WO2002037625A2 - Laser a reseau de bragg regle par compression - Google Patents

Laser a reseau de bragg regle par compression Download PDF

Info

Publication number
WO2002037625A2
WO2002037625A2 PCT/US2001/047356 US0147356W WO0237625A2 WO 2002037625 A2 WO2002037625 A2 WO 2002037625A2 US 0147356 W US0147356 W US 0147356W WO 0237625 A2 WO0237625 A2 WO 0237625A2
Authority
WO
WIPO (PCT)
Prior art keywords
grating
compression
fiber
tube
optical waveguide
Prior art date
Application number
PCT/US2001/047356
Other languages
English (en)
Other versions
WO2002037625A3 (fr
Inventor
Mark R. Fernald
Timothy J. Bailey
Matthew B. Miller
James M. Sullivan
Michael A. Davis
Robert N. Brucato
Martin A. Putnam
Jon Thomas Kringlebotn
Alan D. Kersey
Paul E. Sanders
Original Assignee
Cidra Corporation
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
Application filed by Cidra Corporation filed Critical Cidra Corporation
Priority to AU2002226036A priority Critical patent/AU2002226036A1/en
Publication of WO2002037625A2 publication Critical patent/WO2002037625A2/fr
Publication of WO2002037625A3 publication Critical patent/WO2002037625A3/fr

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES 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
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/0675—Resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
    • G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
    • G02B6/02195—Refractive index modulation gratings, e.g. Bragg gratings characterised by means for tuning the grating
    • G02B6/022—Refractive index modulation gratings, e.g. Bragg gratings characterised by means for tuning the grating using mechanical stress, e.g. tuning by compression or elongation, special geometrical shapes such as "dog-bone" or taper
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES 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
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/0632—Thin film lasers in which light propagates in the plane of the thin film
    • H01S3/0635—Thin film lasers in which light propagates in the plane of the thin film provided with a periodic structure, e.g. using distributed feed-back, grating couplers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES 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
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/08004—Construction or shape of optical resonators or components thereof incorporating a dispersive element, e.g. a prism for wavelength selection
    • H01S3/08009—Construction or shape of optical resonators or components thereof incorporating a dispersive element, e.g. a prism for wavelength selection using a diffraction grating
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES 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
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/105—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the mutual position or the reflecting properties of the reflectors of the cavity, e.g. by controlling the cavity length
    • H01S3/1055—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the mutual position or the reflecting properties of the reflectors of the cavity, e.g. by controlling the cavity length one of the reflectors being constituted by a diffraction grating

