Nortel Networks Corporation

Northern Telecom Limited

Corning Incorporated

Rockstar Consortium US LP

Systemes Pavemetrics Inc.

Richard A Habel

Kim Byron Roberts

Alan Glen Solheim

Kim Bryon Roberts

James St Harley

Maurice Stephen O'Sullivan

Robert William Keys

Nigel Baker

Nigel Edward Jolley

Duncan John Forbes

Ian Hardcastle

Giuseppe Bordogna

David John Danagher

Takis Hadjifotiou

Bipin Patel

Michael John Yadlowsky

Kevin Wallace Bennett

Mark A Newhouse

Paul Anthony Jakobson

Peter Jeremy Anslow

Fiona Davis

Daniel Lefebvre

Franz Li Mok

Avid E Lemus

Eric Samson

James St Leger Harley

Jeffrey Alan Weslowski

Franz Li Hsien Mok

Jean-François Hebert

Mathieu Dutrisac

Christopher Brendan Kennedy

A method for controlling a laser profiler, the laser profiler being configured for generating a laser line on a surface to be inspected, the method comprising: receiving an image of the laser line; determining an actual intensity of the laser line; calculating an amplification factor for the laser line based on the actual intensity of the laser line, a target intensity for the laser line, a power of the laser, a camera gain of the camera and an exposure time of the laser line on the surface to be inspected, the amplification factor allowing the actual intensity of the laser line to reach the target intensity while minimizing the power of the laser; and based on the calculated amplification factor, adjusting at least one parameter of the laser profiler so that the actual intensity of the laser line corresponds to the target intensity.

Method and system for controlling a laser profiler

A protected light source for generating seed light for at least two wavelength division multiplexed passive optical networks (WDM-PONs). The protected light source includes an optical coupler having N&#x2267;2 input ports and M&#x2267;2 output ports, each output port being optically connected to supply seed light to a respective set of one or more WDM-PONs. A respective multi-wavelength light source (MWLS) is optically coupled to supply seed light to each input port of the optical coupler. A controller unit controls operation of each multi-wavelength light source (MWLS).

Protected light source for multiple wavelength division multiplexed passive optical networks (WDM-PONs)

Protected light source for multiple wavelength division multiplexed passive optical networks (WDM-PONS)

An out of band vehicle for an optical network is used for transporting overhead (OH) data between 3R network elements, irrespective of the format or/and rate of the OH data. At the first 3R network element, the OH data is up-converted at a frequency f , and the resulting signal is combined with the traffic and transmitted to a second 3R network element. The inverse operation is effected at the second 3R network element by down-converting the combined signal. The frequency f is selected to be in a null of the traffic spectrum, so as to not interfere with the traffic.

Out-of-band vehicle for optical channel overhead information

The method of monitoring the quality of an optical signal at the site of a R or R regenerator, without performing a clock recovery operation, is based on slicing the recovered voltage with a threshold voltage, manipulated according to a pattern, and averaging the output of the slicer. An eye diagram is simulated by a diagram representing the average voltage versus the threshold voltage.

Eye quality monitor for a 2R regenerator

A method and apparatus for embedding control information in an optical signal transporting optical data, consisting of encoding the control information as a control signal having an amplitude proportional to a controllable modulation depth. The optical signal is then optically modulated in accordance with the amplitude of the control signal. The control signal is subsequently detected and the control information is decoded. A major feature of the invention lies in determining a level of similarity between the encoded and decoded control information and varying the modulation depth according to this level of similarity. Hence, the modulation depth yielding a given bit-error rate (BER) or signal-to-noise ration (SNR) can be minimized, in order to reduce the degradation of the optical channel data. The invention also provides a means for modulating the control information about a carrier frequency, and varying this carrier frequency if the SNR is below a certain tolerance value. This is useful in countering the periodic interference spectrum of framed data signals, which may be unknown or time-varying. Furthermore, the bit rate of the control signal can be adjusted to carry a required amount of information, so as to meet the system's evolving control requirements.

Robust variable-bit-rate optical channel overhead

The power of an optical signal (s,) travelling on a channel (&lgr;,) of a WDM transmission system, is measured using a signature bit pattern (s,) which is inserted in the frame of the optical signal (s,). The power level of s,is adjusted at the launching point to a predetermined ratio (m) with the power of the optical signal. At a point of interest, the fiber is tapped and a fraction of the tapped signal, that includes a corresponding fraction of s,, is converted to an electrical signal. The fraction of s,is extracted from a the electrical signal and power of s,is measured. This gives the optical power of s,as (m) is known and also the calibration constant for the respective channel (&lgr;,) is known. The method can be applied for any and all channels of the WDM transmission system.

