Multilevel pulse position modulation for efficient fiber optic communication
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Accused Products
Abstract
Decreasing the average transmitted power in an optical fiber communication channel using multilevel amplitude modulation in conjunction with Pulse Position Modulation (PPM). This multilevel PPM method does not entail any tradeoff between decreased power per channel and channel bandwidth, enabling a lower average transmitted power compared to On/Off Keying (OOK) with no reduction in aggregate data rate. Therefore, multilevel PPM can be used in high-speed Dense Wavelength Division Multiplexed (DWDM) systems where the maximum number of channels is traditionally limited by nonlinear effects such as self-phase modulation (SPM), cross-phase modulation (XPM), four-wave mixing (FWM), stimulated Brillouin scattering (SBS), and stimulated Raman scattering (SRS). This modulation technique can enable an increased number of channels in DWDM systems, thereby increasing aggregate data rates within those systems.
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Citations
36 Claims
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1-21. -21. (canceled)
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22. A method for decreasing the transmitted power in a channel of an optical fiber communication system while maintaining a channel bandwidth, the method comprising the steps of:
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receiving one or more digital input signals;
creating a digital input word having n bits from the digital input signals;
converting each digital input word to a corresponding output symbol representing one of 2n distinct values, wherein the output symbol comprises a multilevel pulse position modulated symbol; and
generating an output signal comprising a series of output symbols, wherein the output signal has an aggregate data rate equal to a sum of the data rates of the digital input signals. - View Dependent Claims (23, 24, 25)
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26. An optical fiber communication system comprising:
a transmitter for combining n input signals for transmission over an optical fiber communication link using a series of output symbols, each symbol characterized by a position modulated, multilevel pulse representing one of 2n unique values. - View Dependent Claims (27, 28)
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29. A transmitter for use in an optical fiber communications system, comprising:
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an encoding circuit operative to encode at least two on-off keyed input signals into a single multilevel pulse position modulated output signal; and
an optical source for transmitting the output signal over a link of the optical fiber communications system. - View Dependent Claims (30, 31)
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32. A transmission link for transmitting a multilevel, pulse position modulated optical signal over an optical fiber, the optical transmission link comprising:
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an encoder for receiving one or more input data signals comprising a series of pulses, each pulse having one of two distinct pulse levels, wherein the encoder is operative to convert the input data into a single output signal, the output signal being characterized by a series of pulses, each pulse having one of a plurality of unique amplitudes and one of a plurality of unique chip positions; and
an optical source for transmitting the output signal over the optical fiber.
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33. A method for optical communication, comprising the steps of:
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receiving a plurality of signals carrying digital information;
producing an optical signal that comprises a plurality of optical pulses, each having a discrete amplitude selected from one of at least three possible discrete amplitudes, wherein a discrete amount of time separates each optical pulse from a preceding optical pulse; and
encoding the digital information on the optical signal in response to selecting the discrete amplitude and the discrete amount of time for each optical pulse. - View Dependent Claims (34, 35, 36)
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Specification