Abstract: Disclosed herein are coherent transceivers and methods of using the same. One exemplary coherent transceiver may be provided with a coherent transmitter operable to transmit a first optical signal and a coherent receiver comprising a processor executing processor-executable code that when executed causes the processor to receive a second optical signal, the second optical signal being a reflection of the first optical signal, analyze the second optical signal to determine a first parameter indicative of a chromatic dispersion of the second optical signal, and determine a second parameter based on the first parameter. The second parameter may be indicative of a distance travelled by the first optical signal and the second optical signal through one or more fiber optic link having a known first location.

Abstract: A method is described in which a coherent transmitter transmits a first optical signal having customer data through a fiber optic link. A control signal is provided to the coherent transmitter to cause the coherent transmitter to transmit a second optical signal devoid of customer data. A reflection of the second optical signal is detected via the coherent receiver. Then, a chromatic dispersion of the reflection of the second optical signal is determined and correlated with known parameters indicative of an amount of chromatic dispersion per unit length of the fiber optic link to determine a distance travelled by the second optical signal.

Abstract: An optical network element for a hardware configured optical network includes a first optical port that receives an input optical signal comprising receive control information from the hardware configured optical network. A demodulator optically coupled to the first optical port decodes the receive control information for configuring the optical network element. A modulator having an electrical modulation input that receives transmit control information imparts a modulation onto an optical carrier thereby generating a transmit optical control signal representing the transmit control information. A second optical port transmits the transmit optical control signal representing the transmit control information to the hardware configured optical network.

Abstract: The present invention relates to a fiber branch structure for spatial optical communication for transmitting information by emitting communication light. The fiber branch structure is provided with: a light emitter configured to emit communication light; a light emission controller configured to control the light emitter; an optical fiber configured to transmit the light emitted from the light emitter; a distributor configured to distribute the light, the distributer being optically coupled to an output terminal of the optical fiber; and an optical fiber group optically coupled to a plurality of output terminals of the distributor. According to the present invention, a communication area can be established without blind spots. That is, the fiber branch structure for spatial optical communication according to the present invention includes an optical fiber group optically coupled to a plurality of output terminals of the distributor.

Abstract: A transmitter may include a digital signal processor (DSP) to generate an electrical signal associated with a beacon and a data signal. The transmitter may include an electro-optical component to convert the electrical signal to an optical signal to be transmitted by the transmitter. The beacon and the data signal may be on a common wavelength in the optical signal. A power of the beacon within the optical signal may be based on a value of an amplitude modulation factor applied to the beacon by the DSP in association with generating the electrical signal.

Abstract: A DFB laser DC-coupled output power configuration scheme belongs to the field of laser drivers in optical communication integrated circuits. The present invention solves the existing problems in the conventional DFB laser power supply configuration scheme. The power configuration scheme of the present invention utilizes an external or internal power configuration unit to provide two electric DC power supplies with a fixed voltage difference for the transmitting unit TX of the DFB laser and the optical transceiver integrated chip, and at the same time optimizes the transmitting unit TX. The optimization scheme is that: the transistors in the transmitting unit TX are all low-voltage high-speed tubes, the transmitting unit TX includes a negative capacitance structure composed of capacitors C1 and C2, serving as an auxiliary structure for improving bandwidth. After optimization, the minimum voltage of the power supply voltage port TVCC of the transmitting unit TX is 2.7V.

Abstract: An example system includes an optical gateway, plurality of hub transceivers, and a plurality of edge transceivers. The optical gateway is operable to receive a plurality of signals from an optical communications network at a plurality of ports of the optical gateway, where each port of the optical gateway comprises one or more respective photodiodes. Further, the optical gateway is operable to determine, for each port, a respective link of the optical communications network communicatively coupling the port with at least one hub transceiver of the plurality of hub transceivers or with at least one edge transceiver of the plurality of edge transceivers, and an identity of the at least one hub transceiver or the at least one edge transceiver.

Abstract: An optical repeater is a C+L-band repeater inserted between a first transmission path fiber and a second transmission path fiber. The optical repeater includes: a first optical fiber amplifier inserted in a first line, for amplifying a C-band signal; a second optical fiber amplifier inserted in a second line, for amplifying an L-band signal; a third optical fiber amplifier inserted in a third line, for amplifying a C-band signal; a fourth optical fiber amplifier inserted in a fourth line, for amplifying an L-band signal; and a first loopback means provided between an input to the first optical fiber amplifier or an output from the first optical fiber amplifier and an input to the third optical fiber amplifier or an output from the third optical fiber amplifier.

