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: 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 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 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: 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: 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.

Abstract: An optical amplification mechanism that introduces optical pump(s) into one port of an optical circulator. The optical circulator directs the optical pumps from that port into another port that is coupled to the output of a gain stage. The optical pump(s) then pass from the output to the input of the gain stage while amplifying an optical signal passing from the input to the output of the gain stage. A residual amount of optical pump(s) that exits the input of the gain stage is reflected back into the input of the gain stage. The reflected optical pump(s) then further assists in the amplification of the optical signal. Other embodiments are also disclosed.

Abstract: Optical amplification by combining two or more optical signals from separate optical fibers, amplifying the combined signal using an optical fiber, and separating the amplified signals into their constituent optical signals. The separated optical signals may then be sent further in the direction they had been heading before combination. This allows multiple optical signals to be amplified using a single optical amplifier, perhaps even in a single optical fiber. Although not required, the two optical signals may even be travelling in different directions.

Abstract: A submarine optical repeater that shares optical pump power in multiple gain stages such that approximately the same wavelengths of optical pump is provided to each of the gain stages. Also, tilt control mechanism may adjust gain dependency on wavelength by adjusting the amount of optical pump power delivered to the optical gain stages. Residual optical pump power from both forward and backward Raman amplification may be used to power corresponding optically pumped amplifiers.

Abstract: Cross-distribution of the output pump power from optical pump units amongst multiple amplifier gain stages even in a single direction of an optical link in an optical communications system. For example, an optical pump unit may output optical pump power that is shared amongst a discrete optical amplification unit and a distributed optical amplification unit (such as a forward and/or backward Raman amplifier). Such sharing has the potential to increase reliability and/or efficiency of the optical communications system.

Abstract: An optical communication system is operable to communicate a plurality of wavelength signals at a bit rate of at least 9.5 gigabits per second over a multiple span communication link spanning at least 400 kilometers without optical regenerators. The plurality of wavelength signals include a bandwidth of more than 32 nanometers separated into at least 160 optical channels. The system includes a plurality of optical transmitters implementing a forward error correction (FEC) coding technique. The FEC encoded wavelength signals comprise a bit error rate of 10?09 or better after FEC decoding. The system also includes at least five (5) optical add/drop multiplexers (OADMs), each coupled to one or more spans of the multiple span communication link. The system further includes a plurality of amplifiers each coupled to one or more spans of the communication link, at least a majority of the amplifiers comprise a distributed Raman amplification stage.

Abstract: Embodiments described herein relate to an optical fiber stretch that may experience forward Raman amplification in which the peak optical signal power occurs at some distance from the transmitter. Smaller effective area optical fiber is used at a portion of the optical fiber stretch in which the optical signal power is increasing, while larger effective area optical fiber is used at a more remote stretch of the optical fiber stretch that experiences the peak optical signal power. Thus, the quality of the signal is better preserved since the larger effective area fiber reduces maximum optical signal density thereby reducing non-linear degradations on signal quality.