INTRUSION RESISTANT PASSIVE FIBER OPTIC COMPONENTS

The present invention relates to passive fiber optic components for a fiber optic network that are modified to add security and intrusion resistance.

BACKGROUND OF THE INVENTION

Single mode and multimode fiber optic backbone cables are being deployed to connect sections of high-speed networks together. To secure these high-speed networks, software based Intrusion Detection Systems (IDSs) have been introduced. These systems capture and analyze all packets for unusual patterns that point to an intrusion. However, this adds to the complexity of the network. Current IDSs are hampered by Base-Rate Fallacy limitation, which is the inability to suppress false alarms. Additionally, software-based IDSs do not protection against passive optical fiber tapping, which can go undetected by the network hardware.

It is well known, by those skilled in the technology, that optical fibers are easily tapped and the data stream intercepted. One relatively simple non- interruptive tapping method involves placing a bend coupler on the fiber to be tapped. Physical layer intrusion detection systems (PIDS) exist which can detect both the attenuation introduced by said tapping, as well as the physical handling associated with an intrusion attempt. A method of tapping that is not easily detected involves capturing scattered light surrounding passive components in the optical path. Several of these potentially vulnerable components will be described.

SUMMARY OF THE INVENTION

It is one object of the present invention to provide an improved fiber optic network which reduces the possibility for intrusion.

According to a first aspect of the invention there is provided an optical fiber network comprising: at least two optical fibers arranged for transmission of light signals along the fibers containing data; at least one passive optical component in the network connected to at least one of the fibers; and a covering layer of an opaque material over the passive optical component arranged to contain and/or absorb stray emissions from the light signals in order to inhibit eaves-dropping attempts.

Preferably the layer of an opaque material encloses the passive optical component.

Preferably there is provided a layer of the opaque material at least partly covering the fiber adjacent its connection with the passive optical component.

Preferably the layer is formed at least partly by a foil which is opaque to light.

Preferably the layer contains pigment which is opaque to light. Preferably the layer is bonded to an exterior surface of the passive component.

Preferably the layer forms a separate covering which is closed around the passive component.

Preferably the passive component comprises a splice tray and

wherein the layer is provided by a separate covering which encompasses the splice tray.

Preferably the separate covering is a flexible bag.

Preferably the splice tray includes a lid which can be attached to the tray both of which are formed from the layer of an opaque material.

Preferably the covering is sealed with a tamper-evident device that can actively or passively alarm upon an attempt at breaching the opaque covering.

Preferably the passive component comprises a splice between two butting ends of the fibers and wherein the layer is provided by a sleeve which surrounds the splice and adjacent portions of the fibers.

Preferably the passive component comprises a fiber connector connected to one end of a fiber and wherein the layer is provided by a sleeve which surrounds the connector and an adjacent portion of the fiber. According to a second aspect of the invention there is provided a splice tray for mounting in an optical fiber network for connecting at least two optical fibers arranged for transmission of light signals along the fibers containing data, the splice tray including a layer of an opaque material arranged to contain and/or absorb stray emissions from the light signals in order to inhibit eaves- dropping attempts.

According to a third aspect of the invention there is provided a splice connector for mounting in an optical fiber network for connecting at least two optical fibers arranged for transmission of light signals along the fibers containing data, the splice connector including a covering sleeve of an opaque

material arranged to contain and/or absorb stray emissions from the light signals in order to inhibit eaves-dropping attempts.

According to a fourth aspect of the invention there is provided a fiber connector for mounting in an optical fiber network for connecting an optical fiber to a component arranged for transmission of light signals along the fiber containing data, the fiber connector including a covering sleeve of an opaque material arranged to contain and/or absorb stray emissions from the light signals in order to inhibit eaves-dropping attempts.

According to a fifth aspect of the invention there is provided an encasement sleeve for protecting or enabling a slice or connection of fibers, including but not limited to fusion splices and couplers, comprised of a sleeve of an opaque material arranged to contain and/or absorb stray emissions from the light signals in order to inhibit eaves-dropping attempts.

