E. Tsuchiya

Switching-circuit-free point-to-point audio/data signal transmission through optical fiber

The authors describe a novel switching-circuit-free point-to-point audio/data signal transmission system established by using a sender, optical fibers, and receivers. Each of these is specified by its own address consisting of a single or multiple frequency signals. During the time of transmitting the audio/data signal from the sender to the receivers, a single or multiple frequency address signal issued together with the audio/data signal in a specific frequency domain specifies a specific receiver among the others in a manner that resembles multiple frequency radio-wave propagation in a free space. An experimental setup where the sender was connected to three receivers arranged in parallel and the audio signals were transmitted satisfactorily over the frequency range of 20 Hz to 20 kHz is discussed.<<ETX>>

Optical-fiber data-word transmission system for use with microcomputer controller

Experiments were carried out on a new type of data word transmission system employing a GI glass fiber. A frequency division multiplexed scheme was employed because of simple circuit configuration and low cost. Parallel data consisting of multiple frequency signals occupy separate frequencies in a specified frequency domain. The frequency domain used for the parallel data transmission system is described. A square wave frequency modulation (SWFM) scheme was used. Since the SWFM scheme enables the transmission system to be constructed very simply, a data word is easily recovered from the received SWFM signal by using a 4-b parallel data detector. For applying the new system to the industrial field, a Z80 data processor was built into the receiver to process the data words and to output the instructions to the associated external devices. This optical fiber transmission system has high reliability against electromagnetic interference.<<ETX>>

70 MHz fiber optic transmission from satellite DBS receiving antenna

A broadcast satellite signal after conversion into an intermediate frequency (IF) signal at 70 MHz has been transmitted through an optical fiber in order to distribute the signal to the DBS (direct broadcasting satellite) receiver in a remote location. Based on experiments, it was found that a fiber-optic link allowed the designers to have greater flexibility than coaxial cables, and that light emitting diodes were attractive not only in terms of cost-effectiveness but also in terms of simplicity. The optical transmitter and receiver circuits built for experimental use were inexpensive and simple in circuit configuration. The distortion factor of the audio signal was less than 1% with a signal-to-noise ratio (SNR) of 70 dB. The differential gain and differential phase of the fiber-optic transmission system were less than 1% and 1 degree, respectively, and the SNR of the video signal was 46 dB.<<ETX>>

Optical IF signal distribution circuits for DBS receivers

Describes two optical transmission systems, each of which is designed to transmit the direct broadcasting satellite (DBS) IF signal from the low-noise converter (LNC) to the DBS receiver through optical fiber. One transmits the IF signal for a specific channel from the LNC to the DBS receiver while the control signal is transmitted through the same optical fiber in the opposite direction. The other transmits the IF signal for all the channels with no control signal transmitted, after the DBS IF signal sent from an LNC is converted into an IF wideband signal of 300 MHz (35-335 MHz). The frequency spectrum of the IF signal is shown.<<ETX>>

Bidirectional audio and video signal transmission system by optical wavelength division multiplexed scheme

Describes a novel wavelength division multiplexed 850/1300 nm system for bidirectionally transmitting square wave frequency modulated (SWFM) audio and video signals and PCM (pulse code modulation) FSK (frequency shift keying) data. One channel for the composite audio-video signal and four channels for PCM data are provided to concurrently transmit SWFM signals in both directions through an optical fiber. The audio signal distortion was 0.5% with a signal-to-noise ratio (SNR) of 70 dB. The distortion when PCM data were used for the voice signal was 1.0% with an SNR of 60 dB. The DG and DP for the video signal were under 5% and 5 degrees with an SNR of 50 dB.<<ETX>>

Processing circuits for addressed audio signal transmission through GI glass fibers

An audio signal covering the 20-Hz-to-20-kHz frequency range and an address signal consisting of one or more pulse-wave or sine-wave frequency signals, whose frequencies are allocated in the 150-kHz-to-600-kHz frequency range, are mixed together and then applied to a SWFM (square wave frequency modulation) circuit to obtain a SWFM signal. The SWFM signal is transmitted from a sender to a specific receiver through an optical fiber after being converted into an optical signal at 850 nm. This concept has been used in full-duplex communication. The signal-to-noise ratio was greater than 40 dB with a distortion factor of less than 1%.<<ETX>>

Audio signal distribution circuit for local optical fiber communication

Audio signal and address distribution circuits are established to construct a local optical fiber communication system. During the time of distributing an audio signal from the transmitter to the specified receiver, a series of multiple frequency address signals are issued together with the audio signal in a specific frequency domain. Since the system has an isolated transmission path actualized by optical fibers in an extremely wide frequency bandwidth, the audio signal and address can simultaneously be sent on a GI optical fiber after they are modulated by an FM square-wave.<<ETX>>

Pulse-width-modulated video signal transmission through optical fiber

The optical fiber transmission of audio and video signals using the pulsewidth modulation (PWM) technique is proposed and experimentally verified. The PWM signal is clocked at 12 MHz or at 14.32 MHz and then converted into the optical pulse. The optical pulse at 850 nm is generated by using a light-emitting diode (LED), transmitted through an optical fiber of up to 2-km long, and received by a p-i-n photodiode (PIN-PD). The differential gain (DG) and differential phase (DP) are under 5% and 5 degrees , respectively, and the SNR was above 45 dB.<<ETX>>

Audio, video and data signal transmission system employing optical wavelength division multiplexer

The authors described a new wavelength division multiplexed 850/1300-nm system for transmitting audio, video, and data signals. Six channels of audio signals, three channels of video signals, and one channel of data can be transmitted through an optical fiber cable with two cores. The audio distortion was under 0.3% with an SNR of 65 dB. High quality has been achieved in terms of the frequency response, linearity, and SNR. The SNR was above 55 dB (unweighted).<<ETX>>

Optical-fiber multi-channel audio and video signal transmission system for use in clinical applications

A multi-channel audio and video signal transmission system constructed by using optical fiber cables as signal transmission media is described. With this system up to four audio signal and up to four video signal channels can be used with a bidirectional operation-aid voice channel. The PFM (pulse frequency modulation) scheme was used to modulate the audio and video signals. The SNR of the video signal was above 55 dB. The differential gain and differential phase were under 3% and 3 degrees , respectively. The SNR of the audio signal was 65 dB and the distortion factor was under 0.3%. The practical use of this system at a surgical center is described.<<ETX>>