Abstract: The present invention provides a fiber-cut detection method, apparatus, and system. When a fiber cut occurs, power of input signal light decreases quickly at a fiber-cut location. When the fiber-cut location is relatively far away from an amplifier, pump light consumption of the input signal light in the remaining fiber reduces due to reduction of the input signal light, which causes an increase of remaining pump optical power in the fiber and an increase of an actual gain value of the amplifier. A gain-locking function of the amplifier works, which decreases pump power of the pump light and maintains a gain of the amplifier unchanged basically. Output optical power of the amplifier decreases quickly with decrease of input optical power, and when power of an output optical signal decreases to power that is lower than preset power of the output optical signal, it is determined that a fiber cut occurs.

Abstract: An access control device includes a time of flight circuit configured to determine a distance information related to a distance between the access control device and a peripheral device. The access control device further includes a control module configured to control a transmission of a modulated light transmit signal by the time of flight circuit to the peripheral device. The modulated light transmit signal includes the distance information determined by the time of flight circuit of the access control device.

Abstract: A method of registering an optical network unit (ONU) in an optical line terminal (OLT). The OLT determines a lane to be used by the ONU based on a transmission rate supported by the ONU, combines or distributes data of a dataflow based on a rate of the lane by comparing the rate of the lane to a rate of the dataflow of a media access control (MAC) client interface, and, when the OLT and the ONU are connected through multiple lanes, transmits and receives data between the OLT and the ONU through channel bonding for more effective use of a network.

Abstract: Techniques are disclosed for enhancing indoor navigation using light-based communication (LCom). In some embodiments, an LCom-enabled luminaire configured as described herein may include access to a sensor configured to detect a given hazardous condition. In response to detection of a hazard, the LCom-enabled luminaire may adjust its light output, transmit an LCom signal, or both, in accordance with some embodiments. A given LCom signal may include data that may be utilized by a recipient computing device, for example, in providing emergency evacuation routing or other indoor navigation with hazard avoidance, emergency assistance, or both. In a network of such luminaires, data distribution via inter-luminaire communication may be provided, in accordance with some embodiments, via an optical interface or other wired or wireless communication means. In some cases, the network may include a luminaire that is not LCom-enabled yet still configured for inter-luminaire communication.

Abstract: A switch configured to connect a plurality of remote radio units with a plurality of main units in a radio access network. The switch comprises a first stage comprising one or more first units configured to receive a signal originating from a remote radio unit, and configured to output one or more spectral component having a wavelength. The switch further comprises a central stage configured to receive the one or more optical wavelength, and transfer the spectral component to an output port determined by the wavelength. The switch further comprises a second stage comprising one or more second units configured to receive the one or more spectral component from the central stage and output a signal towards a main unit. The first unit is configured to control the wavelength of the output spectral component such that the spectral component is transferred by the central stage to a selected one of said second units.

Abstract: A microwave photonic notch filter comprising: a modulator to modulate an optical signal with an electrical signal to generate a first sideband and a second sideband; a configurable optical processor to generate a modified optical signal by adjusting the power of the sidebands to achieve a power difference between first sideband and second sideband and by producing an antiphase relationship between light within two sidebands corresponding to the selected frequency band; an optical resonance to adjust the power of the first sideband of the modified optical signal corresponding to the selected frequency band by a resonance power adjustment to generate a resonance output signal; an optical-to-electrical converter to generate a copy of the electrical signal with suppressed frequency components within the selected frequency band; and a control unit to re-configure the configurable optical processor to adjust the power difference between two sidebands towards the resonance power adjustment.

Abstract: An optical data transmitter includes vertical cavity surface-emitting lasers and an all-optical spatial mode multiplexer. Each vertical cavity surface-emitting laser is configured to output a data modulated optical carrier at a center wavelength of less than one micrometer. The all-optical spatial mode multiplexer has an optical output and optical inputs. Each vertical cavity surface-emitting lasers is optically connected to one or more of the optical inputs of the all-optical spatial mode multiplexer. The all-optical spatial mode multiplexer is configured to cause at least two of the vertical cavity surface-emitting lasers to excite linearly independent combinations of one or more optical spatial propagating modes of an optical fiber in response to the optical output being coupled to a near end of the optical fiber.

Abstract: A method of controlling a parameter in the generation of a coherent optical signal, the method comprising the steps of: receiving a set of signal samples relating to detection of a coherent optical signal; transforming the set of signal samples into a set of spectrum samples in the frequency domain, the set of spectrum samples being an estimation of the spectrum of the coherent optical signal; calculating at least one feedback variable based on the spectrum samples; and adjusting the parameter based on the at least one feedback variable.

Abstract: Optical systems and methods for transmission of multiple beams and direct detection of those beams are described. One transmitter for use in a free space optical communication system includes a broad spectrum light source and an optical component including a plurality of sections positioned to receive an optical beam produced by the broad spectrum light source. The sections of the optical component are formed to introduce optical path differences into portions of the optical beam that impinge on the optical component such that each section introduces a delay into a corresponding portion of the optical beam. The introduced delays cause each portion of the optical beam to lack coherence with other portions of the optical beam. A direct detection receiver detects the intensity of the aggregate beams and produces a signal with improved signal-to-noise ratio. The disclosed technology can be used with modulated optical beams such as intensity modulated beams.

