Kenji Hisadome

Adaptive network access with 100 Gb/s Ethernet by Packet-based Lane Bundling

Lambda-on-demand network access with 100 Gb/s Ethernet interface is achieved for SuperHD video/image transfer by using adaptive inverse multiplexing onto parallel 10 Gb/s optical paths assigned individually over optical transport networks.

Prototype of an optically pumped cesium beam frequency standard

The prototype of an optically pumped cesium beam frequency standard is composed of three modules: a cesium beam tube, a microwave module, and a laser diode module. In the cesium beam tube, background lights from the windows are reduced. In the microwave module, an automatic level controller is used in order to reduce long-term frequency instabilities caused by the microwave level fluctuation. In the laser diode module, three laser diodes are connected to the cesium beam tube by polarization maintaining fibers and fiber couplers. The short-term frequency stability (two-sample standard deviation), which is estimated from the preliminary experimental results gained from the prototype, is about sigma /sub y/( tau )=1*10/sup 12// square root tau .<<ETX>>

Performance evaluation of packet multiplexing with flow aggregation in multi-wavelength optical packet networks

In this paper, we evaluate the performance of packet multiplexing with three flow aggregation strategies in multiwavelength optical packet networks. The results showed flow aggregation based on destination AS can increase bandwidth utilization most efficiently.

Short-Term Frequency Stability Estimation of an Optically Pumped Cesium Beam Frequency Standard

A theory is proposed for the calculation of the short-term frequency stabiliry of any optically pumped Cs beam frequency standard. This theory takes into account the influence of fluorescence photon statistics and laser linewidths. The accuracy of the theory is confirmed by measuring the signal to noise ratio of an optically pumped Cs beam resonator and then estimating the short-term frequency stability of the standard based on the resonator. The theory predicts the observed performance well.

An Atomic Beam Collimator for Cs Beam Frequency Standards

It is necessary to predict the directivity of atomic beam collimators when designing Cs beam frequency standards. This paper presents an improved beam collimator theory. Collision processes are not neglected in this theory. This theory can analyze the temperature characteristics of a Cs atomic beam collimator of various lengths. Systematic experiments using three atomic beam collimators (lengths of 17, 34, and 50 mm) are performed. Beam profiles and peak beam intensities are compared with calculated values. Beam profiles calculated with this theory agree well with the measured profiles.

Adaptive minimum filter that achieves precise time synchronization on IP networks

Time synchronization protocols, such as NTP (Network Time Protocol), are frequently used on IP (Internet protocol) networks. These protocols estimate the clock time offset by measuring the Round Trip Time (RTT). In this estimation, errors may occur by delay variation, which is included in the measured RTT values. To avoid this, a conventional minimum filter technique using a fixed sample size has been developed previously. For the conventional filter to work efficiently, it is necessary to select the appropriate number of samples from which the minimum value is selected, while considering the tradeoff between the filtering effect and synchronization stability. This paper investigates an alternate filter, called an adaptive minimum filter, which controls the number of samples depending on the variation of the RTT values. This filter achieves a sufficient filtering effect as well as superior clock control stability. A computer simulation is used to evaluate the time synchronization protocol that employs the adaptive minimum filter. The simulation results show that the synchronization protocol with the adaptive minimum filter achieves better time accuracy and stability than that with the conventional minimum filter.

An Evaluation of Effects on Packet Loss Rate by Optical Packet Multiplexing Based on BGP Flow Aggregation

We apply our proposed packet multiplexing mechanism with BGP flow aggregation to asynchronous OPS networks and evaluate packet loss ratio in a FDL buffer through simulation based on real traffic trace data.

Packet multiplexing based on BGP routing information on slotted OPS networks

In this paper, we propose a packet multiplexing technique with flow aggregation based on BGP routing information for slotted optical packet switching (OPS) networks and evaluate its performance.