Kuniaki Utsumi

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.

Radio-over-fiber transmission performance of OFDM signal for dual-band wireless LAN systems

We propose the dual-band wireless LAN system based on radio-over-fiber technique. A demonstration of optical transmission of 5-GHz OFDM signal specified in IEEE802.11a and a feasibility of 2.4/5-GHz dual-band transmission will be reported.

Increasing acceptable number of signals in subcarrier multiple access optical networks in the presence of high optical beat interference

This paper theoretically and experimentally demonstrates that our proposed method improves the carrier-to-noise ratio (CNR) of subcarriers and significantly increases the number of acceptable optical signals in subcarrier multiple access (SCMA) systems using distributed feedback laser diodes (DFB-LDs) with the same center optical frequency. This method reduces optical beat interference by using the multiplied product of the subcarriers and a low-frequency signal. From the experimental results using 1.3 /spl mu/m DFB-LDs, the CNR sufficiently satisfies the required level even if the number of optical signals is three. Theoretically, the number of acceptable optical signals increases as LDs with wider optical line-width or with greater chirp coefficient are used. For example, assuming a laser chirp coefficient of 540 MHz/mA, the maximum number of LDs that can be used while still meeting the minimal CNR requirement is 12. This number corresponds to 66 optical beat interferences. Thus, this proposed beat-interference reduction technique is very effective in SCMA systems using DFB-LDs without optical frequency control.

Multiband wireless LAN distributed antenna system using radio-over-fiber

In this paper, we propose a novel radio-over-fiber multiband wireless LAN distributed antenna system and also describe a noise canceling technique applied to counteract the problem of received RF signal degradation caused by the noise generated by the O/E in a remote antenna unit.

Optical access links suppressing optical beat interference with FP-LDs for microwave transmission

Uncooled Fabry-Perot laser diodes (FP-LDs) without isolators realize cost-effective optical access links for microwave transmission. The optical spectrum broadening using low-frequency intensity-modulation can effectively suppress optical beat interference in the up link and make FP-LD performance stable.

Bit-error rate of M-QAM signal and its analysis model for composite distortions in AM/QAM hybrid transmission

In cable television (CATV) systems that deliver digital video services by employing a hybrid fiber and coaxial network, it is important to consider digital channel deterioration due to composite distortions, as well as the amplitude-modulation vestigial-sideband channel. Furthermore, it is essential to clearly estimate a digital channels quality in designing CATV transmission systems. However, there have been few studies on statistical models and an analysis method to estimate the bit-error rate (BER) of M-ary quadrature amplitude-modulation signals for composite distortions. This paper shows statistical properties of composite distortions and a new BER analysis method to handle them. In the evaluations, the amplitude distributions of composite distortions are given by Weibull distributions with skewness levels of 2.3 for composite second-order distortion and 1.5 for composite triple-beat distortion. We propose a new BER analysis method that uses the Weibull distributions for the composite distortion statistical features and demonstrate the effectiveness of the new BER analysis method in estimating BER by comparing its measurement results to calculation results.

High-performance long-distance fiber-optic transmission using unisolated Fabry-Perot laser for mobile radio systems

We demonstrate that spectrum broadening with low-frequency intensity modulation (LFM) is very effective in stabilizing the characteristics of unisolated Fabry Perot laser diodes in long-distance transmission, and that the system performance is enough for cellular phone systems in 20 km transmission.

Low-cost and high-speed optical transceiver using 850-nm VCSEL and hard polymer clad fiber

Summary form only given. In conclusion, the optical coupling between the lensless 850-nm VCSEL and the hard polymer clad fibre (H-PCF) was examined, and optical transmission at 3.2 Gbps over 100 m was demonstrated. This means that the developed optical transceiver is useful for low-cost multigigabit digital interface, such as IEEE1394.

Error statistic of QAM channel in AM/QAM hybrid optical transmission

The error statistic of the QAM channel in an AM/QAM hybrid optical transmission system is measured. Errors occur randomly in optical transmission without clipping. However, errors are found to occur in bursts when the impulsive noise due to clipping degrades the QAM signals BER. The error statistic is critical to properly designing the error correction employed in the hybrid system.