Hybrid SCM video distribution systems which distribute AM, QAM (quadrature amplitude modulation) and FM TV signals simultaneously have been investigated. We describe carrier frequency allocation plans, the required transmission signal qualities, and optical transmitter/receiver configurations for hybrid SCM video distribution systems. A new receiver configuration consisting of a photo detector, filter and plural preamplifiers is proposed. The experimental results confirm that the proposed receiver is suitable for hybrid SCM video distribution systems.

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This paper describes newly developed HDTV studio transmission equipment. This equipment can transmit one channel of uncompressed studio quality HDTV signal and 8 channels of audio signal with 1.485Gbps optical digital transmission technology. This equipment has standard interfaces of video and audio, so it is possible to connect directly to each studio HDTV equipment without signal degradation. Developing some special LSIs, it is realized to minimize equipment size and power consumption These LSIs are Video A/D LSI, Feed Back Clamp LSI, Digital Delay LSI, BTA S-002 Formatting LSI and Deformatting LSI, Y/C Multiplexing・Demultiplexing LSI, and High Speed P/S・S/P LSI. These LSIs can be used for digital studio HDTV equipments.

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One of the problem in FM-FDM optical transmission is intermodulation products (IMPs) due to the nonlinearity of the LD. The CSO and CTB characteristics are shown as the function of m√<N> (N:number of transmitting channels, m:optical illodulation depth). Many frequency-modulated IMPS behave like a random noise, then degrade the CNR performance. Taking these two facts into account, this report gives a designing n:method for getting the maximum CN ratio when the received optical power and the frequency allocation of PM signals are given. Parameters expressing the nonlinearity of an LD can be determined from the measured CSO and CTB in smaller number of channels. The CNR of 25dB is acheived with the received optical power of -18dBm when 40 MUSE-FM signals are transmitted.

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Recently optical transmission systems have been actively introduced in the field of CATV. The system using optical fiber is more effective than one using coaxial cable from the viewpoints of transmission line characteristics and cost. It is applied to trunk lines at present,to home in the future. We have developed fiber optic video transmission equipments using Sub-Carrier Multiplexing (SCM) technique in conformity to satellite broadcast method. With optical fiber amplifiers, this system can transmit 50-channel video signals and distribute optical signal up to several hundreds transmission lines. As for the performance of the system,weighted SNR of 57dB or more is achieved.

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An FDM coherent lightwave communication equipment has been developed. A transmitter includes sixteen 1.55μm-2-electrode MQW DFB-LDs multiplexed by a star coupler. Each of LDs was locked into 10GHz spacing usin a scanning Fabry-Perot interferometer within±100MHz deviation. A receiver was constructed by heterodyne-delay-demodulators using a polarization diversity scheme. The desired channel canbe tuned in 0.3~3second with minium received power of -35.6dBm. 622Mbit/s-16channel HDTV signals have been successfully transmitted in 110km-1.3μm zero dispersion fiber. It was also experimentally revealed thatan allowable maximum launced power into 1.55μm dispersion sifted fiber is limited by fiber four weave mixing to -8.8dBm.

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The influence of cross-phase modulation (XPM) induced by residual intensity modulation in coherent optical CP-FSK-FDM transmission systems is evaluated theoretically and experimentally through signal linewidth broadening. We show that the increment value of the broadened linewidth is proportional to the square of the magnitude of residual intensity modulation. And, we show the relation between the magnitude of residual intensity modulation and Power penalty in optical CP-FSK-FDM transmission systems.

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As an optical compensation for distorted waveform due to optical fiber dispersion, a new approach with optical resonators was proposed for FDM-FSK modulated signal. The effectiveness of the new approach was confirmed by simulation, where allowable dispersion was enlarged to 18000ps/nm and 180000ps/nm by placing the resonator before optical receiver and in each optical linear repeater, respectively.

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The design of dispersion compensating fibers was investigated forcusing on a relative intensity noise. Based on this theoretical investigation, we have fabricated dispersion compensating fibers and conducted a 1.55μm AM-VSB transmission experiment by using them. Distortion was improved without the degradation in other analog transmission characteristics. Theoretically calculated distortion well coincided with measured values. The intrinsic distortion of transmitters was improved by giving a negative dispersion.

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Brillouin scattering in optical fibers is one of the nonlinear phenomena in which an incident light interacts with an acoustic wave in the fiber and is scattered, shifted in frequency by an amount equal to a frequency that is intrinsic to the medium. Horiguchi et al. suggested that optical fiber strains can be determined with high accuracy by measuring the Brillouin gain spectra using the pump probe method. Longitudinal strain distributions can also be measured by using a pulsed light. In this study, we measured the Brillouin gain spectra using a continuous wave (cw) laser and made a basic evaluation of strains applied to optical fibers under various conditions, particularly for ribbon type cables.

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