WO2000067400A1 - Protection intrinseque des liaisons de communication a fibres optiques - Google Patents

Protection intrinseque des liaisons de communication a fibres optiques Download PDF

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Publication number
WO2000067400A1
WO2000067400A1 PCT/AU2000/000382 AU0000382W WO0067400A1 WO 2000067400 A1 WO2000067400 A1 WO 2000067400A1 AU 0000382 W AU0000382 W AU 0000382W WO 0067400 A1 WO0067400 A1 WO 0067400A1
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WIPO (PCT)
Prior art keywords
waveguide
sensing
sensing signal
coupler
signal
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PCT/AU2000/000382
Other languages
English (en)
Inventor
Edward E. Tapanes
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Future Fibre Technologies Pty. Ltd.
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Publication date
Application filed by Future Fibre Technologies Pty. Ltd. filed Critical Future Fibre Technologies Pty. Ltd.
Priority to KR1020017014026A priority Critical patent/KR20020026863A/ko
Priority to JP2000616144A priority patent/JP2002543738A/ja
Priority to EP00920265A priority patent/EP1175743A4/fr
Priority to IL14607500A priority patent/IL146075A/en
Priority to AU40921/00A priority patent/AU760272B2/en
Priority to CA002371576A priority patent/CA2371576A1/fr
Publication of WO2000067400A1 publication Critical patent/WO2000067400A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
    • G01M5/0091—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by using electromagnetic excitation or detection
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/30—Testing of optical devices, constituted by fibre optics or optical waveguides
    • G01M11/33—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter being disposed at one fibre or waveguide end-face, and a light receiver at the other end-face
    • G01M11/335—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter being disposed at one fibre or waveguide end-face, and a light receiver at the other end-face using two or more input wavelengths
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
    • G01M5/0025—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings of elongated objects, e.g. pipes, masts, towers or railways
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
    • G01M5/0033—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by determining damage, crack or wear
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
    • G01M5/0066—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by exciting or detecting vibration or acceleration
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/25—Arrangements specific to fibre transmission

Definitions

  • This invention relates to optical waveguide systems formed for securing live-fibres against tampering and tapping-off of data in optical fibre communication links.
  • Optical devices are commonly used in industry and science and include laser cavities, waveguides, lenses, filters and other optical elements and their combinations. Such optical devices are used in a variety of instruments and installations .
  • Photonics technology has revolutionised the communications and sensor fields. This is mainly due to the rapid development of optical and opto-electronic devices.
  • a wide variety of glass materials, material-dopants and waveguide structures are available and this provisional specification relates to optical waveguide systems formed for securing live-fibres against tampering and tapping-off of data in optical fibre communication links.
  • optical fibres as the main backbone of most communication systems has meant that large amounts of information can be efficiently and cost effectively transferred from point to point.
  • Modern fibre optic communications networks deploy optical fibre over millions of kilometres worldwide, carrying important and confidential information of a government, military, financial and personal nature.
  • optical fibre transmission would be inherently secure, we now know that it is relatively easy to 'tap' information out of an optical fibre with negligible interference to the optical signal. It has became obvious that in order to extract 100% of the information which is transmitted via the fibre optic cable, it is sufficient to bend the fibre only slightly or clamp onto it at any point along its length and photons of light will leak into the receiver of the intruder.
  • Encryption techniques can be very costly, they often slow the system speed considerably/unacceptably and are not ever totally secure.
  • OTDRs Physical security measures are not truly effective in uncovering tampering with a fibre optic communications link since they require the fibre to be cut, fractured or severely bent before the problem can be detected.
  • OTDRs are ineffective at detecting dynamic or transient disturbances to a fibre cable.
  • their functionality limits them to measuring only optical losses, but with relatively low sensitivity, thus they are practically limited to detecting significant and permanent or very slowly changing (and often destructive) effects on the cable.
  • optical fibres can be more than mere signal carriers .
  • Light that is launched into and confined to the fibre core propagates along the length of the fibre unperturbed unless acted upon by an external influence.
  • Specialised sensing instrumentation may be configured such that any disturbance of the fibre which alters some of the characteristics of the guided light (ie., amplitude, phase, wavelength, polarisation, modal distribution and time-of-flight) can be monitored, and related to the magnitude of the disturbing influence.
  • modulation of the light makes possible the measurement of a wide range of events and conditions, including:
  • Fibre optic sensor technology has progressed at a rapid pace over the last decade. Different configurations of fibre sensing devices have been developed for monitoring specific parameters, each differing by the principle of light modulation.
  • Fibre optic sensors may be intrinsic or extrinsic, depending on whether the fibre is the sensing element or the information carrier, respectively. They are designated “point” sensors when the sensing gauge length is localised to discrete regions. If the sensor is capable of sensing a measurand field continuously over its entire length, it is known as a “distributed” sensor; “quasi-distributed” sensors utilise point sensors at various locations along the fibre length.
  • Fibre optic sensors can be transmissive or can be used in a reflective configuration by mirroring the fibre end-face.
  • fibre optic sensors are actually a class of sensing device. They are not limited to a single configuration and operation unlike many conventional sensors such as electrical strain gauges and piezoelectric transducers. Consequently, fibres are now replacing the role of conventional electrical devices in sensing applications to the extent where we are now seeing a multitude of sensing techniques and applications being explored for practical gain.
  • the disturbance may be in the form of physical movement (ie., compression (radially or axially) , elongation, twisting, vibration, etc.) or microphonic effects (ie., travelling stress waves or acoustic emissions) .
  • the ability to vary the sensing length to fit specific applications is a major and unique advantage of this technology. This is particularly relevant if long sensing lengths are required, as is the case when combining the sensing technique with fibre optic communications .
  • the only limitation imposed on the sensing length is in the optical power budget of the system. Therefore, if a longer sensing length is desired a higher power laser is required.
  • the system of this international application provides a simple, effective and inexpensive technique to detect and characterise both small and large disturbances on any optical fibre cable, anywhere along its entire length, and in real-time.
  • This offers the capability of simultaneously utilising a fibre optic communications cable as a tampering-alert, intrusion-alert or integrity- testing sensing cable, thus providing continuous, realtime monitoring of the fibre cable and any structure near the cable (ie., ground, tunnels, ducts, pipes, buildings, equipment, vessels, etc.).
  • One of the key features of the technology is its configuration-flexibility since it is wavelength independent. This makes it possible to use with any type of optical fibre, thus it can be simultaneously retrofitted and integrated into any existing fibre optic communications cable, without requiring the installation and cost of a new cable.
  • this technology was to be capable to be operated simultaneously with a communications system within the same optical fibre or cable, adding significant value to any communications system in regard to security and enabling easy integration of the distributed sensing technology into an existing fibre optic network.
  • Figure (1) illustrates the configuration used for the demonstration of a simultaneous fibre optic communications and sensing system.
  • the system configuration consisted of the fibre link 1, either single or multi moded, with standard 3 dB (50% splitting ratio), 2x2 fibre couplers 3a, 3b at each end to allow for the multiplexing and demultiplexing of the two wavelengths at the transmitter and receiver ends, respectively.
  • the choice of sensing wavelength was important as the responsivity of the InGaAs detector 2b in the communication channel needed to be negligible at the sensing wavelength.
  • the communication channel 2a was chosen to operate at a wavelength of 1300 nm whilst the sensing channel 4a was chosen to operate at either 633 nm or 850 nm. This ensured that inter-channel crosstalk was negligible, as the Si 4b detector utilised in the sensing channel would not respond to the 1300 nm communications signal.
  • Figure (2) illustrates the results from the sensing arrangement shown in Figure (1) when a vibrational disturbance was applied to a short section of the fibre link.
