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.

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: 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: 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: 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: 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: An optical data receiver comprises an optical input for receiving optical data signals, an optical sputter for splitting the optical signals into first and second receiver arms, an optical filter in the first receiver arm, means for increasing an intensity ratio of optical signal strength in the first receiver arm to optical signal strength in the second receiver arm, means for adjusting a phase difference between the first and second receiver arms, and an optical coupler for coupling outputs of the first and second receiver arms to a photodetector. The receiver of the present invention selectively filters a carrier component of received optical data signals, adjusts the relative strength of the carrier component and the received signal and then recombines them. In this way efficient optical transmission can be achieved with direct detection at the receiver, without the need for a complex receiver design including a local oscillator.

Abstract: A wavelength division multiplexing transmission system, the system comprising: a plurality of channels at different wavelengths, each channel comprising a transmitter, a receiver, and one or more amplifiers, the system further comprising an encoder for encoding data with a coding, and; a decoder for decoding transmitted data; prioritizing means for prioritizing the data on each channel; monitoring means for monitoring directly or indirectly, raw (uncorrected) bit errors on each channel; power adjusting means for, varying the power on a channel in response to the bit error rate.

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: 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: 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 invention provides an optical transmitter comprising a differential encoder having first and second outputs, the first and second outputs being of opposite polarity to one another, a first RZ converter connected to the first output of the differential encoder and a second RZ converter connected to the second output of the differential encoder, and a dual electrode Mach Zehnder modulator to which an unmodulated coherent light source is coupled, wherein the output of the first RZ converter is connected to a first electrode of the Mach Zehnder modulator and the output of the second RZ converter is connected to a second electrode of the Mach Zehnder modulator. The invention provides improved signal integrity as compared with existing RZ-DPSK solution through the use of high quality RZ drivers. Furthermore, the invention gives rise to controllable RZ pulse edge chirping, providing rapid pulse compression or broadening through a dispersive fibre length.

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.

Abstract: The invention includes a method for optically encoding data for transmission over a wavelength division multiplexed optical communications system comprising the steps of: generating a periodic series of optical pulses defining a series of time slots, wherein one pulse appears in each time slot; filtering the pulses to produce carrier pulses extending over more than one time slot; and modulating the pulses with data for transmission. Preferably, the filter gives rise to the pulses having a temporal profile with a minimum in the centre of each of the time slots adjacent to the time slot for that pulse. The resulting data format allows for greater spectral efficiency in a WDM optical transmission system as compared with conventional RZ and NRZ data formats.

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: A network node is provided for use in a WDM optical transmission system that includes a plurality of network nodes interconnected by communication links. The network node includes an optical switch having at least one input port for receiving from the transmission system a WDM signal having a plurality of wavelength components. The network node also includes a regenerator arrangement having sufficient regeneration capacity to regenerate a prescribed fraction of the plurality of wavelength components. The prescribed fraction is less than a maximum number of wavelength components that may be received by the node. A network management element is provided so that the network node can for communicate with a network management center in the transmission system.

Abstract: A method, apparatus, and computer program product are provided for optimizing the pulse shape of optical signals output from an optical transmitter. The optical transmitter includes an optical modulator controlled by a bias voltage and a signal drive level, wherein the bias voltage and signal drive level are controlled automatically in a systematic way in dependence on one another to adapt the pulse shape of an optical output signal for optimal transmission over a transmission line.

Abstract: A method for transmitting network packets is provided. Reordered network packets received by a receiving end are put into a buffer queue. When a waiting time expires or when a network packet with a sequence number equal to the current transmission sequence number is received, the receiving end picks and transmits appropriate network packets from the buffer queue. Therefore, reordered network packets are sorted and then sent out sequentially, thereby avoiding waste of network bandwidth caused by retransmitting network packets, and improving the transmitting efficiency of the network.

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.