WO1995020144A1 - Optical wavelength sensor - Google Patents

Optical wavelength sensor Download PDF

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Publication number
WO1995020144A1
WO1995020144A1 PCT/GB1995/000094 GB9500094W WO9520144A1 WO 1995020144 A1 WO1995020144 A1 WO 1995020144A1 GB 9500094 W GB9500094 W GB 9500094W WO 9520144 A1 WO9520144 A1 WO 9520144A1
Authority
WO
WIPO (PCT)
Prior art keywords
cavity
optical
sensor according
wavelength
array
Prior art date
Application number
PCT/GB1995/000094
Other languages
French (fr)
Inventor
David John Pratt
Original Assignee
British Telecommunications Public Limited Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to EP94300440.8 priority Critical
Priority to EP94300440 priority
Application filed by British Telecommunications Public Limited Company filed Critical British Telecommunications Public Limited Company
Publication of WO1995020144A1 publication Critical patent/WO1995020144A1/en

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Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01JMEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRA-RED, VISIBLE OR ULTRA-VIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J9/00Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
    • G01J9/02Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods
    • G01J9/0246Measuring optical wavelength
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01SDEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00Semiconductor lasers
    • H01S5/06Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/068Stabilisation of laser output parameters
    • H01S5/0683Stabilisation of laser output parameters by monitoring the optical output parameters
    • H01S5/0687Stabilising the frequency of the laser

Abstract

An optical wavelength sensor consists of a wedge shaped Fabry Perot etalon (4) which exhibits resonance for different optical wavelengths across its width (X), and an array of detectors xn that detects the spatial disposition of resonant peaks which occur in the etalon, for comparison with stored peak patterns in a processor (6), so as to determine the spectral content of the incident light from an optical fibre (2).

Description

- l -

Optical Wavelength Sensor

Field of the Invention

This invention relates to an optical wavelength sensor which has particular but not exclusive application to use in an optical data transmission network for monitoring channel transmission frequencies.

Background to the Invention

In order to cope with the increasing demand for subscriber services on telecommunication networks, digital optical transmission networks are being introduced in which local access networks, which typically route electrical signals, are interconnected by a fibre optic network. In order to upgrade the capacity of the optical network, wavelength division multiplexing (WDM) techniques have been proposed, which permit the transmission capability of the fibre link to be upgraded to the multi-G bit/s range.

In a WDM system, a number of different wavelength channels are transmitted simultaneously in an optical fibre, each channel being defined typically by a laser source.

In order for the transmission system to operate reliably, it is desirable to monitor the channel wavelengths. Present methods of measuring wavelength involve optical spectrum analysers, wave meters or gas absorption techniques. These known methods however can presently only be used in a laboratory and are expensive or impractical to implement in a telecommunications network.

A known wavemeter is described in " Low cost wavemeter with a solid Fizeau interferometer and fiber optic input" B. Faust et al, Applied Optics., Vol 30 No 36, 20 December 1991. The wavemeter comprises a resonant cavity in the form of a Fizeau wedge which exhibits resonance for different optical wavelengths at spaced locations therein. The wedge operates in reflection, in response to optical radiation from an optical fibre, to direct radiation of different wavelengths to an array of detectors for detecting said different wavelengths from said spaced cavity locations. However, with such wavemeters that operate in reflection, there is an inherent limitation on the wavelength resolution that can be acheived and it would be difficult to use the known wavemeter to resolve WDM channels in an optical telecommunications system.

A wavemeter that operates in transmission, using a Fabry-Perot etalon is described in "A simple real-time wavemeter for pulsed lasers" Ja-Yong Koo et al, Measurement Science And Technology, Nol 2, No 1, January 1991, pp 55- 58. This device can resolve extremely fine wavelength variations and for example can discern 10Hz wavelength jitter in a pulsed laser output. The laser radiation impinges on a Fabry Perot etalon that has parallel semireflctive faces. A resulting fringe pattern in the form of circular rings, is imaged onto a detector array by a lens. The pattern of the rings shifts with very small changes in wavelength. However, for larger changes in wavelength, such as a few nm, that occurs between WDM channels, very substantial changes in the ring pattern would occur and would not be trackable in order to monitor the wavelength.

