Fabrication of semiconductor optical switch module using laser welding technique

The 4/spl times/4, 1/spl times/2, and 1/spl times/4 semiconductor optic-switch modules for 1550 nm optical communication systems were fabricated by using the laser welding technique based on the 30-pin butterfly package. For better coupling efficiency between a switch chip and an optical fiber, tapered fibers of 10-15 /spl mu/m lens radius were used to provide the coupling efficiency up to 60%. The lens to lens distance of the assembled tapered fiber array was controlled within /spl plusmn/1.0 /spl mu/m. A laser hammering technique was introduced to adjust the radial shift, which was critical to obtain comparable optical coupling efficiencies from all the channels at the same time. The fabricated optical switch modules showed good thermal stability, with less than 5% degradation after a 200 thermal cycling. The transmission characteristics of the 4/spl times/4 switch module showed good sensitivities, providing error free transmissions below -30 dBm for all the switching paths. The dynamic ranges for the 4/spl times/4 and 1/spl times/2 switch modules were about 8 dB for a 3 dB penalty and about 17 dB for a 2 dB penalty, respectively.     

Packaging for a 40-channel parallel optical interconnection modulewith an over-25-Gbit/s throughput

NTT is currently working on developing a high-throughput interconnection module that is both compact and cost effective. The technology being developed is called “parallel inter-board optical interconnection technology”, or “ParaBIT”. The ParaBIT module that has been developed is the first step; it is a front-end module with 40 channels, a throughput of over 25 Gbit/s, and a transmission distance of over 100 m along multimode fibers. One major feature of this module is the use of vertical-cavity surface-emitting laser (VCSEL) arrays as very cost-effective light sources. These arrays enable the same packaging structure to be used for both the transmitter and receiver. To achieve super-multichannel performance, high-density multiport bare-fiber (BF) connectors were developed for the module's optical interface. Unlike conventional optical connectors, these BF connectors do not need a ferrule or spring. This ensures physical contact with an excellent insertion loss (less than 0.1 dB per channel). A polymeric optical waveguide film with a 45° mirror for coupling to the VCSEL and photo-diode (PD) arrays by passive optical alignment was also developed. To facilitate coupling between the VCSEL/PD array chips and the waveguide, a packaging technique was developed to align and die bond the optical array chips on a substrate. This technique is called transferred multichip bonding (TMB); it can be used to mount optical array chips on a substrate with a positioning error of only several micrometers. These packaging techniques enabled ultra-parallel interconnections to be achieved in prototype ParaBIT modules     

A 10-Gb/s optical transmitter module with a monolithicallyintegrated electroabsorption modulator with a DFB laser

A compact 10-Gb/s optical transmitter module with small-chirp output was developed by using a monolithically integrated electroabsorption modulator with a distributed-feedback laser. This module can be operated at a bit rate of more than 10 Gb/s at 1.55 μm, and shows a high modulated output power of ~1 dBm with a low optical coupling loss of 3.2 dB between chip and fiber. A multifunctional and compact optical isolator with a monitor photodiode was also developed to decrease noise     

High performance modules of 2.5 Gbps modulator integrated DFBlasers using new RF impedance matching technique

We report the improvement of frequency response characteristics of 2.5 Gbps modulator integrated distributed feedback (MI-DFB) laser modules using new impedance matching technique. Frequency responses for the fabricated module using the `+' shaped microstrip line for impedance matching have been significantly improved such as the RF return loss of 11 dB and the 3 dB frequency bandwidth of 4.1 GHz, compared to 6 dB return loss and 1.5 GHz bandwidth for the conventional module. These results can also be predicted by the simulation of frequency responses for the modules, From the fabricated MI-DFB laser modules, good transmission performance has been obtained up to 640 km     

基于端面耦合的InP基激光器/硅光波导混合集成技术研究

针对硅光子集成回路缺少实用化光源的问题,提出了一种1.55μm波段InP基FP激光器芯片、InP基PIN光电探测器芯片与硅光波导芯片集成模块的设计与制备方法。使用CMOS工艺兼容的硅光无源器件制备工艺,设计并制备了倒拉锥型端面耦合器,与锥形透镜光纤耦合效率为36.7%。采用微组装对准技术将激光器芯片与硅波导芯片耦合、UV固化胶固化后耦合效率为35.8%,1 dB耦合对准容差横向为1.2μm,纵向为0.95μm。     

