Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/35—Non-linear optics
  • G02F1/3525—Optical damage
• • 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
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/264—Optical coupling means with optical elements between opposed fibre ends which perform a function other than beam splitting
• • 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
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/264—Optical coupling means with optical elements between opposed fibre ends which perform a function other than beam splitting
  • G02B6/266—Optical coupling means with optical elements between opposed fibre ends which perform a function other than beam splitting the optical element being an attenuator
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/35—Non-linear optics
  • G02F1/3511—Self-focusing or self-trapping of light; Light-induced birefringence; Induced optical Kerr-effect
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/35—Non-linear optics
  • G02F1/3515—All-optical modulation, gating, switching, e.g. control of a light beam by another light beam
• • 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
  • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
• • 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
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/35—Optical coupling means having switching means
  • G02B6/354—Switching arrangements, i.e. number of input/output ports and interconnection types
  • G02B6/3544—2D constellations, i.e. with switching elements and switched beams located in a plane
  • G02B6/3548—1xN switch, i.e. one input and a selectable single output of N possible outputs
  • G02B6/3552—1x1 switch, e.g. on/off switch
• • 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
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/35—Optical coupling means having switching means
  • G02B6/3594—Characterised by additional functional means, e.g. means for variably attenuating or branching or means for switching differently polarized beams
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/35—Non-linear optics
  • G02F1/365—Non-linear optics in an optical waveguide structure
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F2203/00—Function characteristic
  • G02F2203/52—Optical limiters

Definitions

• the present invention relates to optical power switching devices and methods, and particularly to such devices and methods for interrupting or reducing the optical transmission in response to the transmission of excessive optical power or energy Background of the Invention
• optical power namely, up to several Watts in a single fiber or waveguide
• these high specific intensities or power per unit area are introduced into the systems, many thin film coatings, optical adhesives and even bulk materials, are exposed to light fluxes beyond their damage thresholds and are eventually damaged
• Another issue of concern in such high-power systems is laser safety, where well-defined upper limits are established for powers emitted from fibers
• a passive device that will switch off the power propagating in a fiber or waveguide, when the power exceeds the allowed intensity
• Such a switching device should be placed either at the input of a sensitive optical device, or at the output of a high-power device such as a laser or an optical amplifier, or integrated within an optical device
• Passive devices were proposed in the past for image display systems These devices generally contained a mirror that was temporarily or permanently damaged by a high-power laser beam that damaged the mirror by distortion or evaporation Examples for such devices are described in U S Patents 6384982, 6356392, 6204974 and 5886822
• the powers needed here are in the range of pulsed or very energetic CW laser weapons and not in the power ranges for communication or medical devices
• the distortion of a mirror by the energy impinging on it is very slow and depends on the movement of the large mass of the mirror as well as the energy creating the move
• the process of removing a reflective coating from large areas is also slow, since the mirror is not typically placed in the focus where power is spatially concentrated
• Another passive device was proposed in U S Patent 621658B1, where two adjacent materials were used The first material was heat-absorbing, while the second material was heat- degradable When these two materials were inserted into a light beam, the first material was heated and transferred its heat to the second material to degrade the transparency or reflectivity of
