Abstract: A method for transmitting a signal and a fiber optic system comprising: a frequency modulated source; an optical transmission fiber positioned to receive the output of the frequency modulated source; an optical filter positioned to receive the output of the optical transmission fiber; and an optical receiver positioned to receive the output of the optical filter; characterized in that: an optical spectrum reshaper is positioned between the frequency modulated source and the optical transmission fiber; and wherein the optical filter is a narrow band pass filter relative to the bit rate of the transmitted signal; and further wherein the frequency excursion of the frequency modulated source is between 20% and 120% of the bit rate frequency.

Abstract: A fiber optic communication system is disclosed having an optical signal source adapted to produce an amplitude and frequency modulated signal encoding binary data wherein high intensity 1 bits are red shifted relative to lower intensity 0 bits. The amplitude and frequency modulated signal is transmitted through a semiconductor optical amplifier (SOA), which may operate in saturation. An optical spectrum reshaper (OSR) is adapted to reshape the output of the SOA.

Abstract: An optical communication system which has an optical signal source adapted to receive a base binary signal and produce a first signal, said first signal being frequency modulated; and an optical spectrum reshaper adapted to reshape the first signal into a second signal, said second signal being amplitude modulated and frequency modulated in which the frequency characteristics of said first signal, and the optical characteristics of said optical spectrum reshaper, being such that the frequency characteristics of said second signal are configured so as to increase the tolerance of the second signal to dispersion in a transmission fiber.

Abstract: An optical transmitter is discloses having a gain section and a phase section. The phase section is modulated to generate a frequency modulated signal encoding data. The frequency modulated signal is transmitted through an optical spectrum reshaper operable to convert it into a frequency and amplitude modulated signal. In some embodiments, a driving circuit is coupled to the phase and gain sections is configured to simultaneously modulate both the phase and gain sections such that the first signal is both frequency and amplitude modulated.

Abstract: A system for generating a return-to-zero differentially-phase-shift-keyed (RZ-DPSK) optical signal comprising: a driver comprising an N-level digital multilevel transformer (DMT) configured to receive a two level digital electrical signal representing 1s and 0s and output a N-level electrical signal, wherein N>2; an FM source configured to receive the N-level electrical signal output by the driver and generate an optical frequency modulated signal; and an optical spectrum reshaper (OSR) configured to receive the optical frequency modulated signal output by the FM source and generate the desired RZ-DPSK optical signal.

Abstract: A method for generating D-N-PSK optical signals is disclosed wherein a laser is modulated to generate optical signal pairs including phase modulated and fixed phase portions, the phase modulated portions having a frequency encoding one or more data symbols and the fixed phase portion having a carrier frequency and a phase corresponding to the immediately preceding phase modulated portion. The output of the laser is passed through an optical spectrum reshaper having a transmission function chosen to attenuate a plurality of the phase modulated portions relative to the fixed phase portions. The phase modulated portions may have N frequency levels located on either side of the carrier frequency. One of the N frequency levels may be equal to the carrier frequency.

Abstract: An optical transmitter is disclosed including an optical signal source generating a frequency modulated signal encoding data. An optical spectrum reshaper is positioned to receive the frequency modulated signal and converts the frequency modulated signal into a reshaped signal having increased amplitude modulation relative to the frequency modulated signal. A third-order dispersive element is positioned to receive the reshaped signal and is adapted to impose third-order dispersion on the reshaped signal to generate a compensated signal having third-order dispersion effective to compensate for second-order dispersion caused by an optical fiber positioned between the optical transmitter and a receiver.

Abstract: The frequency chirp modulation response of a directly modulated laser is described using a small signal model that depends on slow chirp amplitude s and slow chirp time constant ?s. The small signal model can be used to derive an inverse response for designing slow chirp compensation means. Slow chirp compensation means include electrical compensation, optical compensation, or both. Slow chirp electrical compensation can be implemented with an LR filter or other RF circuit coupled to a direct modulation source (e.g., a laser driver) and the directly modulated laser. Slow chirp optical compensation can be implemented with an optical spectrum reshaper having a rounded top and relatively large slope (e.g., 1.5-3 dB/GHz). The inverse response can be designed to under-compensate, to produce a flat response, or to over-compensate.

Abstract: An optical transmitter comprising: an optical source modulated with an input digital data signal so as to generate a first, frequency-modulated digital signal; and an amplitude modulator, modulated with the logical inverse of the input digital data signal, for receiving the first, frequency-modulated signal and generating a second, amplitude-modulated and frequency-modulated digital signal; wherein the optical source and the amplitude modulator are each configured so as to produce positive transient chirp.

Abstract: A fiber optic communication system comprising: an optical signal source adapted to produce a binary amplitude modulated signal; and an optical spectrum reshaper adapted to receive the amplitude modulated signal and to change the instantaneous frequency of the signal at its 0-to-1 and 1-to-0 transitions so as to change the instantaneous frequency of the signal so that it is substantially constant across the 1 pulse. A method for transmitting a signal through a fiber, comprising: generating a second signal from the signal, wherein the second signal comprises a intensity profile and an adiabatic frequency profile; generating a third signal from the second signal, wherein the third signal comprises a intensity profile and a flat-topped frequency profile.

Abstract: A fiber optic transmitter comprising a digital driver adapted to adjust the crossing point of a digital base signal, an optical source adapted to receive the digital base signal and produce a frequency modulated optical signal, and an optical spectrum reshaper adapted to convert the frequency modulated optical signal to an amplitude modulated optical signal. A method for transmitting a signal, comprising: adjusting the crossing point of a digital base signal; providing the adjusted signal to an optical source to produce a frequency modulated optical signal; and providing the frequency modulated optical signal to an optical spectrum reshaper to convert the frequency modulated optical signal to an amplitude modulated optical signal.

