Abstract: A picture image distributing apparatus provided within a passenger moving vehicle, consists of: a head end portion for multichannel FDM picture image signals; an electrical optical for converting the FDM picture image signals into optical signals; an optical amplifier for optically amplifying the optical outputs; one optical fiber transmission path connected to optical taps of unequal distribution for branching halfway on one portion of the optical power except for the branching at a final point, an optical/electrical converter for receiving optical signals branched at the final point or halfway so as to convert them into electrical signals; and a passenger seat picture image receiving terminal connected to the optical/electrical converter so as to receive the electrical signals.

Abstract: The present invention provides an optical disc comprising a main-image signal recording area holding a signal of a main image for a display, and a sub-image signal recording area holding a signal of a sub image to be displayed including an image of a time counted down in accordance with a progress of a sub-image signal reproduction. Furthermore it provides an image signal transmitting apparatus for repeatedly transmitting a main-image signal and a sub-image signal one after the other by utilizing such optical disc, the image signal transmitting apparatus comprising a image signal reproduction device for reproducing the main-image signal and the sub-image signal, a cycle time memory for memorizing a main-image signal transmission cycle, and a control device for obtaining a time difference between the cycle and time required for the main-image signal reproduction as well as control the image signal reproduction device.

Abstract: An optical transmission system provides digital signals which have added bits for error correction by an encoder which are converted into 16-QAM signals with a predetermined carrier frequency by a modulator, and then frequency division muitiplexed with an AM signal so as to be inputted to an optical-electric converter. When the total sum of the light modulation indices of signals to be transmitted is over 1, a light modulation index of an M-QAM signal is set by calculating the light modulation index that marks the onset of diverging from the error rate given by a ratio between receiver noise power and the M-QAM signal power while considering a light modulation index corresponding to a usable transmission margin. The multiplexed signals are transmitted via optical fiber and converted into electric signals by a photo receiver, demodulated by a demodulator, and then outputted after having their errors corrected by an error corrector.

Abstract: The present invention provides a cable broadcasting system and the transmission center employed therein. In the transmission center, plural images are divided into several groups in the same kinds and each image in one kind is repeated not simultaneously so that they are outputted as independent plural image signals, and the image that the subscribers have requested is selected from those plural image signals which is enciphered, modulated, and multiplexed to be transmitted in optical transmission lines through an available channel to the subscribers, while the transmission channel is validated as well as the enciphered image signal is deciphered at the subscribers' end in order to enable the subscribers to watch the image they have requested.

Abstract: A pay-channel transmission system for a CATV has an optical transmission unit and an optical receiver unit. The optical transmission unit includes pay-channel television signals optically multiplexed by a .lambda..sub.1 wavelength semiconductor laser and non-pay-channel television signals optically multiplexed by a .lambda..sub.2 wavelength semiconductor laser. The optical receiver unit includes an optical filter for filtering the .lambda..sub.1 wavelength data. Thus, a non-subscriber having the optical filter is prevented from receiving the pay-channel television signals, and a subscriber having no optical filter is able to receive both the pay-channel television signals and non-pay-channel television signals.