The invention relates to the aspects of implementation of compensation, or equalization devices aimed at nonlinear impairment mitigation in fiber optic communication systems by means of including the spatially varying dispersive characteristics, or parameters of the underlying waveguides and their potential performance improvement from utilization of those parameters.

An object is to provide a dispersion compensating system with a large amount of dispersion compensation and reduced operation costs. Disclosed is a dispersion compensating system in which a core node and an access node are connected through a ring network, the access node includes a delay measurement unit configured to receive delay measurement signals from the core node to measure a delay between the core node and the access node, an average dispersion amount calculation unit configured to calculate an amount of dispersion compensation to be applied to an optical burst signal prior to transmission to the ring network, based on the delay thus measured, and a real-part inverse dispersion application unit configured to perform pre-equalization on a waveform of the optical burst signal prior to the transmission, based on the calculated amount of dispersion compensation.

An object is to provide a dispersion compensating system with a large amount of dispersion compensation and reduced operation costs. Disclosed is a dispersion compensating system in which a core node and an access node are connected through a ring network, the access node includes a delay measurement unit configured to receive delay measurement signals from the core node to measure a delay between the core node and the access node, an average dispersion amount calculation unit configured to calculate an amount of dispersion compensation to be applied to an optical burst signal prior to transmission to the ring network, based on the delay thus measured, and a real-part inverse dispersion application unit configured to perform pre-equalization on a waveform of the optical burst signal prior to the transmission, based on the calculated amount of dispersion compensation.

An apparatus comprising a frontend configured to convert an optical IM signal associated with a remote optical transmitter into a plurality of analog electrical signals, determine a plurality of DC offsets for the analog electrical signals, remove the DC offsets from the analog electrical signals to produce a plurality of DC-free analog signals, and convert the DC-free analog signals into a plurality of DC-free digital signals, and a DSP unit coupled to the frontend and configured to perform fiber dispersion compensation on the DC-free digital signals according to a dispersion value associated with the remote optical transmitter to produce a plurality of DC-free compensated digital signals, and add the DC offsets to the compensated digital signals to produce a plurality of DC-restored compensated digital signals.

An apparatus comprising a frontend configured to convert an optical IM signal associated with a remote optical transmitter into a plurality of analog electrical signals, determine a plurality of DC offsets for the analog electrical signals, remove the DC offsets from the analog electrical signals to produce a plurality of DC-free analog signals, and convert the DC-free analog signals into a plurality of DC-free digital signals, and a DSP unit coupled to the frontend and configured to perform fiber dispersion compensation on the DC-free digital signals according to a dispersion value associated with the remote optical transmitter to produce a plurality of DC-free compensated digital signals, and add the DC offsets to the compensated digital signals to produce a plurality of DC-restored compensated digital signals.

A method of suppressing polarization-dependent loss in a signal. A constant-intensity, analog, optical signal with modulating polarization is transmitted through an optical communications link. The constant-intensity, analog, optical signal with modulating polarization includes an analog radio frequency signal impressed upon a polarization-modulated, laser signal. A polarization-dependent loss of the communications link is determined, the polarization-dependent loss inducing an induced phase shift in the constant-intensity, analog, optical signal with modulating polarization. The constant-intensity, analog, optical signal with modulating polarization is re-oriented using a polarization transformer so as to suppress the induced phase shift.

A quantum communications system includes a quantum key generation system having a photonic quantum bit generator, a low loss dispersion limiting fiber having a length L, for example greater than 200 km, and a photon detector unit and a communications network having a signal generator, a signal channel, and a signal receiver. The low loss dispersion limiting fiber extends between and optically couples the photonic quantum bit generator and the photon detector unit. Further, the low loss dispersion limiting fiber is structurally configured to limit dispersion at an absolute dispersion rate of about 9 ps/(nm)km or less, and preferably 0.5 ps/(nm)km or less, and induce attenuation at an attenuation rate of about 0.175 dB/km or less such that the quantum key bit information of a plurality of photons output by the one or more photonic quantum bit generators is receivable at the photon detector unit at a bit rate of at least 10 Gbit/sec.

A quantum communications system includes a quantum key generation system having a photonic quantum bit generator, a low loss dispersion limiting fiber having a length L, for example greater than 200 km, and a photon detector unit and a communications network having a signal generator, a signal channel, and a signal receiver. The low loss dispersion limiting fiber extends between and optically couples the photonic quantum bit generator and the photon detector unit. Further, the low loss dispersion limiting fiber is structurally configured to limit dispersion at an absolute dispersion rate of about 9 ps/(nm)km or less, and preferably 0.5 ps/(nm)km or less, and induce attenuation at an attenuation rate of about 0.175 dB/km or less such that the quantum key bit information of a plurality of photons output by the one or more photonic quantum bit generators is receivable at the photon detector unit at a bit rate of at least 10 Gbit/sec.

A device (10;150;200) is configured to receive an optical signal. The device comprises a dispersion compensator (210a) comprising a plurality of optical dispersion compensator units (220). Each optical dispersion compensator unit comprises a plurality of delay elements (20;40). The dispersion compensator (210a) is configured to selectively activate one or more of the optical dispersion compensator units (220). The dispersion compensator (210a) is configured to compensate for dispersion of the optical signal with the activated one or more optical dispersion compensator unit (200).

[Problem] A signal distortion generated when a multi-level modulated optical signal is transmitted through an optical transmission path where optical amplifiers are scattered is suppressed and transmission quality is improved. [Solution] An optical transmission system 20 includes Tx 21a to Tx 21n configured to transmit a multi-level modulated optical signal 32 to an optical fiber 25, optical amplifiers 26a to 26f configured to amplify the optical signal 32 transmitted through the optical fiber 25, the optical amplifiers 26a to 26f being scattered on the optical fiber 25, and Rx 24a to Rx 24n configured to receive the amplified optical signal 32 via the optical fiber 25. A pre-dispersion compensation unit 27 of each of the Tx 21a to Tx 21n performs pre-dispersion compensation on the transmitted optical signal 32, based on a pre-dispersion compensation ratio for determining a percentage of dispersion compensation to be performed in advance on a wavelength dispersion to be accumulated in the optical fiber 25, with respect to the dispersion compensation to narrow a bandwidth to be widened by the wavelength dispersion during transmission of the optical signal 32 through the optical fiber 25.