  • a vibrational disturbance was applied to a small section (5 cm) of the fibre link using a cantilever beam arrangement.
  • the fibre was simply taped longitudinally along the beam length.
  • a typical sensor response is shown in Figure (2a) for a 28 km singlemode (SM) link and in
  • continuous-wave (CW) optical signals S and SI are simultaneously launched, preferably from a ⁇ - single light source, into opposite ends of a sensing optical fibre 1 or set of fibres and simultaneously detected by synchronised photodetectors .
  • Pulsing of the optical signal is not necessary, although it may be employed in some arrangements.
  • Any sensed parameter P which acts to alter the counter-propagating signals will effect both signals in the same manner, but because the effected counter- , propagating signals must each continue travelling the remainder of the fibre length to their respective photodetectors there is a resultant time delay or time difference between the detected signals.
  • the time delay is directly proportional to the location of the sensed event along the fibre length.
  • non-sensitive fibre optic delay lines L may be connected to the sensing fibre at either or both ends in order to add additional delay between the transmissive counter-propagating signals and to provide insensitive lead fibres.
  • This technique enables dynamic and transient events to be located in virtually any distributed fibre optic sensing system, and its transmissive counter-propagating technique does not possess the limitations and complexities of OTDR principles.
  • the system has the following advantages: • Operates on virtually any existing type of transmissive distributed fibre optic sensor, enabling dynamic and transient events to be detected, quantified, characterised and located anywhere along the length of the optical fibre.
  • the object of the present invention is to provide optical waveguide systems formed for securing live-fibres against tampering and tapping-off of data in optical fibre communication links, while minimising optical power losses to both the communications and sensing signals.
  • the present invention provides an optical waveguide communication link, including; a waveguide for conveying signals from one location to another location; a data transmitter for launching a data signal at a first wavelength into the waveguide; a data receiver for receiving the data signal from the waveguide; a sensing signal transmitter for launching a sensing signal at a second wavelength different to the first wavelength, into the waveguide; a sensing signal detector for detecting the sensing signal after the sensing signal has travelled through the waveguide; and signal splitting means between the waveguide and the data receiver and the sensing signal detector so that the signal at the first wavelength is separated from the sensing signal at the second wavelength by the signal splitting means so that substantially all of the data signal without significant loss and without any significant component of the sensing signal is directed to the data receiver, and substantially all of the sensing signal without any significant loss and without any significant component of the data signal is directed to the sensing signal detector.
  • both the sensing signal and the communication signal can be launched into a single waveguide and transmitted along the waveguide whereupon the system separates the individual wavelength components of the sensing signal and the data signal for transmission to their respective data receiver and signal sensing detector so that if both signals are received without substantial contamination by the other signal and with minimum optical power loses.
  • sensitivity of the transmitted data signals and sensing signals is greatly enhanced thereby enabling proper communication of data and also proper sensing of any attempt to interfere with the waveguide to tap off data from the waveguide.
  • the signal splitting means comprises a wavelength multiplexing/demultiplexing waveguide coupler.
  • the data signal from the waveguide and the sensing signal from the sensing signal transmitter are received by a wavelength multiplexing/demultiplexing coupler to combine the signals for transmission along the waveguide.
  • WDM waveguide devices to combine and separate the individual wavelength components of the communications and sensing signals in the same optical fibre, minimises the optical power losses.
  • a typical 2x2 coupler splits the transmitted light in either direction into two roughly-equal signals (50/50% power split)
  • a WDM coupler efficiently taps off or inserts specific wavelengths with considerably less loss (typically -10%) .
  • the sensing signal transmitter and sensing signal detector are at the said one location and said another location respectively.
  • the sensing signal transmitter and the sensing signal detector are located both at one or the other of the said one location or the another location and wherein a reflector is provided for reflecting the sensing signal back through the waveguide after separation of the sensing signal from the data signal by the signal splitting means .
  • the reflector comprises a reflective mirror.
  • the sensing signal transmitter comprises a counter-propagating sensing signal transmitter for launching counter-propagating sensing signals into the waveguide and travel in opposite directions through the waveguide to enable the position of any disturbance to the waveguide to be determined by the difference between the time a perturbing sensing event is detected in both counter-current sensing signals.
  • processing means is provided for processing the sensing signal to determine a change in parameter within the signal to identify a disturbance to the waveguide indicative of tampering with the waveguide.
  • the communication link includes a plurality of communication nodes, at least one of the nodes including a said data transmitter, a second node including a said data receiver and a further said data transmitter, and a third node including at least a further said data receiver, the waveguide interconnecting each of the nodes so that the sensing signal passes through the waveguide from the first node to the third node.
  • the waveguide forms a continuous loop including a plurality of communication nodes arranged along the loop, at least one of the loop having a said sensing signal transmitter and a said sensing signal detector.
  • a said signal combining means is provided for directing a data signal from a data transmitter at one of the nodes, to a said data receiver at another of the nodes .
  • the present invention may also be said to reside in an optical waveguide communication link including; a waveguide for conveying signals from one location to another location; a data transmitter for launching a data signal into the waveguide; a first wavelength multiplexing/demultiplexing waveguide device coupled to the waveguide, the waveguide device having a first output arm and a second output arm; a sensing signal transmitter for launching sensing signal having a wavelength different to the wavelength of the data signal into the waveguide for transmission with the data signal along the waveguide; a data receiver coupled to the first output arm for receiving the data signal from the waveguide device; a sensing signal detector coupled to the second output arm for receiving a sensing signal from the waveguide device .
  • the waveguide device comprises a wavelength multiplexing/demultiplexing coupler .
  • a second waveguide device is coupled to the waveguide remote from the first waveguide device, the second waveguide device having a first input arm and a second input arm, the first input arm being coupled to the data transmitter and the second input arm being coupled to the sensing signal transmitter so that the data signal and the sensing signal are transmitted to the second waveguide device for launching into the waveguide .
  • the second waveguide device is coupled to the waveguide by an output arm which receives both the data signal and sensing signal from the second waveguide device.
  • the first waveguide device is coupled to the waveguide by an input arm so that both the sensing signal and data signal are transmitted through the input arm to the first waveguide device.
  • the first waveguide device comprises a first wavelength multiplexing/demultiplexing (WDM) coupler having the input arm and the first and second output arms .
  • WDM wavelength multiplexing/demultiplexing
  • the second waveguide device comprises a second wavelength multiplexing/demultiplexing (WDM) coupler having the first input arm, the second input arm and the output arm.
  • WDM wavelength multiplexing/demultiplexing
  • the waveguide comprises an optical fibre.
  • the optical fibre may be a single mode fibre or a multimode fibre.
  • the second output arm of the first WDM coupler is connected to a reflector to reflect the sensing signal back into the waveguide through the WDM coupler
  • the second input arm of the second WDM coupler is connected to an ancillary coupler
  • the ancillary coupler having first and second ancillary input arms, the first ancillary input arm being connected to the sensing signal transmitter and the second ancillary input arm being connected to the sensing signal detector so that the sensing signal reflected back from the reflector passes through the first WDM coupler, and through the second WDM coupler to the second input arm, through the ancillary coupler to the second ancillary arm and then to the sensing signal detector.
  • the preferred embodiment of the present invention provides a waveguide system for securing live-fibres against tampering and tapping-off of data in optical fibre communication links, which may include:
  • silica waveguide for receiving light from the wavelength multiplexing waveguide light splitter or coupler, the silica waveguide being capable of transmitting the sensing and communications signals in the required manner along its length, but particularly such that the sensing wavelength and the waveguide characteristics satisfy the requirements of the modalmetric sensing and locating techniques described earlier while unaffecting the communications signal; • providing a wavelength demultiplexing waveguide light splitter or coupler (single or multi moded) which efficiently splits or separates the sensing and communications signals into two output waveguide ports while minimising optical power losses to both the communications and sensing signals; and
  • silica waveguides are connected to the first silica waveguide at either or both ends in order to provide insensitive lead waveguides and, if applicable, to add additional delay between the transmissive counter- propagating signals.