Abstract: Embodiments for adaptive inline modulation tuning for optical interfaces is described. The inline modulation tuning is provided by optical nodes, where the optical nodes exchange optical modulation information and node ability information between optical devices in a node pair. An optimal modulation scheme for the node pair is selected based on modulation abilities of each node and associated transceiver, as well as a link quality and performance observed for the optical link.

Abstract: An optical transmission device includes a first detector, a generator, a second detector, and a controller. The first detector detects optical output power of an optical signal for each channel for input to a Mach-Zehnder unit that has asymmetric optical waveguides. The generator superimposes, based on the detected optical output power for each of the channels, a dither signal onto an optical signal in a specific channel from among the plurality of channels for input to the Mach-Zehnder unit. The second detector detects an amplitude value of the dither signal superimposed onto the optical signal in the specific channel output from the Mach-Zehnder unit. The controller adjusts a phase difference in the Mach-Zehnder unit such that the amplitude value of the dither signal superimposed onto the detected optical signal in the specific channel is less than a predetermined threshold.

Abstract: An optical network communication system utilizes a passive optical network (PON) and includes an optical line terminal (OLT) having a downstream transmitter and an upstream receiver, and an optical network unit (ONU) having a downstream receiver and an upstream transmitter. The downstream transmitter is configured to provide a coherent downlink transmission, and the downstream receiver is configured to obtain one or more downstream parameters from the coherent downlink transmission. The system further includes a long fiber configured to carry the coherent downlink transmission between the OLT and the ONU. The ONU is configured to communicate to the OLT a first upstream ranging request message, the OLT is configured to communicate to the ONU a first downstream acknowledgement in response to the upstream first ranging request message, and the ONU is configured to communicate to the OLT a second upstream ranging request message based on the first downstream acknowledgement.

Abstract: A method and apparatus of fiber nonlinear noise monitoring and an optical receiver is provided. The method includes: acquiring a training set including at least two received signal samples obtained after a transmitting signal passes different simulation transmission scenarios, calculating amplitude noise feature values after a digital signal processing, calculating statistics values of fiber nonlinear noises, marking the amplitude noise feature values; taking the amplitude noise feature values as input of a noise monitoring model, taking marks to which the amplitude noise feature values correspond as target output, and training the noise monitoring model according to samples in the training set, so as to obtain a trained noise monitoring model, and inputting a plurality of amplitude noise feature values of received signals to be monitored into the trained noise monitoring model, so as to obtain statistics values of fiber nonlinear noises to which the received signals to be monitored correspond.

Abstract: A radio over fibre system (5) comprises a base station (10, 20) with a first base station node (10) and a second base station node (20) connected by an optical communication link (30). At least one of the base station nodes (10, 20) comprises an optical transmitter (17, 23). A method of determining an operating parameter for the optical transmitter (17, 23) comprises receiving signal quality parameters for a plurality of user equipments (UE) served by the base station (10, 20). The method determines an operating parameter of the optical transmitter using the determined signal quality parameters of the plurality of user equipments (UE). The operating parameter of the optical transmitter can be a modulation parameter.

Abstract: An apparatus includes multiple ports configured to be coupled to multiple optical fibers and to transmit first optical signals and receive second optical signals over the optical fibers. The apparatus also includes a signal source configured to generate a first additional optical signal for inclusion with the first optical signals. The apparatus further includes a signal detector configured to detect a second additional optical signal included with the second optical signals. In addition, the apparatus includes a switch configured to selectively couple the signal source to one of the ports. The switch is configured to couple the signal source to different ones of the ports in different configurations of the switch.

Abstract: An optical transmitter includes optical modulation means for modulating a laser beam with a driving signal and outputting an optical signal; monitor means for detecting a part of the optical signal and outputting a monitor signal; bias voltage applying means for applying, to the optical modulation means, a bias voltage on which a dither signal is superimposed; average optical intensity detection means for detecting an average optical intensity of the optical signal from the monitor signal; top dither signal detection means for detecting, from the monitor signal, a top dither signal that is superimposed on a waveform with maximum optical intensity included in the optical signal; and bias voltage control means for controlling the bias voltage based on the average optical intensity and the top dither signal.