Multichip Integration on a PLC Platform for 16 × 16 Optical Switch Module Using Passive Alignment Technique

We have integrated eight sets of four-channel semiconductor optical amplifier (SOA) array chips on a silica-based planar lightwave circuit (PLC) platform for 16 times 16 optical switch module by flip-chip bonding technique. To accurately bond eight sets of the arrayed SOA chips on a PLC platform, two methods of two-step assembly and one-step assembly were tried. Among the results of two assembly methods, one-step assembly was estimated to be desirable in respect of the horizontal and vertical bonding accuracy. The bonding accuracy was measured to be within 0.5 mum. Also, we demonstrated 16 times 16 optical switch module.     

Planar lightwave circuit platform with coplanar waveguide foropto-electronic hybrid integration

We propose a planar lightwave circuit (PLC) platform constructed on a silica-on-terraced-silicon (STS) substrate for opto-electronic hybrid integration. This platform consists of an embedded silica PLC region, a terraced silicon region for optical device assembly, and a high-speed electrical circuit region. In the electrical circuit region, the coplanar waveguides (CPW) are prepared on a thick-silica/silicon substrate. This structure reduces the propagation loss of the CPW drastically to 2.7 dB/cm at 10 GHz, because the loss tangent (tan δ) of the dielectric constants of silica is much smaller than that of silicon. In order to study the feasibility of this PLC-platform for multi-gigabit operation, we used it to fabricate an LD module in which an LD chip and LD-driver integrated circuits (IC) are assembled on the PLC-platform. A bit error rate measurement of this LD module in a 2.5 Gb/s NRZ showed that this platform is applicable to multi-gigabit optical signal processing     

Spot-size converter integrated polarization insensitivesemiconductor optical amplifiers

Spot-size converter integrated polarization-insensitive semiconductor optical amplifier (SSC-SOA) with angled window has been designed and fabricated using both selective area growth and successive lateral tapering. A narrow beam divergence of 80×15°, 0.2-dB amplified-spontaneous-emission ripple, and 1.5-dB polarization sensitivity within the 3-dB optical bandwidth were obtained at 29.7-dB chip gain. The fiber-to-fiber gain of the SOA module was measured to be 22 dB at 200 mA, i.e., the coupling loss was below 4 dB per each facet     

Fabrication and Characteristics of 40-Gb/s Traveling-Wave Electroabsorption Modulator-Integrated DFB Laser Modules

We have developed 40-Gb/s traveling-wave electroabsorption-modulator-integrated distributed feedback laser (TW-EML) modules using several advanced technologies. First, we have adopted a selective area growth (SAG) method in the fabrication of the 40-Gb/s EML device to provide active layers for the laser and the electroabsorption modulators (EAMs) simultaneously. The fabricated device shows that the measured 3-dB bandwidth of electrical-to-optical (E/O) response reaches about 45 GHz and the return loss (S₁₁) is kept below -10 dB up to 50 GHz. For the module design of the device, we mainly considered electrical and optical factors. The measured S₁₁ of the fabricated 40 Gb/s TW-EML module is below -10 dB up to about 30 GHz and the 3-dB bandwidth of the E/O response reaches over 35 GHz. We also have developed two types of coplanar waveguide (CPW) for the application of the driver amplifier integrated 40 Gb/s TW-EML module, which is a system-on-package (SoP) composed of an EML device and a driver amplifier device in a module. The measured S₁₁ of the two-step-bent CPW is below -10 dB up to 35 GHz and the measured S₁₁ of the parallel type CPW is below -10 dB up to 39 GHz.     

