Abstract: The adjustment of tilt in an optical signal path of a repeater. The repeater includes an optical pump that optically powers a rare-Earth doped fiber amplifier, which amplifies the optical signal. The optical signal path also includes Raman gain stage implemented in a previous optical fiber span in the optical signal path, and which contributes tilt with respect to wavelength. Adjusting the Raman gain and/or the rare-Earth doped gain also adjusts the combined tilt contributed by these gain stages. However, the rare-Earth doped gain operates at least partially in the saturated regime, thereby stabilizing the gain at the output of the rare-Earth doped amplifier. Thus tilt control may be employed by adjusting optical pump power with reduced effect on overall gain.

Abstract: An integrated assembly for switching optical signals. The integrated assembly includes two subassemblies. For instance, the subassemblies might be a shelf assembly and the integrated assembly might be a rack assembly in which the shelf assemblies are connected. Each of the subassemblies includes optical interfaces configured to support communication of optical channels to and from the integrated assembly using the corresponding subassembly. Each subassembly might also include multiple switch fabric assemblies each including a switching mechanism. An inter-subassembly communication interface is provided between each subassembly. An optical signal may be switched from one of the subassemblies (e.g., one of the shelves) to another even though there is no intervening switching circuitry in between the different subassemblies. Instead, the switching operation is distributed between the subassemblies.

Abstract: A repeater amplifier assembly that includes at least two chassis containing optics and electronics. The chassis are connected with a size-adjustment mechanism that can adjust a size of the repeater amplifier assembly by reversibly adjusting the positions of the chassis with respect to each other. To insert the repeater amplifier assembly into a repeater housing, the repeater amplifier assembly is accessed in a contracted position. The amplifier is inserted into the housing, and then a control of the size adjustment mechanism is actuated to urge the chassis outwards until the chassis push against the repeater housing. To remove the repeater amplifier assembly from the repeater housing, the control is actuated to cause the size adjustment mechanism to pull the chassis inwards with respect to each other until the chassis no longer push against the repeater housing. The repeater amplifier assembly may then be freely removed from the repeater housing.

Abstract: A repeater amplifier assembly that includes at least two chassis containing optics and electronics. The chassis are connected with a size-adjustment mechanism that can adjust a size of the repeater amplifier assembly by reversibly adjusting the positions of the chassis with respect to each other. To insert the repeater amplifier assembly into a repeater housing, the repeater amplifier assembly is accessed in a contracted position. The amplifier is inserted into the housing, and then a control of the size adjustment mechanism is actuated to urge the chassis outwards until the chassis push against the repeater housing. To remove the repeater amplifier assembly from the repeater housing, the control is actuated to cause the size adjustment mechanism to pull the chassis inwards with respect to each other until the chassis no longer push against the repeater housing. The repeater amplifier assembly may then be freely removed from the repeater housing.

Abstract: The system-level control of a repeatered optical communications system. In a repeatered optical communications system, two terminals are optically coupled via an optical communications span having one or more repeaters. One of the terminals may perform the control by monitoring quality metrics of optical signals received over the communication span. Based on this monitoring, certain adjustments are determined to be performed, and the repeater controllers of the respective optical repeaters are instructed to perform the adjustments. In some case, the optical repeater adjustments cannot be made without impacting the performance of the optical signals traveling in the opposite direction. In that case, the system-level control uses monitored quality metrics from both terminals to determine the adjustments to be made. The system level adjustment may be automated by software or the like thereby making optimization of the optical communications span easier.

Abstract: A transmission system for transmitting data over a channel in the form of a digital signal comprising bits of data, the system comprising an encoder for encoding the data prior to transmission, the encoder producing coding in the form of an overhead, and a decoder for decoding the data after transmission, characterised in that a first portion only of the data is encoded, the second portion remaining uncoded, the system further comprising a partitioner for partitioning the overhead from the uncoded data portion of the signal, after the first portion data has been encoded.

Abstract: The system-level control of a repeatered optical communications system. In a repeatered optical communications system, two terminals are optically coupled via an optical communications span having one or more repeaters. One of the terminals may perform the control by monitoring quality metrics of optical signals received over the communication span. Based on this monitoring, certain adjustments are determined to be performed, and the repeater controllers of the respective optical repeaters are instructed to perform the adjustments. In some case, the optical repeater adjustments cannot be made without impacting the performance of the optical signals traveling in the opposite direction. In that case, the system-level control uses monitored quality metrics from both terminals to determine the adjustments to be made. The system level adjustment may be automated by software or the like thereby making optimization of the optical communications span easier.

Abstract: An integrated assembly for switching optical signals. The integrated assembly includes two subassemblies. For instance, the subassemblies might be a shelf assembly and the integrated assembly might be a rack assembly in which the shelf assemblies are connected. Each of the subassemblies includes optical interfaces configured to support communication of optical channels to and from the integrated assembly using the corresponding subassembly. Each subassembly might also include multiple switch fabric assemblies each including a switching mechanism. An inter-subassembly communication interface is provided between each subassembly. An optical signal may be switched from one of the subassemblies (e.g., one of the shelves) to another even though there is no intervening switching circuitry in between the different subassemblies. Instead, the switching operation is distributed between the subassemblies.

