Apparatus and method for reducing SPM/GVD in optical systems

An optical communication system for reducing non-linear distortion caused by interaction between Self-Phase Modulation and Group Velocity Dispersion, comprising:

• a transmitter for sending optical pulses at a first wavelength;
• a transponder coupled to receive and convert the optical pulses to a second wavelength, including an opto-electrical device, means for smoothing rise and fall transitions of electrical pulses received from the opto-electrical device, an electrical amplifier, an optical source and an electro-optic modulator;
• a section of optical transmission fiber having an effective length zeff greater than the fiber nonlinear length LNL,
• a receiver coupled to the fiber section.

A method for reducing nonlinear optical distortion caused by the interaction of Self-Phase Modulation and Group Velocity Dispersion, comprising the steps of:

• receiving optical pulses from a transmitter and converting the optical pulses to electrical pulses;
• amplifying the electrical pulses;
• smoothing edges of rise and fall transitions of the electrical pulses;
• modulating an optical carrier signal with the electrical pulses;
• and
• transmitting the modulated optical carrier signal across a plurality of transmission spans having a cumulative length longer than LNL/zeff, wherein LNL is the fiber nonlinear length and zeff is the effective span fiber length.

A transponder for receiving optical pulses at a first wavelength generated by an optical transmitter, modulating an optical carrier with the optical pulses, and alleviating non-linear distortion caused by interaction between Self-Phase Modulation and Group Velocity Dispersion, comprising:

• a photodiode optically coupled to receive and convert the optical pulses to electrical pulses;
• an electrical amplifier, operating in a saturation condition, electrically coupled to receive and amplify the electrical pulses;
• a low-pass filter electrically coupled to receive the electrical pulses from the electrical amplifier, the low-pass filter causing rise and fall times of the electrical pulses to lengthen;
• an optical source providing an optical carrier at a second wavelength;
• and
• an electro-optic modulator positioned to modulate the optical carrier with the electrical pulses from the low-pass filter.

A transponder for receiving optical pulses at a first wavelength generated by an optical transmitter, modulating an optical carrier with the optical pulses, and alleviating non-linear distortion caused by interaction between Self-Phase Modulation and Group Velocity Dispersion, comprising:

• a photodiode optically coupled to receive and convert the optical pulses to electrical pulses;
• an electrical attenuator electrically coupled to receive the electrical pulses from the photodiode;
• an electrical amplifier, operating in a saturation condition, electrically coupled to receive and amplify the electrical pulses from the electrical attenuator;
• an optical source providing an optical carrier at a second wavelength;
• and
• an electro-optic modulator positioned to modulate the optical carrier with the electrical pulses from the electrical amplifier.

A transponder for receiving optical pulses at a first wavelength generated by an optical transmitter, modulating an optical carrier with the optical pulses, and alleviating non-linear distortion caused by interaction between Self-Phase Modulation and Group Velocity Dispersion, comprising:

• a photodiode optically coupled to receive and convert the optical pulses to electrical pulses;
• an electrical attenuator electrically coupled to receive the electrical pulses from the photodiode;
• an electrical amplifier, operating in a saturation condition, electrically coupled to receive and amplify the electrical pulses from the electrical attenuator, wherein the electrical attenuator attenuates the electrical pulses from the photodiode to a predetermined level to prevent the electrical amplifier from operating in deep saturation;
• an optical source providing an optical carrier at a second wavelength;
• and
• an electro-optic modulator positioned to modulate the optical carrier with the electrical pulses from the electrical amplifier.

A transponder for receiving optical pulses at a first wavelength generated by an optical transmitter, modulating an optical carrier with the optical pulses, and alleviating non-linear distortion caused by interaction between Self-Phase Modulation and Group Veloicity Dispersion, comprising:

• a photodiode optically coupled to receive the electrical pulses to electrical pulses;
• a low-pass filter electrically coupled to receive the electrical pulses from the photodiode, the low-pass filter causing rise and fall times of the electrical pulses to lengthen;
• an electrical amplifier, electrically coupled to receive and amplify the electrical pulses from the low-pass filter;
• an optical source providing an optical carrier at a second wavelength;
• and
• an electro-optic modulator positioned to modulate the optical carrier with the electrical pulses from the low-pass filter,

A transponder for receiving optical pulses at a first wavelength generated by an optical transmitter, modulating an optical carrier with the optical pulses, and alleviating non-linear distortion caused by interaction between Self-Phase Modulation and Group Velocity Dispersion, comprising:

• a photodiode optically coupled to receive and convert the optical pulses to electrical pulses;
• an electrical attenuator electrically coupled to receive the electrical pulses from the photodiode;
• an electrical amplifier electrically coupled to receive and amplify the electrical pulses from the electrical attenuator;
• an optical source providing an optical carrier at a second wavelength;
• and
• an electro-optic modulator positioned to modulate the optical carrier with the electrical pulses from the electrical amplifier.