Abstract: A three-arm-Mach-Zehnder interferometer for splitting/combining a first and a second wavelength band, wherein the optical device includes: a first and second optical splitting/combining element; a differential optical delay device comprising a first, a second and a third optical path; each of the first and second optical splitting/combining elements, is of the (25-50-25%)?x(0-0-100%)?y type, wherein ?x is a wavelength with the first optical band and ?y is a wavelength with the second optical band, and the first, second and third optical paths of the differential optical delay device are configured to introduce, at a wavelength ?z within the first optical band, a phase delay ?? of 2?m.

Abstract: Link bandwidth is varied based on the subscriber traffic load. Varying the link bandwidth has the effect of varying the actual noise margin of the link (in an inverse relation), so that the noise margin will vary inversely with the traffic load. A beneficial result is that, because the noise margin is increased during “off-peak” traffic periods, rapidly varying and burst impairments can be absorbed without causing data loss. In effect, the respective probability distributions of error bursts and traffic load are separated. Data loss only becomes a significant risk when peaks in both distributions coincide. However, the probability of that event occurring is comparatively low. This enables a lower noise margin allocation during design of the link, which dramatically reduces the link cost.

Abstract: Implementations of the present principles include methods, systems and apparatuses for transmitting data through a sub-carrier multiplexing and orthogonal frequency-division multiple access passive optical network. In accordance with aspects of the present principles, a plurality of optical network units are assigned electrical carrier frequency bandwidths that are narrower than a system capacity bandwidth. Modulation of optical waves transmitted between an optical line terminal and each optical network unit is conducted on different orthogonal sub-carrier frequencies within the assigned bandwidths such that sampling of said orthogonal sub-carrier frequencies is limited to the assigned electrical carrier frequency bandwidths. The waves are thereafter received and demodulated for the extraction of data.