• the "Fiber Fuse” is a phenomenon that results in the catastrophic destruction of an optical fiber core It has been observed at laser powers on the order of 3x10 6 watts/cm 2 in the core This phenomenon is characterized by the propagation of a bright visible light from the point of initiation toward the laser source
• the term “Fiber Fuse” has been adapted to the phenomenon because of the similarity in appearance to a burning fuse
• the “Fiber Fuse” has been shown to occur when the end of the fiber is contaminated, and it has also been initiated spontaneously from splices and in-core disturbances
• the "Fiber Fuse” event can destroy many kilometers of waveguide or fiber
• the present invention includes at least four different versions of optical power switching devices, as follows
• An assembly of one of the above switches (1 or 2 or 3) together with additional optical components, protecting against the damaging phenomenon called "Fiber Fuse" in the forward and backward optical power throughput Version 1 Two co-linear waveguides separated by a gap, where the switch is interposed transversely in the gap, comprising
• an optical waveguide having an input section and an output section, the two sections are aligned, forming a gap between them, or a pair of opposed surfaces extending transversely through the axes of the waveguide sections, and
• a thin, substantially transparent, layer of electrically conductive or semi conducting material disposed between the opposed surfaces of the waveguide sections, the material forming a plasma or breakdown when exposed to optical signals propagating within the optical waveguide with an optical power level above a predetermined threshold, the plasma or breakdown damaging the opposed surfaces sufficiently to render those surfaces substantially opaque, i e , absorbing and/or scattering the light propagating within the optical waveguide so as to prevent the transmission of such light
• the visible light emitted by the plasma can be detected by a photo- detector and used as an indication that the light intensity passing through the switch exceeds its designed threshold
• Version 3 A waveguide having a mechanically weakened place along its path, the weak place breaks at a predetermined optical power throughput, comprising
• Version 4 An assembly of one of the above switches (version 1 or 2 or 3) together with additional optical components, protecting against the damaging phenomenon called "Fiber Fuse", by confining the damaging phenomenon to a short sacrificial waveguide length inside the switch assembly
• the switch can be manufactured and used as a discrete component, with connectors on both ends or with splices on both ends Alternatively, the switch can be built into a system where waveguides lead to and from the switch, without the use of connectors or splices
• Switches with threshold powers ranging from a few milliwatts up to about a few watts have been built and tested for threshold-power, insertion loss, return loss, added opacity or power drop, after exposure to threshold and higher powers, timing, endurance and visual (microscopic) inspection before and after damage
• the tests included time domain experiments, where switches were exposed to short pulses (down to tens of ns) The switches reacted in the same way as in the continuous-wave case, i e , a large drop in their transparency when impinged by powers over the threshold Insertion losses of less than ldB and return losses higher than 45dB were obtained Additionally, parameters such as broad-spectrum operation of the switch, modulated optical powers at the GHz range and higher, and endurance for hundreds of hours of powers a few dB lower than the threshold, were tested and found satisfactory
• Fig 1 is a schematic, cross-sectional view of an optical power-switching device embodying the present invention
• Fig 2 is a schematic cross-sectional view of a modified optical power switching embodying the invention
• Fig 3 is a schematic cross-sectional view of an optical power-switching device embodying the invention in a connector-like assembly
• Fig 4 is a schematic cross-sectional view of a modified optical power-switching device embodying the invention in a connector-like assembly
• Fig 5 is a schematic cross-sectional view of an optical power-switching device embodying the invention in a ferrule assembly
• Fig 6 is a schematic cross-sectional view of a modified optical power-switching device embodying the invention in a ferrule assembly
• Fig 7 is a schematic cross-sectional view of an optical power-switching device embodying the invention in a bare fiber assembly
• Fig 8 is a schematic cross-sectional view of a modified optical power-switching device embodying the invention in a bare fiber assembly
• Fig 9 is a schematic cross sectional view of the thin layers, conductor only version, in a transverse and angled configuration, in a spliced assembly