According to the present invention, there is provided a method to secure passive optical components of the type described above from eaves dropping attempts. According to this invention, these components are to be covered in opaque material in order to contain and/or absorb stray emissions.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:

Figure 1 is a schematic side elevational view of an encasement sleeve of a fiber optic network according to the present invention.

Figure 2 is a cross-sectional view of the encasement sleeve of Figure 1.

Figure 3 is a cross-sectional view of a modified version of the splice connector of Figure 1.

Figure 4 is a schematic side elevational view of a portion of a fiber of a fiber optic network according to the present invention. Figure 5 is an isometric view of a typical fiber optic splice tray of a fiber optic network according to the present invention.

Figure 6 is an isometric view of a typical fiber optic splice tray of a fiber optic network according to the present invention including a separate covering layer of a flexible material. Figure 7 is side elevational view of a fiber connector of a fiber optic network according to the present invention.

Figure 8 shows a cross-sectional view of the fiber connector of Figure 7.

Figure 9 shows, a typical fiber optic network of the type with which

the present invention is concerned.

In the drawings like characters of reference indicate corresponding parts in the different figures. DETAILED DESCRIPTION

Figure 9 shows a typical network installation and areas of vulnerability including connector 9 connecting fiber to equipment, fusion splice 10 splicing the connector to bare fiber 11 which continues into and is looped within splice tray 12. Exiting fiber is connected at 13, and that connector is fusion spliced 14 to fiber network.

The network can of course include components as well known to

one skilled in the art but as shown there are a number of passive components in the network. The couplers are used in a monitoring system schematically indicated at 20 for monitoring the fibers for intrusion events as described in prior US applications by the present inventors for "AN INTRUSION DETECTION SYSTEM FOR USE ON MULTI-MODE OPTICAL FIBER USING AN OFFSET LAUNCH AND TAP COUPLER", as set out in United States application filed May 26, 2005, Serial No: 11/137,777 and "AN INTRUSION DETECTION SYSTEM FOR USE ON SINGLE MODE OPTICAL FIBER USING A POLARIMETER", as set out in United States application filed June 15, 2005, Serial No: 11/152,681 the disclosures of which are incorporated herein by reference, as well as couplers used for network distribution and monitoring.

Figure 2 illustrates the splice connector 15 which includes an opaque sleeve such as those commonly used for protecting a splice. In this configuration, the sleeve contains an opaque barrier that inhibits the emission of light. The opaque barrier comprises a layer of a foil, a coating of a metal alloy and/or a pigment contained in the material of the layer where the pigment is provided in sufficient quantity to prevent penetration of light to a measurable standard.

Thus when two fibers are joined by a fusion splice 22, they are typically encapsulated in a device that hermetically seals and protects the exposed bare fiber, as well as adding an optional strengthening member possibly in the form of a metal rod to protect this sensitive section from breakage. There are several mechanisms for leakage associated with such a device, including mechanical stress caused by the shrinkage of the protective jacket, micro-

bending and macro-bending from the protective jacket, and scattering from the point of connection of the two fibers. This causes light, in which transmitted intelligence is present, to leak out from around the physical package; and it is not uncommon for a loss of 0.1dB to be introduced here. This light could be detected by an intruder by placement of a detector or other optical configuration in close proximity, without any additional bending or handling of the fiber. The opaque sleeve 21 surrounds the splice 22, the strengthening member and the adjacent portions of the two fibers 10 and 11.

Figure 3 illustrates an opaque sleeve 24 similar to that of Figure 1 above. In this configuration, the sleeve contains both an opaque barrier 25 which inhibits the emission of light, as well as an internal absorptive coating 26 Such coatings are well known, as for example shown in US Patents 5,892,476 and 7,074,351

Figure 4 shows a fiber 10 coated with an opaque barrier. This includes, but is not limited to a coating 28 applied directly to the fiber, a sleeve 27 surrounding the fiber, or furcation tubing.

In multimode and single mode fiber, reflections from splices, connectors, and other events can be re-launched into the cladding, where it will travel a short distance as a cladding mode. This mode is very lossy, and as this loss is caused by radiation of some of the light, it can be detected by a sensitive detector apparatus. Thus the sleeve 27 surrounds the end of the fiber and contains a material