Summary of the Invention

According to the present invention there is provided a wavelength sensor with a cavity that comprises a Fabry Perot etalon having semireflective faces that produce multiple reflections therein, the cavity having a non-uniform thickness between the faces so as to produce said resonance at spaced locations for different wavelengths.

The semireflective faces may be disposed in a non-parallel configuration to provide the non-uniform cavity thickness.

The sensor may include input means to direct optical radiation into the cavity on one side thereof through one of said faces in an axial direction, said detector array extending transversly of the axial direction on another side of the cavity to detect radiation emanating from the cavity through the other of the faces.

The sensor according to the invention may conveniently be included in an optical telecommunications network for monitoring the wavelength of one or more transmission channel, for example in a WDM system. The sensor may be used to provide an alarm when the wavelength of a particular channel moves outside of predetermined limits. Also, the sensor may be used to control the wavelength produced by the optical source, for example in a feedback loop.

Thus, the invention provides a simple and convenient sensor which may readily be incorporated into an optical transmission network for deteαing the wavelengths of WDM channels.

Brief Description of the Drawings

In order that the invention may be more fully understood, an embodiment thereof will now be described by way of example with reference to the accompanying drawings, in which:

Figure 1 is a schematic block diagram of an optical wavelength sensor in accordance with the invention, embodied in an optical telecommunications network; and Figure 2 is a graph illustrating the outputs of the array of deteαors shown in the direαion X of Figure 1.

Description of an Embodiment of the Invention

Referring to Figure 1, the source 1 of optical radiation, shown schematically, may comprise a multi-wavelength source, which produces a plurality of transmission channels in an optical transmission network. The output of the source 1 is direαed into an optical fibre 2 coupled to the network. The source 1 may in praαice comprise a plurality of laser sources each operating at a respeαive different wavelength, with individual modulators that produce an optical modulated bit stream transmitted through the optical fibre 2. The individual laser sources may typically be at a plurality of remote locations and it may be desirable to monitor the wavelength of the various transmission channels to ensure that the telecommunications network is operating according to its design specification.

The optical wavelength sensor shown in Figure 1 comprises a lens 3, a Fabry Perot etalon 4, a deteαor array 5 and an output processor 6. The Fabry Perot etalon 4 consists of a block of optically transmissive material having semirefleαive planar facets 7, 8. The construαion of a Fabry Perot etalon is well known per se and etalons are typically used as filters. The body of the etalon operates as a resonant cavity and the semirefleαive surfaces produce multiple refleαions within the body so as to create a resonance. Resonance occurs at a particular wavelength, dependent upon the refraαive index of the body and spacing between the semirefleαive surfaces which can be approximately charaαerised as follows: nλ_ - 2μd (1) where λr is the resonant wavelength μ is the refraαive index of the cavity material at the resonant wavelength d is the thickness of the cavity between the semirefleαive facets n is a positive integer.

In a conventional Fabry Perot etalon, the facets 7 and 8 are parallel to one another so that the etalon exhibits a resonance for a single wavelength peak.

However, in accordance with the invention, the etalon shown in Figure 1 is slightly wedge shaped, so that the facets 7, 8 are slightly out of parallel. Thus, the thickness of the etalon varies between a minimum value d mm •„ and a maximum value of ^■maχ. As a result, a resonant cavity is provided which exhibits a resonance for different optical wavelengths at spaced locations in the direαion X across the width of the etalon, normal to the direαion of the incident optical beam.

The lens 3 aαs as a beam spreader so as to spread the beam from the optical fibre 2 across the width of the etalon.

