CA1341420C - Laser initiated ordnance system optical fiber continuity test - Google Patents
Laser initiated ordnance system optical fiber continuity test Download PDFInfo
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- CA1341420C CA1341420C CA000576256A CA576256A CA1341420C CA 1341420 C CA1341420 C CA 1341420C CA 000576256 A CA000576256 A CA 000576256A CA 576256 A CA576256 A CA 576256A CA 1341420 C CA1341420 C CA 1341420C
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- optical fiber
- light source
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- 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
- G01M11/31—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter and a light receiver being disposed at the same side of a fibre or waveguide end-face, e.g. reflectometers
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F42—AMMUNITION; BLASTING
- F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
- F42B3/00—Blasting cartridges, i.e. case and explosive
- F42B3/10—Initiators therefor
- F42B3/113—Initiators therefor activated by optical means, e.g. laser, flashlight
Abstract
An apparatus is disclosed for testing the integrity of an optical fiber (23) from a single end of the fiber. A test light source (34) with a wavelength that is different from the primary light source (14) is directed into one end of the optical fiber (23). A spectrally selective dichroic material (32) is attached to the other end of the optical fiber (23).
This material (32) transmits light of the wavelength of the primary light source (14) and reflects light of the wavelength of the test light source (34). A break or discontinuity in the optical fiber (23) can be detected by an attenuation in a pulse of light from the test light source (34) after it is transmitted though the optical fiber (23) and reflected back out of the optical fiber (23) by the dichroic material (32). This system can detect breaks or discontinuities in the optical fiber (23) with a high degree of resolution.
This material (32) transmits light of the wavelength of the primary light source (14) and reflects light of the wavelength of the test light source (34). A break or discontinuity in the optical fiber (23) can be detected by an attenuation in a pulse of light from the test light source (34) after it is transmitted though the optical fiber (23) and reflected back out of the optical fiber (23) by the dichroic material (32). This system can detect breaks or discontinuities in the optical fiber (23) with a high degree of resolution.
Description
~ 341 420 LASER INITIATED ORDNANCE S"YSTF~! OPTICAL FIBER CONTINUTTY TEST
BACKGROUND OF THE INVE«TION
1. Field of the Invention This invention relates generally to fiber optic continuity test systems and specifically to a single-ended tester capable of detecting discontinuities in an optical fiber with a high degree of resolution.
BACKGROUND OF THE INVE«TION
1. Field of the Invention This invention relates generally to fiber optic continuity test systems and specifically to a single-ended tester capable of detecting discontinuities in an optical fiber with a high degree of resolution.
2. Descri tip on of Related Art Fiber optic continuity test systems are usually either single ended or dual ended. Dual ended systems require access to both ends of the optical fiber to measure the amount of light transmitted through the optical fiber. However, in many applications, access to only one end of the fiber is possible.
In such systems, single ended testers rrnzst be employed.
15 Many single ended testers utilise optical time domain reflectometry (OTDR). OTDR systems work by first transmitting pulses of light into a fiber and then measuring the light that is reflected back. The time that it takes for the reflected light to return cx~rresponds to the distance it travels along the 2p fiber. This allows the OTDR system to produce a fiber signature. Two types of reflections occur. Pulse reflections are generated at breaks or joints where the light pulse encounters something other than a continuous glass core. Back scatter reflections are generated uniformly along a fiber as the 25 transmitted pulse travels through the fiber. The back scatter signal provides a measurement of fiber attenuation. OTDR
systems are frequently used for finding breaks in comrn~nication 1 cables which are typically several kilometers long. ~e-half meter is considered excellent resolution for an O~fDR system.
In some systems, where only single ended testers can be used, one meter resolution is not acceptable. Laser initiated ordnance systems are one example. In such a system, a break close to the fiber/ordnance interface could not be distinguished from the end of the optical fiber by an OTDR
system. For example, a break only a millimeter from the fiber/ordinance interface would disable the laser ordinance s0 system but wr~uld not be detected by an Oit'DR system. This is because an OTDR system would have to resolve spikes in a return signal only 67 picoseconds apart to distinguish twa reflections originating one millimeter apart. Current OTDR systems cannot achieve this resolution.
A further discussion of fiber optic testing systems try be found in M. Bininstool, "Integrated C~t'DR/Throughput Loss Measurement System for Environmental Testing of Cabled Optical fibers" in S.P.I.E., Volume 559, Fiber Optics: Short-haul and Long-haul Measurements and A~'lications II, (1985), and R.
Dupuy, "The Present and Future OTDR" in S*P.I.E., Volume 559, Fiber Optics: Short-haul and Long-haul Measurements and A~plicatiOns II, (1985).
Thus, it would be desirable to provide a single ended method of ascertaining fibezv optic link integrity which can :?5 distinguish a break close to the fiber end.
SUt~IARY OF THE INVENTION
The present invention provides a fiber optic continuity test system which can test the integrity of an ;30 optical fiber from a single end of the fiber. In one embodiment of the present invention, a primary light source, for example, a primary laser in a laser initiated ordnance system, is directed into one end of an optical fiber. A secondary light source, for example, a test laser, also directs light. into the same end of 35 the optical fiber. The secondary Light source has a wavelength that is different from the wavelength of the primary :Light source. The optical fiber is covered on its opposite end by a material which reflects the wavelength of light from the test light source and transmits the wave_Length of the primary light source. For example, this may be a dichroic; coating.
