Tomiya Abe

Bidirectional optical coupler for plastic optical fibers

We have developed a low-loss bidirectional optical coupler for high-speed optical communication with plastic optical fibers (POFs). The coupler, which is fabricated by an injection molding method that uses poly (methyl methacrylate), has an antisymmetric tapered shape. We show that the coupler has low insertion and branching losses. The tapered shape of the receiving branch reduces beam diameter and increases detection efficiency coupling to a photodetector, whose area is smaller than that of the plastic optical fiber. The possibility of more than 15-m bidirectional transmission with a signaling bit rate up to 500 Mbits/s for simplex step-index POFs is demonstrated.

Aberration properties in a chirped grating for coarse wavelength division demultiplexing

We studied the imaging performance of a chirped grating for a demultiplexer designed for coarse wavelength division multiplexing using a wavefront aberration analysis and the ray tracing simulation. The demultiplexer was composed of a chirped grating, cylindrical lenses, and a waveguide. The best image point and the spot shape focused by the chirped grating were effectively calculated with the wavefront aberration. We applied the aberration analysis to design a waveguide to connect branched beams to photodetectors, and we confirmed the demultiplexing performance experimentally.

Segmented chirped grating for coarse wavelength division demultiplexing with multimode optical fibers

A chirped grating segmented into partitions each having a constant blaze angle to use in a demultiplexer for coarse wavelength division multiplexing with multimode optical fibers is developed. Its designed configuration utilizes a resonance region to achieve high diffraction efficiency and large dispersion. The width, blaze angle, and diffraction order of each partition were optimized by vector diffraction analysis. The diffraction loss of the manufactured grating was less than 1.5 dB, and polarization-dependent loss was less than 0.6 dB within a wavelength width of at least 70 nm. It is confirmed that a demultiplexer with the developed chirped grating had a wide passband and low cross talk.

Novel polymer materials for optical waveguides and their applications to polymer CWDM devices

We have developed several novel polymer materials for optical waveguides. In the first part of this paper, we described two examples of our developed materials, one is low loss optical waveguide materials for optical communications at near infrared wavelength region, the other is low loss and high heat resistant materials for optical interconnections in the electronic devices at around 850 nm wavelength region, which can resist to the lead-free solder reflowing process. In the second part, we demonstrated two kinds of novel low cost polymer coarse wavelength division multiplexing (CWDM) devices, one is the polymer arrayed waveguide grating (AWG) device and the other is the polymer CWDM device using the polymer diffraction grating. The structures and performances of these devices were described in detail.

A study on extrusion process for a crosslinking resin.

橋かけ性樹脂の押出成形法として, モノマーを細管内に移送させながら重合させ順次押出す手法について, 試料としてラジカル反応で重合速度の早いアクリル系モノマーを用いて検討した. その結果, 押出成形の可否は, 試料がチューブを通過する時の平均管内摩擦係数で整理できることを明らかにした. また, チューブの内径は約1mmが好ましく, これ以下では平均管内摩擦係数が小さくなるにもかかわらず, ポリマを吐出させる圧力が大きくなり表面形状が破壊された成形体が押出された. また, 1mm以上ではポリマー成形体の中央部に未反応部が残っており, 均一に重合したものを得ることが困難であった. この平均管内摩擦係数を, 滑剤を用いて低減することにより, 表面の平滑な成形体が得られることが判明した.