OEIC WDM transceiver modules for local access networks

The authors report measurements of fibre-optic transceiver modules which use a single optoelectronic integrated circuit (OEIC) subsystem. The optical circuit contains a DFB laser, 3 dB coupler, WDM, monitor photodiode and pin photodetector elements, which are monolithically integrated on a semi-insulating substrate indium phosphide chip. This assembly is designed to provide complete subscriber-termination functionality for bidirectional telephony and unidirectional broadband communication links for access networks. The dual-in-line module provides single fibre network interfacing, is physically compact, is stable for domestic and business environments, requires no cooling, and has the potential to be manufacturable at low cost     

Milled-groove method for fiber-to-waveguide couplers

We report a simple milled-groove process integrated with a two-step ion-diffused waveguide fabrication for efficient coupling between single-mode fibers and integrated optical waveguides andY- branches. We demonstrate such a coupling technique using a) a multimode transition to single-mode waveguide coupler, and b) an integrated optical 3-dB branching waveguide coupler from a single-mode fiber to silver/sodium ion-enchanged waveguide components. The coupling loss was about 1-2 dB over a propagation length of 2 cm at an operating wavelength of 633 nm.     

Silica-based 8×8 optical matrix switch module with hybridintegrated driving circuits and its system application

A compact, low-crosstalk 8×8 optical matrix switch module has been developed. A thermooptic switch chip and driving circuits with TTL interfaces are integrated on a 100-mm² ceramic substrate. It achieved a low insertion loss of 10.0 dB, a low crosstalk level of -25.9 dB, and had excellent stability in practical operation. A photonic intermodule connector for electronic switching systems in the near future is also demonstrated through the use of these optical switch modules     

Compact and stable electroabsorption optical modulator modules

Very compact electroabsorption optical modulator modules that demonstrate high coupling efficiency and high stability have been developed. The modules show very good potential such as an insertion loss as low as 5 dB, or ultrahigh speed modulation of up to 46 GHz. The module fabrication techniques are also applicable to other optical devices that require fiber connections at both facets     

High-performance compact optical WDM transceiver module for passivedouble star subscriber systems

High-performance transceiver-type optical WDM interface modules with a volume of only 36 cc have been developed for PDS subscriber systems. The new module comprises an optical WDM sub-module, hybrid-integrated transmitter and receiver circuits. In the WDM sub-module, a planar lightwave circuit chip was hermetically sealed together with laser and photodiode chips in order to minimize the size of the transceiver module. The lightwave circuit was formed on an optical-waveguide chip by adopting a high-silica based optical-waveguide technology. The circuit has a 3-dB directional coupler for bi-directional transmission with a 1.3-μm wavelength through a single fiber and a wavelength division multiplexer between both 1.3-μm and 1.55-μm wavelengths. The overall characteristics of the fabricated WDM sub-module achieved were a responsitivity of 0.25±0.05 A/W, an insertion loss approximately 3 dB at 1.55 μm and an isolation of 35 dB between both wavelengths. Optical output power of the fabricated transceiver module was -3.8 dBm. Also, receiver sensitivity of less than -35 dBm with an overload of over -14 dBm were obtained by introducing high-speed automatic gain and threshold control techniques. Thus, an allowable span loss of over 30 dB and an optical dynamic range of over 20 dB were attained. The preamble bit length required to reach stable receiver operation was confirmed to be within three bits     

Integrated circuits for a 200 Mbit/s fiber-optic link

A set of three bipolar integrated circuits for a new fiber-optic link is described. The link operates at data rates of 5-200 Mb/s NRZ. The optical transmitter and receiver modules are compact and fit into standard 16-pin dual-in-line sockets. The power consumption of the transmitter module is 530 mW and the receiver module dissipates 310 mW. The optical loss budget is 20 dB, which is sufficient for link lengths of up to 5 or 6 km. The circuits have been designed in a 3-/spl mu/m bipolar process. The chip sizes are 2 mm/spl times/1.75 mm each.     