Definitions

  • CC- 0234A entitled “Temperature Compensated Optical Device", filed October 30,2000, and U.S. 'Patent Application Serial No. (CiDRA Docket No. CC-0129D), entitled “Compression-Tuned Bragg Grating-Based Laser”, filed contemporaneously herewith, contains subject matter related to that disclosed herein, and which are incorporated by reference in its entirety.
  • This invention relates to tunable lasers, and more particularly to a compression- tuned Bragg grating-based laser.
  • Bragg gratings embedded in the fiber may be used in compression to act as a tunable filter or tunable fiber laser, as is described in US Patent No. 5,469,520, entitled “Compression Tuned Fiber Grating” to Morey, et al and US Patent No. 5,691,999, entitled “Compression Tuned Fiber Laser” to Ball et al..
  • the very narrow linewidth ( ⁇ 10kHz) of single mode fiber lasers will, depending on the application, be an advantage (low phase noise) or a disadvantage (high power and narrow linewidth causes stimulated Brillouin scattering and hence loss). In telecom this should not be a problem since the lasers will be modulated, creating side-bands and hence effectively broadening the spectrum and increasing the threshold for Brillouin scattering.
  • fiber lasers in series or in parallel can be pumped using one semiconductor pump laser reducing the cost per fiber laser.
  • parallel fiber lasers can be pumped by several pumps through a series of cross-connected couplers to form a pump redundancy scheme. With Er-lasers the pump absorption is very low and hence effectively broadening the spectrum and increasing the threshold for Brillion scattering.
  • DFB lasers have a limited temperature tenability (l-2nm).
  • Using sampled grating DBR cavities or combination of narrowband sampled grating filtering and broadband co directional filtering using forward coupling between two parallel waveguides wide tuning ranges (->40-100nm) with relatively stable single mode operation can be realized (cf. Altitium laser).
  • a problem with such designs is that they typically require 4 section cavities (gain, coupler, phase, reflector) with three individually/relatively controlled currents, making relatively complex and long lasers. Note that there are also various ways to make multi-wavelength wavelength selective semiconductor laser arrays.
  • DFB lasers using one phase-shifted FBG co-located with the gain medium should offer the best performance in terms of robust single mode operation, but require a highly photosensitive, high gain fiber, either Er or Er:Yb, and a relatively sophisticated FBG writing setup.
  • DFB lasers should be able to provide the shortest grating based lasers.
  • DBR lasers consisting of two FBG end-reflectors can be easier to realize, since separate gain fibers and grating fibers can be used (this requires low loss splicing), and the grating specs are relaxed. Mode-hopping can be a problem with DBR lasers.
  • Both DFB and DBR fiber lasers are continuously tunable through uniform strain of the whole cavity, including the gratings, in which case the cavity mode(s) and the Bragg wavelength are tuned equally [G. Ball and W.W. Morey, Opt. Lett., Vol. 17, pp. 420-422]. A practical tuning range in the order of lOnm should be feasible. Both DFB and DBR fiber lasers can be designed to operate in a single polarization.
  • a sample grating DBR uses two sampled grating end-reflectors with comb-like reflection spectra over a wide wavelength range, and where the two gratings have different comb period. Using the Vernier effect this provides wide step-wise tuning with less compression/strain than required than for DFB/DBR lasers to get the same tuning range (a reduction by a factor of 10 probably have to be quite long (several cm) to get sufficiently strong reflection from each peak.
  • a fiber laser can be designed to achieve single longitudinal mode lasing, as is discussed in US Patent No. 5,305,335, entitled “Single Longitudinal Mode Pumped Optical Waveguide laser Arrangement", US Patent No. 5,317,576, entitled “Continuously Tunable Single-Mode Rare-Earth Doped Pumped Laser Arrangement", and US Patent No. 5,237,576, entitled “Article Comprising an Optical Fiber Laser”, which are incorporated herein by reference in their entirety.
  • a general fiber laser and amplifier arrangement similar to a Master Oscillator Power Amplifier (MOPA) arrangement is described in US Patent No. 5,594,747 entitled “Dual- Wavelength Pumped Low Noise Fiber Laser”, and US Patent No. 5,666,372 entitled “Embedded Bragg Grating Laser Master-Oscillator And Power- Amplifier", which are incorporated herein by reference.
  • MOPA Master Oscillator Power Amplifier
  • Objects of the present invention include a tunable Bragg grating-based laser that allows the grating to be compression-tuned without creep and without requiring sliding ferrules or a mechanical supporting structure for the ferrules.
  • a compression-tuned laser comprises a tunable optical waveguide having an outer dimension of at least 0.3 mm.
  • the optical waveguide includes an inner core disposed along the longitudinal axis of the optical waveguide.
  • the inner core includes a dopant to provide an optical gain, and a first and second sampled grating disposed within the core along the longitudinal axis.
  • the first and second sampled gratings are spaced a distance apart.
  • the outer dimension of the optical waveguide about the first sample grating is different than the outer dimension of the optical waveguide about the second sample grating.
  • a compression-tuned laser comprises a first optical waveguide having an outer dimension of at least 0.3 mm.
  • the first optical waveguide includes an inner core disposed along the longitudinal axis of the first optical waveguide, and a first sampled grating disposed within the core along the longitudinal axis.
  • a second optical waveguide includes an inner core disposed along the longitudinal axis of the second optical waveguide, and a second sampled grating disposed within the core along the longitudinal axis.
  • a gain element optically optically is disposed between the first and second optical waveguide. At least the first optical waveguide is compression-tunable.
  • Fig. 1 is a side view of a device for compressing a tube-encased fiber grating, in accordance with the present invention.
  • Fig. 2 is a side view of an alternative device for compressing a tube-encased fiber grating, in accordance with the present invention.
  • Fig. 3 is a side view of an alternative device for compressing a tube-encased fiber grating, in accordance with the present invention.
  • Fig. 4 is a side view of a tube-encased fiber grating, in accordance with the present invention.
  • Fig. 5 is a side view of a tube-encased fiber grating having an alternative geometry for the tube, in accordance with the present invention.
  • Fig. 6 is a side view of a tube-encased fiber grating having an alternative geometry for the tube, in accordance with the present invention.
  • Fig. 7 is a side view of a tube-encased fiber grating where the tube is fused on opposite axial ends of the grating area, in accordance with the present invention.
  • Fig. 8 is a side view of more than one grating on a fiber encased in a tube, in accordance with the present invention.
  • Fig. 9 is a side view of two fiber gratings on two separate optical fibers encased in a common tube, in accordance with the present invention.
  • Fig. 10 is an end view of the embodiment of Fig. 9, in accordance with the present invention.
  • Fig. 11 is an end view of two fiber gratings on two separate optical fibers encased in a common tube and separated by distance, in accordance with the present invention.
  • Fig. 12 is a side view of a tube-encased fiber grating where the tube is fused on the fiber only over the length of the grating, in accordance with the present invention.
  • Fig. 13 is a side view of a tunable distributed feedback (DFB) fiber laser encased in a tube, in accordance with the present invention.
  • DFB distributed feedback
  • Fig. 14 is a side view of a device for compressing a tube-encased fiber grating using an actuator to tune the grating, in accordance with the present invention.
  • Fig. 15 is a side view of a device for compressing a tube-encased fiber grating using a precise pressure source to tune the grating, in accordance with the present invention.
  • Fig. 16 is a side view of a device for compressing a tube-encased fiber grating using a precise pressure source to tune the grating, in accordance with the present invention.
  • Fig. 17 is a side view of a large diameter optical waveguide having a grating disposed therein, in accordance with the present invention.
  • Fig. 18 is a side view of a tunable Bragg grating-based laser, in accordance with the present invention.
  • Fig. 19 is a side view of another embodiment of a tunable Bragg grating-based laser, . in accordance with the present invention.
  • Fig. 20 is a side view of a temperature compensated Bragg grating-based laser, in accordance with the present invention.
  • Fig. 21 is a side view of another embodiment of a tunable Bragg grating-based laser having a LiNb0 3 electro-optic Mach-Zehnder waveguide modulator, in accordance with the present invention.
  • Fig. 22 is a side view of a tunable Bragg grating-based Master Oscillator Power Amplifier (MOPA), in accordance with the present invention.
  • MOPA Master Oscillator Power Amplifier
  • Fig. 23 is a side view of a plurality of Bragg grating based laser coupled in series, in accordance with the present invention.
  • Fig. 24 is a side view of a sampled grating DBR laser, in accordance with the present invention.
  • Fig. 25 is a side view of another embodiment of a sampled grating DBR laser in accordance with the present invention.