The etalon may be made of silica or other suitable materials according to techniques well known per se. The wedge angle and the thicknesses m^n and dmaχ are seleαed according to the range of wavelengths to be deteαed and can be determined by routine methods as will readily be apparent to those skilled in the art. The device may typically be configured to c scriminate between WDM channels within the usual optical telecommunication wavelength bandwidths centered on 1300 or 1500 nm

The array of deteαors 5 comprises a linear array of deteαors xj, x2 ... xn which may comprise CCD devices arranged in the direαion X across the width of the incident optical beam. In this example the deteαors are serially clocked by a clocking signal Cl produced by the output processor 6 on line 9 so that the outputs of the dαeαors are fed serially on line 10 to the output processor. Also, the array of dαeαors 5 may comprise comprise a photodiode array. Suitable arrays are available commercially as will be evident to those skilled in the art.

The output of the deteαors Xj - xn for wavelengths λj and λ2 is shown in Figure 2. Considering the wavelength λj, the resonant condition defined by equation (1) occurs for two different values of the etalon thickness d in the direαion X across the incident beam at deteαor positions x^j j x^j 2- F°r t e second wavelength λ2, resonance occurs at different deteαor positions x^ i xλ22* Thus, the spacings of the resonances x^j j, x^ i or x^ 2> x\22 provide a measure of the wavelength of the incident beam. It will be seen that the output from the deteαor array 5 can be readily digitised and compared in the output processor 6 with predetermined patterns held in a digital memory. The pattern and relative disposition of the resonant peaks thus provides an indication of the channel wavelengths incident from the optical fibre 2. The processor 6 can thus provide an output on line 11 indicative of the channel wavelengths and also can provide an indication of when each channel wavelength moves outside of a predetermined wavelength range, so as to monitor the integrity of data transmission in the network.

Typically, the laser sources 1 are at remote locations so that it will not be readily possible to adjust the sources. However, if at least one laser source is proximate to the wavelength deteαor for example being in the same exchange building, it is possible to provide feedback on line 12 to the laser source so as to control its wavelength in a feedback loop, so as to keep its emission wavelength withm a predetermined range.

As previously mentioned, the etalon 4 is preferably made of a material which has a low dependence of optical length on temperature so as to minimise changes in the produα μd with temperature. It will be seen from equation (1) that changes of the produα μd as a funαion of temperature will alter the position at which the resonant peaks occur as a funαion of temperature. Preferably, the etalon is made of material such as fused silica for temperature stability. Furthermore, temperature compensation can be achieved by means of a temperature sensor 13, attached to the cavity 4 which provides a signal on line 14 to the processor 6 in order to permit the processor to compensate the signals on lines 11, 12 as a funαion of temperature. .Alternatively, or additionally, the etalon may be provided with some means, such as a Peltier element, to control the etalon's temperature.

Thus, by means of the described arrangement, it is possible to monitor the individual channel wavelengths of a WDM optical network. The deteαor may be initialised by firstly transmitting a known reference frequency through the optical fibre 2 to provide datum positions for the resonant peaks. As used herein, in both the description and the claims, the term "optical" includes visible light and non visible radiation such as ultra-violet and infrared radiation.

