Abstract: Optical amplifier apparatus (100) comprising: an input (102) for an incoming optical signal (IN) comprising an optical supervisory channel, OSC, signal and service channel signals at channel wavelengths of a WDM channel wavelength grid; an output (112) for an outgoing optical signal (OUT); an optical amplifier, OA, (106) having an operating bandwidth including the WDM channel wavelength grid; a first optical drop filter (104) configured to drop from an IN signal an out-of-band, OOB, OSC signal at a wavelength outside the OA operating bandwidth; a second optical drop filter (108, 208) configured to drop from an IN signal an in-band, IB, OSC signal at a wavelength within the OA operating bandwidth; an OSC signal output (114) configured to output the dropped OSC signal; an OSC signal input (116) configured to receive an outgoing OOB OSC or IB OSC signal; and an optical add filter (110, 210) configured to add an outgoing OOB OSC or IB OSC signal to service channel signals at channel wavelengths of the WDM channel

Abstract: A method of power control of an optical signal transmitted by a first network element. The first network element comprising a laser and a bandpass filter operating on the optical signal produced by said laser, whereas the method comprises receiving (106) information indicative of a power level of the optical signal transmitted by the first network element; and tuning (110) the laser output wavelength in response to said received information.

Abstract: 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.

Abstract: An optical node (100) for multiplexing optical signals is disclosed. The optical node (100) comprises an add port (102), a common port (104), an auxiliary port (106), an optical transfer module (110), and a reflecting element (108) coupled to the auxiliary port. The optical transfer module (110) is configured to couple a signal received on the add port (102) and matching an operational wavelength of the optical node (100) to the common port (104), and to couple a signal received on the add port (102) and not matching an operational wavelength of the optical node (100) to the auxiliary port (106). The reflecting element (108) is configured to reflect a signal received on the auxiliary port (106) to the add port (102). Also disclosed are an optical transceiver and methods for operating and optical node and an optical transceiver.

Abstract: A method of power control of an optical signal transmitted by a first network element. The first network element comprising a laser and a bandpass filter operating on the optical signal produced by said laser, whereas the method comprises receiving (106) information indicative of a power level of the optical signal transmitted by the first network element; and tuning (110) the laser output wavelength in response to said received information.

Abstract: There is provided an apparatus for fiber optic line continuity detection. The apparatus comprises an optical input connectable to a first optical fiber of a fiber optic line, an optical output connectable to a second optical fiber of the fiber optic line an optical interface unit configured to transmit and receive optical signals; and an optical switch having a first configuration and a second configuration. In the first configuration the optical switch is configured to pass optical signals received at the optical input to the optical interface unit and to pass optical signals received from the optical interface unit to the optical output. Whereas, in the second configuration the optical switch is configured to pass optical signals received at the optical input to the optical output.

Abstract: There is provided an apparatus for fiber optic line continuity detection. The apparatus comprises an optical input connectable to a first optical fiber of a fiber optic line, an optical output connectable to a second optical fiber of the fiber optic line an optical interface unit configured to transmit and receive optical signals; and an optical switch having a first configuration and a second configuration. In the first configuration the optical switch is configured to pass optical signals received at the optical input to the optical interface unit and to pass optical signals received from the optical interface unit to the optical output. Whereas, in the second configuration the optical switch is configured to pass optical signals received at the optical input to the optical output.

Abstract: 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 (4081 to 408M). The network node (400) comprises a second band filter (405) and a third band filter (407) adapted to aggregate a plurality of band signals (4081 to 408M) 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 (4081 to 408M) between the first band filter (403) and either the second band filter (405) or the third band filter (407).

Abstract: An apparatus (20) is configured as a remote unit for communication with a main unit (10) in an optical communication network (30), wherein the main unit and remote unit are configured to detect a fault in the optical communication network. The apparatus comprises a modulation converter (22;62) configured to receive a first optical signal from the main unit on the optical communication network, wherein the first optical signal has a first modulation type. The modulation converter is configured to convert the first optical signal having the first modulation type to a second optical signal having a second modulation type. The second modulation type is different to the first modulation type. The modulation converter (22;62) is a passive device. The apparatus is configured to send the second optical signal having the second modulation type to the main unit (10) using the optical communication network (30).

Abstract: A network node (400) for use with a single-fiber bidirectional communication link comprises a filter (300). The filter (300) comprises at least four ports. A first port (301) is configured to communicate with the single-fiber in a west direction. A second port (303) is configured to communicate with the single-fiber in an east direction. A third port (305) is configured to add/drop in the west direction. A fourth port (307) is configured to add/drop in the east direction. The network node is configured to add a first wavelength (?A) to the west direction and the east direction, and configured to drop a second wavelength (?B) from the west direction and the east direction.

Abstract: 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 (4081 to 408M). The network node (400) comprises a second band filter (405) and a third band filter (407) adapted to aggregate a plurality of band signals (4081 to 408M) 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 (4081 to 408M) between the first band filter (403) and either the second band filter (405) or the third band filter (407).