• Fig 10 is a schematic cross sectional view of the thin layers, conductor and anti reflection layers version, in a transverse and angled configuration, in a spliced assembly
• Fig 11 is an experimental curve of output power versus input power for a switch having a 30 dBm-input-power threshold
• Fig 12 is an experimental curve of output power versus input power for a switch having 24 dBm-input-power threshold
• Fig 13 is an experimental curve of output power versus time for the switches above
• Fig 14 is an experimental microscopic view of a damaged (opaque) switch with a crater or craters in the core of the waveguide
• Fig 15 is a schematic illustration of a further embodiment of the invention that includes a light detector detecting discharge-emitted light for switch failure detection
• Fig 16 is a schematic illustration of an embodiment of the invention that includes a plurality of switches in one stack, for corresponding waveguides in a stack
• Fig 17 is a schematic illustration of a further embodiment of the invention that includes a plurality of switches in one stack, for corresponding optical fibers in a stack
• Fig 18 is a schematic illustration of a further embodiment of the invention that includes a detector for back-reflected light for switch failure detection
• Fig 19 is a schematic illustration of a further embodiment of the invention that includes PC or APC connectors end connections for the optical switch
• Fig 20 is a schematic illustration of a further embodiment of the invention that includes spliced end connections for the optical switch
• Fig 21 is a schematic illustration of a further embodiment of the invention that includes PC or APC connectors end connections for an optical switch made of high- numerical-aperture fibers
• Fig 22 is a schematic illustration of a further embodiment of the invention that includes SMF-spliced end connections for an optical switch made of high-numerical- aperture fibers
• Fig 23 is a schematic illustration of a further embodiment of the invention that includes an electrical lead interruption at the core area for the detection of switch failure
• Fig 24 is a schematic representation of another embodiment of a switching device according to the invention, which consists of an absorbing waveguide
• Fig 25 is a schematic illustration of a switching device having an absorbing waveguide and a notch
• Fig 26 is a schematic illustration of a protection device against "Fiber Fuse" using a circulator in the device
• Fig 27 is a schematic illustration of a protection device against "Fiber Fuse” using a core area reduction in the device
• Fig 28 is a schematic illustration of a protection device against "Fiber Fuse” using a splitter in the device
• an optical power or energy switching device 2 composed of an optical waveguide 4, e g , a solid waveguide or a fiber, cut transversely to form two waveguide sections 4' and 4 "
• the waveguide 4 is composed of a central core 6, in which most of the light propagates, and an outer cladding 8
• the waveguide has an input end 10 and an output end 12 Interposed between the two waveguide sections 4' and 4", and transversing the path of optical energy propagating from the input end 10 to the output end 12, is a partially transparent conductive layer 14
• the layer 14 is very thin (only a few atomic layers, typically 1 to
• a conductive metal such as rhodium, aluminum, gold, silver, chromium or nickel, or a combination or alloy of such metals
• Such thin layers of conducting material are known to enhance the electric field strength in their vicinity due to local irregularities of their surface, where the surface irregularities induce field concentration, resulting in lower power needed to create an electrical breakdown, and damage
• Such thin nanometric layers may be modeled as a plurality of aggregates of nano-particles (see, e g , M Quinten, “Local Fields Close to the Surface of Nanoparticles and Aggregates of Nanoparticles," Appl Phys B 73, 245- 255 (2001) and the book “Absorption and Scattering of Light by Small Particles” by C F Bohren and D R Huffmann, Wiley-Interscience (1998), Chapter 12 [showing strong field enhancement factors (up to 10 5 ) for few-nanometer particles as well as wide extinction spectra for various materials and shapes]
• the visible light that may be emitted when the damage occurs, can be detected by a monitoring device, to signal when the switch has been exposed to optical power higher than the threshold
• the switch is its insertion (or transmission) loss
• a low insertion loss at the operating powers is desirable, in order to avoid power losses
• the conducting layer generally absorbs and reflects light
• the reflection can be minimized by the addition of anti-reflective layers 16 and 18 on both sides of the conducting layer 14