In the test mode, the primary light source is decoupled from the optical fiber and the secondary light source is coupled to the fiber. The secondary light source then generates a pulse of l~~ght into the end of the optical fiber. This pulse is transmitted through the length of the optical fiber. and is reflected by the dichroic coating a.t the opposite end of the fiber. A
photodetector is ~>ositioned near true test light source wheres it can detects the pulse of light that is reflected.
If there is a break in the optical fiber, the pulse of light. that is reflected back to the photodetector will be of lower intensity than would be expected. This is because less light from the pulse i:~ transmitted through the break to the dichroic coating and also because the pulse' is again attenuated as it passes through the break a second time as it travels back toward the detector.
If the amplitude of the detected pulse indicates that the optical fiber has no break, the ~~ont~.nuity test is complete. The system is there :witched. from the test mode to the operating mode. This is accomplished by decoupling the test light source from the optical fiber and coupling the primary light source t:o the optical fiber. The dichroic ccaating at the end of t:he optical fiber will then transmit light at the wavelength of the primary light source without significant reflection or attenuation. The primary _Light source can then perform its intended function.
According to one aspect of the present invention, there is provided apparatus for testing the integrity of an optical fiber from a single end of the fiber comprising:
,A
3a (a) a primary light source which emits light at a primary wavelength;
(b) a test light source which emits light at a test wavelength wherein said test wavelength is different from said primary wavelength;
(c) means for c~.irecti.ng light fx-om the primary light source into a first end of the optical fiber;
(d) means for directing light from the test light source into the first end of the optical. fiber;
(e) means for alternately interrupting light from either the primary Light source or from the test light source;
(f) a reflective and transmissivE: member mounted on a second end of the optical fiber, having the property of substantially transmitting light of the primary wavelength and also substantially reflecting light of the test wavelength;
(g) means for pulsing the test light source;
(h) means for detecting pulses of light from the test light source which are directed out of t:he first end of the optical fiber after they are ref~.ected by the x-eflective and transmissive member; and (i.) means for measuring the intensity of the light pulses detected by the detector means whereby a discontinuity in the optical fiber can be sensed by a reduction in the intensity of the reflected light pulses.
According to another aspect of the present invention, there is provided apparatus for testing the integrity of an optical fiber in a lasex° initiated ordnance system from a single end of the fiber corriprising:
(a) a primary light source comprising a laser which emits light at a primary wavelength;
;~
:3b (b) a test light source comprising a low energy laser diode which emi ts light at a test wavelength whereinsaid test wavelength is different from said primary th;
waveleng (c) means for directing light from the rimary Eight p '~ source into rst e:nd of th.e optical f fiber;
a fi (d) means for directing light from the test light source into the first end of the optical. fiber;
(e) means for alternately intex:rupting light from either the primary test light :Light source or from the source;
(:E) a dichroic coating mounted ors a second end of the optica7_ fiber, having the property of substantially transmitting light of the primary wavelength and also substantially reflecting light of the test wavelength;
(g) means for pulsing the test light source;
(h) a photodiode for detecting pulses of light from the test light source which are directed out of the first end of the optical fiber after they <~x:~e reflected by the dichroic coating; and (i.) means for measuring the intensity of the light pulses detected by the phot.odiode during a fixed period of time whereby a discontinuity in the optical fiber can be sensed by a reduction in the intensity of the reflected light pulses.
BRIEF DESCRIPTION OF THE DRAWINGS
Various other advantages will become apparent to one skilled in the art after reading the fol:l.owing specification and by reference to the drawings in which:
In such systems, single ended testers rrnzst be employed.
15 Many single ended testers utilise optical time domain reflectometry (OTDR). OTDR systems work by first transmitting pulses of light into a fiber and then measuring the light that is reflected back. The time that it takes for the reflected light to return cx~rresponds to the distance it travels along the 2p fiber. This allows the OTDR system to produce a fiber signature. Two types of reflections occur. Pulse reflections are generated at breaks or joints where the light pulse encounters something other than a continuous glass core. Back scatter reflections are generated uniformly along a fiber as the 25 transmitted pulse travels through the fiber. The back scatter signal provides a measurement of fiber attenuation. OTDR
systems are frequently used for finding breaks in comrn~nication 1 cables which are typically several kilometers long. ~e-half meter is considered excellent resolution for an O~fDR system.
In some systems, where only single ended testers can be used, one meter resolution is not acceptable. Laser initiated ordnance systems are one example. In such a system, a break close to the fiber/ordnance interface could not be distinguished from the end of the optical fiber by an OTDR
system. For example, a break only a millimeter from the fiber/ordinance interface would disable the laser ordinance s0 system but wr~uld not be detected by an Oit'DR system. This is because an OTDR system would have to resolve spikes in a return signal only 67 picoseconds apart to distinguish twa reflections originating one millimeter apart. Current OTDR systems cannot achieve this resolution.
A further discussion of fiber optic testing systems try be found in M. Bininstool, "Integrated C~t'DR/Throughput Loss Measurement System for Environmental Testing of Cabled Optical fibers" in S.P.I.E., Volume 559, Fiber Optics: Short-haul and Long-haul Measurements and A~'lications II, (1985), and R.
