Methods of Bi-Directional Optical Communication and Optical Transceiver

A method of bi-directional optical communication, the method comprising:

• generating a first optical communication signal for transmission in one direction through an optical fiber, wherein generating the first optical communication signal comprises:
• receiving information for transmission and generating a baseband signal comprising a representation of the information;
• performing digital upconversion of the baseband signal to form an upconverted baseband signal;
• performing optical modulation of an optical carrier signal with the upconverted baseband signal;
• and
• restricting an optical spectrum of the first optical communication signal to a first portion of an optical channel frequency slot by performing one of digital filtering in addition to digital upconversion and optical filtering after optical modulation;
• and receiving a second optical communication signal transmitted in an opposite direction through the optical fiber, the second optical communication signal having an optical spectrum occupying a second portion of the optical channel frequency slot, separate to the first portion.

An optical transceiver comprising:

• a digital signal processor configured to:
• receive information for transmission and generate a baseband signal comprising a representation of the information, and perform digital upconversion of the baseband signal to form an upconverted baseband signal;
• a digital to analogue converter configured to convert the upconverted baseband signal into a modulation signal;
• optical signal generation apparatus configured to receive the modulation signal and to modulate an optical carrier signal with the modulation signal to generate a first optical communication signal for transmission,
• wherein the digital signal processor is additionally configured to perform digital filtering in addition to digital upconversion to restrict an optical spectrum of the first optical communication signal to a first portion of an optical channel frequency slot or the optical signal generation apparatus additionally comprises an optical filter to restrict an optical spectrum of the first optical communication signal to a first portion of an optical channel frequency slot;
• and
• coherent optical demodulation apparatus configured to receive a second optical communication signal and configured to perform coherent detection of the second optical communication signal, wherein the second optical communication signal has an optical spectrum occupying a second portion of the optical channel frequency slot, separate to the first portion.