Synchronous amplitude modulation for improved performance of optical transmission systems
AssigneeTyco Telecommunications (US) Inc.
InventorNeal S. Bergano
Life of this patent
Estimating the term…
Abstract
A method and apparatus is provided that yields improved performance of both single channel and WDM long-distance optical transmission systems by synchronously modulating of the transmitted signal's amplitude. An amplitude modulator receives an optical signal onto which data has been modulated at a predetermined frequency. The modulator re-modulates the amplitude of the optical signal in a continues fashion with a waveform that is periodic, whose fundamental frequency is equal to the same predetermined frequency at which the data is modulated onto the optical signal. The resulting signal (which is neither a pure NRZ or RZ signal) is more tolerant to the distortions usually found in lightwave transmission systems, thus giving superior transmission performance.
Claims49
An apparatus for transmitting an optical signal comprising:
- an optical signal source for generating an optical signal onto which data is modulated at a predetermined frequency;
- a data modulator coupled to said optical signal source, said data modulator configured to modulate said optical signal;
- an amplitude modulator coupled to the optical signal source for modulating the intensity of said data modulated signal;
- and
- a clock coupled to said amplitude modulator and said data modulator, said clock having a frequency that determines the modulation frequency of the amplitude modulator, said frequency of the clock being phase locked and equal to said predetermined frequency.
An apparatus for transmitting an optical signal comprising:
- an amplitude modulator receiving an optical signal onto which data has been modulated at a predetermined frequency;
- a data modulator configured to modulate said optical signal;
- and
- a clock coupled to the amplitude modulator having a frequency that determines the frequency of the modulation cycle, said frequency of the clock being phased locked and equal to said predetermined frequency.
A method for transmitting an optical signal comprising the steps of:
- generating an optical signal onto which data is modulated by a data modulator at a predetermined frequency;
- and
- modulating the amplitude of said data modulated signal at a frequency phase locked and equal to said predetermined frequency.
A transmission system comprising:
- a transmitter including:
- an optical signal source for generating an optical signal;
- a data modulator coupled to said optical signal source for modulating data at a predetermined frequency;
- an amplitude modulator coupled to the optical signal source for modulating the intensity of said data modulated signal;
- a clock coupled to the amplitude modulator having a frequency that determines the frequency of the amplitude modulator, said frequency of the clock being phase locked and equal to said predetermined frequency;
- an optical transmission path coupled to said transmitter;
- and
- a receiver coupled to the optical transmission path.
An apparatus for transmitting an optical signal comprising:
- an optical signal source;
- a data modulator coupled to said signal source, said data modulator configured to modulate data onto said optical signal;
- a pulse forming circuit coupled to said data modulator, said circuit configured to provide an electrical modulation signal to said data modulator;
- a data source coupled to said pulse forming circuit;
- and
- a clock coupled to said data source, said clock having a frequency that determines the modulation frequency of said pulse forming circuit.
Dependencies are inferred from the claim text.