Optical pulse testing method and optical pulse testing device

An optical pulse test method comprising:

• a second input procedure of inputting a test optical pulse in a first higher-order mode from one end of an optical fiber under test that is obtained by connecting optical fibers of the same type in series, the test optical pulse having such a wavelength that the test optical pulse can propagate through the optical fiber under test in a basic mode and the first higher-order mode;
• a second measurement procedure of receiving return light that is generated by the test optical pulse input in the second input procedure and measuring intensity distributions of a basic mode component and a first higher-order mode component of the return light relative to the distance from the one end;
• a second loss calculation procedure of calculating a loss L3 of the basic mode component and a loss L4 of the first higher-order mode component of the return light at a connection point at which the optical fibers of the same type constituting the optical fiber under test are connected in series, from the intensity distributions measured in the second measurement procedure;
• and a second computation procedure of computing a transmission loss L01 of the basic mode at the connection point and a transmission loss L11 of the first higher-order mode at the connection point by substituting the losses L3 and L4 calculated in the second loss calculation procedure into second expressions that are simultaneous equations obtained from expressions that express the losses L3 and L4, the transmission loss L01 of the basic mode, and the transmission loss L11 of the first higher-order mode by using efficiencies of coupling between the modes at the connection point.

An optical pulse test device comprising:

• first input means for inputting a test optical pulse in a basic mode from one end of an optical fiber under test that is obtained by connecting optical fibers of the same type in series, the test optical pulse having such a wavelength that the test optical pulse can propagate through the optical fiber under test in the basic mode and a first higher-order mode;
• first measurement means for receiving return light that is generated by the test optical pulse input by the first input means and measuring intensity distributions of a basic mode component and a first higher-order mode component of the return light relative to the distance from the one end;
• first loss calculation means for calculating a loss L1 of the basic mode component and a loss L2 of the first higher-order mode component of the return light at a connection point at which the optical fibers of the same type constituting the optical fiber under test are connected in series, from the intensity distributions measured by the first measurement means;
• and first computation means for computing a transmission loss L01 of the basic mode at the connection point and a transmission loss L11 of the first higher-order mode at the connection point by substituting the losses L1 and L2 calculated by the first loss calculation means into first expressions that are simultaneous equations obtained from expressions that express the losses L1 and L2, the transmission loss L01 of the basic mode, and the transmission loss L11 of the first higher-order mode by using efficiencies of coupling between the modes at the connection point.