  • a compression-tuned Bragg grating comprises a known optical waveguide 10, e.g., a standard telecommunication single mode optical fiber, having a Bragg grating 12 impressed (or embedded or imprinted) in the fiber 10.
  • the fiber 10 has an outer diameter of about 125 microns and comprises silica glass (Si0 2 ) having the appropriate dopants, as is known, to allow light 14 to propagate along the fiber 10.
  • any wavelength- tunable grating or reflective element embedded, etched, imprinted, or otherwise formed in the fiber 28 may be used if desired.
  • the term "grating” means any of such reflective elements.
  • the reflective element (or grating) 12 may be used in reflection and/or transmission of light.
  • the fiber 10 may be made of any glass, e.g., silica, phosphate glass, or other glasses, or made of glass and plastic, or solely plastic. For high temperature applications, optical fiber made of a glass material is desirable. Also, the fiber 10 may have an outer diameter of 80 microns or other diameters. Further, instead of an optical fiber, any optical waveguide may be used, such as, a multi-mode, birefringent, polarization maintaining, polarizing, multi-core, or multi-cladding optical waveguide, or a flat or planar waveguide (where the waveguide is rectangular shaped), or other waveguides.
  • any optical waveguide may be used, such as, a multi-mode, birefringent, polarization maintaining, polarizing, multi-core, or multi-cladding optical waveguide, or a flat or planar waveguide (where the waveguide is rectangular shaped), or other waveguides.
  • the light 14 is incident on the grating 12 which reflects a portion thereof as indicated by a line 16 having a predetermined wavelength band of light centered at a reflection wavelength ⁇ b, and passes the remaining wavelengths of the incident light 14 (within a predetermined wavelength range), as indicated by a line 18.
  • the fiber 10 with the grating 12 therein is encased Within and fused to at least a portion of a cylindrical glass capillary tube 20, discussed more hereinafter.
  • the tube 20 is axially compressed by a compressing device or housing 50.
  • One end of the tube 20 is pressed against a seat 51 in an end 52 of the housing 50.
  • the housing 50 also has a pair of arms (or sides) 54, which guide a movable block 56.
  • the block 56 has a seat 57 that presses against the other end of the tube 20.
  • the end 52 and the block 56 have a hole 58 drilled through them to allow the fiber 10 to pass through.
  • An actuator 60 such as a stepper motor or other type of motor whose rotation or position can be controlled, is connected by a mechanical linkage 62, e.g., a screw drive, linear actuator, gears, and/or a cam, to the movable block 56 (or piston) which causes the block 56 to move as indicated by arrows 64.
  • the stepper motor 60 can set a predetermined amount of force on the block to compress the tube 20 to provide a desired reflection wavelength of the grating 12.
  • the tube 20 may contact the ends 52,56 with a flush contact.
  • the stepper motor 60 may be a high resolution stepper motor driven in a microstepping mode. Other higher or lower resolution stepper motors may be used if desired.
  • the stepper motor 60 is driven by a control circuit 63 which provides drive signals on lines 61 needed to drive the stepper motor 60, and hence the block 56, to the desired position, to provide the desired Bragg wavelength ⁇ b of the grating 12.
  • a control circuit 63 which provides drive signals on lines 61 needed to drive the stepper motor 60, and hence the block 56, to the desired position, to provide the desired Bragg wavelength ⁇ b of the grating 12.
  • other actuators may be used if desired, as discussed hereinafter with Fig. 14.
  • a housing 70 instead of using the movable block 56, a housing 70 may be used which has two end caps 72,74 and outside walls 76. In that case, the holes 58 are in the end caps 72,74 to allow the fiber 10 to exit.
  • the stepper motor 62 is connected to the end cap 74 by the mechanical linkage 62. When the stepper motor 62 pushes on the end cap 74, the walls 76 compress or deflect, the tube 20 is compressed and the reflection wavelength of the
  • FIG. 3 another embodiment of the present invention, comprises a cylindrical-shaped housing 90 comprising an outer cylindrical wall 98, two end caps 95, and two inner cylinders (or pistons) 92 each connected at one end to one of the end caps 95.
  • the tube 20 (with the grating 12 encased therein) is disposed against the other ends of and between the two pistons 92.
  • Other cross-sectional and/or side-view sectional shapes may be used for the housing 90 elements 98,95,92 if desired.
  • the end caps 95 may be separate pieces or part of and contiguous with the pistons 92 and/or the outer cylinder 98.
  • the stepper motor 60 applies an external axial force on the end cap 95 on the left side of the housing 90.
  • the pistons 92 have holes 94 having a diameter large enough to allow the fiber 10 pass through.
  • the pistons 92, the outer cylinder walls 98, the end caps 95, and the tube 20 may be made of the same or different materials.
  • the tube 20 has the outer diameter d2 of about 2 mm (0.07 inches) and a length LI of about 12.5 mm (0.5 in.), the pistons 92 each have outer diameters d5 of about 19J mm (0.75 inches), the length L5 of each of the pistons 92 is about 6.25 cm (2.5 in.), the diameter of the holes 94 in the pistons 92 is about 1 mm (1000 microns), the overall length L4 of the housing 90 is about 12J cm (5 inches), the thickness tl of the outside walls 98 is about 1.0 mm (0.04 inches), and the gap gl between the inner dimension of the outer walls 98 and the outer dimensions of the pistons 92 is about 1.52 mm (0.06 inches).
  • the dimensions, materials, and material properties e.g., Poisson's ratio, Young's Modulus, Coefficient of Thermal Expansion, and other known properties
  • the resolution and range for setting the reflection wavelength are scalable by controlling these parameters. For example, if the overall length L4 is increased, the sensitivity ⁇ L/L will increase.
  • the axial length L4 of the housing 90 decreases by an amount ⁇ L due to compression and/or deflection of the outer walls 98.
  • a predetermined portion of the total axial length change ⁇ L' is seen at the tube 20 due to compression of the tube 20. Compression of the tube 20 lowers the Bragg reflection wavelength ⁇ l of the grating 12 by a predetermined amount which provides a wavelength shift. If the pistons 92 have a spring constant higher than that of the glass tube 20, the tube 20 will be compressed more than the pistons 92 for a given force. Also, for a given external force, a predetermined amount of the force is dropped across the outside walls 98, and the remainder is seen by the tube 20.
  • the walls 98, pistons 92 and end caps 95 are all made of titanium having the dimensions discussed hereinbefore, for an external force of 2200 lbf, about 2000 lbf is dropped across (or used to compress/deflect) the outside walls 98, and about 200 lbf is dropped across the tube 20.
  • the cylinder walls 98 act similar to a diaphragm or bellows which compress or deflect due to increased external pressure.
  • the housing 90 may be assembled such that a pre-strain or no pre-stain exists on the tube 20 prior to applying any outside forces.
  • the material of the housings 50,70, 90 and/or one or more of the components thereof may be made of a metal such as titanium, high nickel content alloys such as Inconel®, Incoloy®, Nimonic® (registered trademarks of Inco Alloys International, Inc.) containing various levels of Nickel, Carbon, Chromium, Iron, Molybdenum, and Titanium, stainless steel, a glass material (such as discussed hereinafter for the tube 20), or other high strength, or corrosion resistant, or high temperature or heat resistant metals or alloys may be used, or other materials having sufficient strength to compress the tube 20 may be used. Other materials having other properties may be used if desired depending on the application.
  • a metal such as titanium, high nickel content alloys such as Inconel®, Incoloy®, Nimonic® (registered trademarks of Inco Alloys International, Inc.) containing various levels of Nickel, Carbon, Chromium, Iron, Molybdenum, and Titanium, stainless steel, a glass material (such as discussed
  • the tube 20 may be compressed by another actuator 154, such as a peizoelectric actuator, solenoid, pneumatic force actuator, or any other device which is capable of directly or indirectly applying an axial compressive force on the tube 20 may be used.
  • the actuator 154 may be disposed on a housing 150 (analogous to the frame 50; Fig. 1) and creates a force on a movable block 152 (analogous to the movable block 56; Fig. 1) which moves in the direction of the arrows 155.
  • the housing 150 also has a pair of sides 157 which guide the movable block 152. One of the sides 157 may be removed if desired.
  • the block 152 has the seat 57 that presses against the other end of the tube 20.
  • the actuator 154 is connected to a control circuit 158 which provides the necessary signals on a line 156 to the actuator 154 to set the desired force on the tube 20 which sets the desired Bragg wavelength ⁇ b of the grating 12.
  • the force may be set by the controller 158 by providing a signal (e.g., an electrical voltage) on the line 156 to the actuator 154 in an open loop configuration.
  • the force may be set on the actuator 154 by providing a signal on the line 156 to the actuator 154 and measuring the force or position of the actuator 154 on a line 160 in a closed loop control configuration on the actuator 154.
  • the fiber 10 may enter on one end of the housing 150 and pass through a hole 162 in the end 153. If a feed-through (double ended fiber) design is used, the block 152 may have a hole 164 part or all the way through it, and the other end of the fiber 10 may be fed out the side or passed through a hole 166 in the actuator 154 and in the other end of the housing 150.
