Lucent Technologies Inc.

Alcatel-lucent USA Inc.

Tektronix, Inc.

University of Rochester

University of Oregon

Christophe Jean Dorrer

Inuk Kang

Dan Mark Marom

Christopher Richard Doerr

Peter Johannes Winzer

Xiang Liu

Alan H Gnauck

Chongjin Xie

Clinton R Giles

Howard Roy Stuart

Daniel Charles Kilper

Robert A Marsland, Jr

Mihaela Dinu

Ian Walmsley

Michael Raymer

Coherent optical signal processing is performed in a coherent receiver (or diagnostic/testing apparatus) that converts an amplitude and/or angle-modulated optical signal into two electrical signals. A simple receiver can only detect one phase of the signal and only the polarization that is aligned with a local oscillator laser polarization. To detect both phases and both polarizations, two sets of two interferometers, one each with a &#x3c0;/2 phase shift are required. Coherent optical signal processing methods, apparatus, techniques, etc. are disclosed that include individual components comprising a polarization combiner, a Savart device and photodetection apparatus with substantially reduced temperature and alignment sensitivity operating in optical communication systems and/or subsystems. The various embodiments can be used alone or in such combinations to provide improved coherent optical signal processing in a receiver.

Coherent optical signal processing

Methods and apparatus are provided for transmitting alternate-polarization phase-shift-keyed data. The output of a laser is modulated to optically encode electronic data using phase shift keying (PSK) to generate an optical signal. An alternate polarization PSK (APol-PSK) signal is generated by alternating the polarization of the optical signal using a modulator such that successive optical bits have substantially orthogonal polarizations.

Method and apparatus for optical transmission

A communication system adapted to use wavelength (frequency) division multiplexing for quantum-key distribution (QKD) and having a transmitter coupled to a receiver via a transmission link. In one embodiment, the receiver is adapted to (i) phase-shift a local oscillator (LO) signal generated at the receiver, (ii) combine the LO signal with a quantum-information (QI) signal received via the transmission link from the transmitter to produce interference signals, (iii) measure an intensity difference for these interference signals, and (iv) phase-lock the LO signal to the QI signal based on the measurement result. In one configuration, the QI signal has a plurality of pilot frequency components, each carrying a training signal, and a plurality of QKD frequency components, each carrying quantum key data. Advantageously, the system can maintain a phase lock for the QKD frequency components of the QI and LO signals, while the QKD frequency components of the QI signal continuously carry quantum key data.

Phase locking in a multi-channel quantum communication system

Techniques for characterizing the response of an optical device comprising modulating at least one signal using the device; coupling the modulated signal with a reference signal in a variety of ways; detecting the coupled signals; and obtaining the response of the modulator by analyzing the detected signals, are described. In a heterodyne embodiment, the method includes modulating a first optical signal using the optical device to produce a modulated first optical signal, the modulated first optical signal is combined with a second optical signal in a different spectral region; and the response of the optical device is determined from the intensity of the combined optical signal. A homodyne method using various splitting and recombining of the modulated optical signal with a reference signal is also described.

Method and apparatus for characterization of the response of optical devices

A method and apparatus for polarization-independent RF spectrum analysis of an optical source, the apparatus including a coupler for coupling the light from an optical source under test with light from a continuous-wave (CW) laser. A nonlinear apparatus is coupled to the coupler for modulating the electric field of the light from the CW laser using the temporal intensity of the light from the source under test to generate a modulated signal. The nonlinear apparatus is adapted to mitigate or compensate for any phase difference between polarization components of signals propagated through the nonlinear apparatus. A polarizer is coupled to the nonlinear apparatus for generating a linearly polarized signal from the modulated signal. An optical spectrum analyzer is coupled to the polarizer for measuring the optical spectrum of the linearly polarized signal to determine an RF spectrum of the optical source under test.

Method and apparatus for polarization-independent RF spectrum analysis of an optical source

An optical data signal can be sampled by linearly combining the optical data signal with optical sampling pulses, and delivering the combination to first and second balanced detectors. The optical data signal and the optical sampling pulse are configured to have a first phase difference at the first balanced detector and a second phase difference at the second balanced detector. Typically, a difference between the first phase difference and the second phase difference is configured to be about 90 degrees. In-phase and quadrature balanced detector outputs can be combined as a sum of squares to produce a linear sampling signal representative of data signal intensity, and the sample pulses can be configured to temporally step through the optical data signal so that a sampled representation of the optical data signal is obtained.

Linear optical sampling methods and apparatus

Time magnification and heterodyning are combined to allow the single-shot characterization of the electric field of optical waveforms. The electric field of the source under test is obtained by Fourier processing of the magnified temporal intensity of the source heterodyned with a monochromatic source. An experimental implementation of this technique is characterized and used to measure various optical signals.

