Pluggable photonic circuit platform using a novel passive alignment method

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 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 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 novel fabrication method and structure of a planar lightwave circuit (PLC) platform for hybrid integration of an optical module by passive alignment technology is presented. Precise formation of V-grooves in the PLC platform can be easily obtained by the proposed process. The passive alignments of optical elements, including optical fiber, are achieved in one-mask. LD modules were implemented by the proposed method.

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>

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.

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.

In this presentation we will present a new passive alignment method used to obtain highly efficient optical fibre coupling from VCSELs (vertical-cavity surface-emitting lasers). This method is compatible with low-cost, high-yield volume production of compact transceivers for applications in rugged environments. Coupling efficiencies larger than 94% have been obtained using this visually-aided passive alignment method for the coupling between a rounded-tip, 50μm core graded-index fibre and an 850nm VCSEL having an emission area diameter of approximately 25μm. Our alignment procedure was used to make compact, high-speed (2Gbps) transceivers that can work from -50 to 105oC. They have shown to be able to resist to mechanical shocks of more than 200g. They have also shown to maintain a constant coupling efficiency while being submitted to 35Grms random vibration tests around 200Hz.© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We present innovations in Planar Lightwave Circuits (PLCs) that make them ideally suited for use in advanced defense and aerospace applications. We discuss PLCs that contain no micro-optic components, no moving parts, pose no spark or fire hazard, are extremely small and lightweight, and are capable of transporting and processing a range of optical signals with exceptionally high performance. This PLC platform is designed for on-chip integration of active components such as lasers and detectors, along with transimpedance amplifiers and other electronics. These active components are hybridly integrated with our silica-on-silicon PLCs using fully-automated robotics and image recognition technology. This PLC approach has been successfully applied to the design and fabrication of multi-channel transceivers for aerospace applications. The chips contain hybrid DFB lasers and high-efficiency detectors, each capable of running over 10 Gb/s, with mixed digital and analog traffic multiplexed to a single optical fiber. This highlyintegrated functionality is combined onto a silicon chip smaller than 4 x 10 mm, weighing &lt; 5 grams. These chip-based transceivers have been measured to withstand harsh g-forces, including sinusoidal vibrations with amplitude of 20 g acceleration, followed by mechanical shock of 500 g acceleration. The components operate over a wide range of temperatures, with no device failures after extreme temperature cycling through a range of &gt; 125 degC, and more than 2,000 hours operating at 95 degC ambient air temperature. We believe that these recent advancements in planar lightwave circuits are poised to revolutionize optical communications and interconnects in the aerospace and defense industries.

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.

To develop polarization-insensitive semiconductor optical amplifier (SOA) gates into more efficient and functional optical components by using hybrid integration with a planer lightwave circuit (PLC) platform, vertical tapered spot-size converters were integrated into a SOA gate with a narrow mesa-stripe structure of submicrometer width leading to low coupling loss (2.6 dB). Very-low polarization dependence of gain ( 30 dB) were achieved in a wide wavelength range (40 nm). High-speed (<1 us) gate operation was also demonstrated. These results indicate that the spot-size converted SOA integrated on a PLC platform will perform well in wavelength-division-multiplexing (WDM) applications.

A hybrid-integrated coherent receiver module has been achieved using flip-chip bonding technology, consisting of a silica-based 90°-hybrid planar lightwave circuit (PLC) platform, a spot-size converter integrated waveguide photodiode (SSC-WG-PD), and a dual-channel transimpedance amplifier (TIA). The receiver module shows error-free operation up to 40Gb/s and OSNR sensitivity of 11.5 dB for BER = 10−3 at 25 Gb/s.

The environmental and mechanical reliability of a planar lightwave circuit (PLC)-type optical splitter modules is investigated with reference to the Bellcore requirements. The module is composed of Y-branching silica-based waveguides on Si connected to optical fiber with UV-curable adhesives and is packaged in a metal case which is filled with humidity-resistant resin. High optical performance such as low loss, low reflection, and thermal stability are obtained through the use of this fiber connection technique. Ten reliability tests including long-term environmental and mechanical tests were carried out for more than ten PLC splitter modules. Under one of the most severe sets of conditions (75/spl deg/C and 90% RH), all the 19 samples we tested were stable for more than 5000 hours. Other tests confirmed that the PLC splitters offer long-term stability and that their optical characteristics have sufficient mechanical strength. These results indicate that the PLC splitters can be used for practical applications.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>