to design 3-D 4-branch waveguides. It is exemplified that 4-branch waveguides with low-loss and equal splitting can be realized by the proposed method.

The longitudinal chromatic dispersion in single-mode fibers is investigated theoretically and experimentally. With a fabricated tapered fiber evaluation of longitudinal chromatic dispersion is clarified by using simple equation.

Polarization-maintaining optical fibers with Al2O3 doped silica glass as stress-applying parts (SAPs) and fluorine doped silica glass as cladding are investigated. A high modal birefringence of 1.210-3 due to both thermally and mechanically induced stress is achived.

The characteristics of W-type single-mode fiber with low-dispersion below 2 ps/km/nm over the 1.5-1.6µm wavelength range are theoretically discussed. It is clarified that the tolerance of the core radius and refractive index difference satisfying this dispersion conditions are 0.05µm and 0.01%. Bend-optimized W-type fibers are designed so as to minimize the bending sensitivity. It is also clarified that the allowable bending radius is reduced to less than 4 cm for the W-type fibers with a mode field diameter of 7µm.

The polarization dependence of the resonance wavelength of long period fiber gratings (LPFGs) that employ the photoelastic effect is investigated based on a simple model. The proposed model for estimating the birefringence of these LPFGs provides a good explanation of the experimental results.

A model for estimating the bending loss of 1.3 µm zero-dispersion single-mode fibers at 1.58 µm from the value at 1.55 µm is investigated experimentally and theoretically. An approximated equation for estimating the bending loss ratio of 1.58 µm to 1.55 µm is proposed, which provides good agreement with the experimental results.

This paper presents a novel dual-band comb-line filter using a pair of hybrid resonators. The resonator consists of a half-wavelength stripline resonator short-circuited at both ends and a quarter-wavelength resonator of coplanar waveguide that is nested in the half-wavelength resonator. Numerical calculations by an electromagnetic simulator clarify the characteristics of dual-frequency resonance of the hybrid resonator when the structural parameters are changed. The surface current density on the resonator is also investigated at the resonant frequencies. A typical model of the resonator is fabricated and its resonance frequency characteristics are measured.

In this paper, we describe design considerations for inverse dispersion fiber (IDF) whose chromatic dispersion is designed to compensate for that of conventional 1.3 µm zero-dispersion single-mode fiber (SMF). We clarify the appropriate structural parameters for W-type, triple-clad-type and ring-type refractive index profiles to realize a hybrid transmission line composed of SMF and IDF taking into consideration the bending sensitivity and the available wavelength bandwidth that achieves an average chromatic dispersion of below 1 ps/nm/km in the 1.55 µm region. We also show that, when the launched power is less than 0 dBm/ch, a hybrid transmission line composed of SMF and IDF provides better 40 Gbps 8 ch dense wavelength division multiplexing (DWDM) transmission performance than a conventional dispersion compensation scheme with a dispersion compensating fiber (DCF) module.