System for optically transmitting digital communications over an optical fiber with dispersion at the operating wavelength
First Claim
1. A system, comprising:
- an electrical-to-optical converter at a transmitting end of the system, responsive to a digital signal, for providing a frequency-shift-keyed (FSK) modulated optical output signal;
an optical fiber with dispersion at an operating wavelength of the system, responsive to the FSK modulated optical output signal, for providing a fiber-transmitted FSK modulated optical output signal;
an optical-to-electrical converter at a receiving end of the system, responsive to intensity variations of the fiber-transmitted FSK modulated optical output signal, for providing an electrical signal that corresponds to the intensity variations in the fiber-transmitted FSK modulated optical output signal; and
a decider, responsive to the intensity variations of the electrical signal froe the optical-to-electrical converter, for providing a recovered digital signal.
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Accused Products
Abstract
When digital signals are transmitted over optical fibers (3), which have a considerable chromatic dispersion at the wavelength being used, the length of the transmission path is very limited when the digital signal to be transmitted is converted into an optical signal by means of intensity modulation. If frequency modulation (also called FSK=Frequency Shift Keying) is used instead of the intensity modulation, the bridgeable path can be greatly increased, but requires a suitable optical receiver at the receiving end. The invention utilizes a simple optical receiver (4), which is not sensitive to frequency modulation, but to intensity modulation. This is possible, because an intensity variation is created, due to the chromatic dispersion of the optical fiber (3) and the resulting running time differences of signal portions at different wavelengths (λ0, λ1) from the initial frequency modulation during the transmission over the optical fiber (3), which process is contained in the digital signal.
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Citations
22 Claims
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1. A system, comprising:
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an electrical-to-optical converter at a transmitting end of the system, responsive to a digital signal, for providing a frequency-shift-keyed (FSK) modulated optical output signal; an optical fiber with dispersion at an operating wavelength of the system, responsive to the FSK modulated optical output signal, for providing a fiber-transmitted FSK modulated optical output signal; an optical-to-electrical converter at a receiving end of the system, responsive to intensity variations of the fiber-transmitted FSK modulated optical output signal, for providing an electrical signal that corresponds to the intensity variations in the fiber-transmitted FSK modulated optical output signal; and a decider, responsive to the intensity variations of the electrical signal froe the optical-to-electrical converter, for providing a recovered digital signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An installation at a receiving end of a system for optical transmission of a digital signal over a dispersion-affected optical fiber, wherein the digital signal is optically transmitted over the optical fiber by modulating a semiconductor laser by frequency-shift-keying (FSK) according to values of the digital signal, wherein the installation at the receiving end comprises:
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an optical-to-electrical converter, responsive to intensity variations of the optically-transmitted digital signal, for providing an electrical signal having intensity variations; and a decider, responsive to the electrical signal, for recovering the digital signal from the intensity variations of the electrical signal, wherein the optically-transmitted digital signal to which the optical-to-electrical converter is responsive is the optical signal transmitted over the dispersion-affected optical fiber. - View Dependent Claims (14, 15, 16)
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17. A method for use of an optical fiber with dispersion at a predetermined wavelength, comprising the steps of:
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modulating by frequency-shift-keying (FSK) an optical input signal input to the fiber with a digital signal; transporting the FSK modulated optical input signal over the fiber for converting the optical input signal into an optical output signal; and directly demodulating intensity variations in the optical output signal from the optical fiber, for recovering the digital signal without having to frequency demodulate the optical output signal.
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- 18. A system for optically transmitting a digital signal over an optical fiber by means of an optical sender at a transmitting end of the system, with an optical receiver at a receiving end of the system, the receiver comprising an optical-electrical converter with a photodiode responsive to the optically transmited digital signal for providing a detected signal and a decision circuit responsive to the detected signal for providing a recovered digital signal, wherein the system at the receiving end further comprises a device, responsive to the recovered digital signal for providing an actual visual diagram signal indicative of the recovered digital signal wherein the system at the receiving end further comprises a computer, responsive to the actual visual diagram signal, for comparing the actual visual diagram signal with a predetermined visual diagram signal, for determining and providing one or more correction variable signals wherein one or both of the optical sender and optical receiver are responsive to a corresponding one or more of the correction variable signals for being adjusted thereby.
Specification