  • the sensing wavelength output port of the wavelength demultiplexing waveguide coupler is ⁇ terminated with a reflective mirror so as to operate the sensing technique in a reflective mode.
  • a mirrored waveguide could be connected to the sensing wavelength output port of the wavelength demultiplexing waveguide coupler.
  • the detector means comprises:
  • a photodetector for receiving the transmitted or reflected radiation from the sensing signal in the silica waveguide; and • processing means for receiving signals from the photodetector and analysing the signals in order to register the sensed events.
  • the detector means comprises :
  • first and second photodetectors for simultaneously receiving the radiation from the counter-propagating signals in the silica waveguide; and • processing means for receiving signals from the first and second photodetectors and analysing the signals in order to register the sensed events and determining the time delay or difference between the counter-propagating signals effected from the same disturbance, thus determining the location of the sensed events.
  • the silica waveguide is a multimoded fibre at the sensing wavelength and the lead waveguides are singlemode fibres at the sensing wavelength.
  • the distributed sensing technique is based on a modalmetric technique utilising the fusion splicing of insensitive singlemode fibre to sensitive multimode fibre.
  • the transmissive counter- propagating signal method for locating events is employed, and suitable optical devices are employed at one or both ends of the system to detect the signals.
  • the wavelength multiplexing/demultiplexing (WDM) couplers are 2x1 WDM couplers. In other embodiments they may be any suitable multi-port device, such as 2x2, 3x1, 4x2, etc.
  • optical fibres and fibre devices are connected by fusion splices.
  • optical fibres and fibre devices may be connected by any suitable or appropriate technique, such as mechanical splices, connectorised leads and through- adaptors, etc.
  • the WDM couplers may be replaced with alternate wavelength filtering, conditioning, combining, splitting or directing devices.
  • a plurality of WDM couplers are utilised in a ring topology network, forming junction by- pass arrangements for the sensing signal in order to extend the sensing fibre length beyond one communication node.
  • the waveguide comprises at least one optical fibre and/or at least one optical fibre device.
  • the waveguide may merely comprise an optical fibre without any additional elements.
  • the optical fibre can include passive or active elements along its length.
  • the optical fibre can include sensing elements along its length and those sensing elements can comprise devices which will respond to a change in the desired parameter in the environment of application and influence the properties and characteristics of the sensing electromagnetic radiation propagating in the waveguide to thereby provide an indication of the change in the parameter.
  • any suitable CW or pulsed single or multiple wavelength source or plurality of sources may be employed.
  • a CW or pulsed coherent laser diode is utilised to supply the optical signal.
  • multiple light sources may be used to generate the sensing signal or a plurality of sensing signals.
  • the preferred embodiments of the present invention offer the potential to utilise all-fibre, low-cost optical devices in conjunction with laser diodes, light emitting diodes, photodetectors, couplers, WDM couplers, isolators and filters.
  • any suitable light source, coupler and photodetector arrangement may be used with the sensor and locating systems.
  • the required optical properties of the light source are such that light may be launched into and propagated in the singlemode waveguide.
  • the light propagated in a singlemode fibre must remain singlemoded during the entire period of travel in the singlemode fibre.
  • the light Once the light is launched into the multimode fibre from the singlemode fibre, several modes may be excited and the multimoded fibre will be sensitive to various parameters.
  • the singlemode fibre Once the light is launched back into the singlemode fibre from the multimode fibre, only a single mode is supported and travels to the optical components of the system.
  • Lead- in/lead-out fibre desensitisation and sensor localisation is achieved in this manner.
  • the singlemode fibre should be made sufficiently long to attenuate all cladding modes in order to improve the signal-to-noise ratio. This preferred embodiment applies for both directions of travel of the transmissive counter- propagating optical signals.
  • electromagnetic radiation at the sensing wavelength is launched into an optical waveguide (single or multi moded) , such as an optical fibre, from a light source, such as a pigtailed laser diode, fibre laser or light emitting diode, and propagates along the optical waveguide.
  • the optical waveguide is fusion spliced, or otherwise connected (temporarily or permanently) , to one input arm of an optical waveguide wavelength multiplexing light splitter or coupler (single or multi moded) and when the electromagnetic radiation reaches the coupler the electromagnetic radiation can branch out into the output waveguide arm of the coupler.
  • electromagnetic radiation at the communications wavelength is launched into another optical waveguide (single or multi moded) , such as an optical fibre, from a light source, such as a pigtailed laser diode, fibre laser or light emitting diode, and propagates along the optical waveguide.
  • the optical waveguide is fusion spliced, or otherwise connected (temporarily or permanently), to the second input arm of the wavelength multiplexing coupler and when the electromagnetic radiation reaches the coupler the electromagnetic radiation can likewise branch out into the same output waveguide arm of the coupler as the sensing signal.
  • the wavelength multiplexing coupler efficiently combines both the sensing and communications signals into a single output waveguide arm.
  • the output arm of the wavelength multiplexing coupler is fusion spliced, or otherwise connected (temporarily or permanently), directly to the main waveguide transmission link (single or multi moded for the communications signal and multimoded for the sensing signal). Both the communications and sensing signals propagate along the entire length of the waveguide, without interfering with one another, until they reach the opposite end of the link.
  • the main waveguide is then fusion spliced, or otherwise connected (temporarily or permanently), to the input arm of a wavelength demultiplexing coupler and when the signals reach the coupler they are efficiently separated and branched out into two separate output arms of the coupler.
  • the output arms of the wavelength demultiplexing coupler are then terminated at appropriate photodetectors .
  • Appropriate electronics, signal processing schemes and algorithms process the signals from the photodetectors to obtain the desired information.
  • the WDM couplers are 2x1 WDM couplers. In other embodiments they may be any suitable multi-port device, such as 2x2, 3x1, 4x2, etc.
  • a plurality of WDM couplers are utilised to form junction by-pass arrangements for the sensing signal in order to extend the sensing fibre length beyond one communication node.
  • optical fibres and fibre devices are connected by fusion splices.
  • optical fibres and fibre devices are connected by any suitable or appropriate technique, such as mechanical splices, connectorised leads and through- adaptors, etc .
  • the sensing wavelength output port of the WDM coupler is terminated with a reflective mirror so as to operate the sensing technique in a reflective mode.
  • a mirrored fibre could be connected to the output port of the WDM coupler.
  • the transmissive counter- propagating signal method for locating events is employed, and suitable optical devices are employed at one or both ends of the system to detect the signals.
  • the WDM couplers may be replaced with alternate wavelength filtering, conditioning, combining, splitting or directing devices .
  • the instrument optical and electronic arrangements will utilise noise minimisation techniques.
  • all the optical and electrical components will be located in a single instrument control box, with individual optical fibre input/output ports.
  • Optical devices electro-optic devices, acousto-optic devices, magneto-optic devices and/or integrated optical devices may also be utilised in the system.
