Abstract: Exemplary embodiments are directed to a blind carrier recovery system for blind detection and/or correction of carrier frequency offset between the signal laser source and local oscillator (i.e., carrier frequency recovery) for optical systems employing quadrature amplitude modulation (QAM). Exemplary embodiments can be implemented using an improved fast Fourier transform (FFT)-based approach. Some embodiments can include a frequency sign detection technique that uses parallel, concurrently implemented FFTs having a modified FFT architecture. Some embodiments can include a frequency sign detection technique that uses time-domain slope detection based on constellation classification.

Abstract: A particular method includes applying light pulses to an optical fiber and receiving backscattered light at a phase-sensitive optical time domain reflectometry (OTDR) device. The backscattered light includes portions of the applied light pulses that are backscattered by the optical fiber. The method also includes determining a difference between the backscattered light and a backscatter pattern associated with the optical fiber. The method also includes determining a communication signal encoded in the backscattered light based on the difference, where the communication signal is encoded in the backscattered light responsive to mechanical waves applied to the optical fiber at a location remote from the phase-sensitive OTDR device.

Abstract: An optical receiver according to the invention includes a polarization diversity unit receiving a polarization multiplexed optical signal obtained by multiplexing two optical signals having a same frequency band of carrier waves and polarization states orthogonal to each other, and a frequency domain equalization unit receiving signal components parallel to mutually orthogonal polarization axes from the polarization diversity unit, wherein the frequency domain equalization unit includes filters for which filter coefficients thereof are set for compensating degradation of transmission characteristics in one optical signal without polarization multiplexing by means of the frequency domain equalization.

Abstract: The invention provides a system and method, for an optical communication network to compensate impairments in the network, using electronic dispersion compensation, said system comprising optical means comprising two or more optical-to-electrical converters for generating at least two electrical signals, comprising amplitude and instantaneous frequency of a received distorted optical signal, and an electrical circuit adapted to perform a full-field reconstruction of the received distorted optical signal using said electrical signals. The system is characterised by a dispersive transmission line circuit with compensation parameters updated at a selected rate to process said full-field reconstructed signal and compensate for coarse chromatic dispersion; and an adaptive electronic equalization circuit with compensation parameters updated at a rate faster than those in the said dispersive transmission line circuit to provide a fine impairment compensation of said reconstructed signals.

Abstract: An apparatus for transmitting data for visible light communication sets up the pulse width control step of pulse width modulation (PWM) in a unit time interval, modulates each symbol of VLC source data input into a PWM signal in accordance with the pulse width control step, generates a visible light modulation signal by controlling the turn-on time or turn-off time of a plurality of light emitting diodes (LEDs) in response to the PWM signal, and transmits the visible light modulation signal.

Abstract: A method of monitoring optical parameters of a modulated optical signal comprises receiving a first optical power, Xi, of said optical signal for a first bandwidth, Bi, across the said optical signal and receiving a second optical power, Xj, of said optical signal for a second bandwidth, Bj, across the said optical signal. The method comprises obtaining a power spectral density description of said optical signal. The method comprises determining an optical signal to noise ratio of said optical signal. The optical signal to noise ratio depends on said first optical power, Xi, said second optical power, Xj, and said power spectral density description. The method also comprises generating a data signal indicative of said optical signal to noise ratio.

Abstract: In a first aspect, the invention includes a radio frequency photonic transceiver, comprising: a radio frequency receiver; a radio frequency photonic transmitter; and a switch between the input of the radio frequency photonic receiver and the output of the radio frequency photonic transmitter. In a second aspect, the invention includes an apparatus, comprising: a radio frequency photonic receiver; a radio frequency photonic transmitter; and a switch between the input of the radio frequency photonic receiver and the output of the radio frequency photonic transmitter. In a third aspect, the invention includes a radio frequency, photonic transceiver, comprising: means for generating a radio frequency modulated optical signal; a radio frequency photonic transmitter; and means for switching between the input of the radio frequency photonic receiver and the output of the radio frequency photonic transmitter.

Abstract: An optical network terminal (ONT) for use in an optical access network and comprising: an optical transceiver arranged to communicate with an optical line terminal using a wavelength which is modulated to carry sub-channels; a second transceiver arranged to communicate with a number of subscriber equipment using respective subscriber equipment channels; the ONT arranged to automatically map each subscriber equipment channel to a respective sub-channel of the wavelength without using an address associated with the respective subscriber equipment.

Abstract: Coded light has been proposed to enable advanced control of light sources and transmit information using light sources. An assignment for the identification frequencies of light sources enables more unique frequencies to be assigned, i.e. more light sources to be uniquely identified in the system. An available frequency band is divided into non-uniform frequency regions and frequencies are selected from a set of uniformly spaced frequencies in the non-uniform frequency regions. A receiver is based on a successive approach and is enabled to analyze higher harmonics of the received light signals. The light contributions are successively estimated group by group.

Abstract: Disclosed herein are a combined communication and broadcasting dual switching system and method. The system includes broadcasting transmission means, an Optical Line Terminal (OLT), an optical detection unit, an active path determination unit, an optical switch unit, and a combining unit. The broadcasting transmission means converts a Radio Frequency (RF) broadcast signal into an optical signal. The OLT includes dual lines and selectively outputs an Internet data signal. The optical detection unit detects a line from which the Internet data signal is being output. The active path determination unit determines that the line is an active path. The optical switch unit receives the optical signal from the broadcasting transmission means, and switches to the active path. The combining unit receives the optical signal output after having been switched, receives the Internet data signal from the OLT, and multiplexes the received optical signal and the received Internet data signal.

Abstract: A method and a device for an optical power budget in a passive optical network are disclosed in the present invention, wherein said method includes: acquiring a corresponding minimum optical link loss according to a transmission requirement of a passive optical network with a large splitting ratio or long distance (710); selecting an optical transmitter with large power and an optical receiver with high sensitivity as a combination of an optical transmitter of an Optical Line Terminal (OLT) and an optical receiver of an Optical Network Unit (ONU) in an optical link, as well as a combination of an optical receiver of the OLT and an optical transmitter of the ONU in the optical link according to the minimum optical link loss to compose a passive optical network system comprising the OLT, an Optical Distribution Network (ODN), and ONUs connected in sequence (720).

Abstract: An optical network unit for a passive optical network (10), configured to: initiate an upstream wavelength (wus) for an upstream signal (US) from the optical network unit to an optical line terminal (10); iteratively, until an iteration criterion is met, i) transmit the upstream signal (US) to the optical line terminal (10), ii) receive from the optical line terminal (10) power level data (p) for the upstream signal (US) as measured by the optical line terminal (10), and iii) set the upstream wavelength (wus) for the upstream signal (US) to a new wavelength-value; and adjust the upstream wavelength (wus) to a wavelength-value previously set for the upstream signal (US) and associated with power level data corresponding to a certain power level. A passive optical network system, the optical line terminal and related methods are also disclosed.

Abstract: In a communication device using a plurality of signal enhancement mechanisms, a system and method are provided for managing signal processing power consumption. A receiver accepts a communications signal and analyzes signal integrity. In response to analyzing the signal integrity, a signal enhancement mechanism is changed, and device power consumption is modified in response to changing the signal enhancement mechanism. In one aspect, the receiver changes a receiver signal enhancement mechanism, and modifies its power consumption. For example, one or more of the following receiver signal enhancement mechanisms may be selected: forward error correction (FEC), equalization, dc voltage level, and physical coding sublayer (PCS).

Abstract: In accordance with an embodiment of the present disclosure a method for adaptively spacing channels of an optical network comprises determining a first desired power level of a first channel of an optical network. The method further comprises determining a second desired power level of a second channel of the optical network, the second desired power level being less than the first desired power level. Additionally, the method comprises determining a first spectral space between the first channel and one or more channels neighboring the first channel based at least on the first desired power level. The method also comprises determining a second spectral space between the second channel and one or more channels neighboring the second channel based at least on the second desired power level, the second spectral space less than the first spectral space.

Abstract: A method of monitoring (200) an optical fiber comprises modulating (210) an optical signal with a traffic signal; modulating (220) the optical signal with an incoherent optical frequency domain reflectometry, IOFDR, test signal; transmitting (230) the doubly modulated optical signal onto an optical fiber at a first end of the fiber; detecting (240) scattered radiation output from the first end of the fiber; and analyzing (250) the detected scattered radiation using incoherent optical frequency domain reflectometry to determine a distance to a break in the optical fiber. Apparatus suitable for carrying out the method is also described, as well as an optical communications network employing the method.

Abstract: A transmitting apparatus using visible light communication generates a light source control signal from color information representing additional information and transmits additional information with a color of light that is emitted by a light source by controlling an on/off time of a plurality of LEDs according to the light source control signal. Therefore, a user can intuitively know additional information from a color of light that is emitted by the light source.

Abstract: A communications device includes a transmitter device including first and second optical sources, a first optical coupler coupled to the first and second optical sources, and a first modulator coupled to the first optical coupler and to modulate a combined carrier signal including the first and second optical carrier signals with an RF input signal. The communications device includes a receiver device having a second modulator to further modulate the modulated combined carrier signal with an LO signal, a FM-PM discriminator coupled to the second modulator and to convert the modulated combined carrier signal to an intensity modulated combined carrier signal based upon the LO signal, a second optical coupler coupled to the FM-PM discriminator and to generate first and second intensity modulated carrier signals, and an optical-to-electrical converter coupled to the second optical coupler and to generate an IF signal.

Abstract: The present invention relates to an optical transmitter that includes an optical modulator configured to modulate an optical signal with a digital data stream, and a heater configured to apply heat to the optical modulator. The optical transmitter also includes an optical receiver configured to receive the modulated optical signal and to convert the modulated optical signal into a received digital data stream. A circuit is configured to compute bit errors in the received digital data stream by comparing the received digital data stream with the digital data stream, and control the heater based on the computed bit errors.

Abstract: A system for bi-directional data transmission includes a first array coupled to a first subsystem and a second array coupled to a second subsystem. The first array includes a first plurality of transmitters that produce first optical signals that are transmitted through free space, and a first plurality of receivers. The second array includes a second plurality of transmitters that produce second optical signals that are transmitted through free space to the first plurality of receivers, and a second plurality of receivers that is configured to receive the first optical signals. An image-forming apparatus is operatively positioned between the first and second arrays and is configured to concurrently form an image of the first plurality of transmitters on the second plurality of receivers and an image of the second plurality of transmitters on the first plurality of receivers.

Abstract: The present invention provides a method and apparatus for phase aligning two optical signals within an optical transmitter to each other (and, in some embodiments, to a pulse carved optical signal) using integrated complimentary taps and a dither signal. The phase of a first signal may be intentionally offset relative to the phase of a second signal. Based on the offset, a correction factor may be calculated. The correction factor may be used to shift the phase of the first signal and/or the second signal in order to generally align the signals. This procedure may be automatically performed in a feedback loop to cause the signals to come into alignment and maintain the alignment of the signals during operation of the transmitter.