Transmitting apparatus and transmitting method

A transmitting apparatus, comprising:

• a first processor circuit;
• a second processor circuit;
• a modulation circuit;
• and
• a switch circuit,
• wherein the first processor circuit is configured to
• execute a generating process that includes
• mapping each of a plurality of bit strings to a symbol in predetermined order for each number of bits according to a multivalued degree of a multilevel modulation method, and
• generating a symbol information piece according to the symbol,
• wherein the modulation circuit is configured to modulate light in accordance with the symbol information piece based on the multilevel modulation method;
• wherein the second processor circuit is configured to
• execute a detecting process that includes detecting each of inputs of a plurality of data signals,
• wherein the switch circuit is configured to select the plurality of bit strings based on a detection result of inputs of the plurality of data signals,
• wherein the second processor circuit is further configured to
• execute a first selecting process when an input of each of the plurality of data signals is detected by the detecting process, the selecting process being configured to cause the switch circuit to select a bit string included in each of the plurality of data signals, and
• execute a second selecting process when an input of at least one of the plurality of data signals is not detected by the detecting process, the second selecting process being configured to cause the switch circuit to select a bit string included in the data signal the input of which is detected instead of the data signal the input of which is not detected such that the identical symbol information pieces are serially generated in the predetermined order,
• wherein the switch circuit is configured to output the plurality of bit strings from a plurality of output ports to the generating process in the first processor circuit,
• wherein the second selecting process is configured to cause the switch circuit to output a bit string included in the data signal the input of which is detected from at least two output ports among the plurality of output ports.