A network node (400) for use as a hub node of a network that further comprises one or more remote nodes, wherein the network node (400) is coupled to at least first and second connections (410, 412) for communication with one or more remote nodes, comprises a first band filter (403) adapted to separate a first aggregated signal (404) comprising a plurality of channel signals into a plurality of band signals (408.sub.1 to 408.sub.M). The network node (400) comprises a second band filter (405) and a third band filter (407) adapted to aggregate a plurality of band signals (408.sub.1 to 408.sub.M) into a second aggregated signal (406) comprising a plurality of channel signals and a third aggregated signal (413) comprising a plurality of channel signals, respectively. A switching module (409) is adapted to switch on a per-band granularity the plurality of band signals (408.sub.1 to 408.sub.M) between the first band filter (403) and either the second band filter (405) or the third band filter (407). The first band filter (403) may be adapted to aggregate the plurality of band signals (4081 to 408M) into the first aggregated signal (404); the second band filter (405) and a third band filter (407) may be adapted to separate the second aggregated signal (410) and third aggregated signal (412), respectively, into the plurality of band signals (408.sub.1 to 408.sub.M); and the switching module (409) may be adapted to switch on a per-band granularity the plurality of band signals (408.sub.1 to 408.sub.M) between either the second band filter (405) or the third band filter (407) and the first band filter (403).

Provided is a network node for a coherent optical wavelength division multiplex (WDM) transmission network including at least one remote port which is adapted to receive from and/or output to neighboring network nodes an optical WDM signal including one or more optical channel signals each lying within an optical channel of an optical WDM transmission band and a predetermined number N of local ports, each local port being adapted to receive from a dedicated coherent optical transmitter an optical add channel signal which is to be integrated in an optical WDM signal that is output at a remote port and/or each local port being adapted to output to a respective dedicated optical receiver an optical drop channel signal. The network node includes an optical router device that defines the at least one remote port and further defines an internal remote port, the optical router device being configured to route one or more selected or all optical channel signals included in the optical WDM signal received at a selected remote port as optical drop channel signals to the internal remote port and/or to route one or more optical add channel signals received at the internal remote port to one or more selected remote ports or to all remote ports. The network node further includes a passive optical filter device which is connected, at an internal remote port of the passive optical filter device, to the internal remote port of the optical router device, and which further defines the predetermined number N of local ports. The passive optical filter device is configured to define N optical bandpass filter functions each of which describes a bandpass filter characteristic between the internal remote port of the passive optical filter device and a selected, respectively differing local port. The passband of each optical bandpass filter function covers two or more neighboring optical channels. The passbands of all optical bandpass filter functions differ from each other with respect to the optical channels covered.

Free-space communication systems and methods are provided. The systems include a transmitter that combines multiple sets of radio-frequency-modulated optical carrier frequencies for transmission across free space using multiple transmission apertures. Different sets of signals are filtered to form single sideband signals. The different sets of single sideband signals are then combined to form dense wavelength division multiplexed signals. In addition, combined sets of signals of different polarizations can be combined. A receiver can include a single receive aperture.

Provided are wavelength switching and configuration methods and devices for a Passive Optical Network (PON). The switching method includes the following operations. An Optical Network Unit (ONU) responds to a ranging request message sent by an Optical Line Terminal (OLT) on a first uplink wavelength supported by the ONU. The ONU receives ranging information sent by the OLT. The ONU uses the received ranging information as ranging information about a second uplink wavelength of the ONU, and performs data transmission on the second uplink wavelength according to a bandwidth allocation from the OLT. A path transmission time difference caused by a wavelength interval between the first uplink wavelength and the second uplink wavelength is less than a corresponding fault tolerance range when the OLT receives data. The ranging information is obtained by the OLT according to a ranging response sent by the ONU on the first uplink wavelength.

A bidirectional optical device includes a first optical component, wherein a portion of a first interface of the first optical component has a reflector coating, wherein a second interface of the first optical component has an optical coating, and wherein the first optical component includes an internal splitting interface disposed between the first interface and the second interface, and a second optical component including a reflector aligned to the second interface of the first optical component, wherein the first optical component and the second optical component comprise an unbalanced Mach-Zehnder (MZ) interferometer.

The invention relates to a free space optical communications device (10) multiplexed in wavelengths of between 400 nm and 1600 nm, said device including demultiplexing means (11) that are designed so as to separately dissociate a number n1 of wavelengths from one another, the demultiplexing means (11) including one or more detectors (110) having a number n2 of optical filters (111) and active elements (112) which correspond to the number n1 of wavelengths, each active element (112) being arranged to selectively detect one wavelength from among said wavelengths (I.sub.d . . . n) via an optical filter (111) separate from the active element (112) which is included in a housing (113), the optical filter (111) being in contact with a protection means (114), inserted between the optical filter (111) and the active element (112), said protection means (114) closing said housing (113).

A method and apparatus for transporting data through a single optical fiber (SOF) the method comprising the steps of providing (S1) transmission Tx, wavelength division multiplexed, WDM, data channels and reception Rx, wavelength division multiplexed, WDM, data channels having the same frequency grid with frequency gaps between the WDM data channels; frequency shifting (S2) the Tx-WDM data channels and/or the Rx-WDM data channels to avoid spectral overlap between the Tx-WDM data channels and the Rx-WDM data channels; combining (S3) the frequency shifted Tx-WDM data channels and the frequency shifted Rx-WDM data channels; and transporting (S4) data via the combined WDM data channels through said single optical fiber (SOF) in opposite directions.

There is described a transmitter device for transmitting an optical signal in the form of a plurality of subcarrier channels having different wavelengths. The device comprises first and second optical carrier emitters for emitting light in first and second subcarriers at first and second frequencies or polarizations respectively. First and second modulators are provided for modulating the first and second subcarriers with first and second modulation signals. An interleaver is provided for interleaving the first and second modulated subcarriers into the optical signal. First and second digital signal processing units are configured to pre-emphasize the first and second modulation signals to compensate for a wavelength-dependent power transfer function of the interleaver.

A bidirectional optical device includes a first optical component, wherein a portion of a first interface of the first optical component has a reflector coating, wherein a second interface of the first optical component has an optical coating, and wherein the first optical component includes an internal splitting interface disposed between the first interface and the second interface, and a second optical component including a reflector aligned to the second interface of the first optical component, wherein the first optical component and the second optical component comprise an unbalanced Mach-Zehnder (MZ) interferometer.

Fabrication-tolerant on-chip multiplexers and demultiplexers are provides via a lattice filter interleaver configured to receive an input signal including a plurality of individual signals and to produce a first interleaved signal with a first subset of the plurality of individual signals and a second interleaved signal with a second subset of the plurality of individual signals; a first Bragg interleaver configured to receive the first interleaved signal and produce a first output signal including a first individual signal of the plurality of individual signals and a second output signal including a second individual signal of the plurality of individual signals; and a second Bragg interleaver configured to receive the second interleaved signal and produce a third output signal including a third individual signal of the plurality of individual signals and a fourth output signal including a fourth individual signal of the plurality of individual signals.