  • Figure 1 shows an integrated fibre optic sensing and communications system, utilising the modalmetric sensing technique
  • FIG. 1 Figure 2a, Figure 2b, Figure 2c and Figure 2d are graphs showing the results from the sensing arrangement shown in
  • Figure 3 shows the basic principle of the waveguide transmissive counter-propagating signal method for locating events in fibre optic sensing systems
  • Figure 4 shows a combined fibre optic sensing and communications arrangement, utilising a modalmetric sensing technique and the ability to locate disturbances formed by the method of Figure 3;
  • Figure 5 is a view showing a general embodiment of the present invention for a transmissive sensing arrangement operating over a singlemode optical fibre telecommunication link;
  • Figure 6 is a view showing a general embodiment of the invention for a reflective sensing arrangement operating over a singlemode optical fibre telecommunication link
  • Figure 7 is a view showing a general embodiment of the invention for a two-ended counter-propagating sensing and locating arrangement operating over a singlemode optical fibre telecommunication link
  • Figure 8 is a view showing a general embodiment of the invention for a single-ended counter-propagating sensing and locating arrangement operating over a singlemode optical fibre telecommunication link
  • Figure 9 is a view showing another general embodiment of the invention for a transmissive sensing arrangement operating over a multimode optical fibre telecommunication link;
  • Figure 10 is a view showing another general embodiment of the invention for a reflective sensing arrangement operating over a multimode optical fibre telecommunication link;
  • Figure 11 is a view showing another general embodiment of the invention for a two-ended counter-propagating sensing and locating arrangement operating over a multimode optical fibre telecommunication link;
  • Figure 12 is a view showing another general embodiment of the invention for a single-ended counter-propagating sensing and locating arrangement operating over a multimode optical fibre telecommunication link
  • Figure 13 is a view showing a further general embodiment of the invention, utilising a plurality of WDM couplers in a singlemode optical fibre, three-node, point-to-point network arrangement, forming a junction by-pass arrangement for the sensing signal in order to extend the sensing fibre length beyond one communication node;
  • Figure 14 is a view showing a further general embodiment of the invention, utilising a plurality of WDM couplers in a multimode optical fibre, three-node, point-to-point network, forming a junction by-pass arrangement for the sensing signal in order to extend the sensing fibre length beyond one communication node;
  • Figure 15 is a view showing yet another general embodiment of the invention, utilising a transmissive sensing arrangement and a plurality of WDM couplers in an optical fibre ring topology network, forming several junction by- pass arrangements for the sensing signal in order to extend the overall sensing fibre length across the entire ring topology network;
  • Figure 16 is a view showing yet another general embodiment of the invention, utilising a counter-propagating sensing and locating arrangement and a plurality of WDM couplers in an optical fibre ring topology network arrangement, forming several junction by-pass arrangements for the sensing signals in order to extend the overall sensing fibre length across the entire ring topology network.
  • the distributed sensing technique is based on a modalmetric technique utilising the fusion splicing of insensitive singlemode fibre to sensitive multimode fibre;
  • the transmissive counter-propagating signal method for locating events is employed, where appropriate, and suitable optical devices are employed at one or both ends of the system to detect and process the signals;
  • any suitable light source, coupler and photodetector arrangement may be used with the sensor and locating systems.
  • the required optical properties of the light source are such that light may be launched into and propagated in the singlemode waveguide. For localisation, the light propagated in a singlemode fibre must remain singlemoded during the entire period of travel in the singlemode fibre. Once the light is launched into the multimode fibre from the singlemode fibre, several modes may be excited and the multimoded fibre will be sensitive to various parameters.
  • the singlemode fibre should be made sufficiently long to attenuate all cladding modes in order to improve the signal-to-noise ratio. This preferred embodiment applies for both directions of travel of the transmissive counter- propagating optical signals where this technique is utilised;
  • the wavelength multiplexing/demultiplexing (WDM) couplers are 2x1 WDM couplers, in other embodiments they may be any suitable multi-port device, such as 2x2, 3x1, 4x2 , etc . ; and • the optical fibres and fibre devices are connected by fusion splices. In another embodiments the optical fibres and fibre devices are connected by any suitable or appropriate technique, such as mechanical splices, connectorised leads and through-adaptors, etc.
  • Figure 1 illustrates the configuration used for the demonstration of a simultaneous fibre optic communications and sensing system.
  • the system configuration consisted of the fibre link 1, either single or multi moded, with standard 3 dB (50% splitting ratio), 2x2 fibre couplers 3a and 3b at each end to allow for the multiplexing and demultiplexing of the two wavelengths at the transmitter 2a and 4a and receiver ends 2b and 4b, respectively.
  • the choice of sensing wavelength was important as the responsivity of the InGaAs detector 2b in the communications channel needed to be negligible at the sensing wavelength.
  • the communications channel was chosen to operate at a wavelength of 1300 nm whilst the sensing channel was chosen to operate at either 633 nm or 850 nm. This ensured that inter-channel crosstalk was negligible, as the Si detector 4b utilised in the sensing channel would not respond to the 1300 nm communications signal.
  • Figures 2a, to 2d show the results from the sensing arrangement shown in Figure 1 when a vibrational disturbance was applied to a short section of the fibre link using a cantilever beam arrangement.
  • the fibre was simply taped longitudinally along the beam length.
  • Results are shown for a 28 km singlemode (SM) link and a 53 km multimode (MM) fibre link.
  • SM singlemode
  • MM multimode
  • FFTs Fast Fourier Transforms
  • FIG 3 shows the basic principle of the waveguide transmissive counter-propagating signal method for locating events in fibre optic sensing systems.
  • the technique relies on the measurement of the time delay or difference between transmissive counter-propagating optical signals affected by the same event in a two-ended fibre arrangement.
  • continuous- wave (CW) optical signals are simultaneously launched, preferably from a single light source, into opposite ends of a sensing optical fibre or set of fibres and simultaneously detected by synchronised photodetectors. Any sensed parameter which acts to alter the counter- propagating signals will effect both signals in the same manner.
  • the effected counter-propagating signals must each continue travelling the remainder of the fibre length to their respective photodetectors there is a resultant time delay or time difference between the detected signals.
  • d x is the total length of the optical fibre link
  • ⁇ t is the resultant time delay or time difference between the detected signals
  • v is the speed of the optical signal given by c/n f i bre / where c is the speed of light in a vacuum (3xl0 8 m/s) and n fibr ⁇ is the effective refractive index of the optical fibre.
  • the point of disturbance referenced from Port 2 is given by: cl + (v ⁇ t) Point of disturbance Pnrt2 - ⁇ 2 ) Therefore, if the time delay or difference is detected and measured, the location of the event can be determined. At the same time, if a compatible sensing mechanism is being employed the sensed event can be quantified and/or identified (ie., strain, vibration, acoustic emission, temperature transients, etc.). In addition, non-sensitive fibre optic delay lines may be connected to the sensing fibre at either or both ends in order to add additional delay between the transmissive counter-propagating signals and to provide insensitive lead fibres. This may assist engineering the technique into a practical working system.
  • Figure 4 shows a combined fibre optic sensing and communications arrangement, utilising a modalmetric sensing technique and the ability to locate disturbances formed by the method of Figure 3.
  • a modalmetric sensing technique utilising a modalmetric sensing technique and the ability to locate disturbances formed by the method of Figure 3.
  • One method in which this can easily be achieved is by using a multi-fibre cable which will effectively form a single-ended system.
  • one singlemode fibre 1 is utilised as the communications fibre, whilst two fibres 2 and 3, one singlemode and one multimode, are required to set-up the modalmetric intrusion sensor (event detection and location determination) over the specified region of interest (within sleeve 4) .
  • a perturbation P anywhere along the multimode fibre sleeve 4 will generate two counter-propagating perturbation signals. Measuring the time difference in their respective time of arrival at the transmitter end of the link will allow
  • FIG. 5 is a view showing a general embodiment of the present invention for a transmissive sensing arrangement operating over a singlemode optical fibre telecommunication link.
