Abstract: A fiber optic inspection apparatus includes a male connector with a protruding pin or a female connector with a plug hole, a casing, an inspection means, a first control unit and a second control unit. The casing has an accommodating space for installing the inspection means, first control unit and second control unit, and a connecting hole. The inspection means has a connecting end and a pair of moving guide pins, and the connecting end has two through holes for passing the moving guide pins and switching the status of protruding from or being received in the through holes. The first control unit is for fixing the inspection means and coupling the moving guide pins, and a control button is extended from the second control unit and has a side linked with the first control unit for switching the position of the two moving guide pins.

Abstract: Various embodiments include apparatus and methods to measure pressure using an optical fiber. The optical fiber can be structured with fiber Bragg gratings arranged along the optical fiber. Optical signals can be transmitted through the optical fiber, where the optical signals have a wavelength of a slow-light peak of a respective one of the fiber Bragg gratings. Signals resulting from the optical signals transmitted through the optical fiber can be detected and a value of pressure from the detected signals can be determined.

Abstract: Optical time domain reflectometer (OTDR) systems, methods and integrated circuits are presented for locating defects in an optical cable or other optical cable, in which a first optical signal is transmitted to the cable and reflections are sampled over a first time range at a first sample rate to identify one or more suspected defect locations, and a second optical signal is transmitted and corresponding reflections are sampled over a second smaller time range at a higher second sample rate to identify at least one defect location of the optical cable for relaxed memory requirements in the OTDR system.

Abstract: An optical transmission apparatus includes: an optical amplifier configured to amplify a wavelength multiplexing light to be transmitted, the wavelength multiplexing light being input thereto; a combining unit configured to combine a plurality of non-signal lights in such a way that angles formed between polarization planes of the plurality of non-signal lights of a wavelength of wavelengths belonging to an amplification band of the optical amplifier become equal, the wavelength being different from a wavelength of a polarization multiplexing signal light; and a wavelength multiplexer configured to generate the wavelength multiplexing light to be input to the optical amplifier by multiplexing the plurality of non-signal lights combined by the combining unit and the polarization multiplexing signal light.

Abstract: A launch cable assembly for use with an MPO switch and OTDR to test a multi-fiber cable, which includes a mandrel around which is wrapped between twenty-five and two hundred feet of multiple fiber optic strands, where the mandrel and fiber optic strands are housed within a housing, the fiber optic strands are in optical communication with a port in the housing, the fiber optic strands exit the housing from a fiber exit in the housing, and the fiber optic strands terminate in an assembly connector, which is preferably a standard MPO connector.

Abstract: Techniques for analyzing output modal content of optical fibers that support more than one spatial mode are disclosed. These techniques are based on spatially resolving interference between co-propagating modes and constructing a spatial beat pattern between the co-propagating modes. By doing so, these techniques provide information about the modes that propagate along the optical fiber.

Abstract: There is described a distributed optical fiber sensor for detecting one or more physical parameters indicative of an environmental influence on a sensor optical fiber, as a function of position along the sensor fiber. The sensor uses probe light pulses of different wavelengths. At least some of the probe light pulses may also be of different pulse lengths. The relative phase bias between interferometric signals in backscattered probe light of different wavelength pulses may also be controlled.

Abstract: Methods and systems for use in monitoring a physical interface between a structural opening and a medium. A system is provided comprising a medium operable to pass through a plurality of structural openings and a sensing system associated with the medium. The sensing system includes at least one physical interface positioned at locations where the medium passes through one of the plurality of structural openings. The at least one physical interface includes at least one waveguide for monitoring changes to the at least one physical interface.

Abstract: A distributed optical fiber sound wave detection device is provided with an optical pulse emission unit that causes an optical pulse to be incident into the optical fiber, and a Rayleigh scattered light reception unit that receives Rayleigh scattered light produced inside the optical fiber. The optical pulse emission unit outputs the optical pulse that is modulated using a code sequence which has a predetermined length and by which the optical pulse is divided into a plurality of cells. The Rayleigh scattered light reception unit includes a phase variation derivation unit that performs demodulation corresponding to the modulation in the optical pulse emission unit on the Rayleigh scattered light and determines a phase variation thereof from the demodulated Rayleigh scattered light, and a sound wave detection unit that determines a sound wave that has struck the optical fiber from the phase variation determined by the phase variation derivation unit.

