Paul K. J. Park

Real-Time Gesture Interface Based on Event-Driven Processing From Stereo Silicon Retinas

We propose a real-time hand gesture interface based on combining a stereo pair of biologically inspired event-based dynamic vision sensor (DVS) silicon retinas with neuromorphic event-driven postprocessing. Compared with conventional vision or 3-D sensors, the use of DVSs, which output asynchronous and sparse events in response to motion, eliminates the need to extract movements from sequences of video frames, and allows significantly faster and more energy-efficient processing. In addition, the rate of input events depends on the observed movements, and thus provides an additional cue for solving the gesture spotting problem, i.e., finding the onsets and offsets of gestures. We propose a postprocessing framework based on spiking neural networks that can process the events received from the DVSs in real time, and provides an architecture for future implementation in neuromorphic hardware devices. The motion trajectories of moving hands are detected by spatiotemporally correlating the stereoscopically verged asynchronous events from the DVSs by using leaky integrate-and-fire (LIF) neurons. Adaptive thresholds of the LIF neurons achieve the segmentation of trajectories, which are then translated into discrete and finite feature vectors. The feature vectors are classified with hidden Markov models, using a separate Gaussian mixture model for spotting irrelevant transition gestures. The disparity information from stereovision is used to adapt LIF neuron parameters to achieve recognition invariant of the distance of the user to the sensor, and also helps to filter out movements in the background of the user. Exploiting the high dynamic range of DVSs, furthermore, allows gesture recognition over a 60-dB range of scene illuminance. The system achieves recognition rates well over 90% under a variety of variable conditions with static and dynamic backgrounds with naïve users.

Live demonstration: Gesture-based remote control using stereo pair of dynamic vision sensors

This demonstration shows a natural gesture interface for console entertainment devices using as input a stereo pair of dynamic vision sensors. The event-based processing of the sparse sensor output allows fluid interaction at a laptop processor load of less than 3%.

A novel frequency-offset monitoring technique for direct-detection DPSK systems

We propose and demonstrate a novel technique to monitor the frequency offset between the optical signal and delay interferometer in direct-detection DPSK systems. The monitoring range and accuracy of the proposed technique were measured to be /spl plusmn/2 GHz and /spl sim/1 MHz, respectively.

Effect of PDL-induced coherent crosstalk on polarization-division-multiplexed direct-detection systems.

We analyze the effect of polarization-dependent loss (PDL) on the performance of the polarization-division-multiplexed (PDM) signals in direct-detection systems. We present the theoretical analysis of the sensitivity penalty caused by PDL-induced coherent crosstalk and compare the results with experimental data obtained by using a simple variable PDL emulator based on a LiNbO3 Mach-Zehnder modulator. Also presented is the performance degradation caused by the polarization misalignment between the received signals and the polarization beam splitter at the receiver in the presence of PDL.

Touchless hand gesture UI with instantaneous responses

In this paper we present a simple technique for real-time touchless hand gesture user interface (UI) for mobile devices based on a biologically inspired vision sensor, the dynamic vision sensor (DVS). The DVS can detect a moving object in a fast and cost effective way by outputting events asynchronously on edges of the object. The output events are spatiotemporally correlated by using novel event-driven processing algorithms based on leaky integrate-and-fire neurons to track a finger tip or to infer directions of hand swipe motions. The experimental results show that the proposed technique can achieve graphic UI capable finger tip tracking with milliseconds intervals and accurate hand swipe motion detection with negligible latency.

Pilot-tone-based WDM monitoring technique for DPSK systems

To evaluate the effectiveness of the pilot-tone-based monitoring technique in differential phase-shift keying (DPSK) systems, we measure the mutual interactions between the pilot tones and DPSK signals and compare the results with those of on-off keying (OOK) signals. The results show that, by using the DPSK format instead of OOK, it is possible to increase the number of wavelength-division-multiplexed channels that can be monitored simultaneously by using pilot tones without using optical demultiplexers by more than one hundred times

Chromatic Dispersion Monitoring Technique Using Pilot Tone Carried by Broadband Light Source

We propose and demonstrate a simple chromatic dispersion monitoring technique based on the pilot tone generated by a broadband light source (BLS). Previously, the pilot tone has been obtained by directly modulating each transmitter laser with a small sinusoidal current. Thus, for use in the wavelength-division- multiplexed (WDM) network, each transmitter should be modulated with a unique pilot tone. However, we obtain the pilot tone by modulating an additional BLS such as a reflective semiconductor optical amplifier. Thus, there is no need to modulate each transmitter laser. We evaluate the performance of the proposed technique in an 8 times10 Gb/s WDM system. The result shows that, unlike the conventional pilot-tone-based monitoring technique, the performance of this technique is almost insensitive to the polarization-mode dispersion.

Reduction of polarization-induced performance degradation in WDM PON utilizing MQW-SLD-based broadband source

We report on the reduction of polarization-induced performance degradation in WDM PON utilizing MQW-SLD-based ASE source for injection locking to FPLD. The results show that, to suppress the polarization-induced Q penalty sufficiently less than 0.5 dB, the MQW-SLD output should be depolarized within the locking range of the wavelength-locked FPLD.

Optical Burst Add-Drop Multiplexing Technique for Sub-Wavelength Granularity in Wavelength Multiplexed Ring Networks

We demonstrate optical burst add-drop multiplexing as a practical application of the optical burst switching technology in a wavelength-division-multiplexed ring network. To control optical bursts in the network, a burst identifier (BI) for delivering control information, and a BI processor for handling the BI, were designed. Optical bursts of 10- to 100-mus in length were optically multiplexed or demultiplexed in an intermediate node of the ring network. The demonstration shows that the optical burst add-drop multiplexing technique provides sub-wavelength granularity to a ring network.

Optimization of polarization-scrambling frequency in lightwave systems

The polarization-scrambling technique could be used not only to suppress the polarization-induced detrimental effects in a long-haul lightwave system, but also to monitor various polarization-related parameters. However, this technique could interact with polarization-mode dispersion (PMD) and polarization-dependent loss, and then cause timing jitters, irregular intensity modulations, and PMD-induced repolarization. This problem could be substantially reduced by using the optimized scrambling frequency of about 10 kHz.