  • coherent laser light at the sensing wavelength 980 nm is launched into a 980 nm singlemode optical fibre 6a from a pigtailed laser diode with optional integrated isolator 40 and propagates along the optical fibre 6a.
  • the optical fibre 6a is fusion spliced 57 to one input arm 6b of a 980/1550 nm singlemode fibre optic wavelength multiplexing coupler 30 and when the light at the sensing wavelength reaches the coupler 30 it is branched out into the output arm 5a of the coupler 30.
  • laser light at the communications wavelength 1550 nm is launched into a 1550 nm singlemode optical fibre 7a from a pigtailed laser diode with optional integrated isolator 20 and propagates along the optical fibre 7a.
  • the optical fibre 7a is fusion spliced 50 to the second input arm 7b of the 980/1550 nm singlemode fibre optic wavelength multiplexing coupler 30 and when the light at the communications wavelength reaches the coupler 30 it is likewise branched out into the same output arm 5a of the coupler 30 as the sensing signal.
  • the wavelength multiplexing coupler 30 efficiently combines both the sensing and communications signals into a single output coupler arm 5a.
  • the output arm 5a of the wavelength multiplexing coupler 30 is then fusion spliced 52 directly to the main 1550 nm singlemode optical fibre transmission link 1000. Both the communications and sensing signals propagate along the entire length of the 1550 nm singlemode optical fibre transmission link 1000, without interfering with one another, until they reach the opposite end of the link 1000.
  • the 1550 nm singlemode optical fibre transmission link 1000 is then fusion spliced 54 to the input arm 5b of a 980/1550 nm singlemode fibre optic wavelength demultiplexing coupler 32 and when the signals reach the coupler 32 they are efficiently separated and branched out into two separate and respective output arms 6c and 7c of the coupler 32.
  • the 980 nm sensing signal output arm 6c of the wavelength demultiplexing coupler 32 is then fusion spliced 58 to a 980 nm singlemode fibre 6d pigtailed InGaAs detector 42.
  • the 1550 nm communications signal output arm 7c of the wavelength demultiplexing coupler 32 is then fusion spliced 56 to a 1550 nm singlemode fibre 7d which is connected to pigtailed InGaAs detector 22.
  • appropriate electronics, signal processing schemes and algorithms process the signals from the photodetectors to obtain the desired information.
  • Figure 6 is a view showing a general embodiment of the invention for a reflective sensing arrangement operating over a singlemode optical fibre telecommunication link.
  • coherent laser light at the sensing wavelength 980 nm is launched into a 980 nm singlemode optical fibre 6a from a pigtailed laser diode with optional integrated isolator 40 and propagates along the optical fibre 6a.
  • the optical fibre 6a is fusion spliced 60 to one input arm 6e of a 980 nm singlemode coupler 44 and when the light at the sensing wavelength reaches the coupler 44 it is branched out into the output arm 6g of the coupler 44.
  • the unused arm is fractured or otherwise terminated to avoid back- reflections.
  • the light at the sensing wavelength then propagates along optical fibre 6g.
  • the optical fibre 6g is fusion spliced 62 to one input arm 6b of a 980/1550 nm singlemode fibre optic wavelength multiplexing coupler 30 and when the light at the sensing wavelength reaches the coupler 30 it is branched out into the output arm 5a of the coupler 30.
  • laser light at the communications wavelength 1550 nm is launched into a 1550 nm singlemode optical fibre 7a from a pigtailed laser diode with optional integrated isolator 20 and propagates along the optical fibre 7a.
  • the optical fibre 7a is fusion spliced 50 to the second input arm 7b of the 980/1550 nm singlemode fibre optic wavelength multiplexing coupler 30 and when the light at the communications wavelength reaches the coupler 30 it is likewise branched out into the same output arm 5a of the coupler 30 as the sensing signal.
  • the wavelength multiplexing coupler 30 efficiently combines both the sensing and communications signals into a single output coupler arm 5a.
  • the output arm 5a of the wavelength multiplexing coupler 30 is then fusion spliced 52 directly to the main 1550 nm singlemode optical fibre transmission link 1000.
  • Both the communications and sensing signals propagate along the entire length of the 1550 nm singlemode optical fibre transmission link 1000, without interfering with one another, until they reach the opposite end of the link 1000.
  • the 1550 nm singlemode optical fibre transmission link 1000 is then fusion spliced 54 to the input arm 5b of a 980/1550 nm singlemode fibre optic wavelength demultiplexing coupler 32 and when the signals reach the coupler 32 they are efficiently separated and branched out into two separate and respective output arms 6c and 7c of the coupler 32.
  • the 1550 nm communications signal output arm 7c of the wavelength demultiplexing coupler 32 is then fusion spliced 56 to a 1550 nm singlemode fibre 7d pigtailed InGaAs detector 22.
  • the 980 nm sensing signal output arm 6c of the wavelength demultiplexing coupler 32 is then fusion spliced 64 to a 980 nm singlemode fibre 6h terminated with a reflective mirror 46.
  • the sensing signal is thus reflected back in the opposite direction along fibres 6h, 6c, 5b, 1000, 5a, 6b and 6g, and branched through coupler 44 to output arm 6f.
  • the output arm 6f of the coupler 44 is then fusion spliced 66 to a 980 nm singlemode fibre 6d pigtailed InGaAs detector 42.
  • FIG. 7 is a view showing another general embodiment of the invention for a two-ended counter-propagating sensing and locating arrangement, according to the method shown in Figure 3, operating over a singlemode optical fibre telecommunication link.
  • a 980 nm counter-propagating sensing system 300 is used to launch a sensing signal in one direction of the 1550 nm singlemode optical fibre transmission link 1000 and the system 300 is suitably time-synchronised with a second 980 nm counter-propagating sensing system 320 launching a sensing signal in the opposite direction of the 1550 nm singlemode optical fibre transmission link 1000.
  • Any disturbance P that acts to alter the counter-propagating sensing signals along link 1000 will effect both signals in the same manner.
  • FIG. 8 is a view showing yet another general embodiment of the invention for a single-ended counter-propagating sensing and locating arrangement, according to the method shown in Figure 4, operating over a singlemode optical fibre telecommunication link.
  • a single-ended 980 nm counter-propagating sensing system 350 is used to simultaneously launch, propagate and monitor two counter- propagating sensing signals in the 1550 nm singlemode optical fibre transmission link 1000 fusion spliced 74 to another optical fibre (single or multi moded) in the same or nearby cable 1200.
  • Any disturbance P that acts to alter the counter-propagating sensing signals along links 1000 and/or 1200 will effect both signals in the same manner.
  • the effected counter-propagating signals must each continue travelling the remainder of the fibre length to their respective photodetectors in system 350 there is a resultant time delay or time difference between the detected signals.
  • the time delay is directly proportional to the location of the sensed event along the fibre length, as described earlier. Time synchronisation in this case can be easily achieved by utilising a common signal acquisition system.
  • 1310 nm is launched into a 1310 nm singlemode optical fibre 8a from a pigtailed laser diode with optional integrated isolator 41 and propagates along the optical fibre 8a.
  • the optical fibre 8a is fusion spliced 84 to one input arm 8b of a 850/1310 nm multimode fibre optic wavelength multiplexing coupler 34 and when the light at the sensing wavelength reaches the coupler 34 it is branched out into the output arm 5c of the coupler 34.
  • laser light at the communications wavelength 850 nm is launched into a multimode optical fibre 9a from a pigtailed laser diode with optional integrated isolator 25 and propagates along the optical fibre 9a.
  • FIG. 10 is a view showing another general embodiment of the invention for a reflective sensing arrangement operating over a multimode optical fibre telecommunication link.