Abstract: A Wavelength Adaptation Module and a method therein for adapting an Optical Time Domain Reflectometry, OTDR, signal for supervision of Optical Network Terminals, ONTs, in a Passive Optical Network, PON, are provided. The wavelength of the OTDR signal is adapted to have a pre-selected wavelength to enable a splitter in a remote node to forward the OTDR signal to a dedicated group of ONTs in the PON, thereby supervising the fiber links between the remote node and the dedicated group of ONTs. Likewise, a remote node and a method therein for receiving an OTDR signal having a pre-selected wavelength from the Wavelength Adaptation Module and for outputting the OTDR signal to a dedicated group of ONTs with regards to the pre-selected wavelength of the received OTDR signal are provided.

Abstract: A system and method including a semiconductor laser source configured to output radiation over a range of wavelengths at a prescribed rate to a device under test. The prescribed rate is sufficiently above environmental frequency bands. A detector is configured to detect output radiation from the device under test to obtain a detected signal associated with at least one physical property associated with the incident radiation over the range of wavelengths at the prescribed rate. The detected signal includes environmental signal and target signal from the device under test. A processor isolates the environmental signal from the detected signal; and processes the target signal to obtain dispersion information of the device under test. A system output is configured to output the dispersion information of the device under test.

Abstract: Fault analysis of a Passive Optical Network comprising Optical Network Terminal(s) uses Optical Time Domain Reflectometry (OTDR). An OTDR measurement signal is supplied to a multistage splitter having a ratio 2:Nroot. At least one drop link which is connected to the multistage splitter comprises one or more sub-splitters which having a ratio 1:Nbranch. A new event location is determined based on the OTDR measurement signal by analyzing OTDR measurement data relating to the sub-splitter based on distance from the multistage splitter and to the sub-splitter. A fault magnitude is calculated for a given location by subtracting an event magnitude obtained from the new OTDR measurement from a reference OTDR measurement and taking into account the number of drop links connected to the last splitter stage and to the sub-splitter in the reference measurement and the new measurement, thereby enabling determination of position and severity of the fault locations.

Abstract: A method of measuring optical properties of a multi-mode optical fiber during processing of the fiber is described. The method includes: transmitting a light signal through one of the draw end of the multi-mode fiber and a test fiber section toward the other of the draw end and the test fiber section; and receiving a portion of the light signal at one of the draw end and the test fiber section. The method also includes obtaining optical data related to the received portion of the light signal; and analyzing the optical data to determine a property of the multi-mode fiber.

Abstract: Proposed is a method of optical data transmission. The method comprises different steps. A first optical signal and a second optical signal are generated, such that the optical signals possess a same wavelength, respective phases, which are modulated in dependence on respective data values, and respective polarization states, which are essentially orthogonal to each other. A combined optical signal is generated, by combining the optical signals, such that the combined optical signal possesses a polarization state with a predetermined variation. The combined optical signal is transmitter over an optical transmission line and received. Two time-discrete sampled signals are generated, by sampling the received optical signal along two orthogonal polarization planes. Two filtered signals are generated, by filtering the time-discrete sampled signals in the time-discrete domain, using a function that is indicative of the respective predetermined variation.

Abstract: The invention relates to methods and systems for measuring and/or monitoring the chemical composition of a sample (e.g., a process stream), and/or detecting specific substances or compounds in a sample, using light spectroscopy such as absorption, emission and fluorescence spectroscopy. In certain embodiments, the invention relates to spectrometers with rotating narrow-band interference optical filter(s) to measure light intensity as a function of wavelength. More specifically, in certain embodiments, the invention relates to a spectrometer system with a rotatable filter assembly with a position detector rigidly attached thereto, and, in certain embodiments, the further use of various oversampling methods and techniques described herein, made particularly useful in conjunction with the rotatable filter assembly.

Abstract: For example, of a first intensity distribution waveform WF1 indicated by a distance distribution of an intensity of light which returns to one end of a core of a multicore fiber, and a second intensity distribution waveform WF2 indicated by a distance distribution of an intensity of light which returns to the other end of the core, the second intensity distribution waveform WF2 is inverted. Further, for example, an inverted intensity distribution waveform WF3 which is inverted and the first intensity distribution waveform WF1 which is not inverted are added.