• the absorption of the conducting layer is an intrinsic property, which cannot be fully eliminated (it absorbs between 3% and 30% of the power) Therefore, the insertion loss at the operating power is not negligible, and may reach approximately ldB and or even higher
• the switch is required to have a high insertion loss (low transmission) at high powers (above the threshold) This is obtained by the significant and permanent damage to the surfaces adjacent the conducting layer 14, which significantly increases the loss (reduces the transmission)
• Typical values of insertion loss after damage occurs are in the range of 10 to 20 dB (namely, leaving only 1%-10% transmission)
• the thickness of the conductive layer 14 may be varied to adjust the threshold
• the threshold power decreases with increasing thickness of the conductive layer
• the insertion loss at the operating power also changes with thickness, (the thicker the layer, the higher the loss)
• the use of thickness to adjust the threshold is useful only over a limited range of operating powers
• the threshold may be adjusted by using fibers of different core 6, or mode field diameters
• the commonly used fiber in optical communication systems is the SMF-28 single-mode fiber This fiber has a mode field diameter of approximately
• HNA fibers 10 micrometers for 1550 nm wavelengths
• Other fibers have either smaller or larger diameters
• High-Numerical-Aperture (HNA) fibers generally have smaller mode field diameters down to 4 micrometers
• the light intensity (power per unit area) is larger than in SMF-28 fibers operating with the same power Consequently, the power threshold in HNA fibers is lower than that in SMF-28 fibers with the same general structure 2
• the input and output fibers can still be standard SMF-28 fibers
• These can be efficiently fusion-spliced to the HNA fibers or other types of fibers (insertion losses are approximately 0 ldB per splice)
• using different types of fibers, having different mode field diameters, with the same structure 2 can lead to switches having different thresholds and nearly the same insertion loss at the operating powers
• the same principle is used for multi-mode fibers having various
• the conductive layer 14 can be deposited on a surface that extends across the optical waveguide at an angle, i e , not perpendicular to the direction of propagation of the light, thus preventing any back reflection from re- entering the waveguide core, as depicted in Fig 2 (as discussed below)
• the conductive layer may be either a single layer or a layer that is covered on one or on both sides with transparent layers, which can serve as anti-reflective coatings, reducing the optical reflections
• the coating layers 16 and 18 are designed to have minimal reflections
• the anti-reflective layers 16 and 18 can be composed of the same dielectric material, or of two different materials Generally, when using the same material, in order to obtain minimal reflection, the thickness of the layers 16 and 18 is unequal, the difference in thickness of the entry layer 16 and the exit layer 18 is due to a phase change of reflections from conducting surfaces as opposed to no phase
• only one of the two anti-reflective coatings 16 and 18 may be desired
• Fig 2 illustrates a device similar to that shown in Fig 1
• the layers 14, 16 and 18 are not perpendicular to the direction of light propagation in the waveguide, but rather at an angle 20
• the layers 14, 16 and 18 are not perpendicular to the direction of light propagation in the waveguide, but rather at an angle 20
• single-mode optical fibers, e g in single-mode optical fibers, e g .
• the angle 20 is typically 8 degrees
• an optical reflection 22 from the layer 14 does not propagate backwards inside the waveguide
• Fig 3 illustrates the switch of Fig 1 packaged in a connector-like configuration
• the device can be packaged in several ways
• Such a device includes an input fiber, two connectors 34 connected using an adapter 35, an aligning sleeve 32, and input and output fibers
• the difference between the switching device and the standard connector is that either one or both fibers have additional layers 14, 16, 18 on their matching surfaces
• Fig 4 illustrates the switch of Fig 2 packaged in a connector-like configuration
• two commercially available APC (Angled Physical Contact) connectors 34 e g , HPC-S8 66 connector manufactured by Diamond SA, Switzerland
• APC Angled Physical Contact
• the conducting layer 14 and, if needed, the anti-reflective layers 16 and 18, are deposited on one or both angled ferrules 38 (an integral part of connectors 34) to perform the switching operation