  • coherent laser light at the sensing wavelength 1310 nm is launched into a 1310 nm singlemode optical fibre 8a from a pigtailed laser diode with optional integrated isolator 41 and propagates along the optical fibre 8a.
  • the optical fibre 8a is fusion spliced 86 to one input arm 8e of a 1310 nm singlemode coupler 45 and when the light at the sensing wavelength reaches the coupler 45 it is branched out into the output arm 8g of the coupler 45. If a coupler with two output arms is used then the unused arm is fractured or otherwise terminated to avoid back- reflections. The light at the sensing wavelength then propagates along optical fibre 8g.
  • the optical fibre 8g is fusion spliced 87 to one input arm 8b of a 850/1310 nm multimode fibre optic wavelength multiplexing coupler 34 and when the light at the sensing wavelength reaches the coupler 34 it is branched out into the output arm 5c of the coupler 34.
  • a wavelength multiplexing coupler with two output arms If a wavelength multiplexing coupler with two output arms, is used then the unused arm is fractured or otherwise terminated to avoid back-reflections.
  • laser light at the communications wavelength 850 nm is launched into a multimode optical fibre 9a from a pigtailed laser diode with optional integrated isolator 25 and propagates along the optical fibre 9a.
  • the optical fibre 9a is fusion spliced 80 to the second input arm 9b of the 850/1310 nm multimode fibre optic wavelength multiplexing coupler 34 and when the light at the communications wavelength reaches the coupler 34 it is likewise branched out into the same output arm 5c of the coupler 34 as the sensing signal.
  • the wavelength multiplexing coupler 34 efficiently combines both the sensing and communications signals into a single output coupler arm 5c .
  • the output arm 5c of the wavelength multiplexing coupler 34 is then fusion spliced 81 directly to the main multimode optical fibre transmission link 1500.
  • Both the communications and sensing signals propagate along the entire length of the multimode optical fibre transmission link 1500, without interfering with one another, until they reach the opposite end of the link 1500.
  • the multimode optical fibre transmission link 1500 is then fusion spliced 82 to the input arm 5d of a 850/1310 nm multimode fibre optic wavelength demultiplexing coupler 36 and when the signals reach the coupler 36 they are efficiently separated and branched out into two separate and respective output arms 8c and 9c of the coupler 36.
  • the 850 nm communications signal output arm 9c of the wavelength demultiplexing coupler 36 is then fusion spliced 83 to a multimode fibre 9d pigtailed or receptacled Si detector 27.
  • the 1310 nm sensing signal output arm 8c of the wavelength demultiplexing coupler 36 is then fusion spliced 88 to a 1310 nm singlemode or multimode fibre 8h terminated with a reflective mirror 47.
  • the sensing signal is thus reflected back in the opposite direction along fibres 8h, 8c, 5d, 1500, 5c, 8b and 8g, and branched through coupler 45 to output arm 8f .
  • the output arm 8f of the coupler 45 is then fusion spliced 89 to a 1310 nm singlemode fibre 8d pigtailed InGaAs detector 43.
  • appropriate electronics, signal processing schemes and algorithms process the signals from the photodetectors to obtain the desired information.
  • FIG 11 is a view showing another general embodiment of the invention for a two-ended counter-propagating sensing and locating arrangement, according to the method shown in Figure 3, operating over a multimode optical fibre telecommunication link.
  • a 1310 nm counter-propagating sensing system 400 is used to launch a sensing signal in one direction of the main multimode optical fibre transmission link 1500 and the system 400 is suitably time-synchronised with a second 1310 nm counter- propagating sensing system 420 launching a sensing signal in the opposite direction of the main multimode optical fibre transmission link 1500. Any disturbance that acts to alter the counter-propagating sensing signals along link 1500 will effect both signals in the same manner.
  • Figure 12 is a view showing another general embodiment of the invention for a single-ended counter-propagating sensing and locating arrangement, according to the method shown in Figure 4, operating over a multimode optical fibre telecommunication link.
  • a single-ended 1310 nm counter-propagating sensing system 450 is used to simultaneously launch, propagate and monitor two counter- propagating sensing signals in the main multimode optical fibre transmission link 1500 fusion spliced 94 to another optical fibre (single or multi moded) in the same or nearby cable 1700. Any disturbance that acts to alter the counter-propagating sensing signals along links 1500 and/or 1700 will effect both signals in the same manner.
  • the effected counter-propagating signals must each continue travelling the remainder of the fibre length to their respective photodetectors in system 450 there is a resultant time delay or time difference between the detected signals.
  • the time delay is directly proportional to the location of the sensed event along the fibre length, as described earlier. Time synchronisation in this case can be easily achieved by utilising a common signal acquisition system.
  • Figure 13 is a view showing a further general embodiment of the invention, utilising a plurality of WDM couplers in a" singlemode optical fibre, three-node, point-to-point network arrangement, forming a junction by-pass arrangement for the sensing signal in order to extend the sensing fibre length beyond one communication node.
  • Nl coherent laser light at the sensing wavelength 980 nm is launched into a 980 nm singlemode optical fibre 16a from a pigtailed laser diode with optional integrated isolator 140 and propagates along the optical fibre 16a.
  • the optical fibre 16a is fusion spliced 157 to one input arm 16b of a 980/1550 nm singlemode fibre optic wavelength multiplexing coupler 130 and when the light at the sensing wavelength reaches the coupler 130 it is branched out into the output arm 15a of the coupler 130. Simultaneously, at Communications Node 1 laser light at the communications wavelength 1550 nm is launched into a 1550 nm singlemode optical fibre 17a from a pigtailed laser diode with optional integrated isolator 120 and propagates along the optical fibre 17a.
  • the optical fibre 17a is fusion spliced 150 to the second input arm 17b of the 980/1550 nm singlemode fibre optic wavelength multiplexing coupler 130 and when the light at the communications wavelength reaches the coupler 130 it is likewise branched out into the same output arm 15a of the coupler 130 as the sensing signal.
  • the wavelength multiplexing coupler 130 efficiently combines both the sensing and communications signals into a single output coupler arm 15a.
  • the output arm 15a of the wavelength multiplexing coupler 130 is then fusion spliced 152 directly to the main 1550 nm singlemode optical fibre transmission link 2000.
  • Both the communications and sensing signals propagate along the entire length of the 1550 nm singlemode optical fibre transmission link 2000, without interfering with one another, until they reach the opposite end of the link 2000.
  • the 1550 nm singlemode optical fibre transmission link 2000 is then fusion spliced 154 to the input arm 15b of a 980/1550 nm singlemode fibre optic wavelength demultiplexing coupler 132 and when the signals reach the coupler 132 they are efficiently separated and branched out into two separate and respective output arms 16c and 17c of the coupler 132.
  • the 1550 nm communications signal output arm 17c of the wavelength demultiplexing coupler 132 is then fusion spliced 156 to a 1550 nm singlemode fibre 17d pigtailed InGaAs detector 122 at Communications Node 2 N2, where appropriate electronics, signal processing schemes and algorithms process the signals from the photodetector 122 to obtain the desired communications information.
  • the 980 nm sensing signal output arm 16c of the wavelength demultiplexing coupler 132 is then fusion spliced 158 to a 980 nm or 1550 nm singlemode optical fibre 2001 which acts to by-pass Communications Node 2 so that the sensing signal continuous propagating towards Communications Node 3 N3.
  • the sensing signal thus propagates along junction by-pass fibre 2001 until fibre 2001 is fusion spliced 257 to one input arm 116b of a 980/1550 nm singlemode fibre optic wavelength multiplexing coupler 230 and when the light at the sensing wavelength reaches the coupler 230 it is branched out into the output arm 115a of the coupler 230.