Abstract: Systems and methods for identifying a pair of nodes of a plurality of nodes of a virtual optical network (VON); identifying i) an optical route between the pair of nodes and ii) a desired availability of the optical route; determining a probability density function (PDF) of a signal-to-noise ratio (SNR) of a signal of the optical route; determining a SNR threshold such that an integration of the PDF of the SNR of the signal above the SNR threshold corresponds to the desired availability of the optical route; determining a plurality of spectral efficiencies that corresponds to the SNR threshold, each spectral efficiency of the plurality of spectral efficiencies associated with a respective modulation format of a plurality of modulation formats; and identifying a particular modulation format of the plurality of modulation formats that corresponds to a maximum spectral efficiency of the plurality of spectral efficiencies.

Abstract: A method for conveying information through an optical fiber link between a transmitter and a receiver of an optical communication system. The method includes generating, by the transmitter, a predetermined spectral change, and inserting the predetermined spectral change into an optical fiber link for transmission to the receiver. A detector associated with the receiver detects the predetermined spectral change in an optical signal received through the optical fiber link, and generates a detection signal in accordance with the detection result. The detector is independent of a digital signal processor of the receiver that is configured to recover data modulated on the optical signal received through the optical fiber link.

Abstract: In order to change opposed communication destinations in a simple structure, an optical module includes an optical collimator to take in and output collimated light and a mirror capable of taking a tilt angle to make the collimated light and the optical collimator be coupled.

Abstract: An optical transmitter transmits to an optical receiver a multi-carrier modulated signal light by driving a light source with a modulated signal modulated with a multi-carrier modulation scheme. The optical receiver monitors reception characteristic of any of subcarrier signals included in the modulated signal and transmits a monitor result to the optical transmitter. The optical transmitter controls drive conditions of the light source based on the monitor result received from the optical receiver.

Abstract: OADM processes input light containing reference light and multiplexed optical signals. A splitter splits the input light to generate first and second input light. A receiver generates an electric signal representing the second input light. An estimator estimates a difference in optical frequency between the reference light and a specified optical signal based on the electric signal. Alight source generates first and second light. An optical frequency of the second light is shifted by the estimated difference with respect to that of the first light. A demodulator generates a dropped signal representing the specified optical signal. A drive signal generator generates a drive signal in accordance with an inverted signal of the dropped signal. A modulator modulates the second light with the drive signal to generate a modulated optical signal. The first input light, the first light and the modulated optical signal are input to non-linear optical medium.

Abstract: Disclosed are an optical network unit included in an OFDMA-PON system that is capable of reducing OBI (optical beat interference), and a method of controlling the optical network unit. The disclosed optical network unit includes: a signal generator part configured to generate an electrical signal carrying transmission data; an RF tone generator part configured to generate an RF tone; a combiner part configured to combine the electrical signal and the RF tone; and a photoelectric converter part configured to convert the combined signal of the electrical signal and RF tone into an optical signal.

Abstract: One embodiment provides an apparatus for coupling a trunk network to a plurality of leaf passive optical networks (PONs). The apparatus includes one or more uplink ports for coupling to the trunk network, a plurality of downlink ports with a respective downlink port coupled to a leaf PON, and a switch chip for interconnecting the uplink ports and the downlink ports. The switch chip acts as a simple Ethernet switch with no traffic control ability.

Abstract: A method of controlling a multiple sub-carrier optical channel of an optical communications system. The multiple sub-carrier optical channel includes at least two sub-carriers modulated with respective sub-channel data streams within a spectral range allocated to a single optical channel of the optical communications system. A transmitter modem of the optical communications system applies a respective dither signal to each sub-carrier. A receiver modem of the optical communications system detects a respective quality metric of each sub-carrier. A respective optimum power level of each sub-carrier is estimated based on the applied dither signals and the detected quality metrics. A respective power level of each sub-carrier is then adjusted in accordance with the estimated respective optimum power level of each sub-carrier.

Abstract: An optical system may include optical transmitters to provide respective optical signals. Each of the respective optical signals may provide one or more carriers in an optical channel. The optical channel may include multiple carriers associated with the respective optical signals. First and second carriers, of the multiple carriers, may have a particular carrier space width. The particular carrier space width may include a frequency error associated with one or more optical signals of the respective optical signals. The optical system may include a control system to determine the frequency error and cause one or more of the optical transmitters to adjust the particular carrier space width based on the adjusted frequency error.

Abstract: A measurement system that includes a power source and a power meter, said power source is configured to generate both a measurement signal and a power source communication signal, and said power meter is in communication with said power source and configured to receive both said measurement signal and said power source communication signal.