Abstract: According to embodiments of the present disclosure, apparatus is provided for protecting an optical link arranged to carry upstream optical signals and downstream optical signals. The apparatus comprises a first detector arranged to selectively detect a downstream optical signal received at a second port having a first wavelength and a second detector arranged to selectively detect a downstream optical signal received at the second port having a second wavelength different from the first wavelength. The apparatus further comprises control circuitry arranged to cause a protection switch to selectively couple a third port to the second port instead of to the first port based on the detecting by the first detector and the second detector. Also provided is a second apparatus for protecting the optical link.

Abstract: A network node (400) for use with a single-fiber bidirectional communication link comprises a filter (300). The filter (300) comprises at least four ports. A first port (301) is configured to communicate with the single-fiber in a west direction. A second port (303) is configured to communicate with the single-fiber in an east direction. A third port (305) is configured to add/drop in the west direction. A fourth port (307) is configured to add/drop in the east direction. The network node is configured to add a first wavelength (?A) to the west direction and the east direction, and configured to drop a second wavelength (?B) from the west direction and the east direction.

Abstract: According to the present invention, there is provided apparatus for providing protection of an optical link. The apparatus comprises a first port for coupling to the optical link and a second port for coupling to a further optical link. The apparatus further comprises a third port configured to receive an upstream optical signal to be transmitted over the optical link, and to output a downstream optical signal received over the optical link. The apparatus further comprises protection switching apparatus operable to selectively couple the third port to the first port or to the second port. The apparatus further comprises modifying apparatus configured to modify the upstream optical signal, received at the third port, before it is output from the first port, such that the switching upstream optical signal has a distinctive physical characteristic.

Abstract: According to embodiments of the present disclosure, apparatus is provided for protecting an optical link arranged to carry upstream optical signals and downstream optical signals. The apparatus comprises a first detector arranged to selectively detect a downstream optical signal received at a second port having a first wavelength and a second detector arranged to selectively detect a downstream optical signal received at the second port having a second wavelength different from the first wavelength. The apparatus further comprises control circuitry arranged to cause a protection switch to selectively couple a third port to the second port instead of to the first port based on the detecting by the first detector and the second detector. Also provided is a second apparatus for protecting the optical link.

Abstract: According to the present invention, there is provided apparatus for providing protection of an optical link. The apparatus comprises a first port for coupling to the optical link and a second port for coupling to a further optical link. The apparatus further comprises a third port configured to receive an upstream optical signal to be transmitted over the optical link, and to output a downstream optical signal received over the optical link. The apparatus further comprises protection switching apparatus operable to selectively couple the third port to the first port or to the second port. The apparatus further comprises modifying apparatus configured to modify the upstream optical signal, received at the third port, before it is output from the first port, such that the switching upstream optical signal has a distinctive physical characteristic.

Abstract: A communications network element comprises a network element input, a network element output and a monitoring port. An optical splitting device taps a portion of an input optical signal or an output optical signal to form a first signal. An optical signal transforming apparatus applies an optical transfer function to the first signal to form the optical monitoring signal applied to the monitoring port. The optical transfer function preserves the spectral property of the first signal and applies a time-domain obfuscation to the tapped signal. The optical signal transforming apparatus comprises an optical through signal path, an optical splitting device positioned in the optical through signal path and an optical combining device positioned in the optical through signal path. An optical feedback path is connected to the optical splitting device and the optical combining device.

Abstract: An optical transmitter has a modulator for modulating data onto an optical signal for transmission to the receiver, the modulated signal having components at one or more constellations of points of different amplitudes and phases. The modulator is tunable such that distortions of the points of the one or more constellation can be tuned, and a tuning controller is provided for receiving a feedback signal from the receiver indicating a distortion measured at the receiver, and for tuning automatically the modulator to adjust the modulation based on the received feedback signal to pre-compensate for the measured distortion. Such pre-compensation can reduce the amount of distortion in the transmission system and thus enable more transmission capacity, without the need for a complex transmitter.

Abstract: A communications network element comprises a network element input, a network element output and a monitoring port. An optical splitting device taps a portion of an input optical signal or an output optical signal to form a first signal. An optical signal transforming apparatus applies an optical transfer function to the first signal to form the optical monitoring signal applied to the monitoring port. The optical transfer function preserves the spectral property of the first signal and applies a time-domain obfuscation to the tapped signal. The optical signal transforming apparatus comprises an optical through signal path, an optical splitting device positioned in the optical through signal path and an optical combining device positioned in the optical through signal path. An optical feedback path is connected to the optical splitting device and the optical combining device.

Abstract: An optical transmitter has a modulator for modulating data onto an optical signal for transmission to the receiver, the modulated signal having components at one or more constellations of points of different amplitudes and phases. The modulator is tunable such that distortions of the points of the one or more constellation can be tuned, and a tuning controller is provided for receiving a feedback signal from the receiver indicating a distortion measured at the receiver, and for tuning automatically the modulator to adjust the modulation based on the received feedback signal to pre-compensate for the measured distortion. Such pre-compensation can reduce the amount of distortion in the transmission system and thus enable more transmission capacity, without the need for a complex transmitter.