We propose a novel method of precisely measuring the polarization dependence of single pass gain (PDG) in a semiconductor optical amplifier integrated with spot-size convertors (SS-SOA). By averaging the signal gain of a SS-SOA over a wide wavelength range using the amplified spontaneous emission (ASE) of an erbium doped fiber (EDF), the PDG can be accurately estimated. This is because the influence of gain ripples on the measurement results are drastically reduced. We successfully evaluated the PDG of an angled-facet SS-SOA, even before the process of anti-reflection coating, within a small error of 0.5dB. The EDF-ASE technique is useful in sampling tests and selecting angled-facet SS-SOA chips from wafers. The polarization dependence of the coupling efficiency (PDCE) between a SS-SOA and optical fiber is also evaluated by measuring the photo-current of the active layer for TE and TM input signals. It is possible, therefore, to specify the polarization characteristics of the active region and spot-size converter region, which are indispensable parameters for the design of the SS-SOA.

We present an 88 wavelength-routing switch (WRS) that monolithically integrates tunable wavelength converters (TWCs) and an 88 arrayed-waveguide grating. The TWC consists of a double-ring-resonator tunable laser (DRR TL) allowing rapid and stable switching and a semiconductor-optical-amplifier-based optical gate. Two different types of dry-etched mirrors form the laser cavity of the DRR TL, which enable integration of the optical components of the WRS on a single chip. The monolithic WRS performed 18 high-speed wavelength routing of a non-return-to-zero signal at 10 Gbit/s. The switching operation was demonstrated by simultaneously using two adjacent TWCs.

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.

We present a dual traveling-wave electrode InP-based Mach-Zehnder (MZ) modulator with an n-i-n waveguide structure. An electrical input/output interface placed on one side of the chip helps us to drive the modulator in a push-pull configuration. This configuration provides the modulator with great advantages such as reduced driving voltage amplitude, chirp-free operation, and the ability to support advanced modulation formats. The fabricated modulator exhibits good performance. A 40 Gb/s non-return-to-zero (NRZ) signal is successfully generated with a low driving of 1.3 Vpp. In addition, a 10-Gb/s optical duobinary (DB) signal is successfully generated and transmitted over a 240-km single-mode fiber (SMF). We also developed a wavelength tunable transmitter hybrid integrated with a modulator with a wavelength tunable laser. Full C-band 10-Gb/s operation and a 100-km SMF transmission with a low power penalty are confirmed.