Abstract: According to an aspect of an embodiment, a method of modulating supervisory data onto an optical signal includes increasing a first power level of a first polarization component of an optical signal based on supervisory data. The method further includes decreasing a second power level of a second polarization component of the optical signal based on the supervisory data. The decrease in the second power level is substantially the same as the increase in the first power level such that a total power of the optical signal is substantially constant.

Abstract: An optical node apparatus that establishes an optical path between a first optical node and a second optical node in an optical network include a frequency modulation unit that superimposes a supervisory signal on a main signal by frequency-modulating the main signal, and a frequency demodulation unit that frequency-demodulates the supervisory signal superimposed on the received main signal.

Abstract: An optical modulation device includes a generating circuit that generates a low-frequency signal, an average value of amplitude as an alternating-current component of the low-frequency signal being different from a center value of the amplitude of the low-frequency signal, a superimposing unit that superimposes the low-frequency signal on a data signal, an optical modulator that modulates, using the superimposition of the low-frequency signal by the superimposing unit, light from a light source and outputs a light signal, a calculating circuit that calculates an amplitude average value and an amplitude center value of a low-frequency component obtained from the light signal output by the optical modulator, and a controller that controls a bias voltage of the optical modulator such that the amplitude average value is brought closer to the amplitude center value of the frequency component calculated by the calculating circuit.

Abstract: A system and method is disclosed that allows for the monitoring, analyzing and reporting on performance, availability and quality of optical network paths. The correlation of PM parameter metrics to client connections, coupled with threshold-based alarm generation provides a proactive and predictive management, reporting and analyzing of the health and effectiveness of individual path connections to alert Operational Support (OS) staff and/or customers to signal degradation and impending Network Element (NE) failures. The system and method performs in real-time processing intervals required for alarm surveillance in a telecommunications network.

Abstract: A multi-channel optoelectronic device is configured to establish a redundant status link with a remote device. The optoelectronic device can transmit N transmit optical signals to the remote device over a plurality of transmit channels and receive N receive optical signals from the remote device over a plurality of receive channels. The optoelectronic device includes one or more spare transmit and receive channels. When used with a remote device having spare transmit and receive channels, each device can establish a status link with the other and use the status link to switch out transmit and/or receive channels to identify and permanently switch out the worst transmit and/or receive channels. Alternately, the device can interoperate with a non-status-link enabled remote device by determining that the remote device is not status-link enabled, transitioning to a low transmit power mode, and transmitting and receiving over a plurality of default transmit and receive channels.

Abstract: A remotely controlled fiber testing method has the steps of: building a fiber network system including a local fiber station and a remote fiber station; sending a modulated signal to the remote fiber station by the local fiber station; demodulating the modulated signal to obtain a control command by the remote fiber station; executing the control command to obtain a testing result by the remote fiber station; modulating the testing result and sending the testing result back to the local fiber station; and demodulating the testing result by the local fiber station. Only one technician appointed to the local fiber station is sufficient to do the testing action. Therefore, the personnel cost is effectively reduced.

Abstract: A method includes generating a test signal and modulating the test signal. The method may also include transmitting the test signal on an optical path, where the optical path may include a number of add-drop multiplexer devices and amplifiers. The method may also include receiving the test signal at a destination device and converting the received test signal into an electrical signal. The method may further include identifying a portion of the electrical signal that is associated with the modulated test signal.

Abstract: A wavelength-division multiplexing transmission device including: a dummy light source configured to emit and quench dummy light; a monitoring unit configured to monitor an optical level relating to the received wavelength-division multiplexed light; a dummy light controller configured to control the dummy light source to emit dummy light in case where the monitoring unit determines based on the monitored optical level that the wavelength-division multiplexed light is in a condition of input interruption; and a multiplexer configured to multiplex the light of the wavelength modulated based on the transmission data and the dummy light emitted by the dummy light source, wherein the transmitter transmits wavelength-division multiplexed light generated by the multiplexer.

Abstract: A communication device may be operable to determine, in an optical module, a signal quality associated with each of one or more host transmitter filters in a host circuit. The signal quality may be communicated from the optical module to the host circuit via a management interface. The communication device may control, in the host circuit, configuration of each of the host transmitter filters based on the signal quality. The communication device may be operable to determine, in the host circuit, a signal quality associated with each of one or more module transmitter filters in the optical module. The signal quality associated with each of the module transmitter filters may be communicated from the host circuit to the optical module via the management interface. The communication device may control, in the optical module, configuration of each of the module transmitter filters based on the signal quality.

