Eisuke Nihei

High-bandwidth graded-index polymer optical fiber

High-bandwidth (2 GHz/spl middot/km) graded-index polymer optical fiber (GI POF) was successfully obtained by the new interfacial-gel polymerization technique in which the unreactive component was used in order to obtain the quadratic refractive-index distribution. This high-bandwidth GI POF makes it possible to transmit high-speed optical signals in the short range network which was not covered by the step-index type POF commercially available. The high bandwidth GI POF will open the way for great advantages in the high-speed multimedia network. >

Graded-index polymer optical fiber for high-speed data communication.

We successfully obtained a high-bandwidth (1 GHz km) and low-loss (90 dB/km at 0.572 µm of wavelength) graded-index polymer optical fiber by using the interfacial-gel polymerization technique, in which we used an unreactive component to obtain the quadratic refractive-index distribution. This high-bandwidth graded-index polymer optical fiber makes it possible to transmit a high-speed optical signal in a short-range network, which is not possible when we use the step-index type of polymer optical fiber commercially available.

Optimum refractive-index profile of the graded-index polymer optical fiber, toward gigabit data links

The optimum refractive-index distribution of the high-bandwidth graded-index polymer optical fiber (POP) was clarified for the first time by consideration of both modal and material dispersions. The ultimate bandwidth achieved by the POP is investigated by a quantitative estimation of the material dispersion as well as the modal dispersion. The results indicate that even if the refractive-index distribution is tightly controlled, the bandwidth of the graded-index POP is dominated by the material dispersion when the required bit rate becomes larger than a few gigabits per second. It is also confirmed that the material dispersion strongly depends on the matrix polymer and that the use of a fluorinated polymer whose material dispersion [-0.078 ns/(nm km)] is lower than that of poly(methyl methacrylate) [-0.305 ns/(nm km)] allows for a 10-Gb/s signal transmission.

HIGH-POWER AND HIGH-GAIN ORGANIC DYE-DOPED POLYMER OPTICAL FIBER AMPLIFIERS : NOVEL TECHNIQUES FOR PREPARATION AND SPECTRAL INVESTIGATION

Rhodamine B (RB), Rhodamine 6G (R6G), Oxazine 4 perchlorate (O4PC), and 4-Dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl-4H-pyran)-doped graded-index (GI) polymer optical fiber amplifiers (POFAs) were successfully prepared by novel techniques to prevent degradation of organic dyes and to enhance solubility of the dyes in methyl methacrylate and in poly(methyl methacrylate) (PMMA). High-power (620 W) and high-gain (33-dB, 2070 times) amplification was achieved for RB-doped GI POFAs based on the spectral investigation of dyes in PMMA bulk. It should be noted that amplification in the low-loss region of polymer optical fibers was achieved in the R6G- and O4PC-doped GI POFA.

Basic performance of an organic dye-doped polymer optical fiber amplifier

A polymer optical fiber amplifier (POFA) of the graded-index (GI) type, with gain in the visible region, was successfully prepared for the first time, to our knowledge, with the interfacial-gel polymerization technique. An input signal of 0.85Wat 591 nm was amplified to 420W(27-dB gain) by injection of 690W of pump power at 532 nm into a GI POFA with a 0.5-m length. The efficiency of conversion of pump energy to signal amplification was more than 60%.

Formation of the refractive index profile in the graded index polymer optical fiber for gigabit data transmission

Bandwidth characteristics of the large core graded index polymer optical fiber (GI-POF) are theoretically and experimentally clarified. The refractive index profile of the GI-POF was controlled by interfacial-gel polymerization to investigate the relation between the index profile and the bandwidth characteristics. It was experimentally confirmed that the maximum bandwidth of the poly methyl methacrylate (PMMA) base GI-POF is at most 3 GHz for 100 m transmission using a typical laser diode emitting at 650-nm wavelength (3 nm source spectral width) when its refractive index profile is optimized. The maximum bandwidth theoretically estimated by considering both modal and material dispersions is approximately 3 GHz which is exactly the same as the measured value, while higher than 10 GHz for 100 m was expected if only modal dispersion was taken into account. The optimum refractive index profile of the PMMA base GI-POF is theoretically and experimentally clarified by considering the profile dispersion further.

Graded-index plastic optical fiber composed of methyl methacrylate and vinyl phenylacetate copolymers

Graded-index plastic optical fiber whose transmission attenuation is 143 dB/km at 651-nm wavelength was fabricated by heat-drawing the corresponding GI preform rod. This rod is prepared by the interfacial-gel copolymerization technique of methyl methacrylate (MMA) and vinyl phenylacetate (VPAc). The total scattering loss of the GI preform rod is ~60 dB/km at 633 nm. The graded-index profiles of the optical fibers are almost the same as those of the corresponding preforms with cladding sheaths. The index distributions of their core regions are quadratic against the distance from the center axis. The numerical aperture estimated from the index difference is ~0.20.

Compensation for Birefringence of Oriented Polymers by Random Copolymerization Method

Birefringence is caused by orientation of polymer chains during injection molding or extrusion, and is a large obstacle to optical applications. Transparent zero-birefringence copolymers were successfully synthesized by randomly copolymerizing two monomers having positive and negative birefringence, respectively. Since the anisotropic polarization of the negative birefringent monomer units is compensated by the positive birefringent monomer units on the same polymer chain, the birefringence is compensated on the length scale of only several monomer units and becomes zero for any degree of orientation. Methyl methacrylate (MMA) was used as the negative birefringent monomer, and 2,2,2-trifluoroethyl methacrylate (3FMA) as the positive birefringent monomer. Poly(MMA-co-3FMA) copolymer synthesized with a composition of MMA/3FMA=45/55 (wt./wt.) showed no birefringence for any draw ratio when a sample film was uniaxially heat-drawn to 3.5 times its original length. The total scattering loss of the zero-birefringence copolymer was 65.9 dB/km, which is comparable to those of homopolymers.

High-bandwidth, graded-index polymer optical fiber for near-infrared use

We describe graded-index polymer optical fibers with high bandwidth (5.12 GHz for 100-m transmission) and low loss in the near-infrared region (56 and 115 dB/km at wavelengths of 688 and 773 nm, respectively) that we successfully obtained with a new interfacial-gel polymerization technique using an all-deuterated methyl methacrylate monomer and a partially fluorinated acrylate monomer. The necessity for both low attenuation and high bandwidth for a polymer optical fiber is described for its use as a physical media in a high-speed multimedia network.

High-bandwidth, high-numerical aperture graded-index polymer optical fiber

A new large core (0.5-1.0 mm) graded-index polymer optical fiber was proposed to solve the connection problem of the single-mode silica fiber indoor use for high speed multimedia network. The bending loss for 10-mm bending diameter was dramatically decreased from 20 dB to less than 1 dB by preparing the high numerical aperture graded-index polymer optical fiber. The bandwidth was 585.2 MHz km which was one hundred times larger than that of any existent step-index polymer optical fibers, and the attenuation was 150 dB/km at 650-nm wavelength. >