• This 8-degree angled arrangement prevents reflections from entering the core areas of the waveguide portions 4' and 4"
• Fig 5 describes a ferrule switch inner assembly
• two PC ferrules 30 are assembled together, aligned by an aligning sleeve 32, to connect the input waveguide portion 4' with the output waveguide portion 4"
• the conducting layer 14 and, if needed, the anti-reflective layers 16 and 18, are deposited on one or both ferrules 30 to perform the switching operation
• Ferrules 30 with fibers are made of, e g , zirconia, and can be purchased commercially as well as aligning sleeve 32, and are available in
• Fig 6 illustrates a ferrule switch inner assembly having an angled configuration
• two APC (angled) ferrules 38 are assembled, aligned by an aligning sleeve 32, to connect the input fiber 4' with the output fiber 4"
• the conducting layer 14 and, if needed, additional anti-reflective layers 16 and 18, are deposited at an angle on one or both ferrules 38 to perform the switching operation
• the angled arrangement prevents reflections from entering the fiber core area
• Ferrules 38 with fibers are made of, e g , zirconia, and can be purchased commercially as well as aligning sleeve 32, and are available in 1 5 and 2 5 mm diameters
• the inner assembly is held together, e g , using an external, spring-loaded casing holding them axially in contact
• Fig 7 illustrates a bare fiber switch assembly It consists of two bare fiber (e g SMF 28 of 125 micrometers diameter) lengths 4' and 4", cleaved perpendicularly
• the two fiber lengths 4' and 4" are aligned and assembled, using an aligning tube or capillary 24
• the conducting layer 14 and, if needed, the anti-reflective layers 16 and 18, are deposited on one or both of the opposed end surfaces of the input fiber 4' and the output fiber 4"
• the assembly is fixed in position using, e g , a commercially available mechanical envelope such as the "ultra splice" made by the Siemon Company, USA, or a commercially available silicon V-groove made by Orgil Optical Connector, Tel-Aviv, Israel
• Fig 8 illustrates a bare fiber switch assembly having an angled configuration
• two angle-cleaved fibers 4' and 4" are aligned and assembled using an aligning tube or capillary 24, taking care of both linear as well as angular alignment
• the conducting layer 14 and, if needed, additional anti-reflective layers 16 and 18, are deposited on one or both of the input fiber 4' and output fiber 4", on the angled end surfaces This angled arrangement prevents reflections from entering the core area
• the assembly is fixed in position using, e g , a commercially available mechanical envelope such as the "ultra splice” made by the Siemon Company, USA, or a commercially available silicon V-groove made by Orgil Optical Connector, Tel-Aviv,
• Fig 9 illustrates a thin conducting layer 14 that is the only layer between the two waveguides (or fibers) 6 and performs the switching operation Also, the layer 14 can be deposited either perpendicular to or at an angle to the light-propagation direction as shown in the drawing In this case fusion splicing holds the assembly together After splicing, the splice is re-coated or covered by a commercially available shrinkable polymer sleeve
• Fig 10 illustrates a thin conducting layer 14 placed between two anti-reflection layers 16 (at entrance) and 18 (at exit)
• the layers 14, 16 and 18 can be deposited either perpendicular to or at an angle to the light- propagation direction as shown in the drawing
• fusion splicing holds the assembly together
• the splice is re-coated or covered by a commercially available shrinkable polymer sleeve
• Fig 11 is an experimental curve of the output power versus the input power in one example of the switch
• the thin layer was made of chromium (Cr)
• Cr Two non-symmetric, anti-reflective layers on both sides of the Cr layer served as anti-reflecting layers
• Fig 13 presents an experimental curve of output power versus time for the switch described in Fig 12, above, (power is given here in relative units)
• Fig 14 is an experimental microscopic view of a damaged (opaque) switch At the instant when the damage occurs, and the output energy drops, visible light is emitted in all directions from the core at the damaged spot This is mainly due to recombination of ions and electrons in the ionized volume of the core close to the coatings where the crater or craters are developed Visual (microscopic) inspection after the damage revealed a cratered core, with craters a few microns deep covering substantially all the cross-sectional areas of the core (where the optical power flows)
• the crater has similar dimensions to the core, and the large cladding area is not cratered