Electric field measurement of optical waveforms

A method and apparatus are provided for measuring samples of the electric field of light propagated through a device under test and determining a nonlinear property of the device, such as self-phase modulation or cross phase modulation, using the measured samples.

Method and apparatus for determining the nonlinear properties of devices and fibers

A method and apparatus for monitoring PSK optical signals by measuring the RF spectrum of the signal and determining the power spectral density of noise on the optical signal within a predetermined frequency range to determine a measure of the degradation of the optical signal.

Method and apparatus for monitoring phase-shift keyed optical signals

The invention includes a method and apparatus for modulating one or both of spectral phase and amplitude of a received optical signal. The apparatus includes a spatial dispersion mechanism for spatially dispersing the received optical signal to enable optical communication of the received optical signal to an array of modulators. The apparatus includes a modulating mechanism having a first modulating component and a second modulating component. A first portion of the spatially dispersed optical signal is incident on the first modulating component and a second portion of the spatially dispersed optical signal is incident on the second modulating portion. The apparatus further includes a controller coupled to the modulating mechanism. The controller is adapted for moving the first and second modulating components in a direction normal to their planes for modulating one or both of phase and amplitude of the received optical signal.

Apparatus for modulating one or both of spectral phase and amplitude of an optical signal

Temporal phase shifts induced by cross-phase modulation in an optical fiber are directly characterized with a spectral equivalent of the Foucault technique used to spatially resolve wavefronts. The temporal phase induced by a high power pulsed pump on a monochromatic probe via cross-phase modulation is converted in a temporal intensity modulation via spectral filtering. A measurement of the modulated instantaneous power of the filtered signal allows to directly determine the time-resolved nonlinear phase shift. Additionally, an equivalent of the transport-of-intensity equation, which links the evolution of the instantaneous power of the electric field in a dispersive medium to the instantaneous values of the power and phase of the field. This derivation permits the measurement of temporal phase shifts using only intensity information in a direct, non-interferometric manner.

Measurement and characterization of nonlinear phase shifts

An interferometric technique measures the time-dependent electric field of a periodic or a non-periodic (data-encoded) optical signal under test using samples of its interference with a reference source of short optical pulses. The reference signal is a sequence of optical pulses at a repetition rate different from that of the signal under test. The difference in repetition rates of the two signals performs a scanning of the relative delay between the two signals, i.e. each pulse from the reference signal will overlap with the signal under test at a different time. The real and imaginary part of each of the plurality of interference between the two signals are then measured to determine samples of the electric field of the optical signal under test at each of those times. When needed, various types of averaging are performed on the samples of the electric field. If the signal under test is a data-encoded source, averaging is performed on groups of samples corresponding to the same symbol state of the data-encoded source.

Method and apparatus for characterizing the electric field of periodic and non-periodic optical signals

An optical pulse shaper without polarization dependencies includes, a planar lightwave circuit (PLC) having an arrayed waveguide and free space optics, combined with a lens and micromirror array characterized by piston-motion. The micromirror array is coupled to a controller that provides signals to the array for adjusting the positions of the micromirrors, which are used as a spatial light modulator to provide at least phase modulation to one or more of the separated frequency components of an input optical signal. The frequency separated components, including modified components, are recombined and directed back to the PLC to form a synthesized optical pulse. Information regarding the characteristics of the synthesized optical pulse is extracted from a spectrogram of that pulse. Extracted information is provided to the controller and responsive thereto the controller may generate signals for adjusting the position of one or more micromirrors.

Optical pulse shaper having hybrid planar lightwave circuit and free-space optics with MEMS piston-motion micromirrors and feedback control

A method and apparatus for the direct characterization of the phase of an optical signal includes measuring the interference between the optical signal and a sequence of optical pulses and processing the measured interference. The method and apparatus split and combine the optical signal and the sequence of optical pulses in order to measure the real and imaginary part of the interference signal for a least two pulses from the sequence of optical pulses. Processing steps are disclosed to obtain phase information on the optical signal from the measured interference.

Method and apparatus for the direct characterization of the phase of an optical signal

A method and apparatus for characterizing light from an optical source using simplified chronocyclic tomography by modulating the phase of light from an optical source using alternating positive and negative quadratic temporal phase modulation at a desired alternating frequency &#x3a9;; generating an electric signal proportional to the optical power of the modulated light after propagation through an optical frequency resolving device, for a desired optical frequency &#x3c9;; determining a time-invariant and time-varying components of the electric signal; repeating the generating and determining steps for a plurality of optical frequencies; and determining the spectral phase and spectral intensity of the light from the optical source using the time-invariant and time-varying components determined for the plurality of optical frequencies.

Growing community of inventors

Matawan, NJ, United States of America

Christophe Jean Dorrer