Lucent Technologies Inc.

Alcatel Lucent

Alcatel-lucent USA Inc.

Dieter Werner

Chongjin Xie

Bernd Teichmann

Konrad Czotscher

Matthias Richard Feulner

Bianca Buchold

Nathan Myron Denkin

Steffen Reichel

Jianhui Zhou

Matthias Berger

Bernhard Schmauss

Guido Hermann Hunziker

Jiong Ma

Mingjuan Zhu

Bernd Bollenz

Alfons Schinabeck

Methods and apparatus are provided for optical polarization mode dispersion compensator (PMDC) feedback control for APol-DPSK signals. A feedback signal generator includes a delay-line-interferometer (DLI), with a differential delay line delay (D) different from one bit period (Tb). In an exemplary embodiment, the DLI delay is in the range of 0.5 Tb&#x3c;D&#x3c;1.0 Tb, or 1.0 Tb&#x3c;D&#x3c;1.5 Tb, preferably 0.85 Tb or 1.15 Tb. The DLI is coupled to a single-ended detector, whose output is amplified and bandpass filtered around the frequency of half the bit rate. The filtered signal is then applied to an RF power detector to generate the PMDC feedback signal. Generation of the PMDC feedback signal in accordance with the present invention is insensitive to any alignment of the state of polarization (SOP) of the received APol-DPSK signal with the principal state of polarization (PSP) of the transmission link. As a result, there is no need for a polarization scrambler at the transmitter. Additionally, by dispensing with the polarization scrambler at the transmitter, systems in accordance with the present invention can be implemented with reduced complexity and cost and improved performance.

PMDC feedback arrangement for APol-DPSK

The present invention includes apparatus and method of a variable step size dithering control algorithm for polarization mode dispersion controllers (PMDCs). The dithering step size of the PCs is adjusted according to the feedback signal including degree of polarization (DOP).

Effective control algorithm for optical polarization mode dispersion compensators

Raman amplification is used in optical transmission systems, devices and/or components way of for applying Raman amplification avoiding or suppressing detrimental and hence undesirable non-linear effects is provided. Raman amplification in an optical device is provided by firstly determining a pump power () necessary for providing Raman amplification and then by providing a low spectral power density by pumping the optical device with pump power () at a relatively broad pump power spectrum and preferably a low spectral pump power amplitude such that the total output pump power () remains sufficiently high. The pump power () is optically attenuated prior to being coupled to the optical device.

Method and contrivance for applying a Raman amplification in a transmission and/or fibre device

Wavelength control and stabilization of a laser is achieved by a practical, inexpensive, and accurate technique adapted for most optical transmission system applications by a method involving a laser characterization phase and a laser wavelength control and stabilization phase. This technique is applicable to both single mode lasers and multimode lasers. It is especially useful in those applications where the desired laser output power can vary over a wide range, including relatively low power above the lasing threshold.

Laser wavelength control arrangement and method

The dependency of intensity noise is used to determine the wavelength difference between a laser diode gain peak and a reflection peak of a fiber grating in a fiber grating type laser diode. Monitoring and determining the relative noise intensity of such a laser enables the control of the laser diode or the fiber grating such that the intensity noise is as low as possible. Such an approach enables the use of a fiber grating type laser diode as Raman pumps in high-speed transmission systems where low intensity noise is a requirement, especially when the Raman pump power propagates in the same direction as the transmission signals (known as Raman co-pumps).

Low relative intensity noise fiber grating type laser diode

In an optically amplified wavelength division multiplexed (WDM) system having a WDM signal comprising a plurality of optical channels, the per-channel gain of the optical channels is kept relatively constant despite changes in input power at the optical amplifier, such as when individual optical channels of the WDM signal are added and dropped. More specifically, gain of an optical amplifier is controlled by controlling the amount of pump power supplied to the optical amplifier as a function of changes in input power which are measured in a feed-forward monitoring path. The amount of pump power for effecting gain control is adjusted according to a scaled relationship to the measured input power of the optical amplifier. By controlling the pump power directly in response to changes in input power, gain of the optical amplifier can be controlled within a sub-microsecond time scale from the time that a change in input power is detected. Moreover, by maintaining relatively constant per-channel gain in an amplified WDM signal despite changes in input power at the optical amplifier, power excursions are substantially reduced in surviving optical channels of the WDM signal, i.e., those at the output of the optical amplifier.

Fast gain control for optical amplifiers

An apparatus and method are described for controlling response to power transients in an optically amplified wavelength division multiplexed (WDM) network when WDM optical channels are added and dropped, during network reconfigurations, during failure events, and so on. In one embodiment, a variable bandwidth filter circuit operates at a first prescribed bandwidth during a first time period &tgr; to detect a change in signal power (i.e., power transient) caused by a transient event, and operates at a second prescribed bandwidth that is less than the first prescribed bandwidth after the first period of time elapses, e.g., &tgr; &plus;&Dgr;&tgr;, to substantially suppress low level signal variations, such as remnants of the power transient. In this way, the power transient related to the actual transient event will be preserved to trigger control circuitry, e.g., amplifier gain control based on input power changes, while the remnants will be filtered out to prevent unwanted responses by the control circuitry, e.g., remnants misinterpreted as actual transient events.

Method and apparatus for stabilizing transient control in amplified optical networks

The invention relates to a method and an optical transmission system for compensation of dispersion in optical transmission lines in which dispersion compensation fibers are applied, with the dispersion compensation fibers being arranged at the beginning as well as at the end of the line segments of the optical fibers forming the transmission line. The signal distortions due to non-linear effects are reduced by making use of the recognition that non-linearities should only occur at as small as possible an accumulated dispersion. This is obtained by an unequal division of the dispersion compensation fiber applied for the compensation of the dispersion of the optical fiber, with the part of the dispersion compensation fiber attached at the beginning of a line segment being directly connected to the optical fiber and having an accumulated dispersion which is smaller as to amount than the accumulated dispersion of the part of the dispersion compensation fiber attached at the end of the optical fiber.

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Neunkirchen am Brand, Germany

Dieter Werner