Abstract: A repeater amplifier assembly that includes at least two chassis containing optics and electronics. The chassis are connected with a size-adjustment mechanism that can adjust a size of the repeater amplifier assembly by reversibly adjusting the positions of the chassis with respect to each other. To insert the repeater amplifier assembly into a repeater housing, the repeater amplifier assembly is accessed in a contracted position. The amplifier is inserted into the housing, and then a control of the size adjustment mechanism is actuated to urge the chassis outwards until the chassis push against the repeater housing. To remove the repeater amplifier assembly from the repeater housing, the control is actuated to cause the size adjustment mechanism to pull the chassis inwards with respect to each other until the chassis no longer push against the repeater housing. The repeater amplifier assembly may then be freely removed from the repeater housing.

Abstract: There is provided a method and apparatus for tuning an optical discriminator to the carrier frequency of an optical signal to allow superior reception of said signal. The carrier frequency of the signal is dithered during a test phase in order to provide information that allows a subsequent tuning phase to optimise the reception of the optical signal, as measured by a signal quality metric. The tuning phase may comprise adjustment of one or both of the carrier frequency and the optical discriminator.

Abstract: A polarization mode dispersion compensator that includes two stages, one for reducing or eliminating first order polarization mode dispersion of an optical signal, and second stage for reducing or eliminating higher order polarization mode dispersion of the optical signal. In each stage, the polarization is adjusted so as to reduce polarization mode dispersion. Based on the power levels of various polarization states generated at the second polarization controller, the optical signal to noise ratio may be estimated. Furthermore, based on the amount of adjustment used to control the polarization controllers and the differential group delay, the polarization mode dispersion may be estimated.

Abstract: A method for managing Internet Protocol (IP) tunnels is provided. The method is executed by a local host. There is at least one IP tunnel planned between the local host and a remote host. The method comprises the following steps. If the local addresses of the tunnels include dynamic IP addresses, acquire the dynamic IP addresses. All tunnels with known remote addresses are built. If there are known remote addresses and the local addresses include dynamic IP addresses, send a notification to the remote host, wherein the notification includes all local dynamic IP addresses. If any local address changes, all tunnels with changed local addresses and known remote addresses are rebuilt. A message is received from the remote host and classified. If the message is a notification, the tunnels are updated according to the remote addresses included in the message, and an acknowledgement is sent back to the remote host.

Abstract: A system and method are provided for controlling the pre-emphasis applied to an optical signal, in which the output level of individual transmitters is controlled in order to reach a pre-defined desired value of a quality metric. Transmitters are able to adjust their output power without external control in such a way as to optimise the power distribution across the system.

Abstract: An optical assembly in an optical link coupling two optical terminals. The optical assembly receives and demultiplexes two groups of optical wavelength channels which are each treated separately as far as dispersion compensation and discrete amplification are concerned. The optical assembly then multiplexes the two groups back into the same fiber for further transmission. For instance, one group of optical wavelength channels may each be coherent channels, and subject to no dispersion in the optical assembly, while the other group may contain non-coherent channels, which are subject to dispersion compensation in the optical assembly.

Abstract: The mixing of coherent optical wavelength channels with non-coherent optical wavelength channels. Before mixing, a dispersive element introduces dispersion into the coherent optical wavelength channels and/or into the non-coherent optical wavelength channels such that the dispersion map of the coherent optical wavelength channels is different than the dispersion map of the non-coherent optical wavelength channels. By allowing the coherent channels to have a different dispersion map, the dispersion map may be moved further from the zero dispersion point, which can degrade coherent detection. Accordingly, coherent optical channels and non-coherent optical channels may be transmitted effectively over the same optical link.

Abstract: A device and method for depolarising the total field of a wavelength division multiplexed (WDM) signal is provided. A polarization maintaining multiplexor combines a plurality of optical signals to form a polarized multiplexed signal. The multiplexed signal is then passed through a differential group delay (DGD) element adapted to modify the polarization state of one or more optical source signals within the multiplexed signal and thereby to at least partially depolarise the multiplexed signal.

Abstract: A feedforward controller for controlling the polarization state of an optical signal. The feedforward controller includes an optical input for receiving an optical input signal having an input polarization state, an optical output for transmitting an optical output signal having an output polarization state, a polarization controller coupled to the optical input and the optical output, and a transfer function determiner for determining a characteristic polarization transfer function of the feedforward controller from the input and output polarization states. The polarization controller is adapted to modify the polarization state of light passing therethrough in dependence on the characteristic polarization transfer function of the feedforward controller.

Abstract: An optical transmission system or its constituent repeater disposed optically between two terminals. The system includes at least two parallel optical paths between a first node and the repeater (one optical path being used as a backup for another), and another at least two parallel optical paths between a second node and the repeater (again, one optical path being used as a backup for another). The first nodes may, but need not, be terminals, but could also be repeaters, or other optical elements. For a signal traveling from the first terminal to the second terminal, the optical switching mechanism detects which of the at least two parallel optical paths an optical signal is being received from the first node, and channels the optical signal to at least one of the parallel optical paths leading from the repeater to the second node.

Abstract: Polarization multiplexing by encoding data using a return-to-zero format, and by interleaving the constituent orthogonal polarization components such that the data-carrying portion of the bit window from one orthogonal polarization component occupies the zero portion of the bit window for the other orthogonal polarization component.

Abstract: The alteration of the bandwidth of an optical amplifier. Before alteration, optical signals having a first set of wavelengths are provided through a gain medium of the optical amplifier. In addition, a first pump having a set of pump wavelengths is propagated through the gain medium to thereby amplify the optical signals. After alteration, optical signals having at least a partially different set of wavelengths are able to be optically amplified by coupling a second pump into the optical medium. The second pump is at least partially distinct from the first pump in that the second pump includes at least one pump wavelength that was not included in the first pump.