Claims

Claims
1. An optical wavelength sensor comprising a resonant cavity (4) which exhibits resonance for different optical wavelengths at spaced locations therein, and an array of deteαors (xn) for deteαing said different wavelengths from said spaced cavity locations charaαerised in that the cavity (4) comprises a Fabry Perot etalon having semirefleαive faces (7, 8) that produce multiple refleαions therein, the cavity having a non-uniform thickness (d) between said faces so as to produce said resonance at spaced locations for different wavelengths.
2. A sensor according to claim 1 wherein the semirefleαive faces (7, 8) are disposed in a non-parallel configuration whereby to provide said non- uniform cavity thickness.
3. A sensor according to claim 1 or 2 including input means (2) to direα optical radiation into the cavity (4) on one side thereof through one of said faces (7) in an axial direαion, said deteαor array extending transversly of the axial direαion on another side of the cavity to dαeα radiation emanating from the cavity through the other of the faces (8).
4. A sensor according to claim 3 including means (3) for spreading the radiation from the input means (2) transversely of the axial direαion across the cavity for resonance therein.
5. A sensor according to claim 4 wherein the input means comprises an optical fibre (2) and the spreading means comprises a lens (3) disposed in the optical path between the fibre and the cavity.
6. A sensor according to any preceding claim wherein the array of deteαors comprises an array of CCD deteαors (5).
7. A sensor according to any preceding claim including a source of optical radiation (1) to be direαed to the cavity, and output means (6) responsive to the deteαor array for controlling an operational charaαeristic of the source.
8. A sensor according to any preceding claim including output means (11) responsive to the deteαors for providing a given output when the wavelength charaαeristic of optical radiation incident on the cavity departs from a predetermined charaαeristic.
9. A sensor according to any preceding claim including temperature sensing means (13) for sensing the cavity temperature, and compensating means (6) for compensating the output of the output means for changes in the sensed wavelength produced by changes in cavity temperature.
10. A sensor according to any preceding claim wherein the cavity (4) is made of fused silica.
11. A WDM optical network including a deteαor according to any preceding claim for dαeαing the wavelengths of at least one of the WDM channels.
PCT/GB1995/000094 1994-01-20 1995-01-19 Optical wavelength sensor WO1995020144A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP94300440.8 1994-01-20
EP94300440 1994-01-20

Publications (1)

