Optical cable television transmission system
First Claim
1. A system for optically transmitting a frequency-division multiplex signal occupying a wide frequency band over a single optical waveguide, comprising:
- a transmitter unit including;
a filter portion, responsive to a wise frequency band (FB) signal, for providing a first transmission signal covering less than one octave (FB2) and a modulating signal covering more than one octave (FB1);
a modulator, responsive to the modulating signal, for amplitude modulating a carrier (f0) signal, for providing a second transmission signal covering a single sideband (UB1) which, referred to its lowest frequency, is less than one octave wide; and
an electrical/optical converter portion responsive to the first and second transmission signals for conversion, respectively, into first and second optical signals of different wavelengths and for combining said optical signals into a wavelength-division multiplex signal for transmission on an optical cable; and
a receiver including;
a wavelength demultiplexer portion, responsive to the wavelength-division multiplex signal, for providing the first and second optical signals;
an optical to electrical converter portion, responsive to the first and second optical signals for providing the first and second transmission signals;
a demodulator responsive to the second transmission signal for providing the modulating signal; and
means responsive to the modulating signal and the first transmission signal for providing the wide frequency band signal.
1 Assignment
0 Petitions
Accused Products
Abstract
The invention is based on the problem of transmitting a frequency-division multiplex signal occupying a board frequency band, e.g., the cable television frequency band of 47-440 MHz, over an optical waveguide transmission section. According to the invention, in the transmitting unit, the whole frequency band to be transmitted is divided into two sub-bands (FB1, FB2), and the lower sub-band (FB1) is converted by means of single-sideband amplitude modulation of a high-frequency carrier (f0) into a higher-frequency transmission frequency band, e.g. 497-688 MHz, which is less than one octave in width, based on its lowest frequency. The lower sub-band (FB1) and the transmission frequency band produced by the conversion are converted separately into optical signals with different wavelengths (λ1, λ2) and are transmitted in a wavelength multiplex procedure via the optical waveguide. Because of the limitation of less than one octave, second-order intermodulation products, which are usually formed during conversion into an optical signal, fall into unoccupied frequency regions. A corresponding reverse processing is carried out on the receiving side.
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Citations
22 Claims
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1. A system for optically transmitting a frequency-division multiplex signal occupying a wide frequency band over a single optical waveguide, comprising:
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a transmitter unit including; a filter portion, responsive to a wise frequency band (FB) signal, for providing a first transmission signal covering less than one octave (FB2) and a modulating signal covering more than one octave (FB1); a modulator, responsive to the modulating signal, for amplitude modulating a carrier (f0) signal, for providing a second transmission signal covering a single sideband (UB1) which, referred to its lowest frequency, is less than one octave wide; and an electrical/optical converter portion responsive to the first and second transmission signals for conversion, respectively, into first and second optical signals of different wavelengths and for combining said optical signals into a wavelength-division multiplex signal for transmission on an optical cable; and a receiver including; a wavelength demultiplexer portion, responsive to the wavelength-division multiplex signal, for providing the first and second optical signals; an optical to electrical converter portion, responsive to the first and second optical signals for providing the first and second transmission signals; a demodulator responsive to the second transmission signal for providing the modulating signal; and means responsive to the modulating signal and the first transmission signal for providing the wide frequency band signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A transmitter for optically transmitting a frequency-division multiplex signal occupying a wide frequency band over a single optical waveguide, comprising:
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a filter portion, responsive to a wide frequency band (FB) signal, for providing a first transmission signal covering less than one octave (FB2) and a modulating signal covering more than one octave (FB1); a modulator, responsive to the modulating signal, for single-sideband amplitude modulating a carrier (f0) signal, for providing a second transmission signal covering a frequency band (UB1) which, referred to its lowest frequency, is less than one octave wide; and an electrical to optical converter portion responsive to the first and second transmission signals for conversion, respectively, into first and second optical signals of different wavelengths and for combining said optical signals into a wavelength-division multiplex signal for transmission on the optical waveguide.
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22. A receiver for optically receiving a frequency-division multiplex optical signal occupying a wide frequency band over a single optical waveguide, comprising:
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a wavelength demultiplexer portion, responsive to the wavelength-division multiplex signal, for providing first and second optical signals; an optical to electrical converter portion, responsive to the first and second optical signals for providing first and second electrical signals; a demodulator responsive to the second electrical signal for providing a demodulated signal; and means responsive to the demodulated signal and the first electrical signal for combining the demodulated and first electrical signal into a wide frequency band electrical signal.
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Specification