Dupuy, "The Present and Future OTDR" in S*P.I.E., Volume 559, Fiber Optics: Short-haul and Long-haul Measurements and A~plicatiOns II, (1985).
Thus, it would be desirable to provide a single ended method of ascertaining fibezv optic link integrity which can :?5 distinguish a break close to the fiber end.
SUt~IARY OF THE INVENTION
The present invention provides a fiber optic continuity test system which can test the integrity of an ;30 optical fiber from a single end of the fiber. In one embodiment of the present invention, a primary light source, for example, a primary laser in a laser initiated ordnance system, is directed into one end of an optical fiber. A secondary light source, for example, a test laser, also directs light. into the same end of 35 the optical fiber. The secondary Light source has a wavelength that is different from the wavelength of the primary :Light source. The optical fiber is covered on its opposite end by a material which reflects the wavelength of light from the test light source and transmits the wave_Length of the primary light source. For example, this may be a dichroic; coating.
In the test mode, the primary light source is decoupled from the optical fiber and the secondary light source is coupled to the fiber. The secondary light source then generates a pulse of l~~ght into the end of the optical fiber. This pulse is transmitted through the length of the optical fiber. and is reflected by the dichroic coating a.t the opposite end of the fiber. A
photodetector is ~>ositioned near true test light source wheres it can detects the pulse of light that is reflected.
If there is a break in the optical fiber, the pulse of light. that is reflected back to the photodetector will be of lower intensity than would be expected. This is because less light from the pulse i:~ transmitted through the break to the dichroic coating and also because the pulse' is again attenuated as it passes through the break a second time as it travels back toward the detector.
If the amplitude of the detected pulse indicates that the optical fiber has no break, the ~~ont~.nuity test is complete. The system is there :witched. from the test mode to the operating mode. This is accomplished by decoupling the test light source from the optical fiber and coupling the primary light source t:o the optical fiber. The dichroic ccaating at the end of t:he optical fiber will then transmit light at the wavelength of the primary light source without significant reflection or attenuation. The primary _Light source can then perform its intended function.
According to one aspect of the present invention, there is provided apparatus for testing the integrity of an optical fiber from a single end of the fiber comprising:
,A
3a (a) a primary light source which emits light at a primary wavelength;
(b) a test light source which emits light at a test wavelength wherein said test wavelength is different from said primary wavelength;
(c) means for c~.irecti.ng light fx-om the primary light source into a first end of the optical fiber;
(d) means for directing light from the test light source into the first end of the optical. fiber;
(e) means for alternately interrupting light from either the primary Light source or from the test light source;
(f) a reflective and transmissivE: member mounted on a second end of the optical fiber, having the property of substantially transmitting light of the primary wavelength and also substantially reflecting light of the test wavelength;
(g) means for pulsing the test light source;
(h) means for detecting pulses of light from the test light source which are directed out of t:he first end of the optical fiber after they are ref~.ected by the x-eflective and transmissive member; and (i.) means for measuring the intensity of the light pulses detected by the detector means whereby a discontinuity in the optical fiber can be sensed by a reduction in the intensity of the reflected light pulses.
According to another aspect of the present invention, there is provided apparatus for testing the integrity of an optical fiber in a lasex° initiated ordnance system from a single end of the fiber corriprising:
(a) a primary light source comprising a laser which emits light at a primary wavelength;
;~
:3b (b) a test light source comprising a low energy laser diode which emi ts light at a test wavelength whereinsaid test wavelength is different from said primary th;
waveleng (c) means for directing light from the rimary Eight p '~ source into rst e:nd of th.e optical f fiber;
a fi (d) means for directing light from the test light source into the first end of the optical. fiber;
(e) means for alternately intex:rupting light from either the primary test light :Light source or from the source;
(:E) a dichroic coating mounted ors a second end of the optica7_ fiber, having the property of substantially transmitting light of the primary wavelength and also substantially reflecting light of the test wavelength;
(g) means for pulsing the test light source;
(h) a photodiode for detecting pulses of light from the test light source which are directed out of the first end of the optical fiber after they <~x:~e reflected by the dichroic coating; and (i.) means for measuring the intensity of the light pulses detected by the phot.odiode during a fixed period of time whereby a discontinuity in the optical fiber can be sensed by a reduction in the intensity of the reflected light pulses.
BRIEF DESCRIPTION OF THE DRAWINGS
Various other advantages will become apparent to one skilled in the art after reading the fol:l.owing specification and by reference to the drawings in which:
4 1 ~4~ 42U
FIG. 1 is a s~tic diagram representing a fiber optic continuity test system in accordance with the present invention.
FIG. 2 is a graph of the spectxal characteristics of the dichroic coating in the fiber optic continuity test system shown in FIG. 1.
FIG. 3 is a graph of a typical test signal for the fiber optic continuity test system shown in FIG. 1.
DESCRIPTiC~T OF THE PREt'E~;t~k~ D~ODIi4nVT
The fiber optic continuity test system 10 is shown in FIG. 1 adapted for use in a laser initiated ordnance system 12.
