Tropic Networks Inc.

Nortel Networks Corporation

Alcatel Lucent

Alcatel-lucent Canada Inc.

Ping Wai Wan

Derrick Remedios

Patrick Chilufya Chimfwembe

James Benson Bacque

Eddie Kai Ho Ng

Dongxing Jin

Colin Geoffrey Kelly

Paul David Obeda

Robert Michael Bierman

Jason Christopher De Rocher

Leonard Marziliano

Dan R Oprea

Kexing Liu

Walter Carpini

Wen Liu

Chung Y Wu

Marc A Nadeau

Stephen Kieran Adolph

Paul Alan Bruce

James St Leger Harley

Dung Van Nguyen

Benjamin Wai Chan

John Frederick Groves

Ashley A Truscott

Collin G Kelly

Ronald D Hoffe

Derrick Anthony John Remedios

Hamish Iain MacDonald

Various embodiments relate to an in-band measurement of the optical signal-to-noise ratio (OSNR) of an optical signal in an optically-amplified transmission system. A demodulation device may tap a transmission fiber to receive an optical signal containing a low-frequency signal. A filter may implement first and second passbands to filter portions of an optical channel in the optical signal. Once the filtered channel is converted to first and second target electrical signals, a measurement circuit may take measurements of DC and AC components for each of the target electrical signals. Based on measurements of the two target electrical signals, the demodulation device may calculate the OSNR as a function of the DC and AC components, or as a function of the adjustment factors between first and second passbands of the optical channel represented by the first and second target electrical signals.

In-band optical signal-to-noise ratio measurement

A method and apparatus for distributed measurement of chromatic dispersion in an optical network is disclosed. The network comprises optical switching nodes interconnected by optical links. An optical link may comprise multiple spans, each span ending in a transport module which comprises signal-processing components. At least one optical switching node has a probing signal generator transmitting an optical probing signal along a selected path in the network. Probing-signal detectors placed at selected transport modules determine chromatic-dispersion values and send results to a processing unit which determines appropriate placement of compensators or appropriate adjustments of compensators placed along the path. A preferred probing signal has the form of wavelength modulated optical carrier which is further intensity modulated by a periodic, preferably sinusoidal, probing tone. Variation in the phase-shift of the probing tone corresponding to variation of the wavelength of the optical probing signal determines chromatic-dispersion characteristics for different spans of the path.

Method and system for distributed measurement and compensation of chromatic dispersion in an optical network

Signals in an optical communications network, such as optical channels in an optical WDM network for example, are each identified by at least two low frequency dither tones with which the signal is modulated. The dither tones alternate with a predetermined periodicity to produce a cyclically repeated sequence of dither tones. A network parameter, such as a channel identifier for example, is obtained by the detection of the particular combination of dither tones in the sequence. To detect a number of network parameters a signal is modulated with a number of cyclically repeated sequences of dither tones each uniquely identifying a respective network parameter. In some implementations each dither tone in a cyclically repeated sequence of dither tones is repeated with substantially the same phase and coherent averaging is performed over a number of periods to detect dither tones on low power signals.

Signal identification in optical communications networks

Identification of optical channels in wavelength division multiplex (WDM) optical networks may be confounded by unwanted noise tones interfering with pilot/dither tones used for identifying optical channels. The invention describes a method of selecting pilot/dither tones that are selectively restricted to avoid allocating dither/pilot tone frequencies that appear as noise tones along the path of an optical channel in the optical network.

Noise tone avoidance in optical networks

Methods and apparatus for optical-power control in an optical network employing wavelength-division multiplexed (WDM) optical-fiber links are devised to circumvent the effect of crosstalk caused by optical-power scattering. Each carrier signal is amplitude-modulated by an identifying tone, with the power of an identifying tone having a predetermined ratio to the power of its carrier signal. A fiber span within an optical-fiber link is tapped at a preferred monitoring point, and the power spectrum of the envelope of the tapped optical signal is measured. To estimate an individual carrier power, a temporary gain is applied and the power of a corresponding tone is measured. To control optical power of each wavelength carrier in several spans in the network, a network controller selects an order of processing the spans of interest, and selects the order of processing of each channel within each span.

Method and system for power management in optical networks

This invention provides a method for commissioning and upgrading an optical ring network using its internal amplifiers as Automatic Spontaneous Emission sources of light that are used in making measurements. A modular segmented approach is adopted and the network is commissioned segment by segment. A flexible method is used for upgrading a commissioned network by adding or deleting a node or changing the internal configuration of a node. The method uses techniques for the correction of the Optical Signal to Noise Ratio induced error as well as the Spectral Filtering Error during the loss computation required for adjusting the gains of the amplifiers at each network node to an appropriate value. Since the method does not require an external laser source that needs to be moved manually from node to node it greatly reduces the commissioning time. Since it uses only the components of the network itself and does not deploy any additional device it also leads to a significant saving in cost.

Method for network commissioning and upgrading using amplified spontaneous emission (ASE) sources

A method and apparatus for encoding optical power and non-payload data in an optical signal is described. The method involves producing a dither modulating signal having an amplitude of indicative of the optical power in the optical signal and having a phase representing the non-payload data, and modulating the optical signal with the dither modulating signal. The apparatus involves a waveform generator for producing an amplitude adjusted waveform having an amplitude responsive to the optical power of the optical signal and a binary phase shift keying modulator for binary phase shift keying the amplitude adjusted waveform in response to the non-payload data to produce a dither modulating signal having an amplitude indicative of the optical power in the optical signal and having a phase representing the non-payload data.

Method and apparatus for encoding optical power and non-payload data in an optical signal

This invention provides a method for commissioning an optical network using internal Automatic Spontaneous Emission (ASE) light inherently present in the optical network as a light source (the ASE light source) for measuring losses inside and between nodes in the network. A modular segmented approach is adopted and the network is commissioned segment by segment. The method uses techniques for the correction of the Optical Signal to Noise Ratio induced error as well as the Spectral Filtering Error during the loss computation required for adjusting the gains of the amplifiers at each network node to an appropriate value. Since the method does not require an external laser source that needs to be moved manually from node to node, it greatly reduces the commissioning time. Since it uses only the existing components of the network nodes it also leads to a significant saving in cost.

Method for network commissioning using amplified spontaneous emission (ASE) sources

A method and system for identification of a channel in an optical network is provided. The channel is identified by the use of unique combinations of two or more low frequencies, or tones, modulated onto the channel and optionally, a network parameter associated with the channel.

Method and system for identification of channels in an optical network

The invention provides a method and system for selectively canceling a specified frequency band in the payload of an optical communication system. This selected frequency band is to be used for launching pilot tones for power measurement and identification. The method controls the intensity of the optical payload signal through an intensity modulator that is included in the optical communication system. The frequency band in payload to be cancelled is removed where as the other frequency components of the payload are passed without attenuation. An embodiment that uses a feed-forward unit, a feedback unit and a control unit for generating a cancellation signal for the intensity modulator is described. An advantage of the method is that it removes a continuum of payload tones in the specified frequency band to be cancelled.

Method and system for selective optical payload cancellation

Channels in an optical WDM network are each identified by at least two dither tones with which the channel is modulated, the dither tones alternating with a predetermined periodicity so that at any instant each channel is modulated by only one dither tone. The dither tones are continuously generated at precise frequencies. Channel detection by detecting the dither tones, for channels having optical powers over a wide dynamic range, makes use of an FFT process which can detect dither tones for high power channels in a single operation. Coherent averaging of FFT results over time is used to detect dither tones for low power channels over multiple FFT operations.

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Ottawa, Canada

Ping Wai Wan