  • laser light at the communications wavelength 1550 nm is launched into a 1550 nm singlemode optical fibre 117a from a pigtailed laser diode with optional integrated isolator 220 and propagates along the optical fibre 117a.
  • the optical fibre 117a is fusion spliced 250 to the second input arm 117b of the 980/1550 nm singlemode fibre optic wavelength multiplexing coupler 230 and when the light at the communications wavelength reaches the coupler 230 it is likewise branched out into the same output arm 115a of the coupler 230 as the sensing signal.
  • the wavelength multiplexing coupler 230 efficiently combines both the sensing and communications signals into a single output coupler arm 115a.
  • the output arm 115a of the wavelength multiplexing coupler 230 is then fusion spliced 252 directly to the second main 1550 nm singlemode optical fibre transmission link 2002.
  • Both the communications and sensing signals propagate along the entire length of the 1550 nm singlemode optical fibre transmission link 2002, without interfering with one another, until they reach the opposite end of the link 2002.
  • the 1550 nm singlemode optical fibre transmission link 2002 is then fusion spliced 254 to the input arm 115b of a 980/1550 nm singlemode fibre optic wavelength demultiplexing coupler 232 and when the signals reach the coupler 232 they are efficiently separated and branched out into two separate and respective output arms 116c and 117c of the coupler
  • the 1550 nm communications signal output arm 117c of the wavelength demultiplexing coupler 232 is then fusion spliced 256 to a 1550 nm singlemode fibre 117d pigtailed InGaAs detector 222 at Communications Node 3.
  • the 980 nm sensing signal output arm 116c of the wavelength demultiplexing coupler 232 is then fusion spliced 258 to a 980 nm singlemode fibre 116d pigtailed InGaAs detector 242.
  • appropriate electronics, signal processing schemes and algorithms at Communications Node 3 process the signals from the photodetectors to obtain the desired information.
  • the sensing signal was propagated along two optical fibre links 2000 and 2002, while still utilising only one transmitter 140 end and one detector 242 end.
  • the 980 nm sensing wavelength it is possible to also use true multimode fibre in place of the singlemode fibres 2000, 2001 and 2002 if the communications system was operating over a multimode link.
  • Figure 14 is a view showing a further general embodiment of the invention, utilising a plurality of WDM couplers in a multimode optical fibre, three-node, point-to-point network, forming a junction by-pass arrangement for the sensing signal in order to extend the sensing fibre length beyond one communication node.
  • coherent laser light at the sensing wavelength 1310 nm is launched into a multimode optical fibre 18a from a pigtailed laser diode with optional integrated isolator 141 and propagates along the optical fibre 18a.
  • the optical fibre 18a is fusion spliced 184 to one input arm 18b of a 850/1310 nm multimode fibre optic wavelength multiplexing coupler 134 and when the light at the sensing wavelength reaches the coupler 134 it is branched out into the output arm 15c of the coupler 134. Simultaneously, at
  • Communications Node 1 laser light at the communications wavelength 850 nm is launched into a multimode optical fibre 19a from a pigtailed laser diode with optional integrated isolator 125 and propagates along the optical fibre 19a.
  • the optical fibre 19a is fusion spliced 180 to the second input arm 19b of the 850/1310 nm multimode fibre optic wavelength multiplexing coupler 134 and when the light at the communications wavelength reaches the coupler 134 it is likewise branched out into the same output arm 15c of the coupler 134 as the sensing signal.
  • the wavelength multiplexing coupler 134 efficiently combines both the sensing and communications signals into a single output coupler arm 15c.
  • the output arm 15c of the wavelength multiplexing coupler 134 is then fusion spliced 181 directly to the main multimode optical fibre transmission link 2150.
  • Both the communications and sensing signals propagate along the entire length of the multimode optical fibre transmission link 2150, without interfering with one another, until they reach the opposite end of the link 2150.
  • the multimode optical fibre transmission link 2150 is then fusion spliced 182 to the input arm 15d of a 850/1310 nm multimode fibre optic wavelength demultiplexing coupler 136 and when the signals reach the coupler 136 they are efficiently separated and branched out into two separate and respective output arms 18c and 19c of the coupler 136.
  • the 850 nm communications signal output arm 19c of the wavelength demultiplexing coupler 136 is then fusion spliced 183 to a multimode fibre 19d pigtailed or receptacled Si detector J.27 at Communications Node 2, where appropriate electronics, signal processing schemes and algorithms process the signals from the photodetector 127 to obtain the desired communications information.
  • the 1310 nm sensing signal output arm 18c of the wavelength demultiplexing coupler 136 is then fusion spliced 188 to a multimode or 1310 nm singlemode optical fibre 2160 which acts to by-pass Communications Node 2 so that the sensing signal continuous propagating towards Communications Node 3.
  • the sensing signal thus propagates along junction by-pass fibre 2160 until fibre 2160 is fusion spliced 284 to one input arm 118b of a 850/1310 nm multimode fibre optic wavelength multiplexing coupler 234 and when the light at the sensing wavelength reaches the coupler 234 it is branched out into the output arm 115c of the coupler 234.
  • laser light at the communications wavelength 850 nm is launched into a multimode optical fibre 119a from a pigtailed laser diode with optional integrated isolator 225 and propagates along the optical fibre 119a.
  • the optical fibre 119a is fusion spliced 280 to the second input arm 119b of the 850/1310 nm multimode fibre optic wavelength multiplexing coupler 234 and when the light at the communications wavelength reaches the coupler 234 it is likewise branched out into the same output arm 115c of the coupler 234 as the sensing signal.
  • the wavelength multiplexing coupler 234 efficiently combines both the sensing and communications signals into a single output coupler arm 115c .
  • the output arm 115c of the wavelength multiplexing coupler 234 is then fusion spliced 281 directly to the second main multimode optical fibre transmission link 2170. Both the communications and sensing signals propagate along the entire length of the multimode optical fibre transmission link 2170, without interfering with one another, until they reach the opposite end of the link 2170.
  • the multimode optical fibre transmission link 2170 is then fusion spliced 282 to the input arm 115d of a 850/1310 nm multimode fibre optic wavelength demultiplexing coupler 236 and when the signals reach the coupler 236 they are efficiently separated and branched out into two separate and respective output arms 118c and 119c of the coupler 236.
  • the 850 nm communications signal output arm 119c of the wavelength demultiplexing coupler 236 is then fusion spliced 283 to a multimode fibre 119d pigtailed or receptacled Si detector 227 at Communications Node 3.
  • the 1310 nm sensing signal output arm 118c of the wavelength demultiplexing coupler 236 is then fusion spliced 288 to a multimode or 1310 nm singlemode fibre 118d pigtailed InGaAs detector 243.
  • appropriate electronics, signal processing schemes and algorithms at Communications Node 3 process the signals from the photodetectors to obtain the desired information.
  • FIG. 15 is a view showing yet another general embodiment of the invention, utilising a transmissive sensing arrangement and a plurality of WDM couplers in an optical fibre ring topology network, forming several junction bypass arrangements for the sensing signal in order to extend the overall sensing fibre length across the entire ring topology network.
  • ring topology network (RTN) nodes 500, 502, 504, 506, 508 and 510 are interconnected via optical fibre (single or multi moded) links 600, 602, 604, 606, 608 and 610 by a logical sequence of appropriate WDM couplers 550, 552, 554, 556, 558, 560, 562, 564, 566, 568, 570 and 572.
  • RTN ring topology network
  • a sensing signal is launched from a pigtailed laser diode with optional isolator 520 around the network fibres 600, 602, 604, 606, 608 and 610 by the same logical sequence of appropriate WDM couplers 550, 552, 554, 556, 558, 560, 562, 564, 566, 568, 570 and 572 and junction by-pass fibres (single or multi moded) 650, 652, 654, 656 and 658 until the signal is finally received at detector 540, in a similar fashion as that described in detail for Figures 13 and 14.