In this embodiment, the laser initiated ordnance system 12 comprises a pri.mazy laser 14 which emits light at a wavelength of 1.06 microns. The output energy per pulse of this laser may range from 50 millijoules to 500 millijoules. In the operating mode, a light pulse from the primaxy laser 14 is directed through a rhomboid prism 16, and then through a set of focusing lenses 18. The focusing lenses 18 focus the light from the o primary laser 14 into the optical fiber assembly 20. The optical fiber assembly 20 comprises an optical fiber 22. a connector 24, a second connector 28, a pigtail 30 and a dichroic coating 32.
In the preferred embodiment, the dichro:ic coating 32 ?5 is a vacuum deposited multilayer dielectric coating that has high transmittance at the wavelength of the primary laser. This wavelength is I.06 microns. As shown in ~'IG 2, this transmittance is approximately 98 percent. Thus, a high percentage of the energy from the primary laser is transmitted ;3o through the dichroic c:oatinq to initiate an explosive device 33 shown in FIG. 1. If there are any bad connections or breaks in the optical fiber assembly 20, the laser initiated ordnance system 12 may not work because of attenuation of light-from the prilr~ary laser 14 at the point of the break or bad connection.
~341~+~0 To test the integrity of the optical fiber assembly 20, the fiber optics continuity test system 10 is put into the test mode. This is accomplished by sliding a second rhomboid prism 34, a deviating prism 36 and a shutter 38 5 into the path of t:he Eight f tom the primary laser 14 as shown in FIG. 1. In the test mode, light. from the primary 20, laser 14 may nat enter the optical fiber assembly 20, but light from a test. laser 40 :is directed into the optical fiber assembly 20. In this embodiment, the test laser 40 is a laser diode with a wavelength between .08 microns and .88 microns. A :pulse generator circuit 42 drives the test laser 40. The test laser 40 then emits a pulse of less than 20 nanoseconds duration with a total energy of about .10 nanojoule. 'this energy level is low enough so that it ma~,~ safely be employed without risk of initiating the explosive 33.
Light from the test laser 40 i ~ directed into a set of lenses 44, thr~~ugh a beam splinter 46 and into the rhomboid prism 34. The light is then directed from this prism 34 into the first rhomboid prism :L6 and then to focussing lenses 18, which direct the light into the optical fiber assembly 20. After the test light pulse travels the optica:~ fiber assembly 20, it is reflected by the dichroic coating 32. FIG. 2 illustrates the trans-mittance of the dichro:ic coating :3~? whic:h is near zero percent for the wavelength test laser. Thus, almost all of the light will be n-eflected by the d:ichroic coating back through the optir~al fiber assembly 20 and also through focusing lenses 18, first prism 10, second prism 34 and to beam sp:litter 46. A portion of this beam is reflected by beam sputter 40 and is direci~ed into a photodiode 48.
An example of the signal detected by the photodiode 48 is shown in FI:G. 3. When the test pulse from the laser diode 40 is transmitted into the optical fiber assembly 20, some of the light from this pulse will be 'A
5a reflected by the connectors in the optical fiber assembly 20. For example, connector 24 will A
FIG. 1 is a s~tic diagram representing a fiber optic continuity test system in accordance with the present invention.
FIG. 2 is a graph of the spectxal characteristics of the dichroic coating in the fiber optic continuity test system shown in FIG. 1.
FIG. 3 is a graph of a typical test signal for the fiber optic continuity test system shown in FIG. 1.
DESCRIPTiC~T OF THE PREt'E~;t~k~ D~ODIi4nVT
The fiber optic continuity test system 10 is shown in FIG. 1 adapted for use in a laser initiated ordnance system 12.
In this embodiment, the laser initiated ordnance system 12 comprises a pri.mazy laser 14 which emits light at a wavelength of 1.06 microns. The output energy per pulse of this laser may range from 50 millijoules to 500 millijoules. In the operating mode, a light pulse from the primaxy laser 14 is directed through a rhomboid prism 16, and then through a set of focusing lenses 18. The focusing lenses 18 focus the light from the o primary laser 14 into the optical fiber assembly 20. The optical fiber assembly 20 comprises an optical fiber 22. a connector 24, a second connector 28, a pigtail 30 and a dichroic coating 32.
In the preferred embodiment, the dichro:ic coating 32 ?5 is a vacuum deposited multilayer dielectric coating that has high transmittance at the wavelength of the primary laser. This wavelength is I.06 microns. As shown in ~'IG 2, this transmittance is approximately 98 percent. Thus, a high percentage of the energy from the primary laser is transmitted ;3o through the dichroic c:oatinq to initiate an explosive device 33 shown in FIG. 1. If there are any bad connections or breaks in the optical fiber assembly 20, the laser initiated ordnance system 12 may not work because of attenuation of light-from the prilr~ary laser 14 at the point of the break or bad connection.
~341~+~0 To test the integrity of the optical fiber assembly 20, the fiber optics continuity test system 10 is put into the test mode. This is accomplished by sliding a second rhomboid prism 34, a deviating prism 36 and a shutter 38 5 into the path of t:he Eight f tom the primary laser 14 as shown in FIG. 1. In the test mode, light. from the primary 20, laser 14 may nat enter the optical fiber assembly 20, but light from a test. laser 40 :is directed into the optical fiber assembly 20. In this embodiment, the test laser 40 is a laser diode with a wavelength between .08 microns and .88 microns. A :pulse generator circuit 42 drives the test laser 40. The test laser 40 then emits a pulse of less than 20 nanoseconds duration with a total energy of about .10 nanojoule. 'this energy level is low enough so that it ma~,~ safely be employed without risk of initiating the explosive 33.
