Optoelectronic hybrid integration is a promising technology for realizing the optical components needed in optical transmission, switching, and interconnection systems that use wavelength division multiplexing (WDM) and time division multiplexing (TDM). We have already developed versatile optical hybrid integrated modules using a silica-based planar lightwave circuit (PLC) platform. However, these modules consist solely of the optoelectronic semiconductor devices such as laser diodes (LDs) and photo diodes (PDs) and monolithic optoelectronic integrated circuits (OEICs). To carry out high-speed and versatile electric signal processing functions in future network systems, it is necessary to install semiconductor electrical integrated circuits (ICs) on a PLC platform. In this paper, we describe novel technologies for high-speed PLC platforms which make it possible to assemble both ICs and optoelectronic devices. Using these technologies, we fabricated a two-channel hybrid integrated optical transmitter module which is hybrid integrated with an LD array chip and an LD driver IC. On this PLC platform, we use microstrip lines (MSLs) to drive the LD driver IC. We also considered the effect of heat interference on the LD array chip caused by the LD driver IC when designing the layout of the chip assembly region. The LD array chip and the LD driver IC were flip-chip bonded with solder bumps of a different material to avoid any deterioration in the coupling efficiency of the LD array chip. The optical transmitter module we fabricated operated successfully at 9 Gbit/s non-return-zero (NRZ) signal. This approach using a PLC platform for the hybrid integration of an LD array chip and an LD driver IC will carry forward the development of high-speed optoelectronic modules with both optical and electrical signal processing functions.

A photonic ATM switch based on wavelength-division multiplexing will include several lossy passive devices, erbium-doped fiber amplifiers, and semiconductor optical amplifiers (SOAs) in a cascade configuration for fast switching of ns order. Its level diagram, which is very different from those of optical transmission links, has not been adequately studied. This paper investigates the concept of basing the level design of the photonic asynchronous-transfer-mode (ATM) switch we are developing on its Q-factor. First, we derive formulation of the Q-factor in a single PD and a dual-PD in a Manchester-encoded signal, which has several merits in packet switching and that we believe will become popular in photonic packet switches. Using this formula, we show an example of the level-diagram design including the Q factor calculation in an optical combiner and distributor section without SOA in our photonic ATM switch. Next, we showed experimentally that the pattern effect in SOAs can be suppressed by using a Manchester-encoded signal. Finally, we confirm that the allowable minimum level diagram in the switch can be based on a simple Q calculation and easy measurement of a bit error rate (BER) in a back-to-back configuration when using a Manchester-encoded signal. These results show that basing the level design of photonic ATM switches on the Q factor is feasible when using a Manchester signals. This approach can be applied to various types of photonic packet switches.

A photonic ATM switch based on wavelength-division multiplexing will include several lossy passive devices, erbium-doped fiber amplifiers, and semiconductor optical amplifiers (SOAs) in a cascade configuration for fast switching of ns order. Its level diagram, which is very different from those of optical transmission links, has not been adequately studied. This paper investigates the concept of basing the level design of the photonic asynchronous-transfer-mode (ATM) switch we are developing on its Q-factor. First, we derive formulation of the Q-factor in a single PD and a dual-PD in a Manchester-encoded signal, which has several merits in packet switching and that we believe will become popular in photonic packet switches. Using this formula, we show an example of the level-diagram design including the Q factor calculation in an optical combiner and distributor section without SOA in our photonic ATM switch. Next, we showed experimentally that the pattern effect in SOAs can be suppressed by using a Manchester-encoded signal. Finally, we confirm that the allowable minimum level diagram in the switch can be based on a simple Q calculation and easy measurement of a bit error rate (BER) in a back-to-back configuration when using a Manchester-encoded signal. These results show that basing the level design of photonic ATM switches on the Q factor is feasible when using a Manchester signals. This approach can be applied to various types of photonic packet switches.

Silica-LiNbO3 (LN) hybrid modulators have a hybrid configuration of versatile passive silica-based planar lightwave circuits (PLCs) and simple LN phase modulators arrays. By combining the advantages the two components, these hybrid modulators offer large-scale, highly-functionality modulators with low losses for advanced modulation formats. However, the reliability evaluation necessary to implement them in real transmissions has not been reported yet. In terms of reliability characteristics, there are issues originating from the difference in thermal expansion coefficients between silica PLC and LN. To resolve these issues, we propose design guidelines for hybrid modulators to mitigate the degradation induced by the thermal expansion difference. We fabricated several tens of silica-LN dual polarization quadrature phase shift keying (DP-QPSK) modulators based on the design guidelines and evaluated their reliability. The experiment results show that the modules have no degradation after a reliability test based on GR-468, which confirms the validity of the design guidelines for highly reliable silica-LN hybrid modulators. We can apply the guidelines for hybrid modules that realize heterogeneous device integration using materials with different coefficients of thermal expansion.

Optical buffering has been one of the major technical challenges in realizing optical packet switching routers and interconnects. We demonstrate a compact optical buffer module, comprising an InP 18 phased-array switch and a silica-based delay line circuit. The integrated delay line circuit is fabricated on the silica-based planar-lightwave circuit (PLC) platform, and has the ladder architecture for reducing the size. In addition, variable optical couplers are integrated to achieve effective power equalization. Tunable and uniform buffering of up to 21 ns is obtained with 3-ns temporal resolution.

Optoelectronic hybrid integration is a promising technology for realizing the optical components needed in optical transmission, switching, and interconnection systems that use wavelength division multiplexing (WDM) and time division multiplexing (TDM). We have already developed versatile optical hybrid integrated modules using a silica-based planar lightwave circuit (PLC) platform. However, these modules consist solely of the optoelectronic semiconductor devices such as laser diodes (LDs) and photo diodes (PDs) and monolithic optoelectronic integrated circuits (OEICs). To carry out high-speed and versatile electric signal processing functions in future network systems, it is necessary to install semiconductor electrical integrated circuits (ICs) on a PLC platform. In this paper, we describe novel technologies for high-speed PLC platforms which make it possible to assemble both ICs and optoelectronic devices. Using these technologies, we fabricated a two-channel hybrid integrated optical transmitter module which is hybrid integrated with an LD array chip and an LD driver IC. On this PLC platform, we use microstrip lines (MSLs) to drive the LD driver IC. We also considered the effect of heat interference on the LD array chip caused by the LD driver IC when designing the layout of the chip assembly region. The LD array chip and the LD driver IC were flip-chip bonded with solder bumps of a different material to avoid any deterioration in the coupling efficiency of the LD array chip. The optical transmitter module we fabricated operated successfully at 9 Gbit/s non-return-zero (NRZ) signal. This approach using a PLC platform for the hybrid integration of an LD array chip and an LD driver IC will carry forward the development of high-speed optoelectronic modules with both optical and electrical signal processing functions.