M. Yanagisawa

Multichip optical hybrid integration technique with planar lightwave circuit platform

A two-step bonding technique for optical device assembly on a planar lightwave circuit platform was developed, which consists of a chip-by-chip thermo-compression prebonding step and a simultaneous reflow bonding step. The technique was used to realize multichip optical integration on the platform. The characteristics of the bonding technique were examined by investigating its strength and accuracy. The bonding accuracies in the horizontal and vertical directions were 1.1 and 0.8 /spl mu/m, respectively, with high bonding strength. The technique was first applied to a 3 chip integrated transceiver module and the 136 fabricated modules exhibited good performance. The average coupling loss between the laser diodes and the waveguide was estimated to be 4.1 dB and stable characteristics were observed during 1200 cycle thermal shock tests between -40 and 85/spl deg/C. Next, the two-step bonding technique was used for a 4 channel laser diode module on which 8 optical device chips were integrated and a low coupling loss was achieved of better than 4.2 dB which is as good as that of the 3 chip integrated optical modules.

New structure of silica-based planar lightwave circuits for low-power thermooptic switch and its application to 8 /spl times/ 8 optical matrix switch

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.

Hybrid integration of spot-size converted laser diode on planar lightwave circuit platform by passive alignment technique

An index alignment technique was developed for a planar lightwave circuit platform. The technique was successfully applied to the hybrid integration of a spot-size converted laser diode on the platform. The fabricated modules exhibited an average coupling loss of 4.2 dB and a maximum optical output power of 10 mW at an injection current of 70 mA.

Low-power consumption silica-based 2 x 2 thermooptic switch using trenched silicon substrate

We propose a silica-based 2/spl times/2 thermooptic switch using heat insulating grooves and trenches on a Si substrate to reduce electric power consumption. The switching power of a fabricated switch was successfully reduced to 135 mW, less than 1/3 that of a conventional switch. No detrimental effect on optical characteristics was observed: we obtained the insertion loss of 1 dB, the extinction ratio of better than 30 dB and no polarization dependency.

A 1.3/1.55-/spl mu/m wavelength-division multiplexing optical module using a planar lightwave circuit for full duplex operation

We developed a hybrid integrated optical module for 1.3/1.55-/spl mu/m wavelength-division multiplexing (WDM) full-duplex operation. The optical circuit was designed to suppress the optical and electrical crosstalk using a wavelength division multiplexing filter, and an optical crosstalk of -43 dB and an electrical crosstalk of -105 dB were achieved with a separation between the transmitter laser diode and the receiver photodiode of more than 9 mm. We used the optical circuit design to fabricate an optical module with a bare chip preamplifier in a package. This module exhibited a full duplex operation of 156 Mbit/s with a minimum sensitivity of -35.2 dBm at a bit error rate of 10/sup -10/.

A 10 Gb/s hybrid-integrated receiver array module using a planar lightwave circuit (PLC) platform including a novel assembly region structure

A planar lightwave circuit (PLC) platform for optoelectronic hybrid integration shows potential for achieving 10 Gb/s operation. It uses AuSn bump-type bonding pads on a silica layer to decrease parasitic capacitance, which limited the CR time constant in the optical chip assembly region, and two-layer electrical wiring to reduce parasitic inductance, which caused resonance in the electrical circuit region. An arrayed receiver module fabricated by integrating a two-channel monolithic opto-electronic integrated circuit (OEIC) chip on the PLC platform demonstrated a 3 dB-bandwidth of 8 GHz in both channels, which is equal to the bandwidth of the OEIC chip. This shows the feasibility of using this PLC platform for multichannel 10 Gb/s operation. Furthermore, this PLC platform can combine the versatile optical circuit functions of a PLC, such as an arrayed-waveguide grating wavelength multiplexer, with the high-speed signal processing function of mature electronic IC circuits. Consequently, this platform is a key device that will lead to high-capacity optical signal processing systems using optical wavelength/frequency routing.

Low-loss and large-tolerance fiber coupling of high- Delta silica waveguides by local mode-field conversion

Small mode-field silica waveguides with a high refractive index difference of 2% that were efficiently coupled to optical fiber using a local mode-field conversion technique are described. The waveguide end was heated locally at 1300 degrees C for 10 h and this had the effect of doubling the mode-field diameter from 5.0 mu m to about 10 mu m with a taper length of 8 mm. It is shown that, as a result, the fiber coupling loss was drastically reduced from 2.4 to 0.1 dB and the alignment tolerance was doubled.<<ETX>>

Four-degree hub switch module using multi-chip planar lightwave circuit integration technology for transparent ROADM ring interconnection

We have developed a PLC-based 32-wavelength 4-degree hub switch module, which consists of a broadcast coupler with a demultiplexer for local-drop, and a WSS with wavelength specific ports for local-add. The module size is 220/spl times/135/spl times/14 mm. The insertion loss of the express path in the WSS is 10.8 dB.

High-speed optoelectronic hybrid-integrated transmitter module using a planar lightwave circuit (PLC) platform

High-speed optoelectronic hybrid-integrated transmitter module has been developed using a silica-based planar lightwave circuit (PLC) platform on which a laser diode (LD) array and a two-channel LD driver IC were integrated. Heat absorption through a highly thermal conductive silicon terrace kept the average output power constant to within 5% during IC operation. Bit-error-rate (BER) measurement showed that this module operated successfully with a 9-Gb/s nonreturn-to-zero (NRZ) signal. This indicates that the PLC platform does not have any adverse effect on the frequency bandwidth of the integrated chips. This approach, using the PLC platform for integrating optoelectronic devices and electronic ICs, will lead to the development of a high-speed optical multichip module for optical signal processing.

32ch Reconfigurable Optical Add Multiplexer Using Technique for Stacked Integration of Chip-Scale-Package PDs on Silica-Based PLC

We have developed a 32ch reconfigurable optical add multiplexer (ROAM) that incorporates inline tap-monitors fully integrated on a silica PLC chip by using a new stacked integration technique. The module exhibited a low insertion loss of 9.8 dB (pass through ports), and monitor PD responsivities of ≫0.7 A/W.