Ciena Corporation

Nortel Networks Corporation

Douglas McGhan

James St Harley

Kim Bryon Roberts

Maurice M O'Sullivan

Mark Andrew Hawryluck

Mohammad Sotoodeh

Anant Grewal

Shahab Oveis Gharan

Mark Edward Rollins

Ian B Betty

Giuseppe Bordogna

Yves Beaulieu

Kim Byron Roberts

Riyaz R Jamal

Alen Chan

Aspects of the subject disclosure may include, for example, obtaining two inputs xand xbased on a digital input signal, and causing a modulator to create two substantially orthogonal output dimensions I and Q based on the two inputs xand x, by performing controlled introduction of a correlation between the two inputs xand xfor the modulator, and detecting a resulting output power of the modulator to facilitate operation of the modulator. Other embodiments are disclosed.

In-phase (I) / quadrature (Q) correlation dither for modulator quadrature control

A transmitter in an optical communications system includes a digital signal processor for processing a data signal to generate a sample stream encoding successive symbols in accordance with a constrained phase modulation scheme having a constellation of at least two symbols and a modulation phase constrained to a phase range spanning less than 4&#x3c0;. A digital-to-analog converter converts the sample stream into a corresponding analog drive signal. A finite range phase modulator modulates a phase of a continuous wavelength channel light in accordance with the analog drive signal, to generate a modulated channel light for transmission through the optical communications system. A receiver in the optical communications system includes an optical stage for detecting phase and amplitude of the modulated channel light and for generating a corresponding sample stream, and a digital signal processor for processing the sample stream to estimate each successive symbol of the modulated channel light.

Constrained continuous phase modulation and demodulation in an optical communications system

The present disclosure provides Radio Frequency (RF) drive level control systems and methods for an Electro-Optic (EO) M-ary Phase-Shift Keying (M-PSK) phase modulator. Specifically, an M-PSK drive waveform is tightly controlled for maximum symmetry in the associated constellation. In an exemplary embodiment, the present disclosure includes an M-PSK transmitter, an M-PSK electro-optic phase modulator, and phase modulation method that each control RF drive level based upon a carrier suppression ratio defined as a measure of ratio of a modulated time-averaged E-field to the magnitude of the E-field. In an exemplary embodiment, the carrier suppression ratio is measured based on a modulation depth measurement.

Radio frequency drive level control system and method for an electro-optic phase modulator

A method of controlling a polar optical transmitter comprising a dual-branch Mach-Zehnder (MZ) modulator driven by a pair of independent electrical drive signals. A cost function is provided which defines a relationship between a control parameter of the optical transmitter and a power level of an output optical signal generated by the MZ modulator. A selected component of the electrical drive signals is dithered using a predetermined dither signal. A modulation depth of the output optical signal power level corresponding to the dither signal is detected, and the control parameter adjusted based on the cost function and the detection result.

Control system for a polar optical transmitter

A method and system enables measurement of polarization dependent loss (PDL) in an optical communications system including a plurality of cascaded optical components. An optical signal having a predetermined initial polarization state is launched into the optical communications system. A polarization state of the signal is detected at a selected detection point downstream of the launch point. The PDE is evaluated using the predetermined initial polarization state and the detected polarization state.

Measurement of polarization dependent loss in an optical transmission system

A method for modulating the E-field of an optical carrier signal utilizes a Mach-Zehnder modulator having a pair of independently controllable branches. A pair of independent branch drive signals V(t) and V(t) are derived. Each branch of the MZ modulator is driven with a respective one of the independent branch drive signals. By this means, a low cost conventional MZ modulator (interferometer) can be used to perform complex modulation of the E-field of the optical carrier. In some embodiments, this functionality is used to facilitate precompensation of optical impairments of an optical communications system.

Optical E-field modulation using a Mach-Zehnder interferometer

A semiconductor optical amplifier (SOA) is placed in the optical path between the tunable laser and the external modulator on a DWDM optical transmitter. The modulator transfer function is measured using low-level amplified spontaneous emission light output from the SOA in order to find the modulator bias corresponding to minimum transmission. The external modulator is biased to the point of minimum transmission to reduce the transmitter output power during laser turn-on. The SOA bias is also turned off to provide further attenuation as the laser is turned on. Similarly, to avoid emitting off-wavelength light during wavelength changes, the transmitter output is attenuated with a combination of low SOA bias current and biasing the modulator to its minimum transmission point. In both cases, the laser wavelength is allowed to stabilize without interfering with adjacent DWDM channels.

Use of amplified spontaneous emission from a semiconductor optical amplifier to minimize channel interference during initialization of an externally modulated DWDM transmitter

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Ottawa, Canada

Douglas McGhan