A phase retarder and an optical comb filter are disclosed. The phase retarder includes a polarization beam splitter, a first air arm, and a second air arm, where the polarization beam splitter is configured to decompose a beam into a first light component propagated in a first direction and a second light component propagated in a second direction, the first direction is perpendicular to the second direction; the first air arm is disposed on a second side wall of the polarization beam splitter, and is configured to receive the first light component and reflect it back; and the second air arm is disposed on a third side wall of the polarization beam splitter, and is configured to receive the second light component and reflect it back. Two light components interfere, and the interference light is emitted from a fourth side wall of the polarization beam splitter.

An optical transceiver may include an optical transmitter and an optical receiver. The optical transmitter and receiver may each include a grid including one or more lanes spaced apart. Each lane may correspond to a predetermined optical signal, or wavelength. The optical transmitter may include one or more sets of lasers to output one or more optical signals corresponding to the grid. Each set of laser may output a set of optical signals. Each set of lasers and, therefore, each set of optical signals may have a different passband. For example, the multiplexing and/or demultiplexing architecture may have a wide passband for the first set of optical signals and a narrow passband for the second set of optical signals. The narrow passband may be determined based on the space between two wider passbands.

To provide a light wavelength separation device and a light wavelength separation method that can be flexibly adapted for various channel intervals of a wavelength-division multiplexed (WDM) signal, a light wavelength separation circuit is provided with: an optical coupler which splits a wavelength-multiplexed optical signal in which optical signals of a plurality of channels are multiplexed; a band-pass filter which is arranged for each of output ports of the optical coupler, separates optical signals included in the wavelength-multiplexed optical signal inputted from the output ports of the optical coupler into channels of which the central frequencies are not adjacent to each other, and outputs the separated optical signals from respectively different output ports; and an optical switch which selects one of paths of the optical signals inputted from the output ports of each band-pass filter.

To provide a light wavelength separation device and a light wavelength separation method that can be flexibly adapted for various channel intervals of a wavelength-division multiplexed (WDM) signal, a light wavelength separation circuit is provided with: an optical coupler which splits a wavelength-multiplexed optical signal in which optical signals of a plurality of channels are multiplexed; a band-pass filter which is arranged for each of output ports of the optical coupler, separates optical signals included in the wavelength-multiplexed optical signal inputted from the output ports of the optical coupler into channels of which the central frequencies are not adjacent to each other, and outputs the separated optical signals from respectively different output ports; and an optical switch which selects one of paths of the optical signals inputted from the output ports of each band-pass filter.

A phase retarder and an optical comb filter are disclosed. The phase retarder includes a polarization beam splitter, a first air arm, and a second air arm, where the polarization beam splitter is configured to decompose a beam into a first light component propagated in a first direction and a second light component propagated in a second direction, the first direction is perpendicular to the second direction; the first air arm is disposed on a second side wall of the polarization beam splitter, and is configured to receive the first light component and reflect it back; and the second air arm is disposed on a third side wall of the polarization beam splitter, and is configured to receive the second light component and reflect it back. Two light components interfere, and the interference light is emitted from a fourth side wall of the polarization beam splitter.

Systems and methods are provided for reducing interference when optical signals are added. One embodiment includes a method for adding an optical channel for communicating data and having a bandwidth within an optical spectrum for transmission along an optical link of an optical network. The method includes creating a lower frequency holding zone having a lower frequency bandwidth adjacent to the bandwidth of the added optical channel and including at least one lower frequency sub-slice having a power spectral density that varies throughout the lower frequency sub-slice. Also, the method includes creating a higher frequency holding zone having a higher frequency bandwidth adjacent to the bandwidth of the added optical channel and including at least one higher frequency sub-slice having a power spectral density that varies throughout the higher frequency sub-slice. The lower frequency holding zone and the higher frequency holding zone are dynamically configured with respect to fiber and channel requirements.

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).

Systems and methods of capacity changes in an optical network having a plurality of optical sections include, responsive to a request for a capacity change for a plurality of channels, bundling the plurality of channels into different steps such that all of the plurality of channels are assigned to a step of the different steps; and causing implementation of the different steps across the plurality of optical sections, wherein each section performs the implementation and the bundling between corresponding Optical Add/Drop Multiplexer (OADM) nodes independently and asynchronously from one another.

To provide a light wavelength separation device and a light wavelength separation method that can be flexibly adapted for various channel intervals of a wavelength-division multiplexed (WDM) signal, a light wavelength separation circuit is provided with: an optical coupler which splits a wavelength-multiplexed optical signal in which optical signals of a plurality of channels are multiplexed; a band-pass filter which is arranged for each of output ports of the optical coupler, separates optical signals included in the wavelength-multiplexed optical signal inputted from the output ports of the optical coupler into channels of which the central frequencies are not adjacent to each other, and outputs the separated optical signals from respectively different output ports; and an optical switch which selects one of paths of the optical signals inputted from the output ports of each band-pass filter.

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.