Susumu Morikura

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.

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.

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.

Approach to Sustainable Smart Town and Role of International Standardization

Sustainable Smart Town (SST) scheme which utilizes networking of energy and information is receiving much attention as a way of stable energy supply and efficient operation in each region and country. SST consists of Smart Grid to supply energy efficiently and energy efficient buildings such as smart homes, condominiums, stores and factories. In addition, new service such as Demand Response Service which takes advantage of networking is beginning to appear in the market.This paper introduces outline of several SST pilot projects, energy consumption reduction in office building, demand response in existing residential house and information security system for facilities. It also mentions the role and future prospect of International Standardization to realize the safe, secure, comfortable and convenient SST.Copyright

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.

Required performance for optical filter and EDFA in 32ch-WDM/310ch-SCM transmission system

We have developed a tunable optical filter (TOF) with 0.05 nm wavelength accuracy and an erbium doped fibre amplifier (EDFA) with a relative intensity noise (RIN) of -136 dB/Hz to realize 32ch-WDM/310ch-SCM systems, taking into account the effect of FM/AM conversion on carrier to noise ratio (CNR) in TOFs and the optimum optical input power into the EDFAs.

Required quality for multichannel digital modulation signals in the transmission system employing optical super wideband FM technique

Summary form only given. Summary form only given. For multichannel video transmission, an analog SCM has been generally adopted. However, it requires a high carrier-to-noise ratio (CNR) and is sensitive to optical multiple reflections. A super wideband FM technique decreases minimum optical received power because of its FM gain and increases the tolerance against optical multiple reflections. Therefore, this technique promises to realize multichannel video transmission on conventional optical telephony networks. In this paper we examined the required DUR (ratio of the demodulated 64-QAM signal power to the total power of the undesired signals in the 64-QAM signalband) for each factor that affects the BER of 64-QAM signals on an analog/digital hybrid transmission system employing the optical super wideband FM technique. Our developed AM-40 channels/64 QAM-30 carriers transmission equipment, which satisfied the required DUR for each factor, achieved error free characteristics (<10/sup -9/) for 64-QAM signals on optical networks with a loss budget of 30 dB.

Novel BER analysis method for M-QAM signal in analog/digital hybrid optical transmission

In practical analog/digital hybrid optical transmission, carriers are modulated by video signals or digital data, and the amplitude of a multiplexed signal composed of these modulation signals is more compressed than that of the carriers. This causes a decrease in the frequency of clipping of the multiplexed signal at the laser threshold. Consequently, the BER of the M-QAM signal in a practical hybrid transmission is lower than that of the experimental results for same optical modulation index (OMI). However, it is difficult to prepare many practical modulation signals for experiments in a laboratory. Therefore, there is demand for a BER analysis method for a multiplexed signal that includes modulation signals needs to evaluate the BER and determine optimum OMI in a practical hybrid transmission. In this paper, we describe such a BER analysis method that can effectively estimate the BER in a practical hybrid transmission by using representative profiles of the modulation signals. In practical systems, a black pictures gives the largest averaged amplitude for the AM-VSB signal, and the most severe conditions for clipping occurrences. However, in such systems, the BER was greatly improved over the BER of a multiplexed signal of carriers. Furthermore, BER degradations due to clipping can be neglected for the AM-VSB signals in setting a practical OMI range.

Novel signal multiplexing method to reduce optical beat interference in subcarrier multiple access networks

We proposed a novel signal multiplexing method to reduce the optical beat interference (OBI) noise in subcarrier multiple access (SCMA) optical fibre networks. Using this method, which sufficiently suppressed the clipping in the presence of the SC signal even if OMI of the HF signal was up to 100%, the OBI noise was reduced 5-8 dB compared with the conventional HF-signal-multiplexing method.