  • a feed-through (double ended fiber) design is used, the block 152 may have a hole 164 part or all the way through it, and the other end of the fiber 10 may be fed out the side or passed through a hole 166 in the actuator 154 and in the other end of the housing 150.
  • CM controller
  • DPT-C-M for a cylindrical actuator
  • Other actuators may be used, as discussed hereinbefore.
  • the tube 20 may be placed in a housing 174, and the grating wavelength set by placing a fluid pressure on the tube 20, similar to a pressure sensor described in co-pending US Patent Application, Serial No. 09/205,944 entitled “Tube-Encased Fiber Grating Pressure Sensor", filed Dec. 4, 1998, which is incorporated herein by reference, and the tube 20 may have any of the geometries and configurations described in such Patent Application.
  • the housing 172 creates a chamber 176 and has a port 178 that is fed to a pressure source 180, which provides a precise source pressure Ps.
  • the chamber 176 may be filled with a fluid (e.g., one or more gasses and/or liquids).
  • the tube 20 may be mounted to one wall 175 or may be suspended in the fluid 176.
  • the optical fiber 10 is fed into the chamber through a known hermetic feedthroughs and has some slack 179 to allow for compression of the tube 20 over pressure.
  • the grating reflection wavelength changes as the pressure Ps changes, similar to the actuator embodiments discussed hereinbefore; however, in this case, the grating wavelength is set by setting a predetermined source fluid pressure Ps.
  • the pressure source 180 may comprise a hydraulic actuator or piston 300 disposed within a chamber 301.
  • the piston 300 is connected by a mechanical linkage 302 to a known hydraulic drive mechanism 304 which precisely sets the position of the piston 300 to set the pressure Ps.
  • the hydraulic drive 304 may be controlled electronically by a known control circuit 308, similar to the controller 158 (Fig. 14), which provides a position command signal on a line 306 to the hydraulic controller 304 for a particular piston position and thus pressure Ps, and thus wavelength ⁇ b of the grating.
  • Other known pressure sources may be used if desired to set the grating wavelength.
  • the housings described herein 50,150,70,90, and any components therein, including the movable blocks 56,152, may have a circular cross-section (i.e., cylindrical shape) or may have other cross- sectional shapes, such as square, rectangular, or other shapes.
  • any device or fixture, which compresses the tube axially may be used for compressing the tube 20 to tune the reflection wavelength of the grating 12 to the desired wavelengths.
  • the exact hardware configuration is not critical to the present invention.
  • the axial end faces of the tube 20 and/or the seats on mating surfaces may be plated with a material that reduces stresses or enhances the mating of the tube 20 with the seat on the mating surfaces.
  • the tube 20 may have an outer diameter dl of about 3 mm and a length LI of about 10-30 mm.
  • the grating 12 has a length Lg of about 5-15 mm.
  • the length LI of the tube 20 may be substantially the same length as the length Lg of the grating 12, such as by the use of a longer grating, or a shorter tube. Other dimensions and lengths for the tube 20 and the grating 12 may be used.
  • the fiber 10 and grating 12 need not be fused in the center of the tube 20 but may be fused anywhere in the tube 20.
  • the tube 20 need not be fused to the fiber 10 over the entire length of the tube 20.
  • the tube 20 is made of a glass material, such as natural or synthetic quartz, fused silica, silica (Si0 2 ), Pyrex® by Corning (boro silicate), or Nycor® by Corning Inc. (about 95% silica and 5% other constituents such as Boron Oxide), or other glasses.
  • a glass material such as natural or synthetic quartz, fused silica, silica (Si0 2 ), Pyrex® by Corning (boro silicate), or Nycor® by Corning Inc. (about 95% silica and 5% other constituents such as Boron Oxide), or other glasses.
  • the tube should be made of a material such that the tube 20 (or the inner diameter surface of a bore hole in the tube 20) can be fused to (i.e., create a molecular bond with, or melt together with) the outer surface (or cladding) of the optical fiber 10 such that the interface surface between the inner diameter of the tube 20 and the outer diameter of the fiber 10 become substantially eliminated (i.e., the inner diameter of the tube 20 cannot be distinguished from and becomes part of the cladding of the fiber 10).
  • the coefficient of thermal expansion (CTE) of the material of the tube 20 should substantially match the CTE of the material of the fiber 10, e.g., fused silica tube and optical fiber.
  • the lower the melting temperature of the glass material the higher the CTE.
  • a silica fiber having a high melting temperature and low CTE
  • a tube made of another glass material such as Pyrex® or Nycor® (having a lower melting temperature and higher CTE) results in a thermal expansion mismatch between the tube 20 and the fiber 10 over temperature.
  • the CTE of the fiber 10 match the CTE of the tube 20 (discussed more hereinafter).
  • tube 20 being made of a glass material
  • other elastically deformable materials may be used provided the tube 20 can be fused to the fiber 10.
  • a tube made of a plastic material may be used for an optical fiber made of plastic.
  • the axial ends of the tube 20 where the fiber 10 exits the tube 20 may have an inner region 22, which is inwardly tapered (or flared) away from the fiber 10 to provide strain relief for the fiber 10 or for other reasons.
  • an area 28 between the tube 20 and the fiber 10 may be filled with a strain relief filler material, e.g., polyimide, silico ⁇ e, or other materials.
  • the tube 20 may have tapered (or beveled or angled) outer corners or edges 24 to provide a seat for the tube 20 to mate with another part (not shown) and/or to adjust the force angles on the tube 20, or for other reasons. The angle of the beveled corners 24 are set to achieve the desired function.
  • the tube 20 may have cross-sectional shapes other than circular, such as square, rectangular, elliptical, clam-shell, or other shapes, and may have side-view sectional shapes other than rectangular, such as circular, square, elliptical, clam-shell, or other shapes.
  • one or both of the axial ends of the tube 20 where the fiber 10 exits the tube 20 may have an outer tapered (or fluted, conical, or nipple) axial section, shown as dashed lines 27, which has an outer geometry that decreases down to the fiber 10 (discussed more hereinafter with Fig. 12).
  • an outer tapered (or fluted, conical, or nipple) axial section shown as dashed lines 27, which has an outer geometry that decreases down to the fiber 10 (discussed more hereinafter with Fig. 12).
  • the fluted sections 27 provides enhanced pull strength at and near the interface where the fiber 10 exits the tube 20, e.g., 6 lbf or more, when the fiber 10 is pulled along its longitudinal axis.
  • the fiber 10 may have an external protective buffer layer 21 to protect the outer surface of the fiber 10 from damage.
  • the buffer 21 may be made of polyimide, silicone, Teflon® (polytetraflouroethylene), carbon, gold, and/or nickel, and have a thickness of about 25 microns. Other thicknesses and buffer materials for the buffer layer 21 may be used. If the inner tapered region 22 is used and is large enough, the buffer layer 21 may be inserted into the region 22 to provide a transition from the bare fiber to a buffered fiber. Alternatively, if the axial end of the tube 20 has the external taper 27, the buffer 21 would begin where the fiber exits the tapered 27 portion of the tube 20.
  • the exposed bare portion of the fiber 10 may be recoated with an additional buffer layer (not shown) which covers any bare fiber outside of the tube 20 and may also overlap with the buffer 21 and/or some of the tapered region 27 or other geometrically shaped axial end of the tube 20.
  • the tube 20 may be heated, collapsed, and fused to the grating 12, by a laser, filament, flame, etc., as is described in copending US Patent Application, Serial No. (CiDRA Docket No. CC-0078A), entitled “Tube-Encased . Fiber Grating", which is incorporated herein by reference.
  • Other techniques may be used for collapsing and fusing the tubes 20 to the fiber 10, such as is discussed in US Patent No. 5,745,626, entitled “Method For And Encapsulation Of An Optical Fiber", to Duck et al, and/or US Patent No.
  • the Bragg grating 12 may be impressed in the fiber 10 before or after the capillary tube 20 is encased around and fused to the fiber 10, such as is discussed in copending US Patent Application, Serial No. (CiDRA Docket No. CC-0078), which is incorporated herein by reference. If the grating 12 is impressed in the fiber 10 after the tube 20 is encased around the grating 12, the grating 12 may be written through the tube 20 into the fiber 10 by any desired technique, such as is described in copending US Patent Application, Serial No. 09/205,845 (CiDRA Docket No. CC-0130), entitled "Method and Apparatus For Forming A Tube-Encased Bragg Grating", filed December 4, 1998.
  • the grating 12 may be encased in the tube 20 having an initial pre-strain from the tube (compression or tension) or no pre-strain. For example, if Pyrex® or another glass that has a larger coefficient of thermal expansion (CTE) than that of the fiber 10 is used for the tube 20, when the tube 20 is heated and fused to the fiber and then cooled, the grating 12 is put in compression by the tube 20.
  • the fiber grating 12 may be encased in the tube 20 in tension by putting the grating in tension during the tube heating and fusing process. In that case, when the tube 20 is compressed, the tension on the grating 12 is reduced. Also, the fiber grating 12 may be encased in the tube 20 resulting in neither tension nor compression on the grating 12 when no external forces are applied to the tube 20.