  • the advantage of this arrangement is that the overall sensing fibre length was extended across the entire ring topology network, while still utilising only one transmitter 520 end and one detector 540 end.
  • FIG 16 is a view showing yet another general embodiment of the invention, utilising a counter-propagating sensing and locating arrangement and a plurality of WDM couplers in an optical fibre ring topology network arrangement, forming several junction by-pass arrangements for the sensing signals in order to extend the overall sensing fibre length across the entire ring topology network.
  • ring topology network (RTN) nodes 700, 702, 704, 706, 708 and 710 are interconnected via optical fibre (single or multi moded) links 800, 802, 804, 806, 808 and 810 by a logical sequence of appropriate WDM couplers 750, 752, 754, 756, 758, 760, 762, 764, 766, 768, 770 and 772.
  • a counter-propagating sensing system 720 simultaneously launches counter-propagating sensing signals around the network fibres 800, 802, 804, 806, 808 and 810 by the same logical sequence of appropriate WDM couplers 750, 752, 754, 756, 758, 760, 762, 764, 766, 768, 770 and 772 and junction by-pass fibres (single or multi moded) 850, 852, 854, 856 and 858 until the signals are finally received at synchronised detectors in the counter-propagating sensing system 720, in a similar fashion as that described in detail in the other figures.
  • the advantage of this arrangement is that the overall sensing fibre length was extended across the entire ring topology network, while utilising only a single instrument control box, with individual optical fibre input/output ports.
  • any fibre optic communications systems which need to be monitored against and detect intrusion, tampering or tapping-off of information from the optical fibres, such as:
  • LANs Multimode local area networks
  • WANs Singlemode wide area networks
  • WANs Multimode wide area networks
  • a ny fibre optic communications systems which are also utilised for sensing applications, including:

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Abstract

L'invention concerne un système de guide d'ondes optiques permettant de protéger des fibres actives contre l'altération et l'interception de données dans des liaisons de communication à fibres optiques. La liaison de communication comprend un guide d'ondes (1000) qui s'étend d'une implantation à une autre, afin de transmettre un signal de données. Un émetteur de données (20) lance le signal de données dans la fibre (1000), et un récepteur de données (22) reçoit ledit signal. Un émetteur de signal de détection (40) lance un signal de détection dans la fibre (1000), et un récepteur de signal de détection (42) reçoit ledit signal pour ladite fibre (1000). Les émetteurs (20, 40) sont couplés à la fibre (1000) à l'aide d'un coupleur (30) de multiplexage/démultiplexage de longueurs d'ondes, via des bras d'entrée (76, 66) du coupleur (30). Les signaux sont transférés aux récepteurs (22, 42) par un autre coupleur (32) de multiplexage/démultiplexage, via des bras d'entrée (7c, 6c). Les coupleurs (30, 32) garantissent que les signaux sont combinés avec une perte de puissance minimum, et sont séparés afin d'être transmis aux détecteurs également avec une perte de puissance minimum, tous les signaux de données étant sensiblement transmis au récepteur (22) et tous les signaux de détection étant transmis au récepteur (42).
PCT/AU2000/000382 1999-05-03 2000-04-28 Protection intrinseque des liaisons de communication a fibres optiques WO2000067400A1 (fr)

Priority Applications (6)

Application Number Priority Date Filing Date Title
KR1020017014026A KR20020026863A (ko) 1999-05-03 2000-04-28 광섬유 통신링크의 본질적인 안전장치 및 그 방법
JP2000616144A JP2002543738A (ja) 1999-05-03 2000-04-28 光ファイバー通信リンクの本質的保護
EP00920265A EP1175743A4 (fr) 1999-05-03 2000-04-28 Protection intrinseque des liaisons de communication a fibres optiques
IL14607500A IL146075A (en) 1999-05-03 2000-04-28 Intrinsic security of fiber optic communication links
AU40921/00A AU760272B2 (en) 1999-05-03 2000-04-28 Intrinsic securing of fibre optic communication links
CA002371576A CA2371576A1 (fr) 1999-05-03 2000-04-28 Protection intrinseque des liaisons de communication a fibres optiques

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AUPQ0126A AUPQ012699A0 (en) 1999-05-03 1999-05-03 Intrinsic securing of fibre optic communication links
AUPQ0126 1999-05-03

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WO2000067400A1 true WO2000067400A1 (fr) 2000-11-09

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EP (1) EP1175743A4 (fr)
JP (1) JP2002543738A (fr)
KR (1) KR20020026863A (fr)
CN (1) CN1349689A (fr)
AU (1) AUPQ012699A0 (fr)
CA (1) CA2371576A1 (fr)
IL (1) IL146075A (fr)
WO (1) WO2000067400A1 (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
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US6934426B2 (en) 2002-10-09 2005-08-23 Senstar-Stellar Corporation Fiber optic security sensor and system with integrated secure data transmission and power cables
US7092586B2 (en) 2003-07-18 2006-08-15 Network Integrity Systems Inc. Intrusion detection system for use on an optical fiber using a translator of transmitted data for optimum monitoring conditions
US7376293B2 (en) 2003-07-18 2008-05-20 Network Intergrity Systems Inc. Remote location of active section of fiber in a multimode intrusion detection system
US7403675B2 (en) 2003-07-18 2008-07-22 Network Integrity Systems Inc. Method of high order mode excitation for multimode intrusion detection
US7403674B2 (en) 2003-07-18 2008-07-22 Network Integrity Systems Inc. Intrusion detection system for a multimode optical fiber using a bulk optical wavelength division multiplexer for maintaining modal power distribution
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Cited By (8)

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Publication number Priority date Publication date Assignee Title
US7519242B2 (en) 2001-03-07 2009-04-14 Future Fibre Technologies Pty Ltd Perimeter security system and perimeter monitoring method
EP1385277A1 (fr) * 2002-07-22 2004-01-28 Agilent Technologies, Inc. - a Delaware corporation - Transmission de données de surveillance dans un système de communication optique
US6934426B2 (en) 2002-10-09 2005-08-23 Senstar-Stellar Corporation Fiber optic security sensor and system with integrated secure data transmission and power cables
US7092586B2 (en) 2003-07-18 2006-08-15 Network Integrity Systems Inc. Intrusion detection system for use on an optical fiber using a translator of transmitted data for optimum monitoring conditions
US7120324B2 (en) 2003-07-18 2006-10-10 Network Integrity Systems Inc. Intrusion detection system for use on an optical fiber using a translator of transmitted data for optimum monitoring conditions
US7376293B2 (en) 2003-07-18 2008-05-20 Network Intergrity Systems Inc. Remote location of active section of fiber in a multimode intrusion detection system
US7403675B2 (en) 2003-07-18 2008-07-22 Network Integrity Systems Inc. Method of high order mode excitation for multimode intrusion detection
US7403674B2 (en) 2003-07-18 2008-07-22 Network Integrity Systems Inc. Intrusion detection system for a multimode optical fiber using a bulk optical wavelength division multiplexer for maintaining modal power distribution

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KR20020026863A (ko) 2002-04-12
IL146075A0 (en) 2002-07-25
JP2002543738A (ja) 2002-12-17
IL146075A (en) 2004-12-15
AUPQ012699A0 (en) 1999-05-27
EP1175743A1 (fr) 2002-01-30
EP1175743A4 (fr) 2003-07-30
CA2371576A1 (fr) 2000-11-09
CN1349689A (zh) 2002-05-15

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