Xtera Communications, Inc.

Alcatel

Richard Oberland

Stephen Michael Webb

Stephen Desbruslais

Stuart Robert Barnes

Stephen Desbrulais

John Ellison

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.

Depolarised WDM source

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. This can be used to mitigate pulse distortion in non-linear transmission links.

Method and apparatus for producing RZ-DPSK modulated optical signals

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.

Adaptive pulse shape control

An optical communications system comprising: an optical input and an output, a source of input signals in an asymmetric format and having a duty cycle, a modulator for modulating the input signals, to produce an asymmetric signal, the modulator comprising a Mach-Zehnder interferometer; drive means for driving the modulator at a predetermined modulator drive voltage; bias means for applying a bias voltage to the modulator; adjustment means for adjusting a first variable chosen from one of the bias voltage, gain voltage, or duty cycle in response to the relationship existing between changes in the amplitude of the asymmetric signal and changes in the first variable, characterized in that the system further comprising varying means for varying a second variable, different to the first variable and chosen from one of the bias voltage, gain voltage or duty cycle in response to adjustments made to the first variable; and a monitor for recording the average optical output power.

Modulator control system

A wavelength division multiplexing optical transmission system, an optical loading-channel transmitters, a WDM optical transmitter and a method of optically loading an optical transmission line with multiple optical loading channels. The multiple optical loading channels are produced in the form of an optical comb by using a periodic optical filtering apparatus incorporated within a resonator constructed as an optical loop. A plurality of optical loading channels of the generated optical comb are then output without data being modulated thereon.

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London, United Kingdom

Richard Oberland