Optical signal power detection with signature bit pattern in WDM systems

A fast means of detecting that a fiber has been disconnected at one end of a bidirectional optical amplifier by monitoring for several signature effects simultaneously. Upon detection of a loss of signal, the pump laser in the corresponding direction is shut off quickly to prevent oscillation from occurring should the other end of the amplifier be subsequently disconnected.

Fast loss of signal (LOS) detection for bidirectional optical amplifiers

In an optical transmission system employing optical amplifiers a method of regulating the gain of such an amplifier uses a non-linear control system whose non-linearity of operation is provided at least in part by the enabling/disabling of a portion of the control system by the operation of a transient magnitude threshold sensor.

Optical amplifier gain control

The variables and parameters previously understood to affect the gain spectrum of an optical amplifier 13 were: (1) the wavelengths to be amplified; (2) the input power levels at those wavelengths; (3) the characteristics of the amplifying medium 20; (4) the insertion loss spectra of the amplifier's components, including any filter(s) used for gain flattening; (5) the pump band chosen to pump the amplifying medium 20; and (6) the total amount of pump power supplied in the chosen pump band. An additional fundamental variable has been identified which can be used to control the gain spectrum of an optical amplifier 13, namely, the center wavelength of the spectrum of the pump's output power within the chosen pump band. Methods and apparatus for using this variable for this purpose are disclosed. For example a, transmission system is disclosed having a transmitter 11 and a receiver 10 connected by an optical fiber 12. A plurality of optical amplifiers 13 are located along the optical fiber 12 to amplify signal channels between the transmitter and receiver. Each of the amplifiers has a pump light source 21, the wavelength of which is such that contributions to differential gain due to pump light wavelength related effects is substantially reduced. Also disclosed is a WDM transmission system having a transmission path including a concatenation of laser diode pumped optical amplifiers 13 wherein the gain spectrum of an amplifier is controlled at least in part by a feedback loop regulating the temperature of its laser diode pump 21. The feedback loop may for instance derive its control signal from a measure of the drive current applied to the pump, of the emission wavelength of the pump, or of the disparity between the power output from the amplifier in one of the multiplexed signal channels and that from at least one other of the channels.

Pump wavelength tuning of optical amplifiers and use of same in

An add/drop multiplexer/demultiplexer (ADM) for switching, modulating and attenuating optical signals in a fiber optic network employing wavelength division multiplexing (WDM) is disclosed. The ADM is equipped an optical multiplexer for splitting an input WDM signal into individual optical signals, leading to respective 2.times.2 switches. Each switch has another input originating from a plurality of 'add lines', and selects one of its inputs to be dropped and the other to continue along a main signal path. The retained signals may be modulated and attenuated prior to being tapped and finally multiplexed together by a WDM multiplexer. The tapped signals are optoelectronically converted and fed back to a controller, preferably a digital signal processor running a software algorithm, which controls the switching, modulation and attenuation. This permits remote control of the ADM functions by encoding instructions for the controller into a low-frequency dither signal that is embedded within the individual optical signals. The ADM can accordingly be instructed to reroute traffic, dynamically equalize or otherwise change optical channel power levels, and add or remove dither, all in real time. A specific optical channel may be reserved for control purposes, allowing a network administrator to 'log in' to the ADM to override the controller software algorithm. Optionally, the optical signals can be tapped upon entry to the ADM. A bidirectional ADM can be constructed from two unidirectional ADMs, and may share the same controller. Also, a single, general multi-input multi-output switch can be used to provide an arbitrary mapping between individual input and output optical signals.

Optical add/drop multiplexer/demultiplexer

The invention is directed to a failure detection system and method for detecting malfunction of an optical amplifier module with one or multiple transmission channels. The failure detection system comprises a unit for measuring a performance parameter of the module; a unit for providing an expected performance parameter; and a comparator unit for receiving the performance parameter and the expected performance parameter and producing an error signal when the performance parameter substantially departs from the expected performance parameter. The system also includes a display/alarm unit for receiving the error signal and accordingly signaling failure of the module. The performance parameter is an output value of the module; a correspondence between an output value and an input value for a transmission channel; a figure of merit (FOM.sup.t=t); a set of gains (g) for all transmission channels; and the dynamic range of the amplifier module.

Method of determining optical amplifier failures

A digital controller for an injection laser diode. The controller maintains the laser diode average and peak power levels constant in spite of temperature and/or aging effects. A pseudo-random sequence is superimposed on the `0` and/or `1` current levels to the laser diode and the optical output is detected by a back facet monitor. The detected signal is compared with preset references and a feedback signal is used to control both the bias current and the modulation current.

Digital control of laser diode power levels

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Ottawa, Canada

Richard A Habel