Abstract: Embodiments of the invention include systems and methods for measuring or otherwise calculating polarization mode dispersion (PMD) of an optical fiber, or other device, by comparing the optical signal through the PMD element with the optical signal obtained directly from the transmitter, and calculating the PMD from the discrepancy between the two. Any distortions on the transmitter signal are effectively calibrated out, increasing measurement accuracy over conventional approaches.

Abstract: A photonic integrated circuit apparatus is disclosed. The apparatus includes a photonic chip and a lens array coupling element. The photonic chip includes a waveguide at a side edge surface of the photonic chip. The lens array coupling element is mounted on a top surface of the photonic chip and on the side edge surface. The coupling element includes a lens array that is configured to modify spot sizes of light traversing to or from the waveguide. The coupling element further includes an overhang on a side of the coupling element that opposes the lens array and that abuts the top surface of the photonic chip. The overhang includes a vertical stop surface that has a depth configured to horizontally align an edge of the waveguide with a focal length of the lens array and that vertically aligns focal points of the lens array with the edge of the waveguide.

Abstract: A fiber optic end face inspection probe that includes a power control, an image control; a probe adaptor and probe end extending from a housing; an electronics module that includes a microprocessor, a memory and an optional wireless transmitter; and an autofocus camera system that includes a lens, a motor adapted to move the lens in order to focus the image through the lens, and an image sensor that is adapted to accept the image passing through the lens and transmit this image to the electronics module.

Abstract: A method for locating a fault of a submarine cable, a device, and a communication system are provided. A light pulse output by a Repeater (RPT) is incident to a location of a fault as a probe light pulse. The RPT obtains a time difference between the probe light pulse and the reflected probe light pulse, and sends the time difference to a terrestrial Submarine Line Terminal Equipment (SLTE) so that the SLTE may easily locate the fault according to principles of an Optical Time Domain Reflector (OTDR). Compared with the prior art, the method may locate the fault of the submarine cable more quickly and accurately, so that maintainers may maintain the submarine cable in time.

Abstract: There are provided a device for monitoring an optical link fault and a method thereof. According to an embodiment of the invention, the device for monitoring an optical link fault and the method thereof apply an optical link fault monitoring signal to an optical link and precisely identify a type of the fault using waveforms of a reflected signal returned from the optical link or a wavelength dependence of reflected signal intensity.

Abstract: The present invention provides an optical time-domain reflectometry signal detection method, including the following steps: modulating, under the control of a correlation code pattern sequence respectively, n detection optical signals transmitted by detection light sources of different wavelengths into n pulse optical signals, where n is a natural number greater than or equal to 2; combining the n pulse optical signals and outputting a detection optical signal to an optical fiber under test; receiving a backscattered optical signal from the optical fiber under test and dividing the backscattered optical signal into n optical signals according to wavelengths; and performing correlation processing on the n optical signals according to the correlation code pattern sequence and outputting a correlation optical time-domain reflectometry signal. The present invention further provides an optical time-domain reflectometry signal detection apparatus.

Abstract: An optical communication system has a power dissipating element that is thermally coupled to an optical transmitter. The currents supplied to the transmitter and the power dissipating element are controlled such that the sum of such currents is constant. Accordingly, temperature fluctuations in the transmitter due to patterns in the transmitted data are prevented or at least reduced, thereby reducing thermal tails on measurements. In one exemplary embodiment, a light source is used as the power dissipating element, and the output of such light source is beneficially used to probe another optical fiber or to enhance the OTDR performance or analysis.

Abstract: A multi-function optical tool may be used for example for built-in fault detection and transceiver source characterization in local optical communication networks. A single device provides swept-heterodyne optical spectrum analysis (SHOSA) and optical frequency-domain reflectometry (OFDR) in an efficient, low-cost package by utilizing a common interrogation laser source, common optical components, and common, low-bandwidth acquisition hardware. The technology provides significant cost, space, and labor savings for network maintainers and technicians.

Abstract: A measuring method of a hole diameter of a holey optical fiber includes calculating an arithmetical mean value I(x) from two backscattering light intensities at a position x of two backscattering light waveforms of the holey optical fiber, in which the two backscattering light waveforms are obtained by OTDR measurement; and obtaining the hole diameter at the position x, based on a correlation between an arithmetical mean value I(x) and an hole diameter of the holey optical fiber that is obtained in advance.

