Kazuhiko Kurata

A surface mount type single-mode laser module using passive alignment

A novel single-mode laser module has been developed using a surface mounting technique. A simple receptacle structure for the module output port is also designed. This module offers high coupling efficiency and optical coupling using the passive alignment technique. A module size of 7.6 mm/spl times/12 mm/spl times/3 mm is achieved, which is very friendly for the automatic assembly line as well as the module mounting process on circuit boards. A laser diode (LD) is passively positioned by utilizing a pair of alignment marks, each of which located on the LD and Si substrate, a single-mode fiber with a microhemispherical lens on the fiber facet is self-aligned on a Si-V groove. The LD to single-mode fiber coupling loss and standard deviation are found to be 5 dB and 1.5 db, respectively. The simple receptacle structure enables one to use this module in the same way as conventional surface mount electrical components. The module assembly process is simplified by successively mounting subassembly parts.

Mass production techniques for optical modules

This paper describes optical packaging techniques to realize mass production. A novel passive alignment technique is developed as a key technique for module assembly. A laser diode (LD) is passively positioned on a Si substrate by detecting a pair of alignment marks located on the LD and Si substrate. A single-mode fiber is self aligned on a Si V-groove. A simple receptacle structure for the module output port is also designed. This structure has realized both automatic module assembly and automatic module mount on a circuit board, for the first time. In addition to packaging techniques, advanced module applications such as a surface mount LD module and a hybrid integrated waveguide module, are introduced.

A 10 Gbps x 12 channel pluggable optical transceiver for high-speed interconnections

We developed a 10 Gbps x 12 channel pluggable optical transceiver. It consists of three photoelectric devices, an FR4 substrate with a microcontroller, a 12 x 2 multimode fiber with three optical connectors for the three photoelectric devices, an electrical connector, and a heat sink. This transceiver can be vertically plugged to the motherboard by using electrical connector. A vertical plug enables the photoelectric conversion devices in the optical transceiver to be located close to the logic LSI on the motherboard at high density to prevent the waveform degrading. Moreover, it is possible to do prompt repairs if the transceiver breaks down because the module is pluggable. We demonstrated error-free operation after 50 m transmission over a GI/50 multimode fiber (MMF). These performance characteristics indicated that this optical transceiver is feasible for implementation in high- throughput interconnections.

Optical interconnection as an IP macro of a CMOS library

With the aim of producing a switch LSI with several-hundred-Gb/s-class throughput, we first developed LAN-LSIs with 10-Gb/s-class optical input/output (I/O) buffer. The optical I/O buffer was supplied as a set consisting of an optical-electrical package, soft or hard macros of the optical interface, and library files for a targeted CMOS technology. Using such library files, system LSI designers can implement an optical interface in their chips in a conventional design manner.

Automated mass production line for optical module using passive alignment technique

Since the growth of fiber optic communications, extremely low cost optical modules have been expected to be realized. Particularly for the subscriber applications and local area networks (LANs), less than half of past module cost is required. In accordance with the spread of fiber optic transmission, higher volume manufacture is also needed. To attain both of low cost and high productivity, we developed passive alignment technique and optical coupling structure that is suitable for automatic assembly. We also developed automatic assemble equipment for producing several types of optical modules. To reduce optical module cost, it is important to cut down the assembly cost and expensive parts such as optical lens. The passive alignment technique brings us to realize easy assembly of modules and minimize the constructed components of optical coupling. Our mass production techniques include not only for optical coupling but also packaging of the module. We have several types of optical modules according to different fiber communication systems; there are laser modules, detector modules, optical interface modules that are integrated optical coupling and electrical circuit, and PLC (Planar Lightwave Circuit) modules that are integrated passive component. Basically all modules have same optical coupling structure and keep the design rules for automatic assembly. Accordingly, we can use the same equipment for the same assembly process. In this paper, we will introduce basic assembly process and our mass production line for optical coupling and packaging by using passive alignment technique.

125-µm-pitch × 12-channel “optical pin” array as I/O structure for novel miniaturized optical transceiver chips

We have developed an optical I/O structure using an array of optical pins for a chip-scale parallel optical module named an “optical I/O core.” The optical pin is a kind of vertical polymer waveguide, which is made from UV curable resins. The optimum shape and combination of resins for the optical pins were determined by ray-trace simulation. The numerical aperture (NA) of the developed optical pins is more than 0.4. A photolithographic technique was used to produce a 125-μm-pitch × 12-channel optical pin array. The coupling losses between a GI-50 multi-mode optical fiber (MMF) and the optical pins for a receiver (RX) and transmitter (TX) were 0.41 dB and 2.3 dB, respectively. Wide coupling tolerance of more than 25 μm was also obtained when the allowable excess loss was 0.5 dB. Furthermore, clear eye diagrams were obtained for 25-Gbps back-to-back transmission by using the optical I/O cores with the optical pins and GI-50 MMF.

1-Gb/s modulation characteristics of a vertical-cavity surface-emitting laser array module

Vertical-cavity surface-emitting lasers (VCSELs) are promising devices for low-cost optical data communications. We fabricated an 8-channel VCSEL array module that is easily push/pull-connected to a mechanically transferable (MT) fiber connector. Modal noise had little adverse effect on bit-error-rate (BER) performance. A BER measurement of 8-channel VCSELs recorded a sensitivity of less than -23.7 dBm at 1 Gb/s and BER=10/sup -11/.

Hybrid WDM transmitter/receiver module using alignment free assembly techniques

A hybrid WDM transmitter/receiver module with a Planar Lightwave Circuit (PLC) has been developed using alignment free assembly techniques. The newly developed WDM module consists of three optical components. One is an LD-fiber coupling unit, the second is a PLC unit on which two kinds of fibers and an LD-fiber coupling unit are mounted, and the last is a ceramic PKG on which a bare receiver-amplifier and photodiodes are mounted. These three components can be assembled without optical adjusting, so that high productivity and a compact size of 36 mm/spl times/12.5 mm/spl times/3 mm are achieved. This WDM module can transmit/receive 1.3 /spl mu/m bidirectional signals by time compression multiplexing and multi/demultiplex 1.3/1.5 /spl mu/m signals.

100-Gbps CMOS transceiver for multilane optical backplane system with a 1.3 cm 2 footprint

A compact 25-Gbps × 4-channel optical transceiver has been fabricated for optical backplane systems. Power consumption was as low as 20 mW/Gbps. A transmission experiment was successfully conducted at 25 Gbps.

A 400 Gbps backplane switch with 10 Gbps/port optical I/O interfaces

A 400 Gbps backplane switch was developed with low-cost, small-size, 8-channels 10 Gbps/port optical I/O and a SiGe Bi-CMOS switch LSI on a 60x60-mm2 BGA package. It indicates the applicability of backplane switch for high throughput backplane interconnections.