Fusao Shimokawa

Self-holding optical waveguide switch controlled by micromechanisms

We propose an n/spl times/n optical switch that is suitable for flexible and reliable optical access networks and for reconfigurable optical inter-module connections in large-scale processing systems. The switch consists of an intersecting waveguide matrix, matching oil, and microactuators. Switching is based on the movement of oil due to capillary pressure, which is controlled by the microactuator. The necessary switching conditions were calculated and the results showed that both the oil volume and the microactuator position must be controlled. A trial optical switch was fabricated to test the switching principle, and switching and self-holding were both confirmed. These results show the feasibility of a very small self-holding n/spl times/n optical switch that uses a waveguide matrix and microactuators made by using microfabrication technologies.

Low-loss intersecting grooved waveguides with low /spl Delta/ for a self-holding optical matrix switch

Our method using low /spl Delta/ waveguides decreases the insertion loss of intersecting optical waveguides with grooves. Theoretical analysis by the beam propagation method or the plane wave expansion method shows the benefit of decreasing the insertion loss. Experimental measurements on a trial matrix (21/spl times/21) showed that the transmission loss greatly decreased with decreasing /spl Delta/. The reflection loss was less sensitive to the positional deviation of the groove than that of conventional /spl Delta/ waveguides. The experimental results were used to calculate the total insertion loss. It decreased from 5.72 to 3.28 dB, when /spl Delta/ decreased from 0.31 to 0.15% for a matrix scale of 50/spl times/50. >

Strictly non-blocking N/spl times/N thermo-capillarity optical matrix switch using silica-based waveguide

We propose a silica-based strictly non-blocking N/spl times/N thermo-capiliarity optical matrix switch. The feasibility of 2-dimensional batch oil injection and multilayered wiring were confirmed by type 16/spl times/16 optical matrix switch.

Fabrication of fluorinated polyimide waveguides on copper-polyimide multilayer substrates for opto-electronic multichip modules

We have developed new opto-electronic substrates, which are key components for constructing opto-electronic multichip modules. These substrates consist of optical waveguides (for OEIC chip-to-chip optical interconnection) on copper-polyimide multilayers for high-speed electrical transmission. Low-loss (0.4 dB/cm) fluorinated polyimide ridge waveguides with nearly vertical and smooth sidewalls (<0.1 p m) on copper-polyimide multilayer substrates are achieved using spincoating, photolithographic patterning, and highly selective dry etching. The low propagation loss is retained even after heat-treatment at the soldering temperature of 300/spl deg/C. The uniformity of the waveguide film thickness is about /spl plusmn/2% and the uniformity of the etched depth in the ridge waveguides (including the fiber-guiding groove) is about /spl plusmn/2% over the whole substrate (9/spl times/9 cm). This new substrate achieves self-aligned fiber-to-waveguide coupling with a low coupling loss deviation (/spl sime/0.1 dB).<<ETX>>

Waveguide optical switch for 8:1 standby system of optical line terminals

Summary form only given. Summary form only given. To reduce the cost of the optical access network without sacrificing system reliability, instead of using a fully duplex standby system, we are planning to allow a single reserve to be shared among several pieces of equipment. We show the planned configuration of a standby system to share a reserved optical subscriber unit (OSU) in an optical line terminal (OLT) for NTTs passive double star (PDS) optical access network. This solution, however, requires an optical switch to have high reliability and low insertion loss and be independent of both wavelength and polarization, inexpensive and self-latching. None of the switches proposed so far meet all these requirements. In this paper we propose an 8:1 optical switch that is suitable for sharing a reserve OSU to reduce the standby cost. Our switch is an intersecting waveguide switch, whose operating principle is based on thermo-capillarity.

Optical switch based on thermocapillarity

Space-division optical switches are essential for the protection, optical cross-connects (OXCs), and optical add/drop multiplexers (OADMs) needed in future fiber-optic communication networks. For applications in these areas, we proposed a thermocapillarity switch called oil-latching interfacial-tension variation effect (OLIVE) switch. An OLIVE switch is a micro-mechanical optical switch fabricated on planar lightwave circuits (PLC) using micro-electro-mechanical systems (MEMS) technology. It consists of a crossing waveguide that has a groove at each crossing point and a pair of microheaters. The groove is partially filled with the refractive-index-matching liquid, and optical signals are switched according to the liquids position in the groove, i.e., whether it is passing straight through the groove or reflecting at the sidewall of the groove. The liquid is driven by thermocapillarity and latched by capillarity. Using the total internal reflection to switch the optical path, the OLIVE switch exhibits excellent optical characteristics, such as high transparency (insertion loss: < 2 dB), high extinction ratio (> 50 dB), and low crosstalk (< -50 dB). Moreover, since this switch has a simple structure and bi-stability, it has wide variety of applications in wavelength division multiplexing (WDM) networks.

Optical device positioning by using Becke lines

A new passive-alignment technique using Becke lines is proposed for assembling optical devices. Optical devices with a waveguide structure, such as planar lightwave circuits and laser diodes, have a core or active layer whose refractive index is slightly higher than that of the surrounding area. The Becke lines are diffractive stripes appearing at the boundary between materials having different refractive indices such as cores and the surroundings. For low-loss optical connection between the devices, their cores must be precisely aligned with each other. In our technique, the optical devices are aligned by observing the Becke lines located on both edges of the core, which make it possible to determine the exact core position. With this technique, optical devices can be precisely aligned without using the thin metal-film markers used for conventional passive alignment. The position of an optical waveguide was experimentally aligned by illuminating it with infrared (IR) light, obseving the Becke lines with video system and moving it with motor-driven stages. The positioning uncertainty was less than 0.2 tm, which is the same as the resolution of the video system used. This technique is thus practical for precisely assembling optical devices.

Low loss intersecting grooved waveguides with low /spl Delta/ for self-holding optical matrix switch

The method using low /spl Delta/ waveguides decreases the insertion loss of intersecting optical waveguides with grooves. Theoretical analysis by the beam propagation method or the plane wave expansion method shows the benefit of decreasing the insertion loss. Experimental measurements on a trial matrix (21/spl times/21) showed that the transmission loss greatly decreased with decreasing /spl Delta/. The reflection loss was less sensitive to the positional deviation of the groove than that of conventional /spl Delta/ waveguides. The experimental results were used to calculate the total insertion loss. It decreased from 5.72 dB to 3.28 dB when /spl Delta/ decreased from 0.3% to 0.15% for a matrix scale of 50/spl times/50.<<ETX>>