Fiber optic seal

A fiber optic bundle is placed through an object to be sealed. Ends of the fibers are spread and threaded through one another in a random dispersion, disorienting the fibers. Randomly reoriented ends are regathered and clamped. A moveable reticle at a light input termini of the fibers creates unique identifiable patterns at the output end of the fibers.

FIELD OF THE INVENTION 
The invention relates to a security seal and more particularly to a 
tamper-resistant, field-identifiable, fiber optic, security seal which can 
be continuously monitored for integrity and indentity. 
BACKGROUND OF THE INVENTION 
Typically, prior art security seals have employed metal tapes or wires 
whose ends are joined by one-time-use clasps, interlocking metal or 
plastic cups, or moldable material carrying an inscribed serial number or 
other type of identifiable mark. Some types of seals have, in addition, 
randomly inscribed marks or randomly distributed particles which are 
photographed prior to use and are re-photographed after the seal has been 
removed and disassembled. Still other seals are identified with the aid of 
ultrasonic scanners. Although these types of seals are generally 
effective, they cannot withstand sustained attach, may be counterfeited, 
are usually not reusable, and cannot be continuously monitored. 
Fiber optic seals with juxtaposed and twisted ends are described in U.S. 
Pat. No. 3,854,792. In devices described in that patent, half of the 
joined end is illuminated, producing a unique pattern of light on the 
other half. 
SUMMARY OF THE INVENTION 
This invention pertains to a tamper-resistant, secure seal whose integrity 
and unique identity can be checked and/or monitored in the field without 
disassembly or removal. The seal employs either commercially available or 
specially prepared glass or plastic optical fiber bundles, and a metal or 
plastic fiber locking assembly. This assembly holds the fiber bundle 
securely in place against accidental disassembly and includes mechanism 
for assuring complete mutual interpenetration of the fibers at each end of 
the bundle. 
To make a seal, an appropriate length of fiber optic bundle material is 
cut; two tapered collars are placed on the fiber bundle near each end, and 
approximately 1.25 inches of the protective plastic jacket is removed from 
each end of the bundle. One of the stripped ends of the fiber bundle is 
then fully inserted into one of the two cylindrical holes in the bottom 
edge of the fiber locking assembly and is secured by seating the tapered 
collar. The free end is then similarly inserted in the remaining 
cylindrical hole and secured. The internal components of the fiber locking 
assembly block are designed to flatten the stripped fiber bundle ends into 
a fan shaped array of fibers so that the fibers from one end of the bundle 
may easily intersect and pass randomly in between the fanned fibers of the 
other end. The ends of the fibers above the intersection will now appear 
in the cylindrical holes at the top or exit edge of the assembly block. 
The fibers in the two fans are then recombined into two individual bundles 
by modified tapered collars analogous to those used to secure the jacketed 
fiber bundle at the base of the fiber locking assembly. These tapered 
collars hold the loose fibers firmly in place at the top edge of the seal. 
The identity of the seal is established in the field by using a small, 
hand-held microscope and illuminator. The completely assembled seal is 
placed in the indexing stage of the field microscope. One end of the fiber 
optic bundle is illuminated by light from a pen-sized flashlight through a 
60 degree prism or mirror. All of the fiber ends are illuminated by this 
reflected light with the exception of those fibers lying directly under a 
reticle containing at least one opaque line whose width is approximately 
equal or slightly larger than the diameter of the optic fibers used in the 
fiber bundle. This reticle may be rotated through an angle of 180 degrees 
with its center of rotation coinciding with the geometric center of the 
bundle. In this manner the light entering every fiber in the bundle may be 
controlled. A provision is made for measuring the angle of rotation of 
this reticle. The light transmitted through the fibers and emerging at the 
opposite end of the bundle is magnified and optically examined with the 
field microscope. The angular position and radial distance from the center 
of the field of view of the microscope (i.e. the polar coordinates r, 
.theta.) of a selected, small set of individual fibers may be measured 
using the eyepiece reticle and recorded along with the seal's serial 
number. This position data may be supplemented by additional observations 
on the size, color, imperfections, and optical transmission properties of 
the individual fibers. Such data obtained on a small, well dispersed 
number of fibers (approximately 5) should be sufficient to uniquely 
identify a seal and should provide reasonable assurance that substitution 
or counterfeiting of a seal could not go undetected. Alternatively, a 
photomicrograph may be taken of the random pattern formed by the fiber 
ends in the field of view of the microscope using a Polaroid or film 
camera. The photographic procedure is recommended where the highest level 
of confidence is required and when it must be determined that a seal left 
unattended and unexamined for significant intervals of time has not been 
compromised. 
