Susumu Nishihara

High-efficiency organic dye-doped polymer optical fiber lasers

A graded-index polymer optical fiber containing rhodamine 6G in poly(methyl methacrylate-co-2-hydroxyethyl methacrylate) has been fabricated. Lasing behavior of the fiber was observed by pumping with a frequency-doubled Q-switched Nd: yttrium–aluminum–garnet laser. A slope efficiency of 43% and a lifetime of 110 000 shots at a repetition rate of 10 Hz have been observed. With a 1.5 mJ pump energy, an output energy of 640 μJ was produced.

Fabrication and properties of polymer optical fibers containing Nd-chelate

Graded-index poly(methyl methacrylate) optical fibers (GI POF) containing a Nd-chelate have been fabricated. The absorption spectrum of the fiber exhibited several strong bands in the visible and infrared regions. We have observed infrared fluorescence (0.90, 1.06, and 1.3 /spl mu/m) of the Nd/sup 3+/ ion of the fiber at room temperature when it was pumped with an Ar/sup +/-pumped dye laser at 580 nm.

Spectroscopic properties of lanthanide chelates in perfluorinated plastics for optical applications

The absorption spectra of neodymium (Nd), praseodymium (Pr), erbium (Er), and thulium (Tm) ions in perfluorinated (PF) plastic solutions were measured, and the Judd–Ofelt parameters of the Er and Nd ions have been calculated. The radiative properties of the Nd and Er ions in PF plastic solutions were determined from the absorption measurements and the Judd–Ofelt theory. The fluorescence spectrum of Nd3+ in a PF plastic solution from 900 nm to 1350 nm was measured for the first time, to our knowledge. Furthermore, the PF plastic films containing lanthanide chelates were fabricated by spin coating, and the refractive indices of the films were measured.

Observation of fluorescence in an optically pumped erbium-containing perfluorinated medium at 1.5 μm

We report what is to our knowledge the first observation of erbium fluorescence at the optical communication wavelength of 1.5 microm in a perfluorinated medium. Using a Nd:YAG (355-nm) source, we observed fluorescence of the 4I(13/2) - 4I(15/2) transition with a peak wavelength of 1.535 microm and with a full width at half-maximum of 28 nm. These results can lead to new active devices that use all-fluorinated polymers.

Rare earth-doped polymer optical fibers for optical amplification

We encapsulated rare earth ions such as europium and neodymium with organic ligands to incorporate them into polymer matrices. Their spectroscopic properties in polymer hosts and organic solutions were studied. Infrared emission has been observed from a neodymium-doped perdeuterated core graded index polymer optical fiber.

Experimental Analysis of LTE Signals in WDM-PON Managed by Embedded Pilot Tone

Dense deployment of many small cells is one promising solution to cope with mobile traffic increases. However, the deployment needs many optical fibers and network operators require efficient management for these cells. To overcome these issues, we have proposed a WDM-PON system managed by an electrically embedded pilot tone and confirmed its feasibility. In this letter, we compare management methods and clarify 128-kb/s pilot tone parameters that negligibly affect LTE signals transported by CPRI option seven experimentally. The results show that the modulation index as high as 20% and carrier frequency as high as 5 MHz are suitable under 1.0-dB optical power penalty.

Plastic optical fibers containing lanthanide chelates and organic dyes for laser and amplifier applications

Absorption spectra of lanthanideions in perfluorinated (PF) plastic solution were measured, and the radiative properties were determined by the absorption measurements and the Judd- Ofelt theory. Fluorescence spectrum of Nd3+ in PF plastic solution from 900 nm to 1350 nm, pumped at 580 nm, were measured for the first time. Lasing properties of a rhodamine 6G-doped graded-index plastic optical fiber laser (GI-POFL) and a rod laser were investigated. All measurements demonstrated the superior performance of the GI-POFL. This paper also discusses the lasing properties on the basis of near-field pattern measurements.