Novel Stacked Packaging Structure Using Silica-Based PLC with Integrated Micro-Mirrors and Its Application to 8ch PD Array Module

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 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.

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.

Silica-based planar lightwave circuit (PLC) devices are starting to be introduced into commercial optical communication systems. PLC devices such as optical splitters, wavelength-insensitive coupler (WINC) arrays, and hybrid- integrated wavelength-division-multiplexing (WDM) transceivers are used to construct cost effective optical access systems. In trunk lines, on the other hand, arrayed-waveguide gratings (AWG) are employed for dense WDM systems to increase the transmission capacity. This paper reviews the current status and recent progress on these practical PLC devices.

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>

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.

We have investigated an optical signal processor using electro-optic polymer waveguides operating at a wavelength of 1.55 mum. Due to recent developments, many useful optical devices have become available such as optical filters, modulators, switches, and multiplexers. It will be useful to have a single optical device, which is reconfigurable to implement all of these functions. We call such a device an ldquooptical signal processor,rdquo which will play a similar role to digital signal processors in electrical circuits. We realize such an optical device in a planar lightwave circuit. Since the planar lightwave circuits are based on the multiple interference of coherent light and can be integrated with significant complexity, they have been implemented for various purposes of optical processing such as optical filters. However, their guiding waveguides are mostly passive, and the only viable mechanism to reconfigure their functions is thermal effects, which is slow and cannot be used for high-speed applications such as optical modulators or optical packet switches. On the other hand, electro-optic polymer has a very high electro-optic coefficient and a good velocity match between electrical and optical signals, thus, permitting the creation of high-speed optical devices with high efficiency. Therefore, we have implemented a planar lightwave circuit using the electro-optic polymer waveguides. As a result, the structure is complex enough to generate arbitrary functions and fast enough to obtain high data rates. Using the optical signal processor, we investigate interesting applications including arbitrary waveform generators.

A waveguide lens, composed of multistage polymer-filled thin grooves in a silica planar lightwave circuit (PLC) is proposed and a low-loss structure has been designed. A waveguide lens in a silica slab waveguide has been fabricated using reactive ion etching (RIE) and formed by filling with polymer. Both an imagding optical system and a Fourier-transform optical system can be configured in a PLC using a waveguide lens. It renders the PLC functional and its design flexible. To obtain a shorter focal length with a low insertion loss, it is more effective to use a multistage lens structure. An imaging optical system and a Fourier-transform optical system with a focal length of less than 1000 µm were fabricated in silica waveguides using a multistage lens structure. The lens imaging waveguides incorporate a 16–24-stage lens, with insertion losses of 4–7 dB. A 4 ×4 optical coupler, using a Fourier-transform optical system, utilizes a 6-stage lens with losses of 2–4 dB.

To achieve much larger capacity in point-to-point wavelength division multiplexing (WDM) transmissions, we must increase their bit rate per wavelength as well as their channel number. Optical networks are continuing to adopt rings and packet-switched systems. These advanced optical systems require highly functional optical devices to exceed the electrical speed limit. I describe recent advances in planar lightwave circuit (PLC) based functional devices, such as dispersion equalizers, large-scale arrayed-waveguide gratings (AWGs), and optical signal processing devices.

Integrated Optical Circuits (IOCs) have been under development for over three decades. In an analogy to electronic integrated circuits, developers of IOCs envision the possibility of combining several or many optical processing functions on a single miniature platform, such as a semiconductor chip, fabricated using processes similar to those used for electronic chip production. Also called Planar Lightwave Circuits (PLCs) or Planar Optical Chips (POCs), these devices incorporate functional optical components such as linear or curved waveguides to conduct light from one location to another, filters fabricated from specially shaped waveguides that control the spectral characteristics of the light, and lenses and mirrors embedded in waveguides to alter the shape of the light. The PLCs may be interfaced to other optical components and devices via optical fibers or other interconnecting devices such as the mode converters described below.

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.

This paper reviewed recent advances in silica-based PLC-SWs on Si including N/spl times/N matrix switches (up to 16/spl times/16), 1/spl times/N switches (up to 1/spl times/128), an N/spl times/N switching sub-system (128/spl times/128). Reliability and the low power consumption structure of PLC-SWs were also mentioned. Further advances in PLC-SWs will contribute greatly to the construction of optical networks.