Masaru Fuse

Quantum stream cipher by the Yuen 2000 protocol: Design and experiment by an intensity-modulation scheme

We investigate the Yuen 2000 (so-called Y-00)-protocol, which can realize a randomized stream cipher with high bit rate (Gbit/s) for long distances (several hundreds km). The randomized stream cipher with randomization by quantum noise based on the Y-00 protocol is called a quantum stream cipher in this paper, and it may have security against known plaintext attacks which has no analog with any conventional symmetric key ciphers. We present a simple cryptanalysis based on an attackers heterodyne measurement and a quantum unambiguous measurement to make clear the strength of the Y-00 protocol in real communication. In addition, we give a design for the implementation of an intensity-modulation scheme and report an experimental demonstration of 1 Gbit/s quantum stream cipher through a 20-km-long transmission line.

Multi-channel wireless LAN distributed antenna system based on radio-over-fiber techniques

We introduce the multi-channel WLAN system based on RoF techniques that realize efficient and flexible network operations. Single-channel optical transmission characteristics of an IEEE802.11a or 11b signal are clarified, and multi-channel transmission performances are discussed.

Transmission performance of multichannel wireless LAN system based on radio-over-fiber techniques

We clarify the transmission performance of our proposed multichannel wireless local area network (WLAN) system based on radio-over-fiber techniques. We developed a practical and effective method for the analysis of multichannel performances from the measurement of single-channel performances by incorporating the spectral distribution of a modulation signal into a calculation of the composite triple beats. Furthermore, using our developed method, we can clarify the maximum capacity of the multichannel WLAN system and its system parameters with a focus on the performance of the orthogonal frequency division multiplexing with 64-quadrature amplitude modulation channel. For example, the cell diameter for realizing the bidirectional transmission of seven-channel WLAN signals becomes 10 m.

Ultrahigh channel capacity optical CATV systems

Summary form only given. It is widely recognized that future CATV systems will require more channels to incorporate new services such as video on demand (VOD). Various CATV systems employing subcarrier multiplexing (SCM) techniques have been proposed, however these systems do not seem to have sufficient capacity for the VOD. In this paper, we show new approaches to ultrahigh channel capacity optical CATV systems using SCM technique and discuss performances of each.

Proposal of RoF transmission system using 850 nm VCSEL and 1.3 /spl mu/m SMF with low-frequency superposition technique

We propose a novel RoF transmission system with a combination of 850 nm VCSEL and 1.3 /spl mu/m SMF. Using the low-frequency superposition technique, we demonstrate the RoF transmission of OFDM-64QAM signal with significant reduction of modal noise and distortions.

Scalable optical access system for multichannel VDSL based on subcarrier multiplexing

This paper reports a novel implementation and demonstration of 50 ch VDSL-over-SCM transmission in bi-directional WDM over 20 km SMF. We propose a new method to calculate the spurious and clarify the scalability of capacity and distance.

Quantum stream cipher part III: design of keyed randomization and experiment

In this talk, we present a design of keyed randomization, and an experiment for quantum stream cipher by Yuen protocol which can realize a randomized stream cipher with Gbps for long distance. A simple explanation of why Y-00 is more secure than any type of the conventional stream cipher is given, showing Y-00 with keyed randomization, for example, overlapping selection keying:OSK. That is, the noiseless Y-00 with OSK is equivalent of the conventional stream cipher, but the noise is inevitable. So one can easily see that the security is enhanced by the noise. In addition, we give a design for the implementation of the intensity modulation scheme and report the experimental demonstration of 1 Gbps quantum stream cipher with OSK randomization through 20~40 km long transmission line. This may provide a way to go toward the broad market applications which require security, high speed, compact size, maintenance free, and low price.

VDSL access system based on rate-adaptive optical sub-carrier multiplexing

The paper proposes an optical access system employing a very high-speed digital subscriber line (VDSL) based on rate-adaptive optical sub-carrier multiplexing (RA-SCM) as a residential gateway for multi-dwelling units in fiber-to-the-building (FTTB). Experiments successfully demonstrate a 20 km transmission of 50 VDSL signals in bidirectional wavelength division multiplexing (WDM) over a single mode fiber as a result of a new method for approximating the spurious levels of an M-ary QAM spectrum that are proportional to constellation size. Calculations examine the trade-off between the maximum transmission distance and the number of subscribers by quantifying the impacts of peak factor fluctuation and chromatic dispersion. Experiments and calculations verify the feasibility and rate-adaptive scalability of the proposed access system based on RA-SCM for first-mile applications in access networks.

Effects of interference on multi-channel wireless LAN distributed antenna system based on radio-over-fiber techniques

The effects of several kinds of interference on multi-channel wireless LAN optical transmission systems are appreciated. It is shown that amplitude distributions of these interferences have large impact on the PER and EVM characteristics.

Design of extended WDM access system for providing broadband communication and broadcast TV services

We propose extended WDM access system employing optical packet/SCM hybrid amplification scheme for supporting larger number of subscribers. For suppressing interference between optical packets and SCM signal, optimum operating conditions of EDFA are discussed.