Abstract: An OTDR device and method for characterizing one or more events in an optical fiber link are provided. A plurality of light acquisitions is performed. For each light acquisition, test light pulses are propagated in the optical fiber link and the corresponding return light signals from the optical fiber link are detected. The light acquisitions are performed under different acquisition conditions, for example using different pulsewidths or wavelengths. Parameters characterizing the event are derived using the detected return signal from at least two of the plurality of light acquisitions.

Abstract: A long-distance polarization and phase-sensitive reflectometry based on random laser amplification for extending a sensing distance includes a long-distance polarization and phase-sensitive reflectometry of a distributed Raman amplification based on optical fiber random lasers generated by unilateral pumps, a long-distance polarization and phase-sensitive reflectometry of a distributed Raman amplification based on optical fiber random lasers generated by bilateral pumps, and a long-distance polarization and phase-sensitive reflectometry of a Raman amplification based on a combination of optical fiber random lasers generated by unilateral pumps and a common Raman pump source, which are applied in optical fiber perturbation sensing and have a capability of greatly improving a working distance of a sensing system and a high practicability.

Abstract: This disclosure concerns a cleaning and inspection system for fiber optics that is rapid, reliable and useful for various types of fiber optics. In an embodiment, the system includes a wide field of view (FOV) camera to image the ferrule and rapidly locate the fiber ends and a narrow FOV camera to provide detailed inspection of fiber ends. A cleaning module with a cleaning tip and a cleaning media that is drawn through the tip is used to clean the fiber ends. Images captured by the dual cameras are automatically enhanced and analyzed to determine the effectiveness of the cleaning process and to identify the types and quantity of defects present. In another embodiment, a single higher resolution camera is provided with a lens that can image an entire fiber array and yet enable defects to be detected by analysis of sub-images of each fiber in the fiber array.

Abstract: The present invention relates to distributed acoustic sensing using fiber-optic system. More particularly, the present invention describes use of frequency pulse labeling techniques and wavelength pulse labeling techniques for providing high bandwidth acoustic sensing in applications such as infrastructure monitoring. In one embodiment, a segmented sensing fiber is used with corresponding circulators in an architecture that controls the interrogation of each segment of the fiber. In another embodiment, a single continuous length of sensing fiber is used, but a plurality of pulse sequences with different wavelengths are used to interrogate. In both configurations, heterodyne beat frequency components are rejected by a processing scheme, resulting in a simple direct measurement of baseband phase information.

Abstract: A lithographic apparatus includes: an illumination system configured to condition a radiation beam; a support constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam; a substrate table constructed to hold a substrate; a projection system configured to project the patterned radiation beam onto a target portion of the substrate, and a deformation sensor to determine deformations of an object of the lithographic apparatus, wherein the deformation sensor includes at least one optical fiber arranged on or in the object, the optical fiber including one or more Bragg gratings, and an interrogation system to interrogate the one or more Bragg gratings.

Abstract: Systems and methods are described for reducing coherence effect in narrow line-width light sources through various modulation techniques. The systems and methods can include a narrow line-width laser source with a thermoelectric cooler thermally coupled thereto and a controller communicatively coupled to the thermoelectric cooler. The controller is configured to provide a varied input signal to the thermoelectric cooler to reduce coherence of the narrow line-width laser source by artificially broadening the narrow line-width on a time averaged basis. The systems and methods can also include direct modulation of the narrow line-width laser source. The systems and methods can include a narrow line-width Optical Time Domain Reflectometer (OTDR). The systems and methods can also include direct modulation of the narrow line-width laser source with or without the varied input signal to the thermoelectric cooler.

Abstract: The present disclosure relates to calibration assemblies and methods for use with an imaging system, such as an endoscopic imaging system. A calibration assembly includes: an interface for constraining engagement with an endoscopic imaging system; a target coupled with the interface on as to be within the field of view of the imaging system, the target including multiple of markers having calibration features that include identification features; and a processor configured to identify from first and second images obtained at first and second relative spatial arrangements between the imaging system and the target, respectively, at least some of the markers from the identification features, and using the identified markers and calibration feature positions within the images to generate calibration data.

Abstract: There is provided a bi-directional optical reflectometric method for characterizing an optical fiber link.

