Optical signal transmission apparatus for generating multi-level optical signal and method performed by the same

An optical signal transmission apparatus comprising:

• an amplifier configured to amplify an electric signal having an intensity of a level selected from a plurality of levels of an intensity of the electric signal;
• an electric-to-optical (E/O) converter configured to convert the amplified electric signal into an optical signal;
• a supervisory signal generator configured to convert a portion of the optical signal into an electric signal and to generate a supervisory signal used to adjust a gain of the amplifier;
• and
• a controller configured to determine a correspondence relationship between the plurality of levels of the intensity of the electric signal and a plurality of levels of an intensity of the optical signal and to adjust the gain of the amplifier based on the determined correspondence relationship.

A method performed by an optical signal transmission apparatus, the method comprising:

• changing an intensity of a control signal based on a predetermined interval, the control signal being input to an electric-to-optical (E/O) converter configured to convert an electric signal into an optical signal or an amplifier configured to amplify the electric signal input to the E/O converter;
• receiving a supervisory signal generated by converting a portion of the optical signal output from the E/O converter into an electric signal in correspondence to the changed intensity of the control signal;
• acquiring a correspondence relationship between the control signal and the optical signal from the supervisory signal;
• and
• determining a use range of the intensity of the control signal based on the acquired correspondence relationship.