Embodiments of the present invention provide data transmission and receiving methods based on an orthogonal frequency division multiplexing technology, and an apparatus. According to the present invention, grouping and differential encoding are performed on multiple subcarriers, and further, carrier location adjustment is performed, so as to effectively improve non-linear tolerance of a multi-subcarrier system.

The present invention relates to an optical fiber which can improve OSNR in an optical transmission system in which Raman amplification and an EDFA are combined. With respect to the optical fiber, a predetermined conditional formula is satisfied by an effective area Aeff.sub.1450 [m.sup.2] at a wavelength of 1450 nm, a transmission loss .sub.1450 [/km] at a wavelength of 1450 nm, and a transmission loss .sub.1550.sub._.sub.dB [dB/km] at a wavelength of 1550 nm. Further, with respect to the optical fiber, another predetermined conditional formula is satisfied by an effective area Aeff.sub.1550 [m.sup.2] at a wavelength of 1550 nm, and a transmission loss .sub.1550 [/km] at a wavelength of 1550 nm.

The present invention relates to an optical fiber which can improve OSNR in an optical transmission system in which Raman amplification and an EDFA are combined. With respect to the optical fiber, a predetermined conditional formula is satisfied by an effective area Aeff.sub.1450 [m.sup.2] at a wavelength of 1450 nm, a transmission loss .sub.1450 [/km] at a wavelength of 1450 nm, and a transmission loss .sub.1550.sub._.sub.dB [dB/km] at a wavelength of 1550 nm. Further, with respect to the optical fiber, another predetermined conditional formula is satisfied by an effective area Aeff.sub.1550 [m.sup.2] at a wavelength of 1550 nm, and a transmission loss .sub.1550 [/km] at a wavelength of 1550 nm.

Enhancements in optical beam propagation performance can be realized through the utilization of ultra-short pulse laser (USPL) sources for laser transmit platforms, which are can be used throughout the telecommunication network infrastructure fabric. One or more of the described and illustrated features of USPL free space-optical (USPL-FSO) laser communications can be used in improving optical propagation through the atmosphere, for example by mitigating optical attenuation and scintillation effects, thereby enhancing effective system availability as well as link budget considerations, as evidenced through experimental studies and theoretical calculations between USPL and fog related atmospheric events.

A transmission device includes a first optical modulator configured to modulate, based on a packet signal for each of packets, input light into an optical packet signal and to output an optical packet signal for each of the packets; a generation circuit configured to generate an adjustment signal that adjusts slopes of a rise and a fall of a waveform of the optical packet signal; and a second optical modulator configured to modulate the optical packet signal from the first optical modulator and adjust, based on the adjustment signal, the slopes of the rise and the fall of the waveform of the optical packet signal.

Enhancements in optical beam propagation performance can be realized through the utilization of ultra-short pulse laser (USPL) sources for laser transmit platforms, which are can be used throughout the telecommunication network infrastructure fabric. One or more of the described and illustrated features of USPL free space-optical (USPL-FSO) laser communications can be used in improving optical propagation through the atmosphere, for example by mitigating optical attenuation and scintillation effects, thereby enhancing effective system availability as well as link budget considerations, as evidenced through experimental studies and theoretical calculations between USPL and fog related atmospheric events.

The present invention relates to an optical fiber which can improve OSNR in an optical transmission system in which Raman amplification and an EDFA are combined. With respect to the optical fiber, a predetermined conditional formula is satisfied by an effective area Aeff.sub.1450 [m.sup.2] at a wavelength of 1450 nm, a transmission loss .sub.1450 [/km] at a wavelength of 1450 nm, and a transmission loss .sub.1550.sub._.sub.dB [dB/km] at a wavelength of 1550 nm. Further, with respect to the optical fiber, another predetermined conditional formula is satisfied by an effective area Aeff.sub.1550 [m.sup.2] at a wavelength of 1550 nm, and a transmission loss .sub.1550 [/km] at a wavelength of 1550 nm.

The invention relates to an optical spectrum inverter, configured for counteracting phase distortion effects in an optical channel over a predefined frequency range, to an inverter node, configured for duplex operation in at least two wavelength channels, and to a method for counteracting phase distortion effects in an optical channel. The optical spectrum inverter comprises an optical receiver comprising a polarization diversity unit configured for polarization resolved detection, wherein the optical receiver is configured for receiving an optical input signal comprising a first wavelength span and for converting the optical input signal to an electrical signal, and an optical modulator connectable to the optical receiver and configured for modulating the electrical signal onto an optical signal, wherein the optical modulator comprises an optical filter which is configured for selecting a second wavelength span of the optical signal corresponding to an optical output side band of an inverted spectrum of the optical channel such that phase distortion effects are counteracted at least partly over the predefined frequency range. In this way, an optical spectrum inverter is provided which is simple and cost-effective to realize and allows higher optical power levels in conjunction with a higher capacity per optical channel and is also adapted for longer transmission distances.

The invention relates to an optical spectrum inverter, configured for counteracting phase distortion effects in an optical channel over a predefined frequency range, to an inverter node, configured for duplex operation in at least two wavelength channels, and to a method for counteracting phase distortion effects in an optical channel. The optical spectrum inverter comprises an optical receiver comprising a polarization diversity unit configured for polarization resolved detection, wherein the optical receiver is configured for receiving an optical input signal comprising a first wavelength span and for converting the optical input signal to an electrical signal, and an optical modulator connectable to the optical receiver and configured for modulating the electrical signal onto an optical signal, wherein the optical modulator comprises an optical filter which is configured for selecting a second wavelength span of the optical signal corresponding to an optical output side band of an inverted spectrum of the optical channel such that phase distortion effects are counteracted at least partly over the predefined frequency range. In this way, an optical spectrum inverter is provided which is simple and cost-effective to realize and allows higher optical power levels in conjunction with a higher capacity per optical channel and is also adapted for longer transmission distances.

Enhancements in optical beam propagation performance can be realized through the utilization of ultra-short pulse laser (USPL) sources for laser transmit platforms, which are can be used throughout the telecommunication network infrastructure fabric. One or more of the described and illustrated features of USPL free space-optical (USPL-FSO) laser communications can be used in improving optical propagation through the atmosphere, for example by mitigating optical attenuation and scintillation effects, thereby enhancing effective system availability as well as link budget considerations, as evidenced through experimental studies and theoretical calculations between USPL and fog related atmospheric events.