Shigeru Tomita

Water sensor with optical fiber

In optical-fiber networks, it is important to monitor water which seeps into splice enclosures. The fibers have residual stress at splicing points, and when water is present, this adversely affects fiber lifetime. A water sensor which has a simple structure for monitoring water at splicing points has been developed. This water sensor causes optical loss due to fiber bending when water seeps into splicing enclosures. The design method using a fiber-bending model and sensor performance are described. >

Suppression of Fiber Fuse Propagation in Hole Assisted Fiber and Photonic Crystal Fiber

We suppressed fiber fuse propagation in hole-assisted fiber (HAF) and photonic crystal fiber (PCF) with input powers above 14 W at 1480 and 1550 nm. This result indicates that the threshold power of fiber fuse propagation in HAF and PCF can be at least 10 times larger than that in conventional single-mode fiber (SMF) in the optical communication band. We also observed the dynamics of fiber fuse termination at a splice point between a test fiber (HAF or PCF) and a conventional fiber (SMF or dispersion-shifted fiber (DSF)). Our experimental results show that air holes in HAF and PCF play an important role in suppressing fiber fuse propagation.

Single-Mode Photonic Crystal Fiber Design With Ultralarge Effective Area and Low Bending Loss for Ultrahigh-Speed WDM Transmission

We propose a new photonic crystal fiber design with a W-shaped effective index profile to achieve the largest effective area (<i>A</i>_eff) for telecommunication use. We realized a 220-μ m²<i>A</i>_eff while achieving both a cable cutoff wavelength of less than 1300 nm and a bending loss compatible with ITU-T recommendations G.655 and G. 656.

Subscriber single-mode optical fiber ribbon cable technologies suitable for midspan access

The loop network configuration and high-fiber-count, single-mode optical fiber ribbon cable and jointing technologies which enable a quick response to service demand and offer high reliability in the subscriber network are described. Fiber parameters were chosen for 1.3/1.55- mu m wavelength division multiplexing (WDM) transmission, and a 1000-fiber cable composed of 8-fiber ribbons was developed. A mass-fusion splicing technique and a multifiber connector were developed for the fiber ribbon. These techniques were evaluated by constructing an experimental line. It was found that they are highly suitable for midspan access, which is indispensable for the high-fiber-count loop network. >

Suppression of galloping oscillation for a self-supporting optical fiber cable

Estimation formulas for wind force coefficients for self-supporting (SS) optical fiber cable are derived. Using these formulas, a procedure for evaluating the critical wind velocity that triggers galloping oscillation is provided. An SS cable with projections is designed to increase the critical wind velocity. >

Long-term reliability of 1000-fiber water-blocking cable

NTT started the ISDN service in 1988 and the demand for this high-speed digital service is growing rapidly. An optical fiber transmission system can provide efficiently these services. Therefore, it is necessary to construct an optical subscriber network for the future infrastructure. Single-mode optical fiber ribbon technology including jointing technology is the key to onstructing these networks. NTT has already developed high-count single-mode optical fiber technologies [1]. The construction of single-mode optical fiber cable for subscriber networks is also progressing rapidly. As this stage it is important to reduce construction and maintenance costs.