Patent application number | Description | Published |
20090086215 | Polarization-Multiplexed Multilevel Differential Phase Shift Keyed Signal Detector - An apparatus and method for detecting a PMUX multilevel DPSK signal having at least two polarization components with equal symbol periods, which comprises utilizing two polarization-independent Optical Delay Interferometers (ODIs), detecting the four outputs of the two ODIs with two balanced detectors, and digitizing the two detected electronic signals at a sampling rate of twice the symbol rate of the said polarization component signals. | 04-02-2009 |
20100215374 | SYSTEM, APPARATUS AND METHOD FOR COMMUNICATING DATA VIA POLARIZATION MULTIPLEXING - Systems, apparatus and method for modulating digital data onto an optical carrier to produce a modulated optical carrier in which symbol-modulated optical signals of orthogonal polarizations are temporally interleaved and adapted to be processed by electronic time-division demultiplexing to recover the digital data modulated onto the orthogonal polarizations of the optical signals. | 08-26-2010 |
20110069975 | Digital Coherent Detection of Multi-Carrier Optical Signal - Embodiments for optical communication are provided in which subbands of a multi-carrier optical signal are digital coherent detected and then processed to recover data carried by the modulated carriers corresponding to at least one of the subbands. An exemplary optical communication system includes a multi-carrier coherent optical receiver for receiving a multi-carrier optical signal having M modulated carriers that are frequency locked, wherein M is greater than 2. The multi-carrier coherent optical receiver includes a subband digital coherent detector configured to provide output signals in a digital form for N different subbands of the multi-carrier optical signal, where N is an integer greater than 1 and less than M; and a digital signal processor configured to process the digital form of the detected output signals in order to recover the data carried by the modulated carriers corresponding to at least one of the subbands of the multicarrier optical signal. | 03-24-2011 |
20110170873 | Apparatus and Method For Generating Frequency-Locked Optical Comb Sources - Frequency-locked optical comb sources are provided that utilize recirculating frequency shifting based on frequency conversion in a modulator, together with a filter. The filter may be a wavelength notch filter and include a plurality of notches. An example apparatus includes a coupler, an I/Q modulator, and a filter. A first input of the coupler receives a first input optical carrier having a first frequency, and a second input of the coupler re receives a set of frequency-shifted carriers from the filter. The input optical carrier may have a plurality of frequencies. The I/Q modulator shifts the frequency of a first output of the coupler. The filter filters modulated output from the I/Q modulator thereby limiting the frequency-shifted carriers to be within an optical bandwidth. A second output of the coupler provides a plurality of frequency-locked carriers containing the first input optical carrier and the set of frequency-shifted carriers. | 07-14-2011 |
20120002283 | METHOD AND APPARATUS FOR RAMAN CO-PUMPS - An example Raman co-pump apparatus includes a control module for controlling output received from at least one of a first laser and a second laser, said output of said first laser and said second laser for combining into a co-pump output, wherein the control module is configured to increase a frequency difference between said first laser and said second laser. The apparatus may also include at least one of a first laser for providing a first output, a second laser for providing a second output and a polarization beam combiner for combining the first and second output into the co-pump output. Spectral overlap of orthogonally polarized pump lasers is avoided via: 1) control of the frequency (wavelength) interleave and the mode spacing of co-pump lasers; 2) control of frequency (wavelength) offset of co-pump lasers to reduce spectral overlap; and 3) use a single co-pump laser with large mode spacing. | 01-05-2012 |
20120177372 | Apparatus And Method For Generating Interleaved Return-To-Zero (IRZ) Polarization-Division Multiplexed (PDM) Signals - Return To Zero (RZ) shaping is performed for a first I/Q modulator whose output corresponds to a first polarization component using a first two digital-to-analog convertors (DACs), each of which is sampled at approximately twice a modulation symbol rate or more and has an output with a first interleaving order that interleaves one of a first pair of intended drive signal patterns and zeros. RZ shaping is also performed for a second I/Q modulator whose output corresponds to a second polarization component using a second two DACs, each sampled at approximately twice the modulation symbol rate or more and having a second interleaving order that interleaves zeros and one of a second pair of intended drive signal patterns, the second interleaving order opposite the first interleaving order. The first polarization and the second polarization may be combined, thereby forming an Interleaved Return To Zero (IRZ) Polarization Division Multiplexed (PDM) signal. | 07-12-2012 |
20130170841 | METHOD AND APPARATUS FOR TRANSMITTING HIGH-LEVEL QAM OPTICAL SIGNALS WITH BINARY DRIVE SIGNALS - Methods and apparatus for power-efficiently and reliably transmitting high-level quadrature amplitude modulation (QAM) optical signals using binary drive signals. Even though binary signals are used to drive a QAM modulator directly, without digital-to-analog conversion, the methods and apparatus disclosed allow the transmission of pilot symbol sequences having near optimal properties, such as a constant power profile in the time domain; a mean power that is approximately the same as the mean power of the data symbols; and roughly uniform amplitude in the frequency domain for non-zero frequency components of the pilot symbol sequence. The binary drive signals can be processed so that the modulated optical signals are selectively constrained to a subset of points of the QAM constellation to form a QAM constellation with reduced size and a mean power that is approximately the same as the mean power of the original QAM constellation. | 07-04-2013 |
20160065311 | FEEDBACK FOR ELECTRONIC PRE-DISTORTION IN AN OPTICAL TRANSMITTER - We disclose an optical transponder, in which one or more all-electronic feedback paths are used to obtain a relatively accurate estimate of the device-specific signal distortions in the transmitter portion thereof. The obtained estimate is used to enable the digital signal processor of the optical transponder to carry out electronic pre-distortion (EPD) that can significantly reduce or cancel these signal distortions without the use of detailed factory-calibration measurements or optics dedicated to feedback purposes. The use of all-electronic feedback paths may enable a beneficial reduction in the cost of the EPD functionality, e.g., by eliminating a significant extra cost associated with the implementation of optically generated feedback. | 03-03-2016 |