Optical reception apparatus, optical transmission apparatus, optical communication system, and skew adjusting method

An optical transmission apparatus comprising:

• a memory;
• and
• a processor coupled to the memory, wherein the processor executes a process comprising:
• outputting pilot symbols obtained by modulating values of bits in a predetermined bit pattern by a BPSK method in an IQ complex plane;
• controlling skew between an I component and a Q component of the pilot symbols based on information relating to skew adjustment;
• and
• converting electrical signals of the I component and the Q component with the skew controlled by the controlling into optical signals, and transmitting the optical signals, wherein
• the controlling includes controlling the skew between the I component and the Q component of the pilot symbols using a control value specified based on a ratio calculated for each of different control values, when the information relating to skew adjustment is received from an optical reception apparatus, the ratio serving as a ratio of an amplitude component to a phase component of the pilot symbols extracted from electrical signals having been subjected to suppression processing, the electrical signals being obtained by converting the pilot symbols included in the optical signals received in the optical reception apparatus, and the suppression processing being performed to suppress fluctuations in amplitude of the electrical signals after the pilot symbols are converted into the electrical signals.

An optical communication system comprising:

• an optical transmission apparatus;
• and
• an optical reception apparatus that receives optical signals transmitted from the optical transmission apparatus,
• the optical transmission apparatus comprising:
• a first memory;
• and
• a first processor coupled to the first memory, wherein the first processor executes a first process comprising:
• outputting pilot symbols obtained by modulating values of bits in a predetermined bit pattern by a BPSK method in an IQ complex plane;
• controlling skew between an I component and a Q component of the pilot symbols based on information relating to skew adjustment;
• and
• converting electrical signals of the I component and the Q component with the skew controlled by the controlling into the optical signals, and transmitting the optical signals, and
• the optical reception apparatus comprising:
• a second memory;
• and
• a second processor coupled to the second memory, wherein the second processor executes a second process comprising:
• receiving the optical signals transmitted from the optical transmission apparatus, and converting the received optical signals into electrical signals;
• performing suppression processing to suppress fluctuations in amplitude of the electrical signals;
• extracting the pilot symbols from the electrical signals having been subjected to the suppression processing;
• calculating a ratio of an amplitude component to a phase component of each of the pilot symbols extracted by the extracting;
• and
• transmitting information relating to skew adjustment based on the ratio of the amplitude component to the phase component for each of a plurality of different control values to the optical transmission apparatus.

A skew adjusting method for adjusting skew between an I component and a Q component in an optical communication system including an optical transmission apparatus that includes an I component modulator and a Q component modular and an optical reception apparatus that receives an optical signal transmitted from the optical transmission apparatus, the skew adjusting method comprising:

• converting pilot symbols obtained by modulating values of bits in a predetermined bit pattern by a BPSK method in an IQ complex plane into an optical signal, and transmitting the optical signal, by the optical transmission apparatus;
• receiving the optical signal transmitted from the optical transmission apparatus, and converting the received optical signal into an electrical signal, by the optical reception apparatus;
• performing suppression processing to suppress fluctuations in amplitude of the electrical signal, by the optical reception apparatus;
• extracting the pilot symbols from the electrical signal having been subjected to the suppression processing, by the optical reception apparatus;
• calculating a ratio of an amplitude component to a phase component of each of the extracted pilot symbols, by the optical reception apparatus;
• and
• adjusting skew between the I component and the Q component, based on the ratio of the amplitude component to the phase component calculated for each of a plurality of different control values, by the optical reception apparatus.