Optical transmission system and method of controlling optical transmission system

An optical transmission system for transmitting an optical signal while compensating for chromatic dispersion, comprising:

• terminal stations for transmitting and receiving an optical signal through an optical fiber transmission path;
• repeaters disposed in said optical fiber transmission path for amplifying said optical signal;
• dispersion compensation modules disposed in said terminal stations and said repeaters for compensating for dispersion of said optical signal;
• and
• a dispersion compensation controller for determining a target value for a nonlinear phase shift,
• which is an indication of a self-phase modulation caused by a transmission medium of the optical fiber transmission path, to have a maximum residual dispersion tolerance, and adjusting at least one of the input powers applied to transmission paths connected to the terminal stations or the repeaters and the input powers applied to the dispersion compensation modules to equalize the nonlinear phase shifts of paths in the optical transmission system to said target value for a dispersion compensation control process;
• wherein with respect to a network having different span losses, said dispersion compensation controller determines the average input power applied to the optical fiber transmission path from an average nonlinear phase shift per span, which is produced by dividing said target value by the number of the spans, and assigns half of the difference between an average span loss and each of the span losses to a power variation of the average input power applied to the optical fiber transmission path thereby to determine the input power applied to the optical fiber transmission path of the span.

A method of compensating for chromatic dispersion that is caused when an optical signal is transmitted, comprising the steps of:

• determining a target value for a nonlinear phase shift, which is an indication of a self-phase modulation caused by a transmission medium, to have a maximum residual dispersion tolerance;
• and
• determining at least one of the input power applied to a transmission path connected to a node disposed in a network and the input power applied to a dispersion compensation module disposed in the network, in order to equalize said nonlinear phase shift of a path in a system to the target value for a dispersion compensation control process;
• wherein with respect to a network having different span losses, the average input power applied to the optical fiber transmission path is determined from an average nonlinear phase shift per span, which is produced by dividing said target value by the number of the spans, and half of the difference between an average span loss and each of the span losses is assigned to a power variation of the average input power applied to the optical fiber transmission path thereby to determine the input power applied to the optical fiber transmission path of the span.

An optical transmission system for transmitting an optical signal while compensating for chromatic dispersion, comprising:

• terminal stations for transmitting and receiving an optical signal through an optical fiber transmission path;
• repeaters disposed in said optical fiber transmission path for amplifying said optical signal;
• dispersion compensation modules disposed in said terminal stations and said repeaters for compensating for dispersion of said optical signal;
• and
• a dispersion compensation controller for determining a target value for a nonlinear phase shift,
• which is an indication of a self-phase modulation caused by a transmission medium of the optical fiber transmission path, to have a maximum residual dispersion tolerance, and adjusting at least one of the input powers applied to transmission paths connected to the terminal stations or the repeaters and the input powers applied to the dispersion compensation modules to equalize the nonlinear phase shifts of paths in the optical transmission system to said target value for a dispersion compensation control process;
• wherein with respect to a network having a HUB node with three or more routes in an optical fiber transmission path, said dispersion compensation controller determines a first nonlinear phase shift per span as a value which is produced by dividing the target value by the number of spans of a reference through path, determines a second nonlinear phase shift per span as a value which is produced by dividing the target value by the number of spans of another path, and wherein if said through path and said other path have substantially the same distance, said dispersion compensation controller determines a nonlinear phase shift per span on a common path as an average value of said first nonlinear phase shift and said second nonlinear phase shift, and if said through path and a HUB path have different distances, said dispersion compensation controller determines a nonlinear phase shift per span on the common path as said first nonlinear phase shift, and assigns the difference between said target value and the nonlinear phase shift per span on the common path to spans which are present from the HUB node to the terminal stations on said through path and spans which are present from said HUB node to terminal stations on said other path.

A method of compensating for chromatic dispersion that is caused when an optical signal is transmitted, comprising the steps of:

• determining a target value for a nonlinear phase shift, which is an indication of a self-phase modulation caused by a transmission medium, to have a maximum residual dispersion tolerance;
• and
• determining at least one of the input power applied to a transmission path connected to a node disposed in a network and the input power applied to a dispersion compensation module disposed in the network, in order to equalize said nonlinear phase shift of a path in a system to the target value for a dispersion compensation control process;
• wherein with respect to a network having a HUB node in an optical fiber transmission path, a first nonlinear phase shift per span as a value which is produced by dividing the target value by the number of spans of a through path is determined, a second nonlinear phase shift per span as a value which is produced by dividing the target value by the number of spans of a HUB path is determined, and wherein if said through path and said HUB path have substantially the same distance, a nonlinear phase shift per span on a common path is determined as an average value of said first nonlinear phase shift and said second nonlinear phase shift, and if said through path and said HUB path have different distances, a nonlinear phase shift per span on the common path is determined as said first nonlinear phase shift, and the difference between said target value and the nonlinear phase shift per span on the common path is assigned to spans which are present from the HUB node to the terminal stations on said through path and spans which are present from said HUB node to terminal stations on said HUB path.