Xueliang Song

Stress-location measurement along an optical fiber by synthesis of triangle-shaped optical coherence function

A triangle-shaped optical coherence function is synthesized, and is applied to real-time stress-location measurement along an optical fiber. We utilize a polarization-maintaining fiber (PMF) as the sensing element. Stress-induced coupling from one eigenpolarization mode to the other is used as the sensing mechanism. The stress-position on PMF linearly corresponds to the delay difference between the two eigenpolarization modes, which is measured with a slope of the synthesized triangle coherence function. The degree of coherence changes linearly from one to zero with respect to the delay difference. By extracting the coherence value, the stress point is figured out in real time.

Integrable multimode interference distributed Bragg reflector laser all-optical flip-flops

A novel fully integrable all-optical flip-flop has been created using distributed Bragg reflector multimode interference bistable laser diodes. The single metal-organic vapor phase epitaxy regrowth offset quantum well structure active/passive integrated flip-flop lases in single mode at 1554 nm and is compatible with standard fabrication methods of InP photonic integrated circuits (PICs). All-optical reset switching through cross-gain saturation was demonstrated over a 52-nm range, at 1522-1574 nm. An optical set has been achieved with -3 dBm and optical reset with less than -5-dBm external light injection. The flip-flop will be useful for integration in PICs of future photonic systems for self-routing and optical memories or buffers

Effect of surface misorientation on the kinetics of GaAs MOVPE examined using selective area growth

The kinetics of Ga species during metallorganic vapor phase epitaxy (MOVPE) of GaAs was examined by analyzing growth rate profiles of selective area MOVPE. The effect of surface misorientation of GaAs(100) substrates was evaluated using the selective area growth technique. Results showed that the higher misorientation angle resulted in higher surface reaction rate constant (k,). The temperature dependency of k, was examined and revealed that below 625°C the activation energy (E a ) ranged from 75.7 to 87.9 kJ/mol depending on the substrate orientation. Above 625°C, E a decreased to less than 4 kJ/mol, possibly due to differences in surface structures and/or gas-phase species.

Simulation of Static Optical XPM in Active MMI Couplers

Based on the FD-BPM and including the distribution of photon density, carrier density, and refractive index, a simulation code is used to analyze the static performance of active MMI couplers in the presence of two different optical signals. To examine the feasibility of a novel all-optical switch based on active MMI; the code is mainly used to evaluate the amount of phase change resulting in the output of one optical signal by varying the intensity of the other at different injected carrier density.

Dynamic operation of all-optical flip-flops with distributed bragg reflectors for self-routing of 10-Gbit/s optical packets

We present the dynamic all-optical flip-flop (AOFF) operation of a multimode interference (MMI) bistable laser diode (BLD) with distributed Bragg reflector (DBR) mirrors, which allow single-mode lasing and on-chip integration with other waveguide devices. The DBR-MMI-BLD has been operated by 10-ns-wide optical set/reset pulse, resulting in 320 ps rising time and 470 ps falling time. Self-routing of 10 Gbit/s optical packets has also been demonstrated using the Mach–Zehnder interferometer (MZI) semiconductor optical amplifier (SOA) all-optical switch driven by the DBR-MMI-BLD AOFF. The 10 Gbit/s optical packets were switched in the optical domain by cross-phase modulation of the SOA. The extinction ratio of the all-optical switch was 8 dB, and an error-free operation was obtained with 1.8 dB power penalty.

28-ps switching window with a selective area MOVPE all-optical MZI switch

The first dynamic all-optical switching of a bandgap-engineered Mach-Zehnder interferometer semiconductor optical amplifier all-optical switch was achieved. A 28-ps switching window was successfully confirmed. This is the first demonstration of a bandgap-engineered large-scale all-optical photonic integrated circuit with either selective-area-growth or quantum-well-intermixing techniques.

All-Optical OTDM DEMUX with Monolithic SOA-MZI Switch by Regrowth-Free Selective Area MOVPE

We achieved first all-optical OTDM DEMUX with regrowth-free selective area MOVPE. 40Gbps to 10Gbps DEMUX was confirmed with SOA-MZI switch. This is the first all-optical OTDM DEMUX with bandgap-engineered PIC, by either selective-area-growth or quantum-well-intermixing.

All-optical wavelength conversion with monolithically integrated Mach-Zehnder interferometer SOA switches by selective area MOVPE

We achieved first dynamic all-optical wavelength conversion in bandgap-engineered MZI SOA all-optical switch. Clear eye-diagram of 2.5Gbps wavelength conversion was confirmed. This is the first wavelength conversion demonstration with a bandgap-engineered PIC with either selective-area-growth and quantum-well-intermixing techniques.

Stress-location measurement along an optical fiber by synthesis of optical coherence function

A triangle-shape optical coherence function is synthesized, and is applied to construct a system for real-time stress- location measurement along an optical fiber. We utilize a polarization maintaining fiber (PMF) for the sensing element, and the coupling from one eigen polarization mode to the other by the stress is used as the sensing mechanism. The delay difference between the two eigen polarization modes linearly corresponds to the stress-position on PMF, which is measured as the degree of coherence linearly changing from 1 to 0, like a triangle. By extracting the coherence value, the stress point is figured out in real time.

Monolithically Integrated Mach-Zehnder Interferometer All-Optical Switches by Selective Area MOVPE

We achieved first dynamic all-optical signal processing with a bandgap-engineered MZI SOA all-optical switch. The wide-gap Selective Area Growth (SAG) technique was used to provide multi-bandgap materials with a single step epitaxy. The maximum photoluminescence (PL) peak shift obtained between the active region and the passive region was 192 nm. The static current switching with the fabricated switch indicated a large carrier induced refractive index change; up to 14 π phase shift was obtained with 60mA injection in the SOA. The carrier recovery time of the SOA for obtaining a phase shift of n was estimated to be 250-300 ps. A clear eye pattern was obtained in 2.5 Gbps all-optical wavelength conversion. This is the first all-optical wavelength conversion demonstration with a bandgap-engineered PIC with either selective area growth or quantum-well intermixing techniques.