Leland Stanford Junior University

Tel Aviv University

University of Southern California

British Telecommunications Public Limited Company

Moshe Tur

Herbert J Shaw

Byoung Y Kim

Janet L Brooks

Alan Eli Willner

Avi Motil

Yair Peled

John E Bowers

Behzad M Moslehi

Kenneth A Fesler

Joseph W Goodman

Robert C Youngquist

Yongxiong Ren

Peter E Barnsley

Yang Yue

Mohammed Shabeer

Yan Yan

Kjell Blotekjaer

David Kennedy Hunter

Nisar Ahmed

Robert H Wentworth

Hao Huang

Peter Jonathon Legg

Moshe J Willner

Ido Sovran

Or Danon

Asher Voskoboinik

A method and a system for ultimately fast frequency-scanning Brillouin optical time domain analysis are provided herein. The method may include: simultaneously launching two pairs each having a pulsed pump wave and a counter-propagating constant wave (CW) probe wave, into an optical fiber, wherein the pulsed pumps have orthogonal States of Polarization (SOPs), and wherein the two CW probe waves have a same SOP; scanning common pump-probe frequency difference, over a frequency range that encompasses a respective Brillouin Gain Spectrum (BGS) and current and expected spectral shifts of the BGS along the optical fiber; deriving, a local Brillouin Frequency Shift (BFS), in a distributed manner along the optical fiber, which is defined as the pump-probe frequency difference which maximizes the Brillouin gain on the BGS; and determining strain and/or temperature in a distributed manner along the optical fiber, based on the respective local BFS.

Method and system for an ultimately fast frequency-scanning brillouin optical time domain analyzer

A method of stimulated Brillouin scattering is proposed in which both slopes of the BGS spectrum are probed to achieve immunity to pump power variations. Suitably applied, the technique can maintain all the benefits of the known Slope-Assisted-BOTDA technique, while using the same setup but at the cost of halving the sampling speed. the method may include: obtaining a reference Brillouin gain spectrum (BGS) representative of steady state or average conditions in various locations of the optical fiber along its length; generating, based on the reference BGS, a probe wave being a complex waveform comprising a first and second set of waveforms, each set having waveforms tailored to match an opposite slope of the reference BGS, at the various locations; performing stimulated Brillouin scattering at the various locations by applying a pump pulse wave to the probe wave; and deducing the local Brillouin frequency shift (BFS) at the various locations.

Pump-power-independent double slope-assisted distributed and fast brillouin fiber-optic sensor

In at least one aspect, a device for Orbital Angular Momentum (OAM) based optical communication includes a first spatial light modulator configured to down-convert a first plurality of higher-order OAM modes from a communication signal to a second plurality of higher-order OAM modes and a first Gaussian mode, a second spatial light modulator configured to drop the first Gaussian mode and add a second Gaussian mode to the second plurality of higher-order OAM modes, and a third spatial light modulator configured to up-convert the second plurality of higher-order OAM modes and the second Gaussian mode to a third plurality of higher-order OAM modes for further communications.

Systems and techniques for orbital angular momentum based reconfigurable switching

A method for conducting fast Brillouin optical time domain analysis for dynamic sensing of optical fibers is provided herein. The method includes the following stages: injecting a pump pulse signal into a first end of an optical fiber and a probe signal into a second end of the optical fiber, wherein the probe and the pump pulse signals exhibit a frequency difference between them that is appropriate for an occurrence of a Brillouin effect; alternating the frequency of either the probe or the pulse signals, so as the alternated signal exhibits a series of signal sections, each signal section having a predefined common duration and a different frequency; measuring the Brillouin probe gain for each one of the alternating frequencies; and extracting physical properties of the optical fiber throughout its length at sample points associated with the sampled time and the frequencies, based on the measured Brillouin probe gain.

Fast brillouin optical time domain analysis for dynamic sensing

Methods and systems used to perform sweep-free stimulated Brillouin scattering-based fiber optical sensing are described. In one aspect, a method includes interrogating different parts of a Brillouin gain spectrum using multiple optical tones in an optical fiber. The interrogating includes sending at least two pump tones into the optical fiber from one end of the optical fiber, such that a frequency spacing between the pump tones is larger than a width of the Brillouin gain spectrum. The interrogating also includes sending at least two probe tones into the optical fiber from another end of the optical fiber, such that a frequency spacing between the probe tones is different from the frequency spacing between the pump tones. The method further includes generating a sensing output based on the interrogating.