Abstract: A system and method for stabilizing a plurality of output frequencies (wavelengths) of a plurality of lasers (106). The laser beams are combined using optical multiplexer (110) and coupled into length-imbalanced (armlength-mismatched) Mach-Zehnder interferometer (MZI) (114) having an optical modulator (e.g. AOM) (122) in one of its arms. The output of the MZI is divided into corresponding beams via optical demultiplexer (128) and each beam is detected by a respective photo-diode (PD) (134). The individual electric signals, so generated, are demodulated using a corresponding plurality of phase-responsive devices (138) and the resulting phase-signals are directed to a plurality of servo-controllers (148) to control the central frequency of the respective lasers (106) via a corresponding plurality of feedback loop circuits (150). The lasers (106) can have different central frequencies which can also be individually tunned using offset modules (141) in the phase-responsive devices (138).

Abstract: An optical apparatus comprising, converting units converting electrical signals into signal lights with different wavelength, polarization control units controlling polarizing states of the signal lights into polarization controlled lights respectively, an optical multiplexer multiplexing the polarization controlled lights into a multiplexed light, an optical branching unit branching the multiplexed light and outputting a branched light, a polarizing unit extracting only signal lights of the specified polarizing state from the branched light into an extracted light, and a control unit detecting intensity of the extracted light. Pilot signals are applied to modulate the electrical signals or the polarization controls. The polarization control units controls the polarizing states of the signal lights based on the pilot signal frequencies of the detection result by the control unit.

Abstract: A system and method for managing the selection of ghost channels in an optical communication system, including components configured to collect one or more first data values indicating the validity of an optical communication channel within a first degree of a node in the optical communication system, collect one or more second data values indicating the optical power level of the optical communication channel, transmit the first and second data values to a second degree of the node, receive the first and second data values at the first degree, and aggregate the first and second data values for the first degree and the second degree at the first degree.

Abstract: A system is provided for identifying signal propagation information. The system includes at least one component configured to receive an optical input signal and to emit an optical output signal. The emitted optical output signal is representative of the optical input signal, and is associated with characteristic information indicative of the component. A processor is also included, the processor being configured to sense the optical output signal and correlate the characteristic information with said component.

Abstract: An apparatus comprising a plurality of optical transmitters coupled to a fiber, a signal generator coupled to the optical transmitters and configured to provide a single pilot tone to the optical transmitters, and a processor positioned within a feedback loop between the fiber and the optical transmitters, the processor configured to adjust a wavelength for each of the optical transmitters to lock the wavelengths. An apparatus comprising at least one processor configured to implement a method comprising receiving an optical signal comprising a pilot tone, detecting an amplitude and a phase of the pilot tone, calculating a quadrature term using the amplitude and the phase, and wavelength locking the optical signal using the quadrature term.

Abstract: An apparatus for driving a wavelength-independent light source is provided. The apparatus includes a seed light signal generation unit configured to generate seed light signals with one or more wavelengths based on a wavelength identification signal, a wavelength light detection unit configured to detect the wavelength identification signal from the seed light signals, an extraction unit configured to extract wavelength information corresponding to the detected wavelength identification signal and extract a driving condition of a wavelength-independent light source corresponding to the extracted wavelength information, and a driving unit configured to drive the wavelength-independent light source according to the extracted driving condition.

Abstract: A polarized-wave-multiplexing optical transmitter including: an optical combiner generating a polarized-wave-multiplexed optical signal by polarized-wave-multiplexing a first optical modulation signal and a second optical modulation signal; an optical power fluctuation portion fluctuating optical power of the first optical modulation signal and the second optical modulation signal periodically; a total-optical-power detection portion detecting fluctuation amount of total optical power of the polarized-wave-multiplexed optical signal; and an optical power controller reducing an optical power difference between the first optical modulation signal and the second optical modulation signal based on detection result of the total-optical-power detection portion.

Abstract: A power-saving mode flag generating unit 101e sets a power-saving mode flag to active (non power-saving mode, turning on the power-source) when it receives a reset signal from a MAC unit 102. Furthermore, the power-saving mode flag generating unit 101e sets the power-saving mode flag to sleep (power-saving mode, turning off the power source) in accordance with a signal-interrupt detection signal obtained by the signal-interrupt detecting unit 101f1 of the packet monitoring unit 101f. Depending on the state of a packet, the power-saving mode flag generating unit 101e changes the power-saving mode flag to active or sleep for the data communication area of the packet; however, for the ranging area of the packet, the power-saving mode flag generating unit 101e always sets the power-saving mode flag to active. A pattern discriminating unit 101g discriminates between the data communication area and the ranging area of the packet.

