Patent application number | Description | Published |
20120219296 | METHODS AND SYSTEMS FOR COHERENT MULTI-SUBCARRIER SOURCE GENERATION - A method of generating a multi-subcarrier optical signal is disclosed. A local oscillator oscillates one or more data signals to generate one or more oscillating data signals. A series of modulators phase modulate a lightwave to generate a phase modulated lightwave, wherein the series of modulators are driven by the one or more oscillating data signals. The intensity modulator modulates the phase modulated lightwave, the intensity modulator being driven by one of the oscillating data signals, to generate the multi-subcarrier optical signal. | 08-30-2012 |
20120230688 | METHOD AND SYSTEM FOR GENERATION OF COHERENT SUBCARRIERS - A method and system for generating multi-subcarriers is disclosed. Re-circulating frequency shifters—based on the frequency shifting in two cascading phase modulators—are used to generate 112 subcarriers with stable architecture since there is no direct current bias in phase modulators. | 09-13-2012 |
20120321248 | MULTI-STAGE OPTICAL INTERLEAVING - Methods and devices are provided to facilitate production of optical signals that exhibit reduced crosstalk noise and intersymbol interference. In some configurations, a multi-stage optical interleaver, including a first and a second optical interleaver, is used to process a first and a second set of input optical channels. The composite optical output of the multi-stage interleaver includes the first set of optical channels and the second set of optical channels, where each of the first and second set of input optical channels is processed once by the first optical interleaver and once by the second optical interleaver. As such, the first and second sets of input optical channels are each filtered twice using only two optical interleavers. | 12-20-2012 |
20120321320 | Generation and Direct Detection of Orthogonal Band Multiplexing OFDM Signal with Optical Carriers - The present method includes providing a continuous wave CW optical source with a fixed frequency spacing, separating multiple wavelengths of said CW optical source into different channels, modulating the multiple wavelengths of the CW optical source to generate an OFDM electrical signal with multiple sub-channels and each sub-channel has a channel subcarrier spacing , mixing the OFDM electrical signal with a radio frequency RF sinusoidal signal at a frequency ξf by an electrical mixer and generating a double sideband optical signal, filtering the double sideband signal to generate a single sideband optical signal, combining all channels of the single sideband optical signal, and directly detecting each sub-band of the single sideband optical OFDM signal with a respective detector, the detector converting the optical signal to an electrical signal for digital signal processing. | 12-20-2012 |
20120321324 | Architecture of 4-ASK Transmitter - The present method is for generating a 4-level optical signal and it includes providing a continuous wave CW optical source; modulating the CW optical source with a first intensity modulator driven by a binary electrical signal a n Gbits/s to generate an optical signal; employing a second intensity modulator as a pulse carving modulator that is driven by an RF signal at n GHz thereby generating a 4 level optical signal for subsequent detection by a receiver. | 12-20-2012 |
20130028603 | METHOD AND APPARATUS FOR PERFORMING TEMPORAL POLARIZATION INTERLEAVING IN AN OPTICAL TRANSMITTING SYSTEM - An optical signal transmitting system, comprising: an optical transmitter including one or more input terminals and an output terminal; and a temporal polarization interleaver including an input terminal and an output terminal, wherein the output terminal of the optical transmitter is communicatively coupled to the input terminal of the temporal polarization interleaver, wherein: the optical transmitter is configured to receive one or more input signals through its one or more input terminals, generate an output signal using the one or more input signals, the output signal including a x-polarized tributary and a y-polarized tributary that is pulse-to-pulse aligned with the x-polarized tributary, and transmit the output signal to the temporal polarization interleaver; and the temporal polarization interleaver is configured to receive the output signal from the optical transmitter and cause a predefined phase delay to one of the x-polarized tributary and the y-polarized tributary. | 01-31-2013 |
