High performance optical switches integrated with silica-based planar lightwave circuits on Si

We demonstrate a low power consumption differential quadrature phase-shift keying (DQPSK) demodulator using silica-based planar lightwave circuit (PLC) technology. A reduction of the power consumption is achieved by suppressing the temperature dependence of the circuit characteristic and eliminating a thermo-electric cooler (TEC) device. The maximum power consumption of the fabricated demodulator with an operating temperature range of -5degC to 70degC is 1.4 W, which is 60% lower than that of a conventional PLC demodulator with TEC. We report experimental results that demonstrate its good demodulation performance for a 43-Gb/s DQPSK system.

Optical splitters are essential for the construction of optical networks such as fiber-to-the home systems. These devices should exhibit not only good optical characteristics such as low loss and polarization insensitivity but also long-term reliability. Silica-based planar lightwave circuits (PLCs) on Si can form one of the most suitable Y-branching splitters because they have the advantages of low loss, low coupling loss to optical fibers and high reproducibility[l]. When PLC splitters are used in practice, the input and output fibers must be connected to waveguides. Therefore, it is necessary to establish a precise connection technique and confirm its long-term stability. However, neither the connection performance of splitters with up to 32 ports nor the long-term reliability of fiber-connected splitters have yet been evaluated in detail. Here, we describe the connection performance and reliability of 1×8 and 1×32 splitter modules. We have chosen strict Bellcore requirements [2] as the first step in evaluation of the PLC splitter reliability. The requirements are recognized as a standard for reliability tests on optical devices, and define the optical criteria as well as the test conditions.

While silica waveguide PLC products have been deployed in various systems and applications, hybrid integration of semiconductor opto-electronic devices on silica-based planar lightwave circuit (PLC) has become the mainstream platform for small form factor, low-cost and high volume integrated transceiver modules. One of the main benefits of hybrid integration is the wafer-scale process, which greatly reduces chip/module size and assembly cost. This paper reviews the development of this technology, and as an example, presents a hybrid integrated transmitter with four wavelengths on silica PLC chip for LX4 and 10GbE applications.

We propose a novel passive alignment method for multiple silica-based planar lightwave circuit (PLC) interconnections. The method employs grooves for fitting formed on a silica-based PLC with optical fibers. We achieved low-loss PLC interconnections with the method. The method is a promising way of realizing cost-effective and pluggable multi-PLC integration.

We propose and demonstrate a new stacked packaging structure using silica-based planar lightwave circuits (PLCs) with integrated micro-mirrors. This structure enables us to integrate active devices on PLCs with certain flexibility as regards optical coupling design and device selection. To achieve this, we developed an integrated micromirror with an accurate reflection angle and shielding structures to prevent crosstalk, and successfully demonstrated an 8-channel photodiode array module with excellent characteristics consisting of a high responsivity of > 0.85 A/W and a low crosstalk of < -65 dB.

We demonstrated a compact 16×16 multicast switch (MCS) made from a silica-based planar lightwave circuit (PLC). The switch utilizes a new electrical connection method based on surface mount technology (SMT). Five electrical connectors are soldered directly to the PLC by using the standard reflow process used for electrical devices. We reduced the chip size to half of one made with conventional wire bonding technology. We obtained satisfactory solder contacts and excellent switching properties. These results indicate that the proposed method is suitable for large-scale optical switches including MCSs, variable optical attenuators, dispersion compensators, and so on.

A monolithically integrated 32-channel client re-configurable optical add/drop multiplexer on silica-based planar lightwave circuit is demonstrated. It can be reconfigured to add/drop any of the 32 input channels from/to any of the 4 add/ drop ports.

The authors propose new wavelength-insensitive directional couplers (WINCs) with series-tapered waveguides in the coupling region. The wavelength-insensitive characteristics are investigated with respect to the geometric symmetry of the series-tapered coupling structure. An approximate analysis of three types of WINC is made using simple transmission matrix multiplication. These new WINC's were fabricated based on silica-based planar lightwave circuits (PLCs) on silicon substrates. The experimental results for the wavelength-insensitive responses of the series-tapered coupler, which was designed in detail with the beam propagation method (BPM), are in good agreement with the calculated results. The novel wavelength-insensitive characteristics of these couplers are also demonstrated for the first time.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

This paper reviews recent progress on low power consumption thermo-optic switches using silica-based planar lightwave circuits. These switches are indispensable for monolithically integrated PLC devices that include many thermo-optic switches.

A correlation-based optical label processor is proposed that recognizes multiple phase-modulated labels. Noise is suppressed by employing a unique label format and differential receiving. The operating principle is confirmed experimentally by using a silica-based planar lightwave circuit.

Optical dense wavelength division multiplexing (WDM) systems have been investigated in order to enlarge transmission capacity and improve network flexibility. Arrayed-waveguide grating (AWG) multiplexers are key components in such systems because they can process plural wavelengths simultaneously. This paper reviews recent work on AWGs based on silica-based planar lightwave circuits and their applications to dense-WDM systems. An AWG consists of plural input/output waveguides, two focal slab waveguides and a waveguide array. Applications investigated include optical add/drop multiplexers, wavelength routers and multi-channel light sources.

La and Ga substituted yttrium iron garnet single-mode buried channel waveguides, prepared using liquid-phase-epitaxial growth and Ar ion beam etching, have been successfully applied as 45/spl deg/ nonreciprocal waveguide rotators (NRWR) for hybrid integrated waveguide isolators at /spl lambda/=1.55 /spl mu/m. The optical and magneto-optical properties of the prepared 45/spl deg/ NRWRs and the epitaxial films are investigated in detail. We describe the assembly procedure and present optical measurement results for the hybrid integrated waveguide isolators. The hybrid isolators are composed of a 45/spl deg/ NRWR, a half-wave plate sheet, thin film-type polarizers, a thin plate-type permanent magnet and a silica-based waveguide on a silicon substrate. We obtained good waveguide isolators with low insertion losses ( 25 dB) in the 1.5 /spl mu/m wavelength band.

A compact arrayed-waveguide grating based 64×64 router module with uniform loss and cyclic-frequency performance has been developed using a silica-based planar lightwave circuit. The circuit was miniaturised sufficiently for integration on a 4-inch substrate using high-contrast 1.5%-Δ waveguides. A low module insertion loss of 5.4 to 6.8 dB was achieved as a result of reducing the loss at intersecting waveguides by employing a horizontally enlarged core.

We propose a novel structure that reduces the switching power of a silica-based thermooptic switch (TOSW). The structure consists of silicon trenches and heat insulating grooves, which are formed beneath and beside the arms of a Mach-Zehnder interferometer, respectively. We optimize the structure using the differential-element method (DEM) and fabricate a 2 /spl times/ 2 TOSW with a switching power of only 90 mW, namely, 75% less than that of a conventional TOSW. We also obtain an insertion loss of about 1 dB and an extinction ratio of over 30 dB with a response time from 0% to 90% of 4.9 ms. We then use the structure to fabricate an 8 /spl times/ 8 matrix switch and confirm a total power consumption of 1.4 W with an average insertion loss of 7.4 dB and an extinction ratio of 50.4 dB for 64 possible optical paths.

Construction of large scale switch matrix by interconnecting integrated optical switch chips with EDFAs