Light from the test laser 40 i ~ directed into a set of lenses 44, thr~~ugh a beam splinter 46 and into the rhomboid prism 34. The light is then directed from this prism 34 into the first rhomboid prism :L6 and then to focussing lenses 18, which direct the light into the optical fiber assembly 20. After the test light pulse travels the optica:~ fiber assembly 20, it is reflected by the dichroic coating 32. FIG. 2 illustrates the trans-mittance of the dichro:ic coating :3~? whic:h is near zero percent for the wavelength test laser. Thus, almost all of the light will be n-eflected by the d:ichroic coating back through the optir~al fiber assembly 20 and also through focusing lenses 18, first prism 10, second prism 34 and to beam sp:litter 46. A portion of this beam is reflected by beam sputter 40 and is direci~ed into a photodiode 48.
An example of the signal detected by the photodiode 48 is shown in FI:G. 3. When the test pulse from the laser diode 40 is transmitted into the optical fiber assembly 20, some of the light from this pulse will be 'A
5a reflected by the connectors in the optical fiber assembly 20. For example, connector 24 will A
1 reflect a small amount of light back toward the photodiode 48;
this will be approximately 3~4% of incident light. This pulse is shown as pulse 50 in FIG. 3. Likewise, connector 28 will reflect some of the light pulse back to the photodiode 42.
This pulse 52 is shown also in FIG. 3. Next, the dichroic coating 32 will reflect almost all of the light it receives from the test pulse. This pulse 54 is also shown in FIG. 3. If there were a bad connection or break in the optical fiber assembly 20, much less light ~uld reach dichroic coating 32 so and, accordingly, this pulse 54 reflected from the dirhroic coating 32 would be much smaller.
In'the preferred embodiment, the existence of a break or bad vonnection in the optical fiber assembly 20 can be detected by first measuring the amplitude of the pulse 54 which is reflected from the dichroic coating in a system where the integrity of the optical fiber assembly 22 is kno~m. A signal level, labeled "threshold level" in FIG. 3, is them chosen slightly below the peak amplitude of the pulse 54. This level may be, for example, 10-20 percent below the peak level.
2o In actual tests, if a signal from the photodiode 40 equals or exceeds the threshold level, then the fiber optic assembly 20 passes the test. If, on the other hand, the signal from the photodiode 40 is below the threshold level, then the fiber optic assembly 20 fails the test. This would indicate ?.5 that there was a break or a bad connection in fiber optic assembly 20 because of the attenuation of the test light pulse.
It will be appreciated that the detection of the threshold level can be accomplished by a number of electrical level detector circuits which are well known in the art. It may also be useful 30 to limit the detection by this circuit to an interval of time which begins slightly before the pulse 54 is expected to occur, and ends slightly after this pulse is expected to occur. This period of time is labeled "gate interval" in FIG.- 3. For example, this gate interval may be > 100 nanoseconds. Gate 1 interval can be virtually any time period, including "open-ended." The gate can be as narrow as a few hundred nanoseconds in which case only the desired pulse is measured, or open, in rich case the Natal output energy is measured. The detector circuit 56 is shown in FIG, 1.
The above test system elpmi,nates the need for the precise timing measurements that would be required in an OTDR
system. Further, this method will detect a break in the optical fiber assembly 20 very close to the end of the optical fiber.
:lo This is because attenuation in the test pulse will occur as a result of the break, whether it is near the end of the optical fiber, or elsewhere. OTDR systems, on the other hand, cannot distinguish a break that is, for example, one millimeter away from the end of the optical fiber.
I5 In another embodiment of the present invention, the gate intezval shown in FIG. ~ is extended to encompass the time during which all of the reflected pulses would be expected to be received by the photodiode 48. In this embodiment, the total returned energy is measured by integrating all the returned pulses. It will be appreciated that a number of integrating circuits may be used to accomplish this integration which are mall known in the art. The integration of all of the return pulses is then compared with the integrati~an for a knawn good optical fiber. If this summation is significantly below the expected level, the optical fiber contains a break or bad connection and the test is failed.
Those skilled in the art will come tra appreciate that other advantages and modifications of the particular example set forth herein are obtainable without departing from the spirit of ;3o the invention as defined in the following claims:
this will be approximately 3~4% of incident light. This pulse is shown as pulse 50 in FIG. 3. Likewise, connector 28 will reflect some of the light pulse back to the photodiode 42.
This pulse 52 is shown also in FIG. 3. Next, the dichroic coating 32 will reflect almost all of the light it receives from the test pulse. This pulse 54 is also shown in FIG. 3. If there were a bad connection or break in the optical fiber assembly 20, much less light ~uld reach dichroic coating 32 so and, accordingly, this pulse 54 reflected from the dirhroic coating 32 would be much smaller.
