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: A fiber optic communication system, comprising: an optical signal source adapted to produce a frequency modulated signal; and an optical spectrum reshaper adapted to receive the frequency modulated signal and output a substantially amplitude modulated signal; wherein the optical spectrum reshaper limits the bandwidth of the frequency modulated signal.

Abstract: A distributed Bragg reflector (DBR) includes a base substrate and a gain medium formed on the base substrate. A waveguide positioned above the base substrate in optical communication with the gain medium and defines a gap extending between the base substrate and the waveguide along a substantial portion of the length thereof. The waveguide may have a grating formed therein. A heating element is in thermal contact with the waveguide and electrically coupled to a controller configured to adjust optical properties of the waveguide by controlling power supplied to the heating element.

Abstract: A fiber optic communication system for receiving an electronic digital data signal and transmitting the same, comprising an optical signal source adapted to receive the digital data signal and to produce a frequency modulated optical signal from a directly modulated semiconductor laser; an optical spectrum reshaper adapted to convert the frequency modulated optical signal into an amplitude modulated optical signal; and compensation apparatus for compensating for the adverse effects of the thermal chirp normally induced in the frequency modulated optical signal by modulating the semiconductor laser with the electronic digital data signal.

Abstract: There is provided a fiber optic transmission system, comprising: an optical signal source adapted to produce a frequency modulated signal; and a multi-ring resonator optical spectrum reshaper (OSR) adapted to convert the frequency modulated signal into a substantially amplitude modulated signal. And there is provided a method for transmitting an optical signal through a fiber comprising: producing a frequency modulated signal; passing the frequency modulated signal through a multi-ring resonator optical spectrum reshaper (OSR) so as to convert the frequency modulated signal into a substantially amplitude modulated signal; and passing the substantially amplitude modulated signal into the 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 distributed Bragg reflector (DBR) includes a base substrate and a gain medium formed on the base substrate. A waveguide positioned above the base substrate in optical communication with the gain medium and defines a gap extending between the base substrate and the waveguide along a substantial portion of the length thereof The waveguide having a grating formed therein. A heating element is in thermal contact with the waveguide and electrically coupled to a controller electrically configured to adjust optical properties of the waveguide by controlling power supplied to the heating element.

Abstract: An optical transmitter comprising: (i) an electrical switch; (ii) a laser array comprising a plurality of tunable laser elements; and (iii) an Optical Spectrum Reshaper (OSR) used to reshape the output pulses from the laser elements in the laser array; wherein the electrical switch takes an input electrical digital signal and selectively directs it to a specific laser element in the DFB laser array.

Abstract: A transmitter includes a frequency modulated laser. An optical spectrum reshaper (OSR) is positioned to receive the frequency modulated signal and has a transmission function effective to convert the frequency modulation to amplitude modulation. An optical fiber channel has a first end positioned to receive the filtered signal and a second end proximate a receiver. A filter is positioned between the second end and the receiver and has a peak transmission frequency thereof located on a transmission edge of the OSR, such as at a peak logarithmic derivative value of the transmission function of the optical spectrum reshaper. In some embodiments a first OSR is positioned to receive the frequency modulated signal and configure to output a filtered signal wherein high frequency portions are more attenuated than low frequency portions. A second OSR at the receiver attenuates the low frequency portions substantially more than the high frequency portions.

Abstract: This invention generally relates to an optical filter for a fiber optic communication system. An optical filter may be used, following a directly modulated laser source, and converts a partially frequency modulated signal into a substantially amplitude modulated signal. The optical filter may compensate for the dispersion in the fiber optic transmission medium and may also lock the wavelength of the laser source.

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: This invention generally relates to an optical filter for a fiber optic communication system. An optical filter may be used, following a directly modulated laser source, and converts a partially frequency modulated signal into a substantially amplitude modulated signal. The optical filter may compensate for the dispersion in the fiber optic transmission medium and may also lock the wavelength of the laser source.

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: The invention, in one form, is a fiber optic system having an optical signal source adapted to produce a frequency and amplitude modulated optical digital signal and a semiconductor optical amplifier adapted to receive the frequency and amplitude modulated optical digital signal and generate negative transient chirp at the transitions between bits. In another form, the invention is a fiber optic system having an optical source adapted to generate a frequency modulated signal, a semiconductor optical amplifier adapted to receive and amplify the frequency modulated signal, and an optical spectrum reshaper adapted to receive the amplified frequency modulated signal and to utilize the amplified frequency modulated signal to increase the amplitude modulation of the signal.

Abstract: A laser is disclosed including a gain section having a distributed feedback grating imposed thereon. An absorption section is embedded in the gain section such that the first and second portions of the distributed feedback grating extend on either side of the electro-absorption section. A controller imposes a substantially DC bias signal on the first and second gain electrodes and imposes a modulation signal encoding digital data on the modulation electrode to generate a frequency modulated signal. In some embodiments, the first and second portions are biased above the lasing threshold and the absorption section is modulated below the lasing threshold to modulate loss in the absorption section.

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: 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 is disclosed having a temperature stabilization system for an optical filter for maintaining constant the frequency response of the filter. The filter is mounted within a housing having a substantially higher thermal conductivity. The housing may include a copper-tungsten alloy and extend along the optical axis of the filter. The housing is in thermal contact with a thermo-electric cooler (TEC) and a temperature sensor. The TEC and temperature sensor are electrically coupled to a controller which adjusts the temperature of the TEC according to the output of the temperature sensor.

Abstract: An optical transmitter is disclosed wherein a modulating signal, such as an NRZ signal, encoding data is combined with a time derivative of the modulating signal and coupled to a directly modulated laser in order to generate artificial transient chirp in the output of the laser effective to substantially compensate for dispersion experienced by the output of the laser traveling through a dispersive medium such as an optical fiber. In some embodiments, the time derivative is added to the modulating signal only at the falling edges of the modulating signal.