A method for all-optical reduction of inter-channel crosstalk for spectrally overlapped optical signals for maximizing utilization of an available spectrum includes receiving a plurality of spectrally overlapped optical signals modulated with data. The method further includes generating conjugate copies of each of the plurality of optical signals using non-linear optics. The method further includes selecting the conjugate copies and adjusting an amplitude, a phase, and a delay of the conjugate copies. The method further includes performing inter-channel interference (ICI) compensation on the spectrally overlapped optical signals in an optical domain by adding the adjusted conjugate copies to the spectrally overlapped optical signals.

A method for all-optical reduction of inter-channel crosstalk for spectrally overlapped optical signals for maximizing utilization of an available spectrum includes receiving a plurality of spectrally overlapped optical signals modulated with data. The method further includes generating conjugate copies of each of the plurality of optical signals using non-linear optics. The method further includes selecting the conjugate copies and adjusting an amplitude, a phase, and a delay of the conjugate copies. The method further includes performing inter-channel interference (ICI) compensation on the spectrally overlapped optical signals in an optical domain by adding the adjusted conjugate copies to the spectrally overlapped optical signals.

A quasi-single-mode optical fiber with a large effective area is disclosed. The quasi-single-mode fiber has a core with a radius greater than 5 μm, and a cladding section configured to support a fundamental mode and a higher-order mode. The fundamental mode has an effective area greater than 170 μm.sup.2 and an attenuation of no greater than 0.17 dB/km at a wavelength of 1530 nm. The higher-order mode has an attenuation of at least 1.0 dB/km at the wavelength of 1530 nm. The quasi-single-mode optical fiber has a bending loss of less than 0.02 dB/turn for a bend diameter of 60 mm for a wavelength of 1625 nm.

A quasi-single-mode optical fiber with a large effective area is disclosed. The quasi-single-mode fiber has a core with a radius greater than 5 μm, and a cladding section configured to support a fundamental mode and a higher-order mode. The fundamental mode has an effective area greater than 170 μm.sup.2 and an attenuation of no greater than 0.17 dB/km at a wavelength of 1530 nm. The higher-order mode has an attenuation of at least 1.0 dB/km at the wavelength of 1530 nm. The quasi-single-mode optical fiber has a bending loss of less than 0.02 dB/turn for a bend diameter of 60 mm for a wavelength of 1625 nm.

A method for calculating configuration of an optical transmission network includes: acquiring an initial value of an input power of an optical cable; based on the initial value, obtaining an output power of each channel at an end of a section of the optical cable according to a loss of the optical cable; taking the output power of each channel at the end of the section as a boundary condition to calculate the input power of each channel at the section based on an amount of optical power transferred from a high-frequency channel to a low-frequency channel due to an SRS effect; and calculating a first parameter value of an optical amplifier of the section using the input power of each channel at the section and the output power of each channel at the end of a preceding section of the section.

A system and method are presented for coupling OAM optical beams to optical fibers. The system may include, for instance, an OAM beam generator, for receiving one or more of a plurality of input signals, and generating a different OAM mode signal for each input signal. The OAM beam generator may further be operative to adjust a location and/or an exit angle of the one or more OAM mode signals before sending the one or more OAM mode signals to a beam combiner that combines the one or more OAM mode signals into a combined mode OAM transmission. The system may further include a controller in communication with at least one crosstalk estimate sensor and the at least one OAM beam generator, the controller operative to optimize the crosstalk estimate by receiving the crosstalk estimate for one of the OAM mode signals, and sending control instructions instructing the OAM beam generator to adjust a location and/or an exit angle of the one or more OAM mode signals to reduce the crosstalk estimate.

Methods and systems may mitigate nonlinear noise (NLN) penalties for optical paths using spectral inversion in optical transport networks. Using a tunable dispersion compensator with an optical amplifier at each span in an optical path, the dispersion along the optical path may be modified to a normalized dispersion for each span. In this manner, the dispersion associated with NLN accumulation may be balanced by NLN compensation to reduce overall NLN levels for the optical path.

A nonlinear compensation unit (300) includes a first compensation unit (350) and a second compensation unit (360). The first compensation unit (350) compensates for each of two polarization signals E.sub.x and E.sub.y so as to cancel a first amount of phase rotation which is the amount of phase rotation calculated based on the signal strength of the two polarization signals E.sub.x and E.sub.y. The second compensation unit (360) compensates for each of the two polarization signals E.sub.x and E.sub.y so as to cancel a second amount of phase rotation which is the amount of phase rotation calculated based on the perturbative component of the two polarization signals E.sub.x and E.sub.y. The first compensation unit (350) includes a strength calculation unit (302), a first filter unit (304), and a first phase modulation unit (306). The second compensation unit (360) includes a perturbative component calculation unit (316), a second filter unit (318), a second phase modulation unit (322), and a third phase modulation unit (330).

A nonlinear compensation unit (300) includes a first compensation unit (350) and a second compensation unit (360). The first compensation unit (350) compensates for each of two polarization signals E.sub.x and E.sub.y so as to cancel a first amount of phase rotation which is the amount of phase rotation calculated based on the signal strength of the two polarization signals E.sub.x and E.sub.y. The second compensation unit (360) compensates for each of the two polarization signals E.sub.x and E.sub.y so as to cancel a second amount of phase rotation which is the amount of phase rotation calculated based on the perturbative component of the two polarization signals E.sub.x and E.sub.y. The first compensation unit (350) includes a strength calculation unit (302), a first filter unit (304), and a first phase modulation unit (306). The second compensation unit (360) includes a perturbative component calculation unit (316), a second filter unit (318), a second phase modulation unit (322), and a third phase modulation unit (330).

Aspects of the present disclosure are directed to the mitigation of multi-path interference from quasi-single-mode fiber using hybrid span configuration and digital signal processing wherein a hybrid span of quasi-single mode fibers and single-mode fibers are used to configure the hybrid span. Additional aspects are directed to introducing a low-baud rate sub-banding signal to reduce the number of DD-LMS taps required when compensating the multi-path interference as the low-baud rate signal requires fewer taps to cover a given range of MPI as compared to a high-baud rate signal. Finally further aspects are directed to an ALMS equalizer which further reduces the number of equalizer taps by shifting its center tap towards the right if higher-order modes transmit slower than a fundamental mode, otherwise the center tap is shifted to the left.