Pluggable optical module and optical communication system

A pluggable optical module comprising:

• a pluggable electric connector configured to connect with an optical communication apparatus;
• a pluggable optical receptor configured to connect with an outer optical fiber, the outer optical fiber being configured to transmit a first optical signal;
• an optical output module configured to output a second optical signal and a local oscillation light;
• an optical reception module configured to coherently receive the first optical signal by interfering with the local oscillation light;
• a first optical fiber configured to transmit the second optical signal from the optical output module to the pluggable optical receptor;
• a second optical fiber configured to transmit the local oscillation light from the optical output module to the optical reception module;
• a third optical fiber configured to transmit the first optical signal from the pluggable optical receptor to the optical reception module;
• and
• an optical fiber housing comprising a plurality of guides configured to form at least a part of circular paths of the first optical fiber, the second optical fiber and the third optical fiber,
• wherein at least one of the circular paths of the first optical fiber, the second optical fiber and the third optical fiber is different from other circular paths.