Publication Number Publication Date
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Cited By (42)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996004702A2 (en) * 1994-07-29 1996-02-15 Litton Systems, Inc. Laser stabilization and tuning with wedged etalon
WO1997005679A1 (en) * 1995-07-27 1997-02-13 Jds Fitel Inc. Method and device for wavelength locking
EP0875743A1 (en) * 1997-05-02 1998-11-04 Hewlett-Packard Company A wavemeter and an arrangement for the adjustment of the wavelength of an optical source
EP1072936A2 (en) * 1999-07-30 2001-01-31 Lucent Technologies Inc. Method and device for obtaining a desired phase of optical characteristic of a fabry-perot etalon
EP1168680A2 (en) * 2000-06-29 2002-01-02 Ando Electric Co., Ltd. Method and apparatus for analyzing wavelength-division multiplexed signal light
WO2002075384A2 (en) * 2001-03-16 2002-09-26 Optical Coating Laboratory, Inc. Variable filter-based optical spectrometer
WO2002075877A2 (en) * 2001-03-15 2002-09-26 Digital Optics Corporation Integrated wavelength locker for use with more than one wavelength and associated methods
WO2002097936A2 (en) * 2001-05-31 2002-12-05 Altitun Ab Apparatus and method for controlling the operating wavelength of a laser
US6639679B2 (en) 2000-01-10 2003-10-28 Telefonaktiebolaget L M Ericsson (Publ) Integrated wavelength monitor
US6836490B2 (en) 2001-09-20 2004-12-28 Sumitomo Electric Industries, Ltd. Optical module
US6859469B2 (en) 2001-12-11 2005-02-22 Adc Telecommunications, Inc. Method and apparatus for laser wavelength stabilization
EP1630532A1 (en) * 2004-08-23 2006-03-01 Palo Alto Research Center Incorporated Wavelength detector
US7038782B2 (en) 2001-12-11 2006-05-02 Adc Telecommunications, Inc. Robust wavelength locker for control of laser wavelength
US7075656B2 (en) 2001-12-11 2006-07-11 Adc Telecommunications, Inc. Method and algorithm for continuous wavelength locking
US7092416B2 (en) 2000-04-05 2006-08-15 Digital Optics Corporation Integrated wavelength locker for use with more than one wavelength and associated methods
EP1801553A1 (en) * 2005-12-22 2007-06-27 Palo Alto Research Center Incorporated Propagating light to be sensed
JP2007171177A (en) * 2005-12-22 2007-07-05 Palo Alto Research Center Inc Transmission of photon energy data by light
US7289544B2 (en) 2001-09-20 2007-10-30 Sumitomo Electric Industries, Ltd. Optical module
US7291824B2 (en) 2005-12-22 2007-11-06 Palo Alto Research Center Incorporated Photosensing throughout energy range and in subranges
US7358476B2 (en) 2005-12-22 2008-04-15 Palo Alto Research Center Incorporated Sensing photons from objects in channels
US7386199B2 (en) 2005-12-22 2008-06-10 Palo Alto Research Center Incorporated Providing light to channels or portions
JP2008145437A (en) * 2006-12-04 2008-06-26 Palo Alto Research Center Inc Monitoring device for light pulses
US7471399B2 (en) 2007-02-05 2008-12-30 Palo Alto Research Center Incorporated Photosensing optical cavity output light
US7502123B2 (en) 2007-02-05 2009-03-10 Palo Alto Research Center Incorporated Obtaining information from optical cavity output light
US7545513B2 (en) 2007-02-05 2009-06-09 Palo Alto Research Center Incorporated Encoding optical cavity output light
US7554673B2 (en) 2007-02-05 2009-06-30 Palo Alto Research Center Incorporated Obtaining information about analytes using optical cavity output light
US7633629B2 (en) 2007-02-05 2009-12-15 Palo Alto Research Center Incorporated Tuning optical cavities
US7701580B2 (en) 2008-02-01 2010-04-20 Palo Alto Research Center Incorporated Transmitting/reflecting emanating light with time variation
US7763856B2 (en) 2008-01-31 2010-07-27 Palo Alto Research Center Incorporated Producing time variation in emanating light
US7817281B2 (en) 2007-02-05 2010-10-19 Palo Alto Research Center Incorporated Tuning optical cavities
US7817254B2 (en) 2008-01-30 2010-10-19 Palo Alto Research Center Incorporated Obtaining information from time variation of sensing results
US8153949B2 (en) 2008-12-18 2012-04-10 Palo Alto Research Center Incorporated Obtaining sensing results indicating time variation
CN102735273A (en) * 2012-06-29 2012-10-17 中国科学院半导体研究所 Optical fiber sensor based on Fabry-Perot cavity
US8373860B2 (en) 2008-02-01 2013-02-12 Palo Alto Research Center Incorporated Transmitting/reflecting emanating light with time variation
US8437582B2 (en) 2005-12-22 2013-05-07 Palo Alto Research Center Incorporated Transmitting light with lateral variation
WO2013187114A1 (en) * 2012-06-11 2013-12-19 コニカミノルタ株式会社 Spectroscopic optical system, spectroscopic measurement device
WO2014116458A1 (en) * 2013-01-26 2014-07-31 Halliburton Energy Services, Inc. Distributed acoustic sensing with multimode fiber
US9029800B2 (en) 2011-08-09 2015-05-12 Palo Alto Research Center Incorporated Compact analyzer with spatial modulation and multiple intensity modulated excitation sources
US9164037B2 (en) 2007-01-26 2015-10-20 Palo Alto Research Center Incorporated Method and system for evaluation of signals received from spatially modulated excitation and emission to accurately determine particle positions and distances
US9307938B2 (en) 2007-12-17 2016-04-12 Palo Alto Research Center Incorporated Controlling transfer of objects affecting optical characteristics
US9395504B2 (en) 2013-09-19 2016-07-19 Sumitomo Electric Industries, Ltd. System to control wavelength and method to control wavelength
US9638637B2 (en) 2007-01-26 2017-05-02 Palo Alto Research Center Incorporated Method and system implementing spatially modulated excitation or emission for particle characterization with enhanced sensitivity

