An optical reception device includes a coefficient update section which optimizes a dispersion coefficient used in compensation of wavelength dispersion of a received signal obtained by receiving an optical signal according to a coherent detection method and a phase rotation amount used in compensation of a nonlinear optical effect of the received signal, and a transmission characteristic estimation section which estimates a transmission characteristic of a transmission line by using the optimized dispersion coefficient and the optimized phase rotation amount.

Described herein are systems and methods that perform coarse chromatic dispersion (CD) compensation by applying precomputed coarse front-end equalizer (FEE) tap weights to a receiver based on an assumed propagation distance. After a waiting period, the FEE tap weights are applied, and it is determined whether the FEE tap weights cause a decision-directed tracking of channel rotations to satisfy a stability metric. In response to the stability metric not being satisfied, the assumed propagation distance is adjusted and used to obtain updated FEE tap weights. Conversely, if the stability metric is satisfied, a fine CD compensation is performed that comprises maintaining the updated FEE tap weights; performing an iterative least-mean-squared (LMS) error adaption to adjust Back-End Equalizer (BEE) tap weights and obtain updated BEE tap weights; and using the updated BEE tap weights to adjust the FEE tap weights to, ultimately, have the BEE output an equalized data bit stream.

An optical modulation system comprises a signal source configured to generate an amplitude modulated electrical signal having a bandwidth and divided into frequency components comprising at least a first frequency component covering a first portion of the bandwidth and a second frequency component covering a second portion of the bandwidth; and an electro-optic modulator for receiving an input optical signal, the modulator having a first optical path and a second optical path, the input optical signal being divided between the first optical path and the second optical path and recombined after propagation along the first optical path and the second optical path to produce an output optical signal, and at least one of the first optical path and the second optical path comprising a phase shifter comprising a pair of electrodes in which each electrode is configured to receive a driving signal; wherein the or each phase shifter is coupled to the signal source to receive at least one of said frequency components as a driving signal for an electrode, and the phase shifters are arranged such that the or each phase shifter receives a different pair of driving signals.

An optical modulation system comprises a signal source configured to generate an amplitude modulated electrical signal having a bandwidth and divided into frequency components comprising at least a first frequency component covering a first portion of the bandwidth and a second frequency component covering a second portion of the bandwidth; and an electro-optic modulator for receiving an input optical signal, the modulator having a first optical path and a second optical path, the input optical signal being divided between the first optical path and the second optical path and recombined after propagation along the first optical path and the second optical path to produce an output optical signal, and at least one of the first optical path and the second optical path comprising a phase shifter comprising a pair of electrodes in which each electrode is configured to receive a driving signal; wherein the or each phase shifter is coupled to the signal source to receive at least one of said frequency components as a driving signal for an electrode, and the phase shifters are arranged such that the or each phase shifter receives a different pair of driving signals.

Provided is a chromatic dispersion compensation method including: dividing a reception signal obtained by receiving an optical signal using a coherent detection scheme into a plurality of frequency bands; adjusting a timing on a time axis of the reception signal for each of the divided frequency bands; performing combination processing for combining the reception signals included in the plurality of frequency bands; performing chromatic dispersion compensation on the reception signal at any timing before or after the combination processing; selecting, before the combination processing, sections in which overlapping parts determined based on lengths of overlap parts are generated; outputting the reception signal for each of the selected sections as a division processing block; and removing the overlap parts from both ends of a processing block generated by combination of the division processing blocks in the combination processing so as to be continuous on a frequency axis.

Provided is a chromatic dispersion compensation method including: dividing a reception signal obtained by receiving an optical signal using a coherent detection scheme into a plurality of frequency bands; adjusting a timing on a time axis of the reception signal for each of the divided frequency bands; performing combination processing for combining the reception signals included in the plurality of frequency bands; performing chromatic dispersion compensation on the reception signal at any timing before or after the combination processing; selecting, before the combination processing, sections in which overlapping parts determined based on lengths of overlap parts are generated; outputting the reception signal for each of the selected sections as a division processing block; and removing the overlap parts from both ends of a processing block generated by combination of the division processing blocks in the combination processing so as to be continuous on a frequency axis.

An Optical Dispersion Compensator (ODC) is disclosed, the ODC being suitable for managing chromatic dispersion of an optical signal for transmission over an optical fiber. The ODC comprises a first ODC unit (202) arranged on a first optical bus (206), a second ODC unit (204) arranged on a second optical bus (208), parallel to the first optical bus (206), and a switching element (210) interconnecting the first and second optical buses (206, 208) between the first and second ODC units (202, 204). The first and second ODC units (202, 204) are operable to provide a delay to the optical signal that varies with frequency. The switching element (210) is configured, in a first state, to switch an optical signal received on one of the first or second optical buses (206, 208) to the other of the first or second optical buses (208, 206) and, in a second state, to maintain an optical signal received on one of the first or second optical buses (206, 208) on the optical bus on which it was received (206, 208). Reflective elements (710) may be included in the ODC, providing bidirectional propagation through one of more ODC units.

An Optical Dispersion Compensator (ODC) is disclosed, the ODC being suitable for managing chromatic dispersion of an optical signal for transmission over an optical fiber. The ODC comprises a first ODC unit (202) arranged on a first optical bus (206), a second ODC unit (204) arranged on a second optical bus (208), parallel to the first optical bus (206), and a switching element (210) interconnecting the first and second optical buses (206, 208) between the first and second ODC units (202, 204). The first and second ODC units (202, 204) are operable to provide a delay to the optical signal that varies with frequency. The switching element (210) is configured, in a first state, to switch an optical signal received on one of the first or second optical buses (206, 208) to the other of the first or second optical buses (208, 206) and, in a second state, to maintain an optical signal received on one of the first or second optical buses (206, 208) on the optical bus on which it was received (206, 208). Reflective elements (710) may be included in the ODC, providing bidirectional propagation through one of more ODC units.

A low-noise amplifier includes a gain medium and two or more amplifier stages. Each amplifier stage includes an optical filter to pass all wavelengths of a respective input optical signal in a given propagation direction over the gain medium and reflect wavelengths above a respective threshold wavelength received in the opposite direction, and a respective Raman pump to inject a pump light centered at a wavelength lower than the threshold wavelength onto the gain medium for transmission in the given direction. A first amplifier stage outputs a first combined optical signal including all wavelengths of the respective input optical signal and a pump light injected by the respective Raman pump. The second amplifier stage receives the first combined optical signal as its input and outputs a second combined optical signal including all wavelengths of the first combined optical signal and a pump light injected by the respective Raman pump.

A low-noise amplifier includes a gain medium and two or more amplifier stages. Each amplifier stage includes an optical filter to pass all wavelengths of a respective input optical signal in a given propagation direction over the gain medium and reflect wavelengths above a respective threshold wavelength received in the opposite direction, and a respective Raman pump to inject a pump light centered at a wavelength lower than the threshold wavelength onto the gain medium for transmission in the given direction. A first amplifier stage outputs a first combined optical signal including all wavelengths of the respective input optical signal and a pump light injected by the respective Raman pump. The second amplifier stage receives the first combined optical signal as its input and outputs a second combined optical signal including all wavelengths of the first combined optical signal and a pump light injected by the respective Raman pump.