In'the preferred embodiment, the existence of a break or bad vonnection in the optical fiber assembly 20 can be detected by first measuring the amplitude of the pulse 54 which is reflected from the dichroic coating in a system where the integrity of the optical fiber assembly 22 is kno~m. A signal level, labeled "threshold level" in FIG. 3, is them chosen slightly below the peak amplitude of the pulse 54. This level may be, for example, 10-20 percent below the peak level.
2o In actual tests, if a signal from the photodiode 40 equals or exceeds the threshold level, then the fiber optic assembly 20 passes the test. If, on the other hand, the signal from the photodiode 40 is below the threshold level, then the fiber optic assembly 20 fails the test. This would indicate ?.5 that there was a break or a bad connection in fiber optic assembly 20 because of the attenuation of the test light pulse.
It will be appreciated that the detection of the threshold level can be accomplished by a number of electrical level detector circuits which are well known in the art. It may also be useful 30 to limit the detection by this circuit to an interval of time which begins slightly before the pulse 54 is expected to occur, and ends slightly after this pulse is expected to occur. This period of time is labeled "gate interval" in FIG.- 3. For example, this gate interval may be > 100 nanoseconds. Gate 1 interval can be virtually any time period, including "open-ended." The gate can be as narrow as a few hundred nanoseconds in which case only the desired pulse is measured, or open, in rich case the Natal output energy is measured. The detector circuit 56 is shown in FIG, 1.
The above test system elpmi,nates the need for the precise timing measurements that would be required in an OTDR
system. Further, this method will detect a break in the optical fiber assembly 20 very close to the end of the optical fiber.
:lo This is because attenuation in the test pulse will occur as a result of the break, whether it is near the end of the optical fiber, or elsewhere. OTDR systems, on the other hand, cannot distinguish a break that is, for example, one millimeter away from the end of the optical fiber.
I5 In another embodiment of the present invention, the gate intezval shown in FIG. ~ is extended to encompass the time during which all of the reflected pulses would be expected to be received by the photodiode 48. In this embodiment, the total returned energy is measured by integrating all the returned pulses. It will be appreciated that a number of integrating circuits may be used to accomplish this integration which are mall known in the art. The integration of all of the return pulses is then compared with the integrati~an for a knawn good optical fiber. If this summation is significantly below the expected level, the optical fiber contains a break or bad connection and the test is failed.
Those skilled in the art will come tra appreciate that other advantages and modifications of the particular example set forth herein are obtainable without departing from the spirit of ;3o the invention as defined in the following claims:
Claims (15)
1. Apparatus for testing the integrity of an optical fiber from a single end of the fiber comprising:
(a) a primary light source which emits light at a primary wavelength;
(b) a test light source which emits light at a test wavelength wherein said test wavelength is different from said primary wavelength;
(c) means for directing light from the primary light source into a first end of the optical fiber;
(d) means for directing light from the test light source into the first end of the optical fiber;
(e) means for alternately interrupting light from either the primary light source or from the test light source;
(f) a reflective and transmissive member mounted on a second end of the optical fiber, having the property of substantially transmitting light of the primary wavelength and also substantially reflecting light of the test wavelength;
(g) means for pulsing the test light source;
(h) means for detecting pulses of light from the test light source which are directed out of the first end of the optical fiber after they are reflected by the reflective and transmissive member; and (i) means for measuring the intensity of the light pulses detected by the detector means whereby a discontinuity in the optical fiber can be sensed by a reduction in the intensity of the reflected light pulses.
(a) a primary light source which emits light at a primary wavelength;
(b) a test light source which emits light at a test wavelength wherein said test wavelength is different from said primary wavelength;
(c) means for directing light from the primary light source into a first end of the optical fiber;
(d) means for directing light from the test light source into the first end of the optical fiber;
(e) means for alternately interrupting light from either the primary light source or from the test light source;
(f) a reflective and transmissive member mounted on a second end of the optical fiber, having the property of substantially transmitting light of the primary wavelength and also substantially reflecting light of the test wavelength;
(g) means for pulsing the test light source;
(h) means for detecting pulses of light from the test light source which are directed out of the first end of the optical fiber after they are reflected by the reflective and transmissive member; and (i) means for measuring the intensity of the light pulses detected by the detector means whereby a discontinuity in the optical fiber can be sensed by a reduction in the intensity of the reflected light pulses.
2. The apparatus of Claim 1 where the test light source is a low energy laser diode.
3. The apparatus of Claim 2 where the laser diode has a wavelength between .08 and .88 microns.
4. The apparatus of Claim 1 where the primary light source is a laser.
5. The apparatus of Claim 4 where the optical fiber is coupled to a laser initiatable ordnance and the primary light source is used to trigger an ordnance initiator device.
6. The apparatus of Claim 1 where the reflective and transmissive member is a bandpass optical filter.
7. The apparatus of Claim 1 where the reflective and transmissive member is a dichroic coating.
8. The apparatus of Claim 7 where the dichroic coating is a vacuum deposited multi-layer dielectric coating.
9. The apparatus of Claim 1 where the means for alternately interrupting light from either the primary light source comprises a shutter, a rhomboid prism and a deviating prism and a means for introducing the shutter, rhomboid prism and the deviating prism into the path of the light from the primary light source.