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Cited By (60)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996004702A3 (en) * 1994-07-29 1996-04-04 Litton Systems Inc Laser stabilization and tuning with wedged etalon
WO1996004702A2 (en) * 1994-07-29 1996-02-15 Litton Systems, Inc. Laser stabilization and tuning with wedged etalon
WO1997005679A1 (en) * 1995-07-27 1997-02-13 Jds Fitel Inc. Method and device for wavelength locking
EP0875743A1 (en) * 1997-05-02 1998-11-04 Hewlett-Packard Company A wavemeter and an arrangement for the adjustment of the wavelength of an optical source
US6043883A (en) * 1997-05-02 2000-03-28 Hewlet-Packard Company Wavemeter and an arrangement for the adjustment of the wavelength of the signals of an optical source
EP1072936A2 (en) * 1999-07-30 2001-01-31 Lucent Technologies Inc. Method and device for obtaining a desired phase of optical characteristic of a fabry-perot etalon
EP1072936A3 (en) * 1999-07-30 2002-10-23 Agere Systems Optoelectronics Guardian Corporation Method and device for obtaining a desired phase of optical characteristic of a fabry-perot etalon
US6639679B2 (en) 2000-01-10 2003-10-28 Telefonaktiebolaget L M Ericsson (Publ) Integrated wavelength monitor
US7092416B2 (en) 2000-04-05 2006-08-15 Digital Optics Corporation Integrated wavelength locker for use with more than one wavelength and associated methods
US7466729B2 (en) 2000-04-05 2008-12-16 Tessera North America, Inc. Wavelength monitor for use with more than one wavelength
EP1168680A2 (en) * 2000-06-29 2002-01-02 Ando Electric Co., Ltd. Method and apparatus for analyzing wavelength-division multiplexed signal light
EP1168680A3 (en) * 2000-06-29 2007-01-03 Yokogawa Electric Corporation Method and apparatus for analyzing wavelength-division multiplexed signal light
WO2002075877A2 (en) * 2001-03-15 2002-09-26 Digital Optics Corporation Integrated wavelength locker for use with more than one wavelength and associated methods
WO2002075877A3 (en) * 2001-03-15 2003-10-16 Alvaro A Cruz-Cabrera Integrated wavelength locker for use with more than one wavelength and associated methods
WO2002075384A2 (en) * 2001-03-16 2002-09-26 Optical Coating Laboratory, Inc. Variable filter-based optical spectrometer
US6785002B2 (en) 2001-03-16 2004-08-31 Optical Coating Laboratory, Inc. Variable filter-based optical spectrometer
WO2002075384A3 (en) * 2001-03-16 2003-04-24 Optical Coating Laboratory Inc Variable filter-based optical spectrometer
WO2002097936A2 (en) * 2001-05-31 2002-12-05 Altitun Ab Apparatus and method for controlling the operating wavelength of a laser
WO2002097936A3 (en) * 2001-05-31 2003-05-01 Altitun Ab Apparatus and method for controlling the operating wavelength of a laser
US7289544B2 (en) 2001-09-20 2007-10-30 Sumitomo Electric Industries, Ltd. Optical module
US6836490B2 (en) 2001-09-20 2004-12-28 Sumitomo Electric Industries, Ltd. Optical module
US7038782B2 (en) 2001-12-11 2006-05-02 Adc Telecommunications, Inc. Robust wavelength locker for control of laser wavelength
US7075656B2 (en) 2001-12-11 2006-07-11 Adc Telecommunications, Inc. Method and algorithm for continuous wavelength locking
US6859469B2 (en) 2001-12-11 2005-02-22 Adc Telecommunications, Inc. Method and apparatus for laser wavelength stabilization
EP1630532A1 (en) * 2004-08-23 2006-03-01 Palo Alto Research Center Incorporated Wavelength detector
JP2006058301A (en) * 2004-08-23 2006-03-02 Palo Alto Research Center Inc Chip-size wavelength detector
US7701590B2 (en) 2004-08-23 2010-04-20 Palo Alto Research Center Incorporated Apparatus, methods, devices, and systems in which differences and/or changes in photosensed positions and/or quantities relate to shifts and/or differences in photon energies
US7310153B2 (en) 2004-08-23 2007-12-18 Palo Alto Research Center, Incorporated Using position-sensitive detectors for wavelength determination
