We realized single-mode hole-assisted optical fiber (HAF) cord whose fiber has a superior bending loss characteristic that complies with ITU-T Recommendation G. 657 for use in highly reliable optical fiber distribution facilities in central offices. The cord has an excellent anti-shock characteristic, and can be scanned by a conventional optical fiber cord identifier despite its very low bending loss. Experiments show that the single-mode HAF cord and its application to optical signal distribution in a central office can provide highly service reliability.

The optical access fiber network is spreading rapidly as a result of the progress made on optical communication technologies and the availability of a wide range of broadband Internet content. If the optical access network is not properly maintained, the service quality will decrease. This paper describes some effective technologies that have been researched and developed to maintain a high quality of service, and to achieve efficient maintenance and operation.

A new method fot the refractive index distribution measurement using a set of single-mode and multimode optical fibers is investigated experimentally. It is confirmed that the optical multiple reflection is neglected, and this leads the accurate measurement with high stability and easy handling.

A Gaussian pulse propagated through a multimode optical fiber is well explained by introducing a weighting function of higher order modes into the theoretical formula, being consistent with experimental results. Extending the equation of the pulse propagation in a single mode fiber into that for the multimode fiber, the calculated waveform with several weighting functions is compared with the experimental pulse of a He-Ne 3.39µm mode-locked laser, which propagated through As-S glass fiber. Cosequently, the most appropriate weighting function is found to be hyperbolic function W(l)l-0.7, which depends only on the radial mode l and is independent of the azimuthal mode m. Physical interpretation about the obtained weighting function is also discussed.

Introducing temperature-dependent terms into the propagation constant and its derivatives, and extinction coefficient of a core material of optical fiber, the equation of pulse propagation in a multimode fiber is derived, allowing us to evaluate the temperature dependence of a pulse waveform such as the peak-intensity, the pulse duration or width and the pulse delay-time at the peak as a function of ambient temperature. Using the weighting function for higher order modes in the above equation, the theoretically calculated waveforms are compared with the mode-locked He-Ne 3.39 µm laser pulses propagated through As-S fiber over the range from room temperature to 220, being in good agreement each other.

Taking into account the higher order dispersions of the complex propagation constant involving its loss term, the equation of a Gaussian pulse propagation is derived for a single-mode optical fiber, by which the pulse-peak intensity, the pulse-width, the pulse-delay time and the skewness can be readily estimated along the fiber length. Then, among various combinations of the dispersion profile between the loss and the phase terms including both normal and anomalous dispersions, two typical cases of the pulse-broadening and narrowing are numerically shown, in which possibility of the compression is especially discussed with the combination of the sharp anomalous absorption-band and the normal phase-dispersions.

We propose an optical fiber connection navigation system that uses visible light communication for an integrated distribution module in a central office. The system realizes an accurate database, requires less skilled work to operate and eliminates human error. This system can achieve a working time reduction of up to 88.0% compared with the conventional work without human error for the connection/removal of optical fiber cords, and is economical as regards installation and operation.

We propose a new fiber endface sealing technique for the optical connection of holey fibers (HFs). We experimentally investigate the optimum sealing condition for physical contact using a carbon dioxide (CO2) laser. We use this technique to fabricate an HF connector, and achieve low splice loss and a high return loss when splicing with a conventional SMF connector. With hole-assisted fiber (HAF), the obtained splice and return losses are almost the same as those obtained with the conventional method. In particular, with photonic crystal fiber (PCF), we obtained a minimum splice loss of 0.2 dB and a return loss exceeding 50 dB at wavelengths of 1.31 and 1.55 µm.