Abstract: A method for monitoring wavelength-division multiplexed (WDM) signal for detecting signal drift of objective signals, including generation of one or more objective signals and a guard signal. The guard signal has a wavelength that is within a range defined by a guard channel. The first and second objective signals and the guard signal are wavelength-division multiplexed to generate a wavelength-division multiplexed signal. The first objective signal, the second objective signal, and the guard signal are assigned to a first multiplexed objective channel, a second multiplexed objective channel, and a multiplexed guard channel, respectively. The wavelength-division multiplexed signal is received by a monitor and then the error rate of the multiplexed guard channel is determined.

Abstract: An optical transmission system method including generating for a tunable laser a pilot tone having an adjustable pilot tone frequency identifying a wavelength division multiplexing channel used by the tunable laser; multiplying the pilot tone with pilot tone data to provide a pilot tone data signal; supplying the pilot tone data signal and a high frequency data signal to the tunable laser generating an optical laser signal output by the tunable laser responsive to the supplied signals; transporting the optical laser signal to a central wavelength to locker; converting the received optical laser signal to provide a pilot tone data signal for wavelength division multiplexing channels demodulated to detect the pilot tone and the pilot tone data for each individual wavelength division multiplexing channel; and identifying the wavelength division multiplexing channel on the basis of the pilot tone frequency of the detected pilot tone and evaluating the pilot tone data.

Abstract: A system for mitigating the effects of polarization hole burning in an optical communication system. The system includes an optical input signal comprising one or more traffic channels, a measurement module configured to check for the existence of ghost channels around the traffic channels, and a ghost channel generation module configured to generate a ghost channel around the traffic channels from amplified spontaneous emission noise of the optical input signal.

Abstract: An optical node apparatus that establishes an optical path between a first optical node and a second optical node in an optical network include a frequency modulation unit that superimposes a supervisory signal on a main signal by frequency-modulating the main signal, and a frequency demodulation unit that frequency-demodulates the supervisory signal superimposed on the received main signal.

Abstract: A method for monitoring a passive optical network (1), PON, having a tree-like structure with a main line (3) and at least two branches (6.1 to 6.3), comprising: transmitting a wake-up signal (10) from the main line (3) to at least two monitoring units (DPM1 to DPM3) arranged in the at least two branches (6.1 to 6.3), in each of the monitoring units (DPM1 to DPM3), detecting the wake-up signal (10) and transmitting a response signal (A, B, C) back to the main line (3), each of the monitoring units (DPM1 to DPM3) generating a pre-defined time delay (?tA to ?tC) between the detection of the wake-up signal (10) and the start of the transmission of the response signal (A, B, C), and receiving the response signals (A, B, C) at the main line (3), the receiving times (R1 to R3) of the response signals (A, B, C) being different from each other, the difference between the receiving times (R1 to R3) being adjusted by the pre-defined time delays (?tA to ?tC) of the monitoring units (DPM1 to DPM3).

Abstract: The invention relates to a method for controlling the center wavelength of at least one narrow band WDM optical channel transmitting device in a WDM network. A reflected signal portion of a WDM channel signal is evaluated at the location of a WDM transmitting device. In order to generate the reflected signal portion, the optical multiplexing device or an additional reflective filter may be used, the additional filter revealing a low reflectivity at the desired channel center wavelength and a sharply increasing reflectivity adjacent thereto. The center wavelength of the WDM transmitting device is tuned to this target center wavelength by wavelength-modulating the center wavelength with a predetermined low modulation frequency and predetermined wavelength amplitude. The center wavelength of the WDM transmitting device is tuned such that the first order modulation frequency component of the reflected signal portion is minimized.

Abstract: This disclosure describes techniques for providing a communication path for upstream communications originating from a node of an optical network. In particular, methods and devices are described for combining upstream communications originating from the node of the optical network with upstream communications originating from subscriber devices coupled to the node. The upstream communication originating from the node may, for example, include status information about the node. The upstream communication, which may include status information about the node, essentially piggy-backs onto upstream communication originating from the subscriber devices coupled to the node.

Abstract: A lock-in ratio measurement system including a plurality of channels. Each of the channels generates and transmits a radiation signal modulated by a sequence of tones. The sequence of tones for each channel being unique in time to that respective channel. Each respective modulated signal is absorbed/reflected from a target or medium and received. Each channel computes a lock-in value based on the received modulation signal. The lock-in values are used to compute ratios between the channels for characterizing a target or medium.