Various approaches to reduce access network cost are discussed with emphasis on system and component technologies. On-going access network opticalization subjects are discussed with respect to PDS-based access systems.

A heterodyne interferometer utilizing a light source with short coherence length has led to a significant improvement in distance resolution of an optical reflectometer. The resolution less than 1 cm along a fiber is easily achieved by a Fabry-Perot type diode as a short coherence length source.

Loss increase due to hydroxyl group formation of a fiber expose to hydrogen gas in measured. Experimental result shows that the loss increase is proportional to 0.57 power of exposure time. Temperature dependence of the loss increase is also estimated from the result.

Fiber-optic access system integration is the key to providing various kinds of services to home users. The combination of ATM- and SCM-PON systems is essential to support a high-speed data service and analog/digital video distribution services. From this viewpoint, a frequency-division- multiplexing technique for digital baseband and subcarrier multiplexed signals is required to achieve system integration. However, system integration for these two access systems has not been fully investigated yet. The SCM-PON system, which uses a super wideband optical FM converter, will enable these two different kinds of access system (ATM and SCM) to be integrated. In this paper, we describe experimentally obtained results for frequency- division-multiplexed signals consisting of digital baseband and subcarrier- multiplexed signals. The experiments were carried out using a 622-Mb/s baseband signal and an FM-converted signal containing AM and 64QAM signals. The experimental results reveal that the inter-channel interference between the digital baseband and FM-converted signals restricts the number of subcarriers for AM and 64QAM. With an intermediate frequency of 3 GHz for the FM-converted signal, an FDM signal consisting of 622-Mb/s baseband, 30 carriers of 64QAM, and 11 carriers of AM was successfully transmitted.

Polarization mode properties of a polarization-preserving fiber having elliptical stress-cladding with barrier layer around the core are clarified theoretically and experimentally. Normalized frequency dependence of modal birefringence and polarization mode dispersion were measured for the polarization-preserving fiber. It is found from theoretically and experimentally evaluated results that the elliptical stress-cladding fiber has polarization-mode properties similar to those of the polarization-preserving fiber having isolated stress-producing lobes. Stress profiles of the elliptical stress-cladding fiber were measured and calculated for confirming the polarization-mode properties of the fiber. It is known from the measured results that the similarities of polarization-mode properties between the elliptical stress-cladding fiber and the fiber will stress-producing lobes are caused by those of differential stress profiles around the core regions between them.