Abstract: An optical transmitter is disclosed for transmitting a signal along a dispersive medium to a receiver. The optical transmitter generates adiabatically chirped profile having an initial pulse width and frequency excursion chosen such that high frequency data sequences include one bits that interfere destructively at a middle point of an intervening zero bit upon arrival at the receiver.

Abstract: A fiber optic communication system comprising: an optical signal source adapted to receive a binary first signal and generate a binary second signal, wherein the binary first signal has an amplitude modulated component, wherein the binary second signal has an amplitude modulated component and a frequency modulated component, and further wherein the binary second signal is characterized in that the higher intensity 1 bits are red shifted relative to the lower intensity 0 bits; a semiconductor optical amplifier (SOA) adapted to receive the binary second signal and generate a binary third signal, wherein the binary third signal has an amplitude modulated component and a frequency modulated component, and further wherein the semiconductor optical amplifier operates in saturation; and an optical spectrum reshaper (OSR) adapted to reshape the binary third signal into a binary fourth signal, wherein the binary fourth signal has an amplitude modulated component and a frequency modulated component.

Abstract: A system for generating a return-to-zero differentially-phase-shift-keyed (RZ-DPSK) optical signal comprising: a driver comprising an N-level digital multilevel transformer (DMT) configured to receive a two level digital electrical signal representing 1s and 0s and output a N-level electrical signal, wherein N>2; an FM source configured to receive the N-level electrical signal output by the driver and generate an optical frequency modulated signal; and an optical spectrum reshaper (OSR) configured to receive the optical frequency modulated signal output by the FM source and generate the desired RZ-DPSK optical signal.

Abstract: A method for transmitting a signal and a fiber optic system comprising: a frequency modulated source; an optical transmission fiber positioned to receive the output of the frequency modulated source; an optical filter positioned to receive the output of the optical transmission fiber; and an optical receiver positioned to receive the output of the optical filter; characterized in that: an optical spectrum reshaper is positioned between the frequency modulated source and the optical transmission fiber; and wherein the optical filter is a narrow band pass filter relative to the bit rate of the transmitted signal; and further wherein the frequency excursion of the frequency modulated source is between 20% and 120% of the bit rate frequency.

Abstract: A method of transmitting a base band binary data contained in respective successive time cells, the data being in the form of a signal obtained by amplitude modulation and frequency modulation of a carrier wave with a 0 bit data having a 0 bit mean amplitude and a 0 bit mean frequency and a 0 bit duration and a 1 bit data having a 1 bit mean amplitude and a 1 bit mean frequency and a 1 bit duration the improvement wherein the amplitude and frequency are modulated with the same binary base band signal whereby to decrease the spectral width of the resulting modulated signal below the spectral width of the base band signal.

Abstract: There is provided method for transmitting binary data contained in respective successive time cells, the data being in the form of an optical signal obtained by amplitude modulation and frequency modulation of an optical carrier wave, with a 0 bit data value having a 0 bit mean amplitude having a 0 bit amplitude time duration and a 0 bit frequency having a 0 bit frequency duration, and a 1 bit data value having a 1 bit mean amplitude having a 1 bit amplitude time duration and a 1 bit frequency having a 1 bit frequency duration; the improvement wherein: independently adjusting the 0 bit mean amplitude relative to the 1 bit mean amplitude; independently adjusting the 0 bit frequency relative to the 1 bit frequency; and independently adjusting time duration of the frequency profile of the 1 bit relative to the time duration of the amplitude profile of the 1 bit, whereby to extend the error-free propagation of the optical signal though a dispersive optical fiber beyond the dispersion limit.

Abstract: A fiber optic communication system comprising: an optical signal source adapted to produce a binary amplitude modulated signal; and an optical spectrum reshaper adapted to receive the amplitude modulated signal and to change the instantaneous frequency of the signal at its 0-to-1 and 1-to-0 transitions so as to change the instantaneous frequency of the signal so that it is substantially constant across the 1 pulse. A method for transmitting a signal through a fiber, comprising: generating a second signal from the signal, wherein the second signal comprises a intensity profile and an adiabatic frequency profile; generating a third signal from the second signal, wherein the third signal comprises a intensity profile and a flat-topped frequency profile.

Abstract: In one form of the present invention, there is provided a fiber optic communication system comprising: an optical signal source adapted to receive a base binary signal and produce a first signal, said first signal being frequency modulated; and an optical spectrum reshaper adapted to reshape the first signal into a second signal, said second signal being amplitude modulated and frequency modulated; characterized in that: the frequency characteristics of said first signal, and the optical characteristics of said optical spectrum reshaper, being such that the frequency characteristics of said second signal are configured so as to increase the tolerance of the second signal to dispersion in a transmission fiber.

Abstract: A fiber optic transmitter comprising a digital driver adapted to adjust the crossing point of a digital base signal, an optical source adapted to receive the digital base signal and produce a frequency modulated optical signal, and an optical spectrum reshaper adapted to convert the frequency modulated optical signal to an amplitude modulated optical signal. A method for transmitting a signal, comprising: adjusting the crossing point of a digital base signal; providing the adjusted signal to an optical source to produce a frequency modulated optical signal; and providing the frequency modulated optical signal to an optical spectrum reshaper to convert the frequency modulated optical signal to an amplitude modulated optical signal.