Abstract: A method of characterizing and correcting effective radius variations in a surface nanoscale axial photonic (SNAP) device that comprises a plurality of separate optical microdevices includes the steps of characterizing an as-fabricated SNAP device to determine local effective radius values of the plurality of separate optical microdevices, calibrating the as-fabricated SNAP device to determine a correction factor defined as a change in effective radius associated with a predetermined corrective treatment and then correcting individual microdevices by the application of a number of refractive index-changing treatments, the number of treatments applied to individual microdevices determined by the amount of correction required and the correction factor determined in the calibrating step. A number of iterations of the characterizing and correcting operations can be performed, achieving less than an Angstrom variation in effective radius variation. An apparatus for performing the method is also disclosed.

Abstract: A modulation method of an optical modem and a signal transmission apparatus performing the method are disclosed. The modulation method of the optical modem includes an optical interface providing a signal to a light source, a photo detector receiving reflected light by an optical link when output light from the light source based on the provided signal is reflected by the optical link, the photo detector measuring and determining characteristics of the optical link using the reflected light, and the optical modem determining a power level and a modulation method for each subcarrier based on the characteristics of the optical link.

Abstract: A repeater that enables both bi-directional optical time domain reflectometry (OTDR) and loop gain monitoring techniques that may be employed, for example, in particularly long repeater spans. In one embodiment, the repeater includes high loss loopback (HLLB) paths configured to couple test signals between incoming and outgoing fiber paths. The HLLB paths are coupled from the outputs to the inputs of amplifiers within the repeater and couple both OTDR and loopback signals from an outgoing fiber path to an incoming fiber path so that may be returned to line monitoring equipment that transmitted the test signals.

Abstract: A sweep sensor may include a signal source, a propagation medium, and a detector. By transmitting an interrogating signal from the signal source into the propagation medium, detectable disturbances along the medium can physically alter the characteristics of the medium, which may cause a measurable change in the backscattered signal at the detector. Based on the change, it may be possible to locate the geographic origins of the physical disturbances along the propagation medium, or to determine the nature of the disturbances, or both. For example, it is generally possible to estimate the approximate distance between the detector and the disturbance given the time required to obtain the backscattered signal and the velocity of the signal source in the propagation medium. Further, in some embodiments, it is possible to quantify the amount of disturbance.

Abstract: A programmable media includes a processing unit capable of independent operation in a machine that is capable of executing 1018 floating point operations per second. The processing unit is in communication with a memory element and an interconnect that couples computing nodes. The programmable media includes a logical unit configured to execute arithmetic functions, comparative functions, and/or logical functions. The processing unit is configured to detect computing component failures, memory element failures and/or interconnect failures by executing programming threads that generate one or more chaotic map trajectories. The central processing unit or graphical processing unit is configured to detect a computing component failure, memory element failure and/or an interconnect failure through an automated comparison of signal trajectories generated by the chaotic maps.

Abstract: A method of operation of a storage control system includes: determining a bit error rate of a page; calculating a slope based on the bit error rate; and adjusting a threshold voltage for the page based on the slope for reading a memory device.

Abstract: An exemplary optical transmission system comprises an optical subassembly (OSA) coupled to an optical receiver via an optical fiber. The OSA comprises a laser diode configured to transmit optical signals across the optical fiber, and the OSA further comprises an avalanche photodiode (APD) configured to receive optical return signals from the optical fiber. The system further comprises a crosstalk canceller configured to estimate an amount of electrical crosstalk affecting measurements of the return signals in order to cancel such crosstalk from measurements of subsequent optical signals received by the APD.

Abstract: Apparatus and methods to monitor optical intensity within optical fibers in a substantially non-invasive fashion are disclosed. Optical monitors are comprised of thin, conductive coatings applied to transparent substrates and patterned to form pairs of resistive elements, one of which intersects an optical beam propagating through optical fiber cables. Systems of distributed optical monitors interconnecting optical fiber links enable automated monitoring of the optical status across a communications networks.

Abstract: Provided is an optical fiber characteristics measurement device that is provided with: a light source for emitting laser light modulated by a specified modulation frequency; an incident means for receiving the laser light from the light source as continuous light and pulse light from one end and the other end of an optical fiber, respectively; and a light detector for detecting light emitted from the optical fiber, the optical fiber characteristics measurement device measuring the characteristics of the optical fiber using the detection results of the light detector, wherein the optical fiber characteristics measurement device is characterized in being provided with a synchronous detector that extracts, from among the detection signals output from the light detector, detection signals obtained by detecting the light in the vicinity of a measurement point set in the optical fiber, and synchronously detects the extracted detection signals using a synchronization signal having a specified period.