  • the capillary tube 20 may have a varying geometry, depending on the application.
  • the tube 20 may have a "dogbone" shape having a narrow central section 30 and larger outer sections 32.
  • the narrow section 30 has an outer diameter d2 of about 1 mm, and a length L2 of about 5 mm.
  • the large sections 32 each have a diameter d3 of about 3 mm and a length L3 of about 4 mm. Other lengths and diameters of the sections 30,32 may be used.
  • the dogbone shape may be used to provide increased sensitivity in converting force applied by the stepper motor 60 or actuator 154 to wavelength shift of the tube-encased grating 12.
  • An inner transition region 33 of the large sections 32 may be a sharp vertical or angled edge or may be curved as indicated by dashed lines 34.
  • a curved geometry 34 has less stress risers than a sharp edge and thus may reduce the likelihood of breakage.
  • the sections 32 of the tube 20 may have the inner tapered regions 22 or the outer fluted sections 27 at the ends of the tube 20, as discussed hereinbefore. Further, the sections 32 may have the tapered (or beveled) outer corners 24 as discussed hereinbefore.
  • the dogbone geometry be symmetric, e.g., the lengths L3 of the two sections 32 may be different if desired;
  • the dogbone may be a single-sided dogbone, where instead of the having the two larger sections 32, there may be only large section 32 on one side of the narrow section 30 and the other side may have a straight edge 37 which may have beveled corners 24 as discussed hereinbefore.
  • the dogbone has the shape of a "T" on its side.
  • Such a single-sided dogbone shall also be referred to herein as a "dogbone” shape.
  • other geometries that provide enhanced strain sensitivity or adjust force angles on the tube 20 or provide other desirable characteristics may be used.
  • the tube 20 may have sections 36 which extend axially along the fiber 10 and attach to the fiber 10 at a location that is axially outside where the force is applied on the large sections 32 by opposing end pieces 104,105, which are equivalent to the end pieces 56,50 (Fig. 1), 74,72 (Fig. 2), 159,153 (Fig. 14), respectively, or the pistons 92 (Fig. 3).
  • the axial length of the sections 36 may be about 20 mm; however, longer or shorter lengths may be used depending on the application or design requirements. Also, the sections 36 need not be axially symmetrical, and need not be on both axial ends of the tube 20.
  • the sections 32 may have the inner tapered regions 22 or the outer fluted sections 27 where the fiber interfaces with the tube 20, as discussed hereinbefore.
  • the region 22 may be within or near to the stepped section 39 as indicated by dashed lines 38.
  • the regions 106 may be air or filled with an adhesive or filler.
  • the tube 20 may have a straight constant cross-section as discussed hereinbefore and as indicated by the dashed lines 107 instead of a dogbone shape.
  • the hole 108 through the end pieces 56,50 (Fig. 1), 74,72 (Fig. 2), 152,150 (Fig. 14), respectively, or the pistons 92 (Fig.
  • the capillary tube 20 may have other axial extending geometries, such as is discussed in the aforementioned copending US Patent Application, Serial No. (CiDRA Docket No. CC-0078B). Also, more than one concentric tube may be used to form the tube 20 of the present invention, as discussed in the aforementioned copending US Patent Application. Also, the axially extended sections 36 may be part of an inner tube.
  • the tube 20 may be fused to the fiber 10 on opposite sides of the grating 12.
  • regions 200 of the tube 20 are fused to the fiber 10 and a central section 202 of the tube around the grating 12 is not fused to the fiber 10.
  • the region 202 around the grating 12 may contain ambient air or be evacuated (or be at another pressure) or may be partially or totally filled with an adhesive, e.g., epoxy, or other filling material, e.g., a polymer or silicone, or another material or may be not filled.
  • the inner diameter d6 of the tube 20 is about 0.01 to 10 microns larger than the diameter of the optical fiber 10, e.g., 125.01 to 135 microns. Other diameters may be used; however, to help avoid fiber buckling in this embodiment, the diameter d6 should be as close as possible to the fiber 10 outer diameter.
  • the same result can be achieved by fusing two separate tubes on opposite sides of the grating 12 and then fusing an outer tube across the tubes, as discussed in the aforementioned copending US Patent Application.
  • the present invention provides high repeatability, low creep and low hysteresis (e.g., about 3 picometers or less), depending on the configuration used.
  • two or more gratings 220,222 may be embedded in the fiber 10 that is encased in the tube 20.
  • the gratings 220,222 may have the same reflection wavelengths and/or profiles or different wavelengths and/or profiles.
  • the multiple gratings 220,222 may be used individually in a known Fabry Perot arrangement.
  • one or more fiber lasers such as that described in US Patent No. 5,666,372, "Compression-Tuned Fiber Laser” (which is incorporated herein by reference to the extent necessary to understand the present invention) may be embedded within the fiber 10 in the tube 20 and compression-tuned.
  • the gratings 220,222 form a cavity and the fiber 10 at least between the gratings 220,222 (and may also include the gratings 220,222, and/or the fiber 10 outside the gratings, if desired) would be doped with a rare earth dopant, e.g., erbium and/or ytterbium, etc., and the lasing wavelength would be tuned accordingly as the force on the tube 20 changes.
  • a rare earth dopant e.g., erbium and/or ytterbium, etc.
  • a tunable fiber laser that may be used is a tunable distributed feedback (DFB) fiber laser 234, such as that described in N.C. Lauridsen, et al, "Design of DFB Fibre Lasers", Electronic Letters, Oct. 15, 1998, Nol.34, No. 21, pp 2028- 2030; P. Vanning, et al, "Erbium Doped Fiber DGB Laser With Permanent ⁇ /2 Phase-Shift Induced by UV Post-Processing", IOOC'95, Tech. Digest, Vol. 5, PD1-3, 1995; US Patent No. 5,771,251, "Optical Fibre Distributed Feedback Laser", to Kringlebotn et al; or US Patent No.
  • DFB distributed feedback
  • the grating 12 is written in a rare-earth doped fiber and configured to have a phase shift of ⁇ /2 (where ⁇ is the lasing wavelength) at a predetermined location 224 near the center of the grating 12 which provides a well defined resonance condition that may be continuously tuned in single longitudinal mode operation without mode hopping, as is known.
  • the two gratings 220,222 may be placed close enough to form a cavity having a length of (N + V_) ⁇ , where N is an integer (including 0) and the gratings 220,222 are in rare-earth doped fiber.
  • the DFB laser 234 may be located on the fiber 10 between the pair of gratings 220,222 (Fig. 8) where the fiber 10 is doped with a rare-earth dopant along at least a portion of the distance between the gratings 220,222.
  • Such configuration is referred to as an "interactive fiber laser", as is described by J J. Pan et al, "Interactive Fiber Lasers with Low Noise and Controlled Output Power", E-tek Dynamics, Inc., San Jose, CA, internet web site www.e-tek.com/products/ whitepapers, which are incorporated by reference in their entirety.
  • Other single or multiple fiber laser configurations may be disposed on the fiber 10 if desired.
  • two or more fibers 10,250 each having at least one grating 12,252 therein, respectively, may be encased within the tube 20.
  • the gratings 12,252 may have the same reflection wavelengths and/or profiles or different wavelengths and/or profiles.
  • the bore hole in the tube 20 prior to heating and fusing the tube 20 would be large enough to contain both fibers 10,250 and may be other than circular, e.g., square, triangle, etc.
  • the bore hole for the tube 20 need not be centered along the center line of the tube 20.
  • the fibers 10,250 may be spaced apart in the tube 20 by a predetermined distance.
  • the distance may be any desired distance between the fibers 10,250 and have any orientation within the outer diameter of the tube 20.
  • part or all of an optical fiber and/or grating may be fused within, partially within, or on the outer surface of the tube 20, as illustrated by fibers 500,502,504, respectively.
  • the tube 20 may be fused onto the fiber 10 only where the grating 12 is located.
  • the inner tapered or flared regions 22 discussed hereinbefore may exist and the areas 28 between the tube 20 and the fiber 10 may be filled with a filler material, as discussed hereinbefore.
  • the term "tube” as used herein may also mean a block of material having the properties described herein.
  • the fiber 10 may be single-ended, i.e., only one end of the fiber 10 exits the housing or the tube 20. In that case, one end of the fiber 10 would be at or prior to the exit point of the fiber 10 from the tube 20 or the housing 50,70,90.
  • a portion of or all of the tube-encased fiber grating 20 may be replaced by a large diameter silica waveguide grating 600, such as that described in copending US Patent Application Serial No. (CiDRA Docket No. CC-0230),- entitled “Large Diameter Optical Waveguide, Grating and Laser", which is incorporated herein by reference.
  • the waveguide 600 has a core 612 (equivalent to the core of the fiber 10) and a cladding 614 (equivalent to the fused combination of the tube 20 and the cladding of the fiber 10) and having the grating 12 embedded therein.
  • the overall length LI of the waveguide 600 and the waveguide diameter d2 are set the same as that described hereinbefore for the tube 20 (i.e., such that the tube 20 will not buckle over the desired grating wavelength tuning range) and the outer diameter of the waveguide is at least 0.3 mm.