• the outer diameter of the cladding is 125 micrometers, and the core diameter is approximately 10 micrometers, covering about 1% of the total cross- sectional area of the optical waveguide
• Fig 15 is a schematic illustration of a further embodiment of the invention that includes a light detector, such as a photodiode, for detecting discharge-emitted light for switch failure detection
• a light detector such as a photodiode
• On-line testing and status reporting of switches is a part of the system status design in many systems There are several methods for status monitoring of the switches described above
• the switch is declared opaque, and is replaced after correcting the malfunctioning channel
• This method requires two detectors and a control loop and is relatively expensive
• Second, a visible light burst produced by the switch may be detected, using a photo detector, e g , a commercially available photodiode After the burst occurrence, the switch is declared opaque This is depicted in Fig 15
• Fig 16 is a schematic illustration of an embodiment that includes multiple switches
• the small dimensions of the switch enable the construction of multiple switches in clusters for use on a plurality of optical fibers or waveguides In this way one can include spares or replacements in the cluster and replace them remotely
• multiple (e g , three) switches 68 are manufactured in a stack 60 of a multiplicity of silica waveguides 66 manufactured on a common substrate (the manufacturing of silica waveguides on silicon substrates is a well established process and offered by many manufacturers, e g Lambda-Crossing, Caesarea, Israel, with each waveguide having input light 62 and output light 64
• the conducting layer that forms the switches 68 are located between the input and the output and deposited there as a single or three-layer switch
• These switches 68 may serve as operating switches and/or spares to replace a switch that becomes opaque when subjected to excessive power
• Fig 17 is a schematic illustration of an embodiment that consists of plurality of switches 70 in a stack 72 of separate fibers, each having input power 62 and output power 64
• the sacrificial coatings that form the switches 70 serve for a plurality of leads as well as having spares in the proximity for quick change
• the input fibers 62 and output fibers 64 may be a commercially available fiber ribbon having multiple fibers in the ribbon, or in spliced configuration, places into plurality of V-grooves on a single wafer
• Fig 18 is a schematic illustration of an embodiment that detects the return (back-reflected) power, which generally changes after the switch turns opaque
• the back-reflected light 48 propagates in the core 6 of the input fiber length 4', in a direction opposite that of the input light, and is split by an optical splitter 49 such as a commercially available fiber coupler, a beam splitter, a circulator or other device
• the splitter 49 directs a portion of the back-reflected light toward an optical detector 44
• Fig 19 is a schematic illustration of an embodiment that includes different end
• Fig 20 shows the external connections as a splice-ready assembly where both the input and output fibers 84 (e g , SMF) are left for future splicing This applies to all the switches described in this patent application and illustrates only the connection to the external world (not the switch itself)
• Fig 21 shows a switch 90 based on a High Numerical Aperture (HNA) fiber
• the input ray 86 is connected through a connector 82 to a standard fiber 84 (e g , SMF), then through a fiber splice 98 to a HNA fiber 92, which is also used in the switch 90
• the light propagates through a HNA fiber 92 to another fiber splice 98 into a standard fiber 84, and then to an output connector 82, from which the output ray 88 is emitted
• HNA High Numerical Aperture
• Fig 22 shows a similar switch 90, based on an HNA fiber, in a splice-ready configuration
• This configuration is similar to that shown in Fig 21, has no external connectors, but with splice-ready standard (e g , SMF) fibers
• splice-ready standard e g , SMF
• both the input ray 86 and the output ray 88 are connected using splices to standard (e g , SMF) fibers 84
• Fig 23 is a schematic illustration of a direct electrical method for status monitoring
• a thin sacrificial conductive layer 52 is deposited as a conductive strip having a width similar to that of the optical fiber core 56
• This layer is deposited across the waveguide or the optical fiber 50, passing through the fiber core When optical power exceeding the threshold power is transmitted through the core, the layer
• the conductive layer 52 may be a metallic sacrificial layer that is deposited in a rectangular shape in the center of the fiber 50 and having a width about the same as the core dimension, e g , approximately 10 micrometers for a single mode fiber
