Optical transmission system

An optical transmission system comprising:

• an optical fiber transmission line that includes an optical fiber with two or more propagation modes;
• and
• a plurality of mode converters that are configured to generate mode coupling between at least one pair of the propagation modes,
• wherein a transmission line length of the optical fiber transmission line is Lt, a converter length of the mode converter is Lg, and the numbers of the mode converters are n,
• wherein in a case where the transmission line length Lt does not include the converter length Lg, standard deviation of an installation interval of the mode converter is equal to or less than a value expressed by a following expression (C2), and
• wherein a relative value of a group delay spread of the optical fiber transmission line in where the mode converter is provided relative to a group delay spread of the optical fiber transmission line itself in where the mode converter is not provided is equal to or less than 0.5,
• Lt/(n+1)×0.4. (C2)

An optical transmission system comprising:

• an optical fiber transmission line that includes an optical fiber with two or more propagation modes;
• and
• a plurality of mode converters that are configured to generate mode coupling between at least one pair of the propagation modes,
• wherein a variation in installation intervals of the plurality of mode converters is equal to or less than a threshold value determined by a transmission line length of the optical fiber transmission line, and
• wherein a sum of the coupling amount of mode coupling of the plurality of mode converters is larger than a threshold value determined by a group delay difference between the propagation modes of the optical fiber transmission line.