  • An optical fiber 622 (equivalent to the fiber 10 in Fig. 1) having a cladding 626 and a core 625 which propagates the light signal 14, is spliced or otherwise optically coupled to one or both axial ends 628 of the waveguide 600 using any known or yet to be developed techniques for splicing fibers or coupling light from an optical fiber into a larger waveguide, that provides acceptable optical losses for the application.
  • the large diameter waveguide with grating 600 may be used in the same ways as the tube encased grating 20 is used herein where the fiber 10 is analogous to (and interchangeable with) the core 612 of the waveguide 600.
  • the waveguide 600 may be etched, ground or polished to achieve the "dogbone" shape described hereinbefore with the tube 20.
  • the "dogbone” shape may be obtained by heating and fusing two outer tubes 640,642 onto opposite ends of the waveguide 600. All other alternative embodiments described herein for the tube 20 and the tube-encased grating are also applicable to the waveguide 600 where feasible, including having a fiber laser or a DFB fiber laser, multiple fibers (or cores), various geometries, etc.
  • the tube-encased fiber grating 20 and the large diameter waveguide grating 600 may each also be referred to herein as a "tunable optical element".
  • the tube-encased grating 20 and the large diameter waveguide grating 600 have substantially the same composition and properties in the locations where the tube 20 is fused to the fiber 10, because the end (or transverse) cross-section of the tube-encased grating 20 and the large diameter waveguide grating 600 are contiguous (or monolithic) and made of substantially the same material across the cross-section, e.g., a glass material, such as doped and undoped silica. Also, in these locations both have an optical core and a large cladding.
  • the waveguide 600 and the tube-encased grating 20 may be used together to form any given embodiment of the sensing element described herein.
  • one or more axial portion(s) of the sensing element may be a tube-encased grating or fiber and/or one or more other axial portion(s) may be the waveguide 600 which are axially spliced or fused or otherwise mechanically and optically coupled together such that the core of said waveguide is aligned with the core of the fiber fused to the tube.
  • a central region of the sensing element may be the large waveguide and one or both axial ends may be the tube-encased fiber which are fused together as indicated by dashed lines 650,652, or visa versa (Figs. 1,H,31).
  • a laser element 700 includes a laser grating(s) 702 is written in a large diameter gain waveguide (i.e., cane) 704, having a single mode core ⁇ 10um diameter and doped with one or more of the rare-earths (e.g. Erbium or Erbium: Ytterbium) to provide gain, and a thick outer cladding to give the fiber an outer diameter of >300 um.
  • a large diameter gain waveguide i.e., cane
  • the rare-earths e.g. Erbium or Erbium: Ytterbium
  • the laser can either be a DFB fiber laser, where the grating is written in the core of the cane 704 (or tube-encased gain fiber), or a DBR laser, which consists of two Bragg grating end reflectors 702, either written in respective highly photosensitive cane elements (or respective tube-encased fibers) with a gain fiber spliced therebetween, or both written within a single cane element, which is formed of gain material, (or tube-encased gain fiber).
  • a DFB fiber laser where the grating is written in the core of the cane 704 (or tube-encased gain fiber)
  • a DBR laser which consists of two Bragg grating end reflectors 702, either written in respective highly photosensitive cane elements (or respective tube-encased fibers) with a gain fiber spliced therebetween, or both written within a single cane element, which is formed of gain material, (or tube-encased gain fiber).
  • a compact, inexpensive compression-tuned Bragg grating-based laser 710 includes a bulk semiconductor pump laser chip 712, launching pump light into the Bragg grating laser cavity through a micro lens 714, e.g., a GRIN lens.
  • the lens 714 can be part of the cane through machining of the end of the cane 704.
  • a fiber output pigtail 716 inside a ferrule/glass capillary 718 is glued to the glass canter with the fiber 716 aligned to the laser element 700.
  • the Bragg grating laser cavity should be designed to emit most light out of the output end by making an asymmetric laser cavity with respect to output coupling.
  • the pump laser 712 can be directed inside the glass cane either at the input and/or at the output of the first laser cavity.
  • the short distance between the pump chip 712 and the stabilizing grating 702 might require an anti reflection coating at the output facet of the pump chip.
  • Normally grating stabilized pump lasers operate in the "coherence collapse" regime with a weak grating separated by ⁇ lm from the pump laser.
  • the laser cavity inside the glass cane can be mechanically compressed to make a continuously wavelength tunable laser 730, basically using the same design, compression actuation and wavelength control as described hereinbefore.
  • BGs pump reflector Bragg gratings
  • the tunable laser 740 provides a fixed laser wavelength with a high degree of wavelength stability can be realized by putting the glass cane 704 in compression with a section of material 742 with higher thermal expansion coefficient as a part of the compressed length.
  • the housing 744 around the compressed length should have a low thermal expansion coefficient.
  • the high thermal expansion material 742 will with increasing temperature compress the laser cavity to counter-act the positive wavelength shift caused by the temperature dependence of the refractive index of the laser element 700.
  • a Bragg grating laser 750 having an external modulator 752 is illustrated.
  • a bulk modulator could possibly be integrated in the fiber laser module.
  • a LiNb03 electro-optic Mach-Zehnder waveguide modulator is aligned with the output of the laser passing a bulk optical isolator 754 put between two GRIN lenses 756,758.
  • a dielectric pump stop filter 760 at the output of the laser is also included in this configuration.
  • the residual pump power at the output of the laser can be used to pump an EDFA 772 in a MOPA (Master Oscillator Power Amplifier) configuration, as illustrated in Fig. 22. Since an optical isolator 774 is needed between the laser and the amplifier, a 1480nm pump source is needed, where the pump light will pass an optical isolator in the 1550 nm laser band.
  • MOPA Master Oscillator Power Amplifier
  • the residual pump power of the laser of Fig. 22 can also be used to pump several other Bragg grating lasers 776 that are optically connected in series, having different wavelengths. These can be compression-tuned separately or together. In making such a multi-wavelength laser array 780, all lasers will laser simultaneously. With Bragg grating-based DFB lasers, the individual lasers can be turned on/off by switching the optical phase-shift inside the laser grating 702, for example by applying local heating or a local strain at 782. This will enable a wavelength selective laser array.
  • phase shifts can also be used to control the relative power between the lasers, for example to dynamically equalize the powers. Note that changing the phase shift will also cause a shift in laser wavelength, with an amount depending on the position of the phase shift. This can be compensated for by changing the compression/strain (or temperature) of the laser. Alternatively changes in phase-shift can be used to modulate the laser frequency.
  • a sampled grating DBR fiber laser 790 to enhance the tuning range of a grating based single frequency laser for a given compression, it is possible to make a sampled grating DBR fiber laser 790.
  • One of the sampled gratings 792 is tuned relative to the other sampled grating 794 to provide stepwise tuning in steps equal to the spectral separation between each peak (which can be made to match the ITU grid).
  • One possible way of doing this is to compress both gratings 702, as illustrated in Fig. 24, making the tuning sensitivity to compression different for the two gratings by writing them in sections of the glass cane 704 having different diameters.
  • the length of the laser element 700 will probably be quite long (e.g., >10 cm).
  • one of the gratings 792 another embodiment of the laser 796 may be maintained fixed and only the second grating 794 is tuned, as illustrated in Fig. 25.
  • the configuration has a coil of gain fiber 798 (e.g. erbium-doped fiber ("EDF")) between the gratings.
  • EDF erbium-doped fiber
  • the length of each sampled grating may be >20 mm to provide sufficient reflection over a wide wavelength range.
  • the sampled grating DBR laser may mode-hop between neighboring longitudinal cavity modes due to the small longitudinal mode-spacing relative to the bandwidth of each reflection peak. Consequently, the length of the coil of gain fiber 798 may to relatively short to reduce mode-hopping.
  • both sampled gratings 702 may be individually tunable to provide quasi-continuous tuning of the laser 796.
  • the invention may be used with a co-doped distributed feedback laser arrangement similar to that described in the articles: J. Kringlebotn et al., "Er+3: Yb+3- Codoped Fiber Distributed-Feedback Laser", Optics Letters, Vol. 19, No. 24, pp 2101-2103 (December 1994); and H. Kogelnik et al, "Coupled- Wave Theory of Distributed Feedback Lasers", J. Appl. Phys., Vol. 43, No. 5, pp 2327-2335 (May 1972), which are incorporated herein by reference in their entirety.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Optics & Photonics (AREA)
  • Mechanical Light Control Or Optical Switches (AREA)
  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)

