Yasufumi Yamada

Low-loss and stable fiber-to-waveguide connection utilizing UV curable adhesive

A low-loss and stable fiber-to-waveguide connection was realized utilizing a newly developed UV curable epoxy resin which has improved humidity durability. The average connection loss was as low as 0.09 dB/point with a return loss of 46 dB. The loss increase was not observed after a heat-cycle test between -40 and 85 degrees C, a high-temperature test at 85 degrees C, or a low-temperature test at -40 degrees C. In a high-humidity test at 70 degrees C and 90% relative humidity, the loss increase was less than 0.2 dB after 400 h.<<ETX>>

Hybrid-integrated 4*4 optical gate matrix switch using silica-based optical waveguides and LD array chips

The fabrication and characteristics of a hybrid-integrated optical gate matrix switch were studied. The switch was composed of a silica-based single-mode guided-wave circuit and two InGaAsP gate array chips, each of which comprised eight laser diode optical gates. The gate array chips were assembled on the guided-wave circuit using a hybrid integration technique. The insertion loss of the fabricated 4*4 matrix switch was scattered among switching paths and ranged from 26 to 33 dB. The switch was applicable to a 400 Mb/s signal system with a bit error rate of 10/sup -9/. The numerical analysis shows that the residual reflectivity at the LD gate and waveguide facets caused the loss scattering among the paths and that reduction of the residual reflectivity is essential for improving the switch characteristics. >

Optical interconnections using a silica-based waveguide on a silicon substrate

Guided-wave optical interconnections for interchip data transmis-sions and clock distributions are demonstrated. The optical interconnection circuit consists of a silica-based guided-wave circuit, laser diodes, and photodiodes. The interconnection topology adopts the star coupler network used in local area networks as a model. The laser diodes and photodiodes are assembled with the guided-wave circuit by the hybrid integration technique. Preliminary experiments on a four-chip interconnection circuit yield a 340 Mbps data rate and a 250 MHz clock frequency.

Optical demultiplexer utilizing an Ebert mounting silicon grating

A two-dimensional optical demultiplexer utilizing an Ebert mounting grating is proposed and discussed. In this demultiplexer, the optical system design to reduce aberration is very important. It is shown that aberration can be greatly reduced by modifying the input/ output facet. The experimentally fabricated demultiplexer has 2.0- 2.6-dB branching loss, >20-dB stopband rejection, and sharp cutoff branching characteristics.

Plastic module of laser diode and photodiode mounted on planar lightwave circuit for access network

Low-cost plastic packaging of laser diodes and photodiodes mounted on planar lightwave circuit (PLC) platform are developed and its reliability is confirmed under various environmental and endurance tests. The high performance of the module is maintained under reliability tests, such as high-humidity high-temperature tests (85/spl deg/C, 85%RH) and temperature cycling tests (-40/spl deg/C/85/spl deg/C). No laser diodes show any device characteristics change during environmental tests and their stability has very little dependence on current bias. Although the photodiodes show an increase in leakage current under high-temperature high-humidity tests and the rate of leakage current increase is proportional to the square root of bias voltage, the increase is negligible for system use. These plastic modules can be applied to actual access networks and other fiber-optic networks.

High-silica multimode channel waveguide structure for minimizing fiber-waveguide-fiber coupling loss

The optimum structure for high-silica channel waveguides which are connected to input and output graded-index fibers having a 50-μm core diameter and a 1.0-percent refractive-index difference is studied theoretically and experimentally. Theoretical optimum waveguide structure is obtained on the basis of ray optic analysis. For the step-index waveguide with 1.0-percent refractive-index difference, the theoretical minimum coupling loss (input coupling loss + output coupling loss) is 1.7 dB for an optimum core of 38 μm both in depth and width. For the graded-index waveguide with parabolic-index profile in the depth direction and step-index profile in the width direction, the theoretical coupling loss is 1.1 dB for an optimum core of 38 μm in width and 50 μm in depth. These estimations were in good agreement with the experimental results, which were 1.8 dB for the step-index waveguide and 1.3 dB for the graded-index waveguide.

Reduction of waveguide facet reflection in optical hybrid integrated circuit using saw-toothed angled facet

A saw-toothed facet structure is proposed to reduce the waveguide facet reflection in an optical hybrid integrated circuit. This structure was used to achieve the hybrid integration of a semiconductor laser amplifier (SLA) on a planar lightwave circuit (PLC) platform. Gain ripple for a flat facet was reduced from 3.6 dB to 0.6 dB by setting a facet angle of 35 degrees. The SLA insertion loss was 3.5 dB at 0 degrees and 4.0 dB at 35 degrees with an SLA injection current of 80 mA. Thus the sawtoothed facet is confirmed to reduce facet reflection effectively without significant insertion loss increase.<<ETX>>

Low-cost hybrid-integrated optical modules for FTTH and WDM subscriber systems

Several types of hybrid-integrated optical modules using PLC platform technologies have been described as low-cost solutions for both FTTH and WDM subscriber systems.