• This layer52 is interrupted in the core area 56 when exposed to optical powers higher than the threshold power, and this interruption is detected by a circuit 54 having a continuity or resistance detector 58
• the interruption means an opaque switch
• Fig 24 is a schematic representation of another embodiment of a switching device according to the invention, which consists of an absorbing waveguide
• an optical power or energy switching device 60 composed of a waveguide 4, e g , a solid waveguide or a fiber, having an input end 10 and an output end 12 Interposed between the two portions 4', 4" of the waveguide 4 and transversing the propagation path of optical energy from input end 10 to output end 12, there is affixed an optical energy-absorbing fiber or waveguide 30
• the core 62 of the fiber 64 may be made of polymer or of doped glasses or of any other partially absorbing material
• the fiber or waveguide may be covered, on one or on both sides, with an index- matching layer 66 When the fiber 64 is impinged by optical energy exceeding a predetermined threshold, the fiber 66 is damaged, e g , melts, shrinks or breaks, and therefore significantly reduces the transmitted optical energy, thus acting as a switch for interrupting energy propagation
• Fig 25 is a schematic illustration of a switching device 68 having an absorbing waveguide 70 and a notch
• the switching device 68 is composed of an optical waveguide 70 having a core 72 and cladding 74
• the waveguide 70 can be composed, for example, of doped silica or polymers
• the waveguide has an input end 10 and output end 12, and is pre-stressed, e g , by bending it into any desired configuration
• the cladding 74 is weakened, e g , by a groove or notch 78
• the core heats up
• the core 72 and cladding 74 break at or near the notch 78 Such breakage separates the input core portion from the output core portion, thus preventing the optical energy from propagating to the output end 12
• Fig 26 describes a switch assembly 116 that is able to protect a device or detector at high threshold powers
• a typical phenomenon occurring in fibers carrying high powers is the "Fiber Fuse" effect where due to the interaction of the high power incoming light with the back reflected light from a perturbation in the fiber, the fiber is disrupted, starting from the perturbation and extending back into the input source The fiber is useless, catastrophically damaged, after a "Fiber Fuse” has passed through it This phenomenon is responsible for destruction of high power fibers, and it is prevented by the switch assembly 116
• Optical power comes in through fiber 106, e g , a silica single mode fiber, into an optical isolator 108 (a one-way optical switch, commercially available) After leaving the optical isolator 108 through fiber 110, the light impinges on a safety switch 112 During normal operation the switch 112 will perform as follows In the case that the power is lower than the threshold power of the switch 11
• Fig 27 illustrates an alternative way to protect against a "Fiber Fuse"
• the optical power enters the system through a fiber 106 (e g , single-mode fiber SMF28 having a core or a MFD- Mode Field Diameter of about lO ⁇ m) into a core diameter reduction box 118, shown enlarged in the figure, where the fiber 106 having a core 122 is spliced to a fiber 120 having core 128 The core 128 is smaller than the core 122
• the switch 112 performs as follows In the case that the power is lower than the threshold power of the switch 112, the light continues into the fiber 132 unperturbed In the case that the power is above the threshold, the switch 112 turns opaque and scattering, thus preventing the light from proceeding onto the fiber 132 In the cases where the power is high enough to enable the "Fiber Fuse” to occur, the switch 112 is designed to have a power threshold just below the "Fiber Fuse” minimal power, and turns opaque and scattering just below the "Fiber Fuse” power, saving the fiber 132 from damage In the cases that "Fiber Fuse" starts, at point A on fiber 120 and proceeds in the direction of the black arrow toward point B, it is stopped at the point 124
• the entire switch assembly 140 is replaced after the event, but the transmission fiber
• the safety switch 112 may be any known safety switch, including those described herein

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• 2003
  • 2003-03-13 AU AU2003209561A patent/AU2003209561A1/en not_active Abandoned
  • 2003-03-13 WO PCT/IB2003/000928 patent/WO2003076971A2/en not_active Ceased
  • 2003-03-13 US US10/507,575 patent/US7162114B2/en not_active Expired - Lifetime
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