The security of this type of fiber optic seal depends upon: (1) the unique 
fingerprint which is generated by the totally random pattern at the ends 
of the fiber optic bundle, (2) the unique scrambled or decoded image of 
the line reticle introduced at the illuminated end of the fiber bundle, 
(3) the ability to verify the optical continuity of every fiber in the 
bundle, (4) the necessity to completely destroy the fingerprint during 
disassembly, (5) the formidable problem which would be encountered in any 
effort to duplicate this unique fingerprint, and (6) the equally 
formidable problem of reestablishing the light transmitting capability of 
the individual fibers interrupted in the process of cutting the fiber 
bundle. 
If there is a requirement to continuously monitor a fiber optic seal, the 
fiber locking assembly block may be inserted into a solid state monitoring 
device. The monitor contains a pulsed LED light source which is used to 
illuminate one end of the fiber bundle, a photo-transistor circuit which 
detects the light transmitted through the fiber optic loop, and a 
microprocessor with the necessary associated components to generate and 
display, or transmit on demand a time ordered random number. Interruption 
of the light transmitted through the fiber optic bundle, harassment of the 
electronic monitor, or electronic failure will clear the random number 
generator with only the last undisturbed number remaining in the memory of 
the unit. These electronic components are housed in a small, secure, 
tamper-indicating container, such as a stressed glass cut. The order of 
the random number generated within the monitor is known only to the 
organization which has installed the seal. The random number sequence 
generated by each seal is, of course, also unique to that seal alone. The 
random number generated by the monitor may be displayed on demand to 
either the inspector, the facility operator where the seal is installed, 
or the number may be transmitted to the organizational headquarters. 
One object of the invention is to provide a tamper-resistant, fiber optic 
security seal. 
Another object of the invention is the provide a security seal whose unique 
identity and optical integrity can be verified in the field without 
disassembly or the removal of the seal. 
Another object of the invention is to provide a tamper-resistant seal which 
can be applied in a wide variety of hostile environments and which is 
capable of withstanding sustained attempts to defeat the seal. 
Another object of the invention is to provide a seal which can be 
identified in the field by using either visually obtained microscopic data 
on the position and appearance of individual fibers or by using 
photomicrographic methods to record the fingerprint and decoded image of 
the line reticle formed by the random distribution of the optical fibers 
at the end of the bundle. 
Still another objective of the invention is to provide a tamper-resistant 
seal which can be continuously monitored for its optical integrity and 
identity over sustained periods during which the seal will be unattended. 
One advantage of the present invention is that the fiber optic seal is 
tamper resistant. 
Another advantage of the invention is that the identity and optical 
integrity of the seal can be established in the field without removal or 
disassembly of the seal. 
Another advantage of the invention is that the seal can be continuously 
monitored in the field for its optical integrity and identity, and if 
desired, an encoded status report on the seal transmitted to headquarters. 
Another advantage of this seal is that it is easily and quickly installed 
during field operations. 
Yet another advantage of the seal is that it is reusable and that it can be 
easily applied in a wide variety of situations. 
One object of the invention is the provision of a fiber optic seal having a 
block with crossed pathways having openings in spaced relationship on 
facial areas of the block and an optic fiber bundle in a pathway within 
the block. 
Another object of the invention is the provision of a fiber optic seal with 
a holder for mounting a portion of an optic fiber bundle in an opening at 
the end of a pathway in a block. 
The invention has as a further object the provision of a fiber optic seal 
with a chuck having an inner bore receiving a fiber optic bundle, having 
an outer portion which engages a passageway and having a tapered outer 
portion with a slit extending from the tapered outer portion to the bore, 
whereby the tapered outer portion is compressed upon a bundle, and a 
collet having an outer portion fitting within the passageway wall having a 
tapered inner opening for cooperating with the tapered outer portion of 
the chuck to clamp a fiber optic bundle. 
Another object of the invention is the provision of a fiber optic seal 
having a spreader mounted near an intersection of passageways in a block 
for spreading fibers in a fiber optic bundle. 
A further object of the invention is the provision of optic fiber spreaders 
having outer portions for fitting in walls of passageways, having distal 
ends facing outward in the passageways and having proximal ends for 
positioning near an intersection of the passageways, the spreaders having 
bores extending inward from distal ends and having channels extending 
inward from the bores, the channels being generally rectangular in cross 
section and having a transverse dimension less than a similar transverse 
diametrical dimension of the bore, whereby fibers are restricted in that 
direction and are spread and fanned outward in the channels. 
A further object of the invention is the provision of optic fiber spreaders 
as described wherein proximal ends of the inserts are configured for 
interengaging and abutting proximal ends of other inserts. 
Another object of the invention is the provision of a fiber optic seal with 
a fiber optic bundle having a first end positioned in one pathway in a 
block, having a medial portion extending from the block and having a 
second end remote from the block. 