Abstract

L'invention concerne un laser à réseau de Bragg réglé par compression comprenant un élément optique réglable (20, 600), lequel comporte soit une fibre optique (10) sur laquelle est imprimé au moins un réseau de Bragg (12) logé dans une partie au moins d'un tube capillaire de verre (20) et fusionné à celui-ci, soit un réseau de guides d'ondes de grand diamètre (600) doté d'un coeur et d'une large gaine. Une première lumière (14) est incidente sur le réseau (12), une seconde lumière (16) étant réfléchie à une longueur d'onde de réflexion μ1. L'élément réglable (20, 600) est soumis à une compression axiale, ce qui provoque un changement de longueur d'onde de réflexion du réseau (12) sans déformation dudit élément. La forme de cet élément peut présenter des géométries variables (forme de bobine, par exemple), et/ou plusieurs réseaux ou paires de réseaux peuvent être utilisés. De même, on peut utiliser plusieurs fibres (10) ou coeurs (612). Une partie au moins de l'élément peut être dopée entre une paire de réseaux (150, 152), d'où la formation d'un laser réglé par compression. Le réseau (12) ou les réseaux (150, 152) peuvent également être conçus sous la forme d'un laser à rétroaction distribuée réglable. Par ailleurs, ledit élément (20) peut comporter une zone intérieure diminuée (22) ou des sections (27) effilées (ou cannelées). La compression peut être réalisée au moyen d'un transducteur piézoélectrique (PZT), d'un moteur pas à pas, d'un dispositif hydraulique ou d'un autre dispositif d'actionnement.
PCT/US2001/047356 2000-11-06 2001-11-06 Laser a reseau de bragg regle par compression WO2002037625A2 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2002226036A AU2002226036A1 (en) 2000-11-06 2001-11-06 Compression-tuned bragg grating-based laser

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US70708400A 2000-11-06 2000-11-06
US09/707,084 2000-11-06

Publications (2)

Publication Number Publication Date
WO2002037625A2 true WO2002037625A2 (fr) 2002-05-10
WO2002037625A3 WO2002037625A3 (fr) 2002-09-26

Family

ID=24840286

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2001/047356 WO2002037625A2 (fr) 2000-11-06 2001-11-06 Laser a reseau de bragg regle par compression

Country Status (2)

Country Link
AU (1) AU2002226036A1 (fr)
WO (1) WO2002037625A2 (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005013444A1 (fr) * 2003-07-28 2005-02-10 Spi Lasers Uk Limited Laser a guide d'ondes haute energie, sans danger pour la vue
CN102074882A (zh) * 2010-12-27 2011-05-25 东南大学 光纤光栅中心波长宽范围调谐装置
CN103884925A (zh) * 2013-10-31 2014-06-25 山东大学 一种堆叠型压电陶瓷蠕变起始时间确定方法
CN108732667A (zh) * 2017-04-17 2018-11-02 华为技术有限公司 一种超结构光栅和可调谐激光器
RU2730879C1 (ru) * 2019-12-30 2020-08-26 Федеральное государственное автономное образовательное учреждение высшего образования "Новосибирский национальный исследовательский государственный университет" (Новосибирский государственный университет, НГУ) Устройство для перестройки длины волны генерации волоконного лазера
CN113790960A (zh) * 2021-09-08 2021-12-14 大连理工大学 监测静荷载作用下断裂失效过程的变灵敏度光纤光栅传感器及使用方法
CN116487984A (zh) * 2023-05-15 2023-07-25 密尔医疗科技(深圳)有限公司 非互易性相移器及激光器