Abstract: A device for shifting the imaging axis of a microscope for inspecting endfaces of a fiber-optic connector having multiple rows of endfaces has a supporting body for receiving a microscope; a first swinging lever mounted on top of the supporting body and rotatable about a first swinging axis perpendicular to the imaging axis of the microscope; a first connecting piece extending from the first swinging lever towards the imaging axis; a second swinging lever pivoted on the first connecting piece and rotatable about a second swinging axis perpendicular to the first swinging axis; and a fitting tip connected to the second swinging lever for interfacing with the fiber-optic connector. Using two sets of biasing means and adjustment drivers, the imaging axis passing through the supporting body and the fitting tip can be shifted in two mutually perpendicular directions to selectively align with any endface of the fiber-optic connector.

Abstract: A method is provided for mapping the position of a customer fiber end on a passive optical network (PON). The method comprises the steps of: connecting an optical reflector to a specific customer fiber end; carrying out an optical time domain reflectometer (OTDR) trace of the a passive optical network utilising a central office OTDR device; identifying a target reflection event in the OTDR trace having an increased amplitude relative to other reflection events in the OTDR trace, consequent upon the presence of the optical reflector; and mapping data associated with the target reflection event to the specific customer.

Abstract: Fiber optic connector assemblies are disclosed that utilize a reverse optical fiber loop within the fiber optic connector to isolate the optical fiber from stresses. In one embodiment, a fiber optic connector assembly includes an optical fiber having a fiber end, and a connector housing, wherein the optical fiber enters the connector housing from a first direction and is secured within the connector housing in a second direction, thereby forming a reverse optical fiber loop that is free to expand or contract within the connector housing. In another embodiment, a fiber optic connector assembly includes an optical fiber having a fiber end, a connector housing, and a substrate within the connector housing. The optical fiber enters the connector housing over a first surface of the substrate then passes by (i.e., crosses) the first surface, and is secured within the connector housing at a second surface of the substrate.

Abstract: A fiber optic tracking system for tracking substantially rigid object(s) is described. The fiber optic tracking system includes a light source, an optical fiber having a sensing component configured to modify optical signals from the light source, the optical fiber being configured to attach to the substantially rigid object, a detection unit arranged to receive the modified optical signals from the sensing component, and a calculation unit configured to determine a pose of the substantially rigid object in six degrees of freedom based on the modified optical signals.

Abstract: A novel optical detection apparatus is disclosed comprising a plurality of photodetectors and a plurality of transimpedance amplifiers wherein the photodetectors and the amplifiers are electrically connected to each other and are located in close proximity to each other, thus allowing the detecting of high frequency optical signals over a large detection area. Further, logical circuitry is disclosed for processing the signals generated from the photodetectors and for determining the strength of incoming light signals on various portions of the detection area.

Abstract: A test apparatus for electro-optical printed circuit boards having optical waveguides comprises a control device, a beamer and a camera, which can be positioned in such a way that light emitted by the beamer can be coupled by means of a first deflecting element to optical waveguides of the circuit board and can be coupled out by means of a second deflecting element into the field of vision of the camera. The beamer is used in a first phase to determine the position for each deflecting mirror of the first deflecting element which a light spot needs to assume in the image projected by the beamer so that the light spot illuminates the deflecting mirror. The beamer is used in a second phase to illuminate at least one deflecting mirror and to carry out the testing of the optical waveguide associated with the at least one deflecting mirror.

Abstract: Techniques and devices for measuring polarization crosstalk in birefringence optical media including polarization maintaining fiber.

Abstract: Proposed is a method of estimating a reflection profile of an optical channel. The method comprises different steps. A measured reflection profile of the optical channel is provided. One or more reflection peaks are estimated within the measured reflection profile. A residual reflection profile is determined, by removing the estimated reflection peaks from the measured reflection profile. Furthermore, a modified residual reflection profile is determined, by modifying one or more estimated crosstalk frequency components within the residual reflection profile. Finally, the estimated reflection profile is determined, by superposing the estimated reflection peaks and the modified residual reflection profile.