10 10. The apparatus of Claim 1 where the means for directing light from the secondary light source comprise:
(a) a first lens assembly for receiving light from the test light source;
(b) a beam splitter for directing light reflected from the optical fiber to the detector means;
(c) a first prism for receiving light from the test light source;
(d) a second prism for receiving light from the first prism; and (e) a focusing lens assembly for directing light from the second prism into the optical fiber.
(a) a first lens assembly for receiving light from the test light source;
(b) a beam splitter for directing light reflected from the optical fiber to the detector means;
(c) a first prism for receiving light from the test light source;
(d) a second prism for receiving light from the first prism; and (e) a focusing lens assembly for directing light from the second prism into the optical fiber.
11. The apparatus of Claim 10 where the means for directing light from the primary light source into a first end of the optical fiber comprises said second prism for receiving light from the primary light source and a focusing lens assembly for directing light from the second prism into the optical fiber.
12. The apparatus of Claim 1 where the means for detecting pulses of light from said test light source comprises a photodiode.
13. The apparatus of Claim 1 where the means for detecting pulses of light from the test light source further comprises means for detecting light only during a small interval of time during which a pulse reflected from the reflective and transmissive member would be expected to be received and means for determining if the detected pulse is above a predetermined threshold whereby a discontinuity in the optical fiber can be detected by a reduction in the height of this pulse.
14. The apparatus of Claim 1 where the means for detecting pulses of light detects light for an interval of time during which any light from the pulse reflected from the optical fiber would be expected to be received, said apparatus further comprising:
(a) means for measuring the intensity of light pulses during said interval; and (b) means for integrating the measured intensity during this interval whereby a discontinuity in the optical fiber is detected by a reduction in the value of this integration.
(a) means for measuring the intensity of light pulses during said interval; and (b) means for integrating the measured intensity during this interval whereby a discontinuity in the optical fiber is detected by a reduction in the value of this integration.
15. Apparatus for testing the integrity of an optical fiber in a laser initiated ordnance system from a single end of the fiber comprising:
(a) a primary light source comprising a laser which emits light at a primary wavelength;
(b) a test light source comprising a low energy laser diode which emits light at a test wavelength wherein said test wavelength is different from said primary wavelength;
(c) means for directing light from the primary light source into a first end of the optical fiber;
(d) means for directing light from the test light source into the first end of the optical fiber;
(e) means for alternately interrupting light from either the primary light source or from the test light source;
(f) a dichroic coating mounted on a second end of the optical fiber, having the property of substantially transmitting light of the primary wavelength and also substantially reflecting light of the test wavelength;
(g) means for pulsing the test light source;
(h) a photodiode for detecting pulses of light from the test light source which are directed out of the first end of the optical fiber after they are reflected by the dichroic coating; and (i) means for measuring the intensity of the light pulses detected by the photodiode during a fixed period of time whereby a discontinuity in the optical fiber can be sensed by a reduction an the intensity of the reflected light pulses.
(a) a primary light source comprising a laser which emits light at a primary wavelength;
(b) a test light source comprising a low energy laser diode which emits light at a test wavelength wherein said test wavelength is different from said primary wavelength;
(c) means for directing light from the primary light source into a first end of the optical fiber;
(d) means for directing light from the test light source into the first end of the optical fiber;
(e) means for alternately interrupting light from either the primary light source or from the test light source;
(f) a dichroic coating mounted on a second end of the optical fiber, having the property of substantially transmitting light of the primary wavelength and also substantially reflecting light of the test wavelength;
(g) means for pulsing the test light source;
(h) a photodiode for detecting pulses of light from the test light source which are directed out of the first end of the optical fiber after they are reflected by the dichroic coating; and (i) means for measuring the intensity of the light pulses detected by the photodiode during a fixed period of time whereby a discontinuity in the optical fiber can be sensed by a reduction an the intensity of the reflected light pulses.
