A method (10) of controlling optical signal power levelling in an optical communication network node configured to apply an optical attenuation, α, to a pass-through optical signal. The method comprises: a. performing the following steps i. to iii. until an attenuation variation value, Δα, is greater than a preselected attenuation variation threshold value (18), Δα.sub.TH: i. measuring (12) an optical signal power of an optical signal; ii. calculating (14) a difference, ΔP, between the measured optical signal power and a target optical signal power; iii. calculating (16) a value for the attenuation variation, Δα, to be applied to the optical attenuation taking account of ΔP; b. obtaining (20) a current value of the optical attenuation, α.sub.n, and obtaining (22) a new optical attenuation value, α.sub.n+1, in dependence on the current value of the optical attenuation, a current value of the attenuation variation, Δα.sub.n, and at least an earlier value of the attenuation variation, Δ.sub.αn−1; and c. generating (24) a control signal arranged to configure the node to apply the new optical attenuation value, α.sub.n+1.

This invention relates to provisioning wavelength-selective switches and reconfigurable optical add-drop multiplexers to minimize the bandwidth narrowing effect from the optical filters. Novel architectures and methods are disclosed that can significantly reduce bandwidth-narrowing on channels in a reconfigurable WDM network where a large number of optical filter elements are cascaded. Instead of blocking unused channels as in the prior art, unused channels are selectively provisioned depending on the state of their adjacent channels. Unused adjacent channels of an active channel are provisioned to follow the same path as the active channels. As each channels is deployed, the channel frequency is selected so as to minimize bandwidth narrowing.

An apparatus includes an optical source of an optical wavelength carrier, an optical modulator to receive the optical wavelength carrier, and an optical data receiver. The optical data modulator is configured to produce, from the optical wavelength carrier, an optical signal to carry separate data on different first and second components thereof in individual modulation periods during data transmission and to carry a training sequence on one of the components during time slots for calibration. The first component is relatively phase offset from the second component in the optical signal. The optical data modulator alternates the one of the components between the first and second components over the time slots for calibration. The optical receiver is connected to receive a portion of the optical signal and to temporally interleave a measurement of a characteristic of the first component and a measurement of a characteristic of the second component over the time slots for calibration. The optical receiver is configured to feedback information to the optical data modulator based on the measured characteristics. The optical data modulator is configured to reduce an imbalance between the two components of the optical carrier during data transmission based on the information.

An optical add/drop device (100) comprising: a common port (102); an add port (106); a first wavelength selective optical filter (110) configured to: receive an optical signal at an add wavelength from the add port and transmit said optical signal at the add wavelength towards the common port; and receive optical signals from the common port and reflect optical signals not at the add wavelength; a second wavelength selective optical filter (114) configured to receive said optical signals from the common port reflected by the first wavelength selective optical filter and transmit an optical signal at a drop wavelength, different to the add wavelength; a drop port (116); and an optical waveguide (118) configured receive said optical signal at the drop wavelength transmitted by the second wavelength selective optical filter and route said optical signal to the drop port.

A method includes establishing an extended optical spectrum having multiple channels for transmission of signals within an optical network. The extended optical spectrum includes at least the C-band (i.e., 1530 nm to 1565 nm) plus one or more sub-bands each having a range of wavelengths including at least one optical channel outside the range of the C-band. The method also includes segmenting the extended optical spectrum into a local band and an express band having different transmission specifications. The local band is configured for transmission of signals between nodes having a relatively shorter distance therebetween and the express band is configured for transmission of signals between nodes having a relatively longer distance therebetween. A combination of the sub-bands covers less than the L-band having a range of wavelengths from 1565 nm to 1625 nm and/or less than the S-band having a range of wavelengths from 1460 nm to 1530 nm.

Signal distribution arrangements are assembled by selecting a terminal body and a tap module combination that provides the desired signal strength at the intended position in an optical network. Each terminal body includes an input connection interface, a pass-through connection interface, a module connection interface, and multiple drop connection interfaces. Each tap module houses an optical tap having an asymmetric split ratio. Most of the optical signal power received at the signal distribution arrangement passes to the pass-through connection interface. A portion of the optical signal power is routed to the drop connection interfaces (e.g., via a symmetrical optical power splitter). The tap module and terminal body combination are selected based on the desired number of drop connection interfaces and to balance the asymmetric split ratio with the symmetric split ratio.

A coherent optical transmitter configured to generate a modulated optical signal within a portion of optical spectrum defined by a spectral position and spectral width, wherein the spectral width is ‘n’ bins where n is an integer greater than 1 and each bin is a same size, and wherein the spectral position and spectral width are specified by to the coherent optical transmitter via a management system.

In order to provide a submarine optical transmission system that utilizes multiple wavelength bands, the submarine branching apparatus is provided with: a first demultiplexing part for demultiplexing a wavelength-multiplex optical signal input from a first terminal station into a first wavelength-multiplex optical signal and a second wavelength-multiplex optical signal; an optical add-drop part for outputting at least a third wavelength-multiplex optical signal included in the first wavelength-multiplex optical signal to a second terminal station, and for outputting a fifth wavelength-multiplex optical signal by multiplexing at least a fourth wavelength-multiplex optical signal included in the first wavelength-multiplex optical signal with a wavelength-multiplex optical signal input from the second terminal station; and a first multiplex part for multiplex the second wavelength-multiplex optical signal with the fifth wavelength-multiplex optical signal input from the optical add-drop part and outputting the resulting signal to a third terminal station.

An object is to perform wavelength filtering of an optical signal while preventing filter narrowing in an optical transmission apparatus. A branching unit branches a wavelength-multiplexed optical signal including an optical signal of a first wavelength into two optical signals. A wavelength selection unit blocks an optical signal of a first wavelength band including the first wavelength in the optical signal. A filter unit allows passage of an optical signal of a second wavelength band including the first wavelength in the optical signal. A multiplexing unit multiplexes and the optical signal and an optical signal of a second wavelength. The second wavelength band is wider than the first wavelength band.

Systems and methods include, for operation on an optical fiber in an optical network with the optical fiber having extended optical spectrum that include a plurality of bands including at least the C-band and one or more additional bands, segmenting the plurality of bands by distance based on different transmission specifications for the plurality of bands based on fiber types and amplifiers used for corresponding bands; and placing one or more channels on the optical fiber in a corresponding band of the plurality of bands based on a distance between nodes associated with each of the one or more channels. The segmenting is based on a metric that is a function of fiber type of the optical fiber and amplifier performance for amplifiers used in the plurality of bands.