Optical transmission system and multi-core optical fiber

An optical transmission system comprising:

• an optical transmitting unit that outputs at least one optical signal having a wavelength included in an operation wavelength band;
• an optical fiber that is connected to the optical transmitting unit, the optical fiber including
• a plurality of cores separated from each other through each of which the optical signal is transmitted, and
• a cladding formed around the cores;
• an applying unit that intentionally applies any one of a bend or a lateral pressure or both to the optical fiber to suppress interferences between the cores;
• an optical multiplexing unit that multiplexes optical signals output from the optical transmitting unit for inputting the optical signals to the cores of the optical fiber;
• an optical demultiplexing unit that demultiplexes the optical signals transmitted through the optical fiber;
• and
• an optical receiving unit that receives the optical signals demultiplexed by the optical demultiplexing unit.