JP2007171177A (en) * 2005-12-22 2007-07-05 Palo Alto Research Center Inc Transmission of photon energy data by light
US7315667B2 (en) 2005-12-22 2008-01-01 Palo Alto Research Center Incorporated Propagating light to be sensed
EP1801553A1 (en) * 2005-12-22 2007-06-27 Palo Alto Research Center Incorporated Propagating light to be sensed
US7386199B2 (en) 2005-12-22 2008-06-10 Palo Alto Research Center Incorporated Providing light to channels or portions
US8437582B2 (en) 2005-12-22 2013-05-07 Palo Alto Research Center Incorporated Transmitting light with lateral variation
US7291824B2 (en) 2005-12-22 2007-11-06 Palo Alto Research Center Incorporated Photosensing throughout energy range and in subranges
US7358476B2 (en) 2005-12-22 2008-04-15 Palo Alto Research Center Incorporated Sensing photons from objects in channels
US7718948B2 (en) 2006-12-04 2010-05-18 Palo Alto Research Center Incorporated Monitoring light pulses
EP1942566A3 (en) * 2006-12-04 2011-01-05 Palo Alto Research Center Incorporated Monitoring light pulses
JP2008145437A (en) * 2006-12-04 2008-06-26 Palo Alto Research Center Inc Monitoring device for light pulses
US9164037B2 (en) 2007-01-26 2015-10-20 Palo Alto Research Center Incorporated Method and system for evaluation of signals received from spatially modulated excitation and emission to accurately determine particle positions and distances
US9638637B2 (en) 2007-01-26 2017-05-02 Palo Alto Research Center Incorporated Method and system implementing spatially modulated excitation or emission for particle characterization with enhanced sensitivity
US7554673B2 (en) 2007-02-05 2009-06-30 Palo Alto Research Center Incorporated Obtaining information about analytes using optical cavity output light
US7471399B2 (en) 2007-02-05 2008-12-30 Palo Alto Research Center Incorporated Photosensing optical cavity output light
US7545513B2 (en) 2007-02-05 2009-06-09 Palo Alto Research Center Incorporated Encoding optical cavity output light
US7817281B2 (en) 2007-02-05 2010-10-19 Palo Alto Research Center Incorporated Tuning optical cavities
US7633629B2 (en) 2007-02-05 2009-12-15 Palo Alto Research Center Incorporated Tuning optical cavities
US7502123B2 (en) 2007-02-05 2009-03-10 Palo Alto Research Center Incorporated Obtaining information from optical cavity output light
US9307938B2 (en) 2007-12-17 2016-04-12 Palo Alto Research Center Incorporated Controlling transfer of objects affecting optical characteristics
US7817254B2 (en) 2008-01-30 2010-10-19 Palo Alto Research Center Incorporated Obtaining information from time variation of sensing results
US7763856B2 (en) 2008-01-31 2010-07-27 Palo Alto Research Center Incorporated Producing time variation in emanating light
US8373860B2 (en) 2008-02-01 2013-02-12 Palo Alto Research Center Incorporated Transmitting/reflecting emanating light with time variation
US7701580B2 (en) 2008-02-01 2010-04-20 Palo Alto Research Center Incorporated Transmitting/reflecting emanating light with time variation
US8153949B2 (en) 2008-12-18 2012-04-10 Palo Alto Research Center Incorporated Obtaining sensing results indicating time variation
US9029800B2 (en) 2011-08-09 2015-05-12 Palo Alto Research Center Incorporated Compact analyzer with spatial modulation and multiple intensity modulated excitation sources
WO2013187114A1 (en) * 2012-06-11 2013-12-19 コニカミノルタ株式会社 Spectroscopic optical system, spectroscopic measurement device
CN102735273B (en) * 2012-06-29 2014-11-05 中国科学院半导体研究所 Optical fiber sensor based on Fabry-Perot cavity
CN102735273A (en) * 2012-06-29 2012-10-17 中国科学院半导体研究所 Optical fiber sensor based on Fabry-Perot cavity
WO2014116458A1 (en) * 2013-01-26 2014-07-31 Halliburton Energy Services, Inc. Distributed acoustic sensing with multimode fiber
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