Abstract: In an optical communication system having flexible transceivers, a transmitter section of one of the flexible transceivers generates a modulated pilot signal whose amplitude or phase or both have been modulated according to a digital code. An optical signal is transmitted from the transmitter section to a receiver section of another of the flexible transceivers. The optical signal conveys data and the modulated pilot signal. The digital code encodes parameter information for the transmitter section and for the receiver section. The receiver section receives the modulated pilot signal, determines the digital code by demodulating the modulated pilot signal, and determines the parameter information from the digital code. The transmitter section and the receiver section adjust their configuration according to the parameter information. The receiver section, while configured according to the parameter information, processes received data or future received data.

Abstract: Provided are methods and systems for receiving and processing optical signals. A dual single side band (SSB) modulation scheme is utilized to take advantage of a given wavelengths' bandwidth. Modulation schemes are employed that modulate each SSB with their In-phase (I) and Quadrature (Q) components. The methods and systems discussed utilize an adaptive equalizer and an LMS algorithm to remove imaging components of the left and right SSBs provided by the modulators. The adaptive equalizer and the LMS algorithm also compensate for linear and nonlinear distortions. Various algorithms can be employed, including but not limited to, algorithms for updating crosstalk coefficients in the equalizer, where the cross talk coefficients are induced from the imaging from the modulation of the dual SSB signal, and for updating coefficients relating to linear and nonlinear distortion.

Abstract: A light fixture includes an array of light-emitting elements for generating light from the light fixture, and the array of light-emitting elements includes a defined sub-array of light-emitting elements. An alternate array of light-emitting elements is coupled in parallel with the defined sub-array of alternate light-emitting elements of the light emitter. Each of the sub-array and the alternate array are coupled with a respective switch element. A control circuit is coupled with the switch elements and configured for selectively switching power between the sub-array and the alternate array for modulating the operation of the sub-array and alternate array of light-emitting elements to generate modulated communication signals.

Abstract: Provided are methods and systems for receiving and processing optical signals are provided. A dual single side band (SSB) modulation scheme is utilized to take advantage of given wavelengths' bandwidth. Modulation schemes are employed that modulate each SSB with their In-phase (I) and Quadrature (Q) components. The methods and systems discussed perform MIMO de-multiplexing algorithms to remove any imaging components of the left and right SSBs provided by the modulators. Various algorithms can be employed, including but not limited to inserting time interleaved training sequences into the channels of the right and left SSB signals or by employing a constant-modulus-algorithm (CMA) de-multiplexing.

Abstract: Consistent with an aspect of the present disclosure, optical signals are transmitted that are modulated in accordance with an 8QAM modulation format. The optical signals carry symbols of data and may be represented by a constellation in the IQ plane that includes four inner points that are symmetrically arranged about the origin, and four outer points that are uniformly distributed about the origin, but rotated relative to the inner points. The rotation is toward inner points that represent symbols for which an erroneous transition between the outer points and such inner points is more likely to result in a single bit error, instead of two bit errors, because the symbol corresponding to the outer point and the symbol corresponding to such inner point differ by just one bit. Accordingly, a binary forward error correction algorithm may be employed to correct the errored bit.

Abstract: Systems and methods described herein include methods and systems for controlling bias voltage provided to an optical modulating device. The optical modulating device is biased at a bias point that is different from a null point of the device such that an offset to the received optical power due to limited extinction ratio is reduced.

Abstract: A self-calibration procedure for an optical transmitter is provided. During the self-calibration procedure, a phase bias of an optical modulator of the optical transmitter is set so that an in-phase path and a quadrature path of the optical modulator are in phase. Stimulus signals are supplied to the in-phase and quadrature paths of the optical modulator, over a frequency range. Detection, with a photodetector, is made of an optical output of the optical modulator at a plurality of frequency steps over the frequency range. A photodetector converts an optical output of the optical modulator to an electrical signal. First and second measurement values are generated from the electrical signal output from the photodetector. A frequency spectrum and/or time delay is computed from the first and second measurement values for each frequency step value over the frequency range.

Abstract: Techniques are described for characterizing a receiver front end of a pluggable optical module. The pluggable optical module receives an optical signal that includes a first portion having a first polarization and a second portion having a second polarization. The first portion and second portion are not coherent with one another and the power of the first portion and second portion is equal.

Abstract: A system for determining a location of a user is provided that comprises a plurality of transmitters, each associated with a predefined physical location and each comprising a light source to provide an optical location signal; and at least one head-worn locator device with an optical receiver for receiving at least one of the optical location signals. To allow the determination of a location of a user that is wearing the head-worn locator device, each transmitter is configured to provide location information in the respectively provided optical location signal, wherein said location information corresponds to said predefined physical location of the respective transmitter.

Abstract: Aspects of the present invention provide techniques for compensating nonlinear impairments of a signal traversing an optical communications system. A parallel array of linear convolutional filters are configured to process a selected set of samples of the signal to generate an estimate of a nonlinear interference field. The predetermined set of samples comprises a first sample and a plurality of second samples. A processor applies the estimated nonlinear interference field to the first sample to least partially compensate the nonlinear impairment.

Abstract: Disclosed is a system and method for using visible light communication (“VLC”) to perform indoor position location. Through use of a system and method configured as set forth herein, the position of any appropriately marked person or item may be found indoors using data interconnected modules that communicate with one another via RF and visible light. A mobile receiver in the form of a tag or badge attached to the person or item to be tracked receives a VLC signal from a plurality of lighting modules, and transmits back to a processor the data it received so that the processor is able determine the tag's or badge's physical position with respect to the individual network modules.