Another object of the invention is the provision of a fiber optic seal 
wherein a portion of a first end of a fiber optic bundle positioned within 
an intersection of the pathways in a block has fibers arranged to randomly 
receive crossed fibers in interstices between fibers. 
Another object of the invention is the provision of a fiber optic seal 
wherein a terminus of a bundle is tightly held in a facial opening at the 
end of a first passageway in a block, and wherein a portion of a fiber 
optic bundle which emerges from an opening at the opposite end of the 
first passageway is tightly held in that opening. 
This invention has as a further object the provision of a fiber optic seal 
as described wherein a free end of the fiber optic bundle has an outer 
covering removed from a length of the bundle from a remote terminus of the 
bundle at least as far along the bundle as a distance from an intersection 
to an opening of a second passageway in the block. 
Another object of the invention is the provision of a fiber optic seal 
having means for selectively controlling the light source for selected 
illumination of optic fiber termini at one end of a bundle. 
A further object of the invention is the provision of a fiber optic seal 
with a reticle between a light source and fiber termini and means for 
moving the reticle. 
The invention has as a further object the provision of a fiber optic seal 
with a reticle having an opaque line diametrically positioned across an 
optical axis connecting a light source and a medial portion of fiber 
termini, the line being slightly wider than a fiber diameter, and a 
rotatable wheel on which the reticle is positioned. 
A further object of the invention is the provision of a fiber optic seal 
having a fiber optic bundle with a plurality of coextensive and coterminal 
optical fibers held together with portions of the fiber near one end of 
the bundle threaded between portions of the fibers near the opposite end 
of the bundle in random arrangement, means to separately hold first and 
second remote termini of the bundle of fibers, means for introducing light 
into the first termini, and means for observing light in the second 
termini, and means for predeterminately interrupting light in the first 
termini and means for recording locus of fiber ends in the second termini 
showing characteristics of interrupted light. 
Another object of the invention is the provision of a fiber optic seal with 
a fiber optic bundle with a medial portion for engaging an object to be 
sealed and end portions having randomly interspersed fibers, means for 
holding termini of the fibers and means for eliminating some of the 
termini and means for receiving illumination of other of the termini, 
reticle means for interposing between the illuminating means and said some 
of the termini for selectively partially preventing illumination, and 
means for moving the reticle means for changing the masking. 
These and other and further objects and features of the invention are 
apparent in the disclosure which includes the above and ongoing 
specification, including the claims and the drawings.

DETAILED DESCRIPTION OF THE DRAWINGS 
FIGS. 1 through 4 show a field assembled, fiber optic seal 1, fiber optic 
bundle 2 and fiber-locking block assembly 4 inserted in the indexing stage 
6 of a hand-held field microscope 8 and illuminator 10 and the camera 12 
used to take the identification photo micrograph. 
To assemble the seal 1 the following operations are performed: An 
appropriate length of fiber optic bundle material is cut to the length 
required to apply the seal. Two tapered collars 14 and 16, as shown in 
FIG. 5, are inserted over the ends of the fiber optic bundle. 
Approximately 11/4 inch of the plastic jacketing 18 surrounding the fiber 
optic bundle is removed from each end of the bundle. One end 20 of the 
fiber optic bundle 2 is fully inserted into one of the openings 22 in the 
bottom face 24 of the fiber locking assembly block 4. Tapered collar 14 is 
securely seated into one passageway 26. The free end of the fiber optic 
bundle is threaded through the object to be sealed and is then inserted 
into the remaining cylinderical passageway 28 in assembly block 4. The 
tapered collar 16 is seated and secured. On completion of these steps the 
fiber optic bundle 2 is now firmly held in place by the tapered collars 14 
and 16. The interior components 30, 32, 34 and 36 of the fiber locking 
assembly block (shown in FIG. 5) flatten the optical fibers permitting 
them to easily intersect at intersection 40 and pass through each other 
and through openings 42 and 46 at the opposite faces 44 and 48 of the 
fiber locking block 4. 
The seal is completed by inserting and firmly seating the tapered collars 
50 and 52 in the top openings 42 and 46 of the top faces 44 and 48 of the 
assembly block 4. This operation brings the fanned fibers termini 54 and 
56 into two circular bundles and holds them securely in place. 