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/087,366 US5270537A (en) | 1987-08-20 | 1987-08-20 | Laser initiated ordance system optical fiber continuity test |
| GB8819800A GB2375906B (en) | 1987-08-20 | 1988-08-19 | Laser initiated ordnance system optical fiber continuity test |
| CA000576256A CA1341420C (en) | 1987-08-20 | 1988-09-01 | Laser initiated ordnance system optical fiber continuity test |
| DE3831797A DE3831797C1 (en) | 1987-08-20 | 1988-09-19 | Laser initiated ordnance fibre=optic continuity test |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/087,366 US5270537A (en) | 1987-08-20 | 1987-08-20 | Laser initiated ordance system optical fiber continuity test |
| CA000576256A CA1341420C (en) | 1987-08-20 | 1988-09-01 | Laser initiated ordnance system optical fiber continuity test |
| DE3831797A DE3831797C1 (en) | 1987-08-20 | 1988-09-19 | Laser initiated ordnance fibre=optic continuity test |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1341420C true CA1341420C (en) | 2003-02-18 |
Family
ID=27808176
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000576256A Expired - Lifetime CA1341420C (en) | 1987-08-20 | 1988-09-01 | Laser initiated ordnance system optical fiber continuity test |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US5270537A (en) |
| CA (1) | CA1341420C (en) |
| DE (1) | DE3831797C1 (en) |
| GB (1) | GB2375906B (en) |
Families Citing this family (22)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5453827A (en) * | 1993-02-24 | 1995-09-26 | Dicon Fiberoptics | Fiberoptic in-line filter and technique for measuring the transmission quality of an optical fiber through the use of a fiberoptic in-line filter |
| CA2215975A1 (en) * | 1995-03-24 | 1996-10-03 | Optiscan Pty. Ltd. | Optical fibre confocal imager with variable near-confocal control |
| US5572016A (en) * | 1995-04-25 | 1996-11-05 | Martin Marietta Corporation | Photoluminescence built-in-test for optically initiated systems |
| US5729012A (en) * | 1995-04-25 | 1998-03-17 | Lockheed Martin Corporation | Photoluminescence built-in-test for optical systems |
| US5965877A (en) * | 1995-04-25 | 1999-10-12 | Lockheed Martin Corporation | Photoluminescence built-in-test for optical systems |
| US5567622A (en) * | 1995-07-05 | 1996-10-22 | The Aerospace Corporation | Sensor for detection of nitrogen dioxide and nitrogen tetroxide |
| US5760711A (en) * | 1996-04-26 | 1998-06-02 | Icg Technologies, Llc | Icing detection system |
| US6052056A (en) * | 1996-04-26 | 2000-04-18 | Icg Technologies, Llc | Substance detection system and method |
| US5729335A (en) * | 1996-08-23 | 1998-03-17 | Mcdonnell Douglas Corporation | Optical fiber monitoring apparatus and an associated method for monitoring bending or strain on an optical fiber during installation |
| US5966206A (en) * | 1996-10-10 | 1999-10-12 | Tyco Submarine Systems Ltd. | Interlocked high power fiber system using OTDR |
| DE19757292A1 (en) * | 1997-12-22 | 1999-07-08 | Siemens Ag | Phosphor for functional monitoring of optical signal lines |
| US6259517B1 (en) | 1998-11-17 | 2001-07-10 | Kaiser Optical Systems, Inc. | Optical fiber breakage detection system |
| US6734411B1 (en) * | 2000-09-29 | 2004-05-11 | Lucent Technologies Inc. | Method and apparatus for controlling power levels of optical signals in optical fiber interconnects |
| US20040070750A1 (en) * | 2002-10-09 | 2004-04-15 | Iannelli John M. | Optical time domain reflectometry system and method |
| EP1650541A4 (en) * | 2003-07-07 | 2007-09-05 | Anritsu Corp | Test system of beam path for searching trouble in beam path from user optical terminal side |
| US20100026992A1 (en) * | 2006-07-28 | 2010-02-04 | Alex Rosiewicz | System and method for built-in testing of a fiber optic transceiver |
| US20080142692A1 (en) * | 2006-12-18 | 2008-06-19 | Lee Lanny R | Intelligent tripwire system |
| CN102369677B (en) * | 2009-02-20 | 2016-01-20 | 泰科电子瑞侃有限公司 | Optical fibre network test device |
| WO2011015239A1 (en) * | 2009-08-05 | 2011-02-10 | Oerlikon Space Ag | Opto-pyro ignition system |
| US8593621B2 (en) | 2010-04-30 | 2013-11-26 | International Business Machines Corporation | Testing an optical fiber connection |
| US8934090B2 (en) * | 2012-03-09 | 2015-01-13 | Lumenis Ltd. | Evaluation of optical fiber integrity |
| WO2015044843A1 (en) * | 2013-09-30 | 2015-04-02 | Koninklijke Philips N.V. | Sound controller for optical shape sensor |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4207561A (en) * | 1975-10-31 | 1980-06-10 | International Telephone And Telegraph Corporation | Intruder alarm arrangement for an optical communication system |
| US4403143A (en) * | 1978-11-03 | 1983-09-06 | Research Energy Of Ohio, Inc. | Detonating cord and continuity verification system |
| JPS5640737A (en) * | 1979-09-11 | 1981-04-17 | Asahi Optical Co Ltd | Damage detector for optical fiber for laser power transmission |
| US4523092A (en) * | 1982-07-29 | 1985-06-11 | Aetna Telecommunications Laboratories | Fiber optic sensors for simultaneously detecting different parameters in a single sensing tip |
| DE3506884A1 (en) * | 1985-02-27 | 1986-08-28 | Philips Patentverwaltung Gmbh, 2000 Hamburg | OPTICAL TIME AREA REFLECTOR WITH HETERODYN RECEPTION |
| US4685799A (en) * | 1986-01-13 | 1987-08-11 | The United States Of America As Represented By The Secretary Of The Navy | Integrated optical time domain reflectometer/insertion loss measurement system |
-
1987
- 1987-08-20 US US07/087,366 patent/US5270537A/en not_active Expired - Lifetime
-
1988
- 1988-08-19 GB GB8819800A patent/GB2375906B/en not_active Expired - Lifetime
- 1988-09-01 CA CA000576256A patent/CA1341420C/en not_active Expired - Lifetime
- 1988-09-19 DE DE3831797A patent/DE3831797C1/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| GB2375906A (en) | 2002-11-27 |
| GB8819800D0 (en) | 2002-10-09 |
| GB2375906B (en) | 2003-03-05 |
| US5270537A (en) | 1993-12-14 |
| DE3831797C1 (en) | 2003-07-10 |
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| MKEX | Expiry |
Effective date: 20200218 |