Multiple-chip precise self-aligned assembly for hybrid integratedoptical modules using Au-Sn solder bumps

We have developed a novel three-dimensional high precision self-aligned assembly using stripe-type Au-Sn solder bumps and a micro-press solder bump formation method. This produces a high bonding precision of 1 μm for optical device assembly in both lateral and vertical directions without the need for time-consuming optical axes alignment. Furthermore, we tested a hybrid integrated 4×4 optical matrix switch, in which multiple SSC-SOAG arrays were simultaneously positioned and optical fibers were passively positioned on a silica based PLC platform using this technology. Four optical chips and seven wiring chips are assembled on a planar lightwave circuit (PLC) platform. The insertion loss for each of these paths at an injection current of 40 mA was within a range of 9±4 dB. The average extinction ratio was 40 dB. This self-aligned assembly technology was shown to be useful for building hybrid-integrated multichannel optical network components     

光子晶体电光调制和粗波分复用集成器件研究

提出了一种用于电光调制和粗波分复用的片上集成器件。该集成器件的电光调制器模块和粗波分复用器模块都是由硅基光子晶体波导和L3型谐振腔组成,两个模块间采用硅基光子晶体波导连接。该器件根据等离子体色散效应,采用L3型谐振腔和PN结实现了对波长的调制;根据微腔与波导的直接耦合理论,采用L3型谐振腔结构实现了滤波。利用基于三维时域有限差分法(3D-FDTD)的Lumerical软件对其进行仿真分析,结果表明该集成器件在工作波长1530 nm和1550 nm下均可以先完成各自的电光调制再进行双通道波长的复用。该器件在工作波长1530 nm和1550 nm下的插入损耗分别为0.70 dB和0.95 dB,消光比分别为20.97 dB和22.05 dB,调制深度均为0.99,信道串扰分别为-29.05 dB和-27.59 dB,器件尺寸仅为17.83μm×17.3μm×0.22μm。该集成器件结构紧凑,易于集成,可应用于高速大容量波分复用光通信系统。     

A new type of demountable optical device for coupling single-mode planar waveguides to a multifiber array using passive alignment

A novel demountable optical device is developed for coupling single-mode waveguides to a multifiber array using passive alignment. This device is fabricated by forming V-grooves on a waveguide chip and precisely molding both end portions of the chip. The 1/spl times/8 coupling device exhibits a low insertion loss of 10.7 dB and a small loss change of /spl plusmn/0.2 dB for 100 reconnections.     

A novel bidirectional optical coupling module for subscribers

To overcome drawbacks and limitations of planar lightwave circuit based modules for bidirectional communications, such as the demand for several chips and in consequence more packaging efforts, we have recently developed a novel optical coupling technique using our unique 155 Mbps bidirectional laser chip. Since the chip is structured with a pin-photodiode monolithically integrated on a laser diode's waveguide, the optical coupling requires only the alignment of the chip with a fiber. To optically couple the laser diode and photodiode simultaneously with a single fiber, we have designed an unusual coupling structure using a fiber having a cleaved surface whose normal is 35/spl deg/ angled to the fiber core axis, and using an index-controlling medium with a refractive index of /spl sim/1.3. The bidirectional chip is flip-chip bonded and the fiber is passively aligned using a V-groove on the same substrate of 2.5/spl times/1.3 mm/sup 2/ in size. Even with this extremely small and simple scheme for bidirectional optical coupling, we could obtain an optical output power of -7/spl sim/-10 dBm and a responsivity of <-30 dBm, which are satisfactory to the STM-1 level telecommunications specifications.     

基于3 μm-SOI的波分复用/解复用器与电吸收型VOA的单片集成

波分复用/解复用器与可调光衰减器的是光通信系统中的重要元器件。为了得到制备工艺简单、响应速度快的二者的单片集成芯片,并且考虑到其与其他不同光器件的集成可能性,在绝缘体上硅材料制作了16通道、信道间隔200 GHz的阵列波导光栅复用/解复用器与电吸收型可调光衰减器的单片集成。该器件的片上损耗小于7 dB,串扰小于-22 dB。电吸收型VOA在20 dB的衰减量下的功耗为572 mW （106 mA,5.4 V）。此外,该器件可以实现光功率的快速衰减,在0~5 V的外加方波电压下,VOA上升及下降时间分别为50.5 ns和48 ns。