Sweep-free stimulated Brillouin scattering-based fiber optical sensing

Reduction of interferometer noise in an optical network

A distributed sensor system using pulsed optical signals optionally produced by a short coherence length source to provide a phase difference output signal representative of conditions affecting a selected sensor. In one preferred embodiment, an array of fiber-optic sensors are organized in a ladder configuration, with the sensors positioned in spaced relation and defining the rungs of the ladder. Light pulses transmitted through the sensors are multiplexed onto a return arm of the ladder. The multiplexed signals are received by an optical fiber compensating interferometer which coherently couples portions of adjacent multiplexed light signals to produce a phase difference signal representing conditions influencing selected sensors. In other preferred embodiments, the system is configured to define a plurality of adjacent Mach-Zehnder interferometers which provide output signal pairs which coherently couple to yield a phase difference signal directly representing the environmental effects on a particular sensor. Functional equivalents of the Mach-Zehnder interferometer configurations comprise configurations including adjacent Michelson interferometers. A phase and amplitude modulation technique is disclosed for providing heterodyned output signals from the distributed sensor system.

Distributed sensor array and method using a pulsed signal source

A technique and system for accurate determination of differential propagation delays in fiber-optic circuits. The method includes providing a sinusoidally modulated optical signal to each of two waveguides defining optical paths. The optical signals received from the optical paths are combined to form a reference output signal which has a null waveform whenever the propagation delay between the optical signals contains an odd number of half periods of the optical signal waveforms. The difference in the sinusoidal modulation frequency producing a first and second null or constant waveform in the reference signal is determined. This difference value between adjacent frequencies forming the null or constant waveforms comprises the inverse of the difference of signal propagation delay in the two optical paths. Accuracy is improved by measuring the sinusoidal modulation frequencies corresponding to first and second waveforms which are not formed by adjacent frequencies. The difference between those nonadjacent frequencies is divided by the difference in the reference waveform orders of the null reference waveforms to obtain the inverse of the differential propagation delay. Further accuracy is achieved by measuring at least one of the waveform nulls at a high waveform order. Still further accuracy is achieved by monitoring the reference waveforms on a network analyzer and using a frequency synthesizer to more precisely match and identify the modulation frequencies corresponding to the null reference signal waveforms. A system is disclosed for implementing this technique optionally using optical sources having a short coherence length. Mathematical relationships are disclosed for use with measured values in obtaining further improved accuracy.

System and method for accurate loop length determination in fiber-optic

A distributed sensor system including an optical source having a short coherence length for optionally continuously monitoring each sensor in the system. In one preferred embodiment, an array of fiber-optic sensors are organized in a ladder configuration, with the sensors positioned in spaced relation and defining the rungs of the ladder. Light transmitted through the sensors is multiplexed onto a return arm of the ladder, with sensor spacing being such that interference between light from different sensors is prevented. The multiplexed signals are received by an optical fiber receiver which couples the multiplexed light with an interfering optical reference signal to produce a phase difference signal representing conditions influencing selected sensors. Embodiments are disclosed for use of either pulsed or continuous wave light sources. In another preferred embodiment, the sensors comprise a plurality of interferometers connected in series configuration by a common optical fiber, which provides multiplexed output signals from the sensors to another plurality of interferometers comprising receivers. Functional equivalents of the series configuration provide sensors and receivers comprising birefringent or two-mode fiber. The optical path length differences between each pair of sensor arms are selected to prevent interference between the multiplexed sensor output signals from the various sensors. The optical path lengths through the sensors and receivers are structured so that each receiver produces a phase difference signal relating to conditions affecting light transmission through a specific sensor. A phase and amplitude modulation technique is disclosed for providing heterodyned output signals from the distributed sensor system.

Distributed sensor and method using coherence multiplexing of

An array (48, 49, 50, 51) of fiber optic couplers coupling an input (45) and an output (46) waveguide. The output waveguide (46) is routed among the couplers of the array such that either backward or forward coupling exists. With backward coupling, energy coupled into the output waveguide (46) in a coupler of the array is guided back to the preceding coupler for coupling back into the input waveguide (45). The backward coupling allows recirculations to occur between couplers to create poles and zeroes in the transfer function of the array which transfer function can be programmed or tailored somewhat to have specific characteristics. Further, the backward coupling allows the array to be used for matrix-vector multiplication.

Optical guided wave signal processor for matrix-vector multiplication

Growing community of inventors

Tel Aviv, Israel

Moshe Tur