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5691999A (en) * 1994-09-30 1997-11-25 United Technologies Corporation Compression-tuned fiber laser
WO2000037969A2 (fr) * 1998-12-04 2000-06-29 Cidra Corporation Selecteur de mode de bragg et laser accordes par compression
WO2000037914A2 (fr) * 1998-12-04 2000-06-29 Cidra Corporation Sonde manometrique a reseau de bragg

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5691999A (en) * 1994-09-30 1997-11-25 United Technologies Corporation Compression-tuned fiber laser
WO2000037969A2 (fr) * 1998-12-04 2000-06-29 Cidra Corporation Selecteur de mode de bragg et laser accordes par compression
WO2000037914A2 (fr) * 1998-12-04 2000-06-29 Cidra Corporation Sonde manometrique a reseau de bragg

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
BALL G A ET AL: "COMPRESSION-TUNED SINGLE-FREQUENCY BRAGG GRATING FIBER LASER" OPTICS LETTERS, OPTICAL SOCIETY OF AMERICA, WASHINGTON, US, vol. 19, no. 23, 1 December 1994 (1994-12-01), pages 1979-1981, XP000484576 ISSN: 0146-9592 *

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005013444A1 (fr) * 2003-07-28 2005-02-10 Spi Lasers Uk Limited Laser a guide d'ondes haute energie, sans danger pour la vue
US7502391B2 (en) 2003-07-28 2009-03-10 Spi Lasers Uk Limited Eye safe high power fibre laser
CN102074882A (zh) * 2010-12-27 2011-05-25 东南大学 光纤光栅中心波长宽范围调谐装置
CN103884925A (zh) * 2013-10-31 2014-06-25 山东大学 一种堆叠型压电陶瓷蠕变起始时间确定方法
CN103884925B (zh) * 2013-10-31 2016-03-30 山东大学 一种堆叠型压电陶瓷蠕变起始时间确定方法
CN108732667A (zh) * 2017-04-17 2018-11-02 华为技术有限公司 一种超结构光栅和可调谐激光器
CN108732667B (zh) * 2017-04-17 2021-01-05 华为技术有限公司 一种超结构光栅和可调谐激光器
US10931085B2 (en) 2017-04-17 2021-02-23 Huawei Technologies Co., Ltd. Super structure grating and tunable laser
RU2730879C1 (ru) * 2019-12-30 2020-08-26 Федеральное государственное автономное образовательное учреждение высшего образования "Новосибирский национальный исследовательский государственный университет" (Новосибирский государственный университет, НГУ) Устройство для перестройки длины волны генерации волоконного лазера
CN113790960A (zh) * 2021-09-08 2021-12-14 大连理工大学 监测静荷载作用下断裂失效过程的变灵敏度光纤光栅传感器及使用方法
CN113790960B (zh) * 2021-09-08 2022-05-27 大连理工大学 监测静荷载作用下断裂失效过程的变灵敏度光纤光栅传感器及使用方法
CN116487984A (zh) * 2023-05-15 2023-07-25 密尔医疗科技(深圳)有限公司 非互易性相移器及激光器

Also Published As

Publication number Publication date
AU2002226036A1 (en) 2002-05-15
WO2002037625A3 (fr) 2002-09-26

Similar Documents

Publication Publication Date Title
US6597711B2 (en) Bragg grating-based laser
US6363089B1 (en) Compression-tuned Bragg grating and laser
CA2353504C (fr) Selecteur de mode de bragg et laser accordes par compression
JP3824323B2 (ja) 圧縮により波長可変としたファイバレーザ
US7088756B2 (en) Polarization maintaining dispersion controlled fiber laser source of ultrashort pulses
US9071037B2 (en) High power short pulse fiber laser
US6452667B1 (en) Pressure-isolated bragg grating temperature sensor
US6826343B2 (en) Multi-core waveguide
CA2394910C (fr) Guide d'ondes optique, reseau grave et laser de grand diametre
US6594288B1 (en) Tunable raman laser and amplifier
CA2402301A1 (fr) Dispositif graphique a base de reseau avec compensation thermique a compression axiale
WO2020244130A1 (fr) Laser à fibres à fréquence unique largement accordable reposant sur un effet d'interférence multimode
Babin et al. Tunable fiber Bragg gratings for application in tunable fiber lasers
US6834142B2 (en) Optical grating-based filter
WO2002037625A2 (fr) Laser a reseau de bragg regle par compression
US20030215185A1 (en) Large diameter optical waveguide having long period grating therein
Luo et al. Tuning fiber bragg gratings by deformable slides
Anzueto-Sánchez et al. Enhanced tuning mechanism in fibre laser based on multimode interference effects
Su et al. Design of wavelength-switching erbium-doped fiber lasers with a multimode fiber Bragg grating using spatial-mode excitation and selection techniques
US8077747B2 (en) Phosphate glass based optical device and method
WO2011007693A1 (fr) Structure d'épissurage par fusion, élément de guide d'ondes optique ayant une structure d'épissurage par fusion et dispositif de source de lumière utilisant un élément de guide d'ondes optique et procédé d'épissurage
Liaw et al. Tunable erbium-doped fiber lasers using various inline fiber filters
Quintela et al. Tunable fiber laser using concatenated non-adiabatic single-mode fiber tapers
Quintela Incera et al. Tunable fiber laser using concatenated non-adiabatic single-mode fiber tapers
Pagé Design and Applications of a Tunable Multi-wavelength SFL

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A3

Designated state(s): AE AG AL AM AT AU AZ BA BB BG BR BY BZ CA CH CN CO CR CU CZ DE DK DM DZ EC EE ES FI GB GD GE GH GM HR HU ID IL IN IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MA MD MG MK MN MW MX MZ NO NZ PL PT RO RU SD SE SG SI SK SL TJ TM TR TT TZ UA UG UZ VN YU ZA ZW

AL Designated countries for regional patents

Kind code of ref document: A3

Designated state(s): GH GM KE LS MW MZ SD SL SZ TZ UG ZW AM AZ BY KG KZ MD RU TJ TM AT BE CH CY DE DK ES FI FR GB GR IE IT LU MC NL PT SE TR BF BJ CF CG CI CM GA GN GQ GW ML MR NE SN TD TG

121 Ep: the epo has been informed by wipo that ep was designated in this application
DFPE Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
REG Reference to national code

Ref country code: DE

Ref legal event code: 8642

122 Ep: pct application non-entry in european phase
NENP Non-entry into the national phase in:

Ref country code: JP

WWW Wipo information: withdrawn in national office

Country of ref document: JP