The identity and optical integrity of the seal is established in the field 
by inserting the fiber locking block 4 of the completed seal into the 
indexing stage 6 of the hand-held microscope illuminator 8 and 10. The 
symmetry of the fiber locking assembly block permits either bundle end to 
be observed under the microscope 8. The orientation of the fiber locking 
assembly may be determined by the presence of the symbol such as "+" 58 in 
a viewing port 60 on the side of the indexing stage 6. The opposite end of 
the fiber optic bundle is illuminated through a 60 degree prism 62 by a 
small pen-sized flashlight 10. A reticle 64 lies in a plane between the 
light source 10 immediately above the ends of the fiber bundle being 
illuminated. The reticle 64 contains at least one inscribed, opaque line 
66 whose width is equal or slightly greater than diameters of the fibers 
used in the fiber bundle 2. This reticle may be rotated through 
180.degree. and the reticle holder 68 is appropriately indexed so that it 
is possible to measure the angle of rotation of the reticle 64. Rotation 
of the reticle 64 permits the controlled illumination of every fiber in 
the bundle. In addition, the image of this line reticle transmitted by the 
fiber optic bundle will be scrambled or decoded at the opposite end of the 
bundle because of the random orientation of the fibers in the two ends of 
the fiber optic bundle. Under the microscope the line image will appear as 
a series of randomly distributed, darkened fibers, which will resume light 
transmission as the reticle is rotated. 
The magnification and the field of view of the hand-held microscope is 
adjusted so that all of the fibers at the light transmitting end of the 
bundle can be observed. The eye piece 70 of the microscope 8 is equipped 
with an additional, rotatable reticle 72, with which the observer may 
measure both the distance of a single fiber from the center of the field 
of view of the microscope as well as the angle through which the reticle 
must be rotated from a fixed, indexed point in order to intersect the 
image of the fiber end. To identify a seal, the observer notes the polar 
coordinates of a small selected number of fibers whose illumination can be 
controlled by the rotatable line reticle 64. The position of the line 
reticle may be fixed at 0.degree. or it may be set at some other 
predetermined angle by the observer. A serial number on the block and the 
reticle degree are recorded in a notebook. The observer then measures for 
the specifically darkened fiber, the radial distance from the center of 
the field of view and angle of the fiber from the 0.degree. point, using 
the reticle in the eye piece of the microscope. This information is also 
recorded in the same field notebook. In addition to the polar coordinates 
of this particular group of fibers, the observer may in addition record 
information on the size, color, imperfections in the fiber ends and the 
light transmitting properties of the fibers. On a subsequent visit the 
identity and optical integrity of the seal is re-established by inserting 
the seal into the stage of the hand-held microscope and reconfirming the 
polar coordinates data and characteristics previously recorded at the time 
that the seal was assembled. 
For certain seal applications, it may be desirable to supplement the type 
of information obtained using the illumination and eyepiece reticles by 
making a photo micrograph of all of the fibers in the end of the bundle 
being observed. This photo micrograph may be made by attaching camera 12 
fitted with an adapter 74 to the microscope occular. It is recommended 
that if a Polaroid camera is to be used for the initial photo micrograph 
taken immediately after the assembling of the seal, Type 105P/N film be 
used in order that a negative of the fiber bundle image may be obtained. 
This negative is then marked with the serial number of the seal, the 
angular position of the line reticle and is filed for future reference. On 
subsequent occasions when the identity and integrity of the seal must be 
checked, a Polaroid positive print is made and the original negative is 
placed over the positive print. Even extremely small variations in fiber 
position, shape imperfections and light transmitting properties can be 
detected in this manner. The probability that this degree of replication 
can be counterfeited is highly unlikely and therefore this seal represents 
a maximum level of protection. 
The present fiber optic seal design can, if the situation requires, be 
supplemented by an electronic monitor which continuously checks the 
optical integrity and the identity of the seal during periods when the 
seal must be left unattended. The condition of the seal may be reported on 
a fixed schedule by the host facility where the seal has been applied and 
checked by an inspector during a routine inspection. It is possible that 
the output of the monitor can be transmitted directly to the headquarters 
of the inspecting agency if very prompt notification of a seal failure or 
of an attempt to remove the seal is required. 
As shown in FIG. 5, clamps 14, 16, 50 and 52 have two parts 76 and 90. Bore 
78 receives fiber optic bundle 2 and outer wall 80 engages an inner wall 
of the passageway. Tapered portion 82 has a slit 84 which extends through 
6 bore 78. Collet 90 has an outer wall which tightly (interference fit) 
engages the inner cylindrical wall of passageway 26. Slope 94 is a few 
degrees different than the slope of taper 82. Consequently, when collet 90 
is forced inward, taper 82 compresses to decrease bore 78, gripping bundle 
2. Fiber spreading inserts 96 have faces 98, which abut chucks 76, and 
internal faces 100 which are configured to abut and interengage similar 
internal faces. Tapers 102 direct fibers in bundles 2 into spreading 
channels 104, which extend across the inserts in one direction, and which 
are laterally restricted in a transverse direction. The combined inserts 
fan fibers at their intersection, facilitating random interspersions of 
fiber ends in interstices between previously inserted fibers. 
Internal tapers 106 and external slopes 108 assure correct interfitting of 
the inserts. 
While the invention has been described with reference to specific 
embodiments, modifications and variations may be constructed and used 
without departing from the scope of the invention, which is defined in the 
following claims.