An optical network for carrying communication signals to or from at least two end points (210, 220, 230, 240) in optical form, the network being adapted to carry voice communication and comprising: i) at least first and second end points (210, 220, 230, 240), each comprising transmitting/receiving apparatus (211, 221, 231, 241, 214, 224, 234, 244) and having an address in the network; ii) at least one optical power source (250, 255) adapted to deliver optical power to the transmitting/receiving apparatus of at least said first end point for conversion to electrical power at the transmitting/receiving apparatus and for transmitting an optical signal carrier to the transmitting/receiving apparatus (211, 221, 231, 241, 214, 224, 234, 244) of at least said first end wherein iii) the transmitting/receiving apparatus (211, 221, 231, 241, 214, 224, 234, 244) of the first end point comprises: an interferometer (300, 410) having a path imbalance, adapted to apply interferometric modulation comprising a voice signal and the address of the second end point to the optical signal carrier to provide an optical communication signal comprising the voice signal for subsequent transmission over the network to the second end point: at least one power conversion device for adapted to convert received optical power to electrical power; and at least one electrical storage device adapted to store at least a portion of the converted optical power; iv) the transmitting/receiving apparatus of the second end point comprises an interferometer having a path imbalance, adapted to detect interferometric modulation in said optical communication signal received over the network so as to receive said voice signal, the path imbalance of the interferometer of the first end point being adjustable to match the path imbalance of the interferometer of the second end point within the coherence length of the source (250, 255); and v) the at least one optical power source (250, 255) delivers the optical power via the optical network. i) at least first and second end points (210, 220, 230, 240), each comprising transmitting/receiving apparatus (211, 221, 231, 241, 214, 224, 234, 244) and having an address in the network; ii) at least one optical power source (250, 255) adapted to deliver optical power to the transmitting/receiving apparatus of at least said first end point for conversion to electrical power at the transmitting/receiving apparatus and for transmitting an optical signal carrier to the transmitting/receiving apparatus (211, 221, 231, 241, 214, 224, 234, 244) of at least said first end iii) the transmitting/receiving apparatus (211, 221, 231, 241, 214, 224, 234, 244) of the first end point comprises: an interferometer (300, 410) having a path imbalance, adapted to apply interferometric modulation comprising a voice signal and the address of the second end point to the optical signal carrier to provide an optical communication signal comprising the voice signal for subsequent transmission over the network to the second end point: at least one power conversion device for adapted to convert received optical power to electrical power; and at least one electrical storage device adapted to store at least a portion of the converted optical power; an interferometer (300, 410) having a path imbalance, adapted to apply interferometric modulation comprising a voice signal and the address of the second end point to the optical signal carrier to provide an optical communication signal comprising the voice signal for subsequent transmission over the network to the second end point: at least one power conversion device for adapted to convert received optical power to electrical power; and at least one electrical storage device adapted to store at least a portion of the converted optical power; at least one power conversion device for adapted to convert received optical power to electrical power; and at least one electrical storage device adapted to store at least a portion of the converted optical power; iv) the transmitting/receiving apparatus of the second end point comprises an interferometer having a path imbalance, adapted to detect interferometric modulation in said optical communication signal received over the network so as to receive said voice signal, the path imbalance of the interferometer of the first end point being adjustable to match the path imbalance of the interferometer of the second end point within the coherence length of the source (250, 255); and v) the at least one optical power source (250, 255) delivers the optical power via the optical network.