20130148971 | DIRECT DETECTION OF OPTICAL ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING (OFDM) SIGNALS - Techniques for timing synchronization in an optical orthogonal frequency division multiplexing (OOFDM) system includes providing a time-domain training symbol having a symmetric distribution and producing the training symbol by transmitting a real-valued PN sequence on each subcarrier under the OOFDM. The training sequence includes an initial value, followed by an odd length palindromic sequence of values. | 06-13-2013 |
20130223843 | NYQUIST WAVELENGTH DIVISION MULTIPLEXING SYSTEM - Aspects of the present invention include apparatus and methods for transmitting and receiving signals in communication systems. A beam splitter splits an optical signal into a plurality of signals. At least one QPSK modulator generates a plurality of QPSK modulated signals from the plurality of signals. An optical multiplexer combines the plurality of QPSK modulated signals into a multiplexed signal. The multiplexed signal is then transmitted. | 08-29-2013 |
20130294783 | METHOD AND APPARATUS OF ALGORITHM FOR COHERENT RECEIVERS WITH M-QAM MODULATION FORMAT - An improved Eighth-Order Statistics (EOS) blind phase recovery method is proposed for high-order coherent modulation formats. The method combining EOS blind phase estimate with maximum-likelihood (ML) carrier phase estimate uses multi-stage feed-forward carrier phase recovery algorithm. Experimental results show that the proposed new algorithm can reduce the required computational effort by more than a factor of 3 for 16-QAM system. | 11-07-2013 |
20130330070 | METHODS AND APPARATUS FOR PRE AND POST EQUALIZATION IN OPTICAL COMMUNICATIONS SYSTEMS - An optical communication system includes a transmission apparatus that transmits a test signal over an optical communication medium using a first optical modulation format, receives a reception report for the test signal, determines, based on the received reception report, a pre-equalization scheme, applies the pre-equalization to data transmitted from the transmitter side to generate pre-equalized data and transmits the pre-equalized data using a second optical modulation format based on the reception report. An optical reception apparatus receives the test signal, computes a channel transfer function based on the received test signal, and transmits the reception report. | 12-12-2013 |
20140050233 | METHOD AND APPARATUS FOR HETERODYNE COHERENT DETECTION - A simplified coherent receiver based on heterodyne detection with only two balanced photo detectors (PD) and two analog-to-digital converters (ADC) is disclosed. The polarization diversity hybrid can be simplified relative to the conventional one. The detected intermediate frequency signals are first down converted to baseband with I/Q separation. | 02-20-2014 |
20140099108 | SYSTEM AND METHOD FOR HETERODYNE COHERENT DETECTION WITH OPTIMAL OFFSET - A heterodyne optical signal detector and method performed thereby, the signal detector including an optical signal spectrum shaper operable to modify the shape of the frequency spectrum of a received optical signal, a laser local oscillator (LO), and polarization beam splitters (PBSs) to divide the signal and the LO into orthogonal components, waveguides in which intermediate frequency (IF) signals are formed, balanced photodetectors (BPDs) arranged to receive the IF signals and operable to convert the IF signals into electric signals, and analog to digital converters (ADCs) that digitize the electric signals. In embodiments, the ADCs have a predetermined bandwidth, the received signal has a spectrum which, if not shaped, would produce IF signals with a bandwidth greater than that of the ADCs, the spectrum shaper modifies the received signal spectrum to produce IF signals that have a bandwidth substantially equal to half the bandwidth of the ADCs, the laser frequency is adjusted produce IF signals in the waveguides having a frequency spectrum centered at the midpoint of the ADCs' bandwidth. | 04-10-2014 |
20140105615 | METHOD AND APPARATUS FOR GENERATION OF COHERENT AND FREQUENCY-LOCK OPTICAL SUBCARRIERS - A method and apparatus for generating sub-carriers is disclosed. Coherent optical sub-carriers with sub-carrier spacing are generated for carrying an orthogonal frequency division multiplexed (OFDM) signal. Multiple peaks are generated by cascading multiple phase modulators driven by different radio frequency sources. | 04-17-2014 |
20140199073 | CHANNEL ESTIMATION IN OPTICAL COMMUNICATION BASED ON ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING - Techniques for optical communications using optical orthogonal frequency division multiplexing (OFDM) include operating a signal transmitter to modulate laser light to produce modulated light that carries, in optical domain, OFDM subcarriers for carrying communication information, without a frequency guard band between the OFDM subcarriers, and pilot subcarriers for channel estimation at a signal receiver, each pilot subcarrier being free of communication information, and controlling optical power of the pilot subcarriers to vary with optical frequencies of the pilot subcarriers so that optical power of a pilot subcarrier at a high optical frequency is different from optical power of another pilot subcarrier at a low optical frequency. | 07-17-2014 |
20140199076 | DIGITAL NON-LINEAR COMPENSATION IN OPTICAL COMMUNICATION SYSTEMS - Systems, devices and techniques for processing an optical signal transmitted from a source over a transmission medium having a length L and performing compensation of non-linear distortions include formulating the compensation as a digital back propagation algorithm by logically dividing the length L into N steps and compensating non-linear distortions for each step as a function of an attenuation adjusting constant parameter that can be selected from a range between 0.3 and 0.7. | 07-17-2014 |
20140211838 | METHOD AND APPARATUS FOR ALGORITHM ON FLEXIBLE SQUARE-QAM COHERENT DETECTION - In Software defined elastic optical networks, modulation format and constellation size may be flexibly modified. As a result, digital signal processing (DSP) algorithm should be compatible with different modulation schemes or readily reconfigurable at the optical coherent receiver. Therefore we propose a novel cascaded adaptive blind equalizers based on decision-directed modified least mean square (DD-MLMS) algorithm for polarization separation and carrier phase recovery. The algorithm is square quadrature amplitude modulation (QAM) independent so that it could be applied in the elastic optical systems. The 28 Gbaud polarization multiplexing quadrature phase shift keying (PM-QPSK) and PM-16QAM back-to-back transmission is demonstrated. The results show that the performance is very close to the general algorithm but with a benefit of the reduced operation complexity. We transmit the 8×240 Gb/s PM-16QAM wavelength division multiplexing (WDM) signal over 1200 km standard single mode fiber (SSMF) based on the proposed blind equalization with a bit error ratio (BER) less than 2×10−2. | 07-31-2014 |
20140212140 | METHOD AND APPARATUS FOR GENERATION OF FREQUENCY- AND PHASE-LOCKED SUBCARRIER - We describe and demonstrate a novel and simple scheme to generate flattened optical subcarriers using only phase modulators driven by single frequency fundamental sinusoidal sources. 160.8 Gb/s PM-QPSK experiment over a single subcarrier has been demonstrated. | 07-31-2014 |
20140233949 | OPTICAL COMMUNICATION BASED ON POLARIZATION DEPENDENT COHERENT OPTICAL NYQUIST FREQUENCY DIVISION MULTIPLEXING - An optical transmitter transmits a dual polarization optical Nyquist frequency domain multiplexed signal. The signal includes a first polarization component and a second polarization component. Each component comprises multiple subchannels, possibly having different subchannel bandwidths and different modulation schemes. An optical receiver receives the signal and recovers transmitted data. | 08-21-2014 |
20140233964 | METHOD FOR GENERATING AN OPTIMIZED RETURN-TO-ZERO PULSE SHAPE AGAINST AGGRESSIVE OPTICAL FILTERING AND AN OPTICAL TRANSMITTER IMPLEMENTING THE METHOD - An optical transmitter comprises: first and second sets of optical in-phase and quadrature modulators; an integrable tunable laser assembly; a first polarization beam splitter that is configured to divide the continuous-waveform optical signal into a x-polarized tributary and a y-polarized tributary, each of the x-polarized tributary and the y-polarized tributary is modulated by one of the first and second sets of optical in-phase and quadrature modulators in accordance with the two respective input signals; a second polarization beam splitter that is configured to combine the modulated x-polarized tributary and the modulated y-polarized tributary into one optical signal; and an optical modulator that is configured to modulate the combined optical signal using a driving voltage, wherein the driving voltage has a bias point that is reduced by a predefined offset from a predefined reference voltage level. | 08-21-2014 |
20140233966 | RECOVERING DATA FROM QUADRATURE PHASE SHIFT KEYING MODULATED OPTICAL SIGNALS - Systems, devices and techniques for processing received QPSK modulated optical signals include sampling the received signal at twice the baud rate, thereby producing samples that are then processed as 9-QAM symbols using a decision directed least squares optimization method. Data bits are then recovered from the resulting symbol estimates. The received optical signal may also include dual polarized signals for increased bandwidth capacity. | 08-21-2014 |
20140314368 | DIRECTLY-MODULATED MULTI-POLARIZATION OPTICAL TRANSMITTERS - The present invention relates to optical transmitters, transceivers, and transponders used for transmission of information or data in any form through a physical medium dependent (PMD) network. The speed of such networks depends, in part, on the density of information that can be transmitted through the physical medium. Optical transmitters or transceivers can be used to transmit multiple independent signals simultaneously through the same medium using different directions or axes of polarization, where the difference in the directions or axes of polarization can be used to distinguish the multiple signals at the receiver. In this invention, we use a master laser (l | 10-23-2014 |
20140334828 | PRE-EQUALIZATION USING PHASE CORRECTION - An optical transmitter determines the transfer function in the reference-based pre-equalization for applying to an optically modulated signal at the transmitter. The determined pre-equalization transfer function is made robust to linewidth inaccuracy of the optical source by performing phase correction during the calculation of the pre-equalization transfer function. The phase correction includes averaging a number of consecutive received phase samples. The determined pre-equalization transfer function is applied to modulated signals prior to the transmission over an optical medium. | 11-13-2014 |
20140363159 | DIGITAL GENERATION OF MULTI-CARRIER OPTICAL SIGNALS - A transmitter of optical signals uses a single light transmitter to modulate a multi-carrier signal. The multi-carrier signal is generated by performing digital signal processing in the digital domain to generate a plurality of components by performing Hilbert transform filtering. The components are modulated on to an optical transmitter as in-phase and quadrature components, thereby generating a multi-carrier waveform using a single optical transmitter. | 12-11-2014 |
20140369398 | DIGITAL FILTER, PARTIAL RESPONSE EQUALIZER, AND DIGITAL COHERENT RECEIVER DEVICE AND METHOD - Aspects of the present invention include devices and methods for receiving signals in communication systems. A partial response equalizer includes a full response linear equalizing device for equalizing a received signal; and a partial response post filter for post filtering the equalized signal. Aspects of the present invention devices and methods for coherently receiving signals in an optical communication system. A receiver front end converts a received partial response optical signal to a partial response digital signal. An equalizing device equalizes the pre-filtered full response digital signal. A full response carrier recovery device performs carrier recovery of the signal equalized by the equalizing device. A post-filter filters the signal having undergone carrier recovery by the full response carrier recovery device. | 12-18-2014 |
20150023667 | SYSTEM AND METHOD FOR COHERENT DETECTION WITH DIGITAL SIGNAL PROCESSION - Aspects of the present invention include apparatus and methods for transmitting and receiving signals in communication systems. A multicarrier generator generates a multicarrier signal. An optical demultiplexer separates the multicarrier signal into separate multicarrier signals. At least one QPSK modulator modulates signals from the separate multicarrier signals. An optical multiplexer combines the QPSK modulated signals into a multiplexed signal. The multiplexed signal is then transmitted. | 01-22-2015 |
20150086212 | SYSTEM AND METHODS FOR FIBER AND WIRELESS INTEGRATION - Embodiments of the present invention pertain to optical wireless architecture and, in particular, to novel optical architecture to provide fiber-optic and wireless communication systems, links, and access networks. Certain embodiments of the invention pertain to a novel method and apparatus to provide 109.6 Gb/s capacity over spans of 80-km SMF and 2×2 MIMO. Conversion of PM-QAM modulated wireless mm-wave signal to an optical signal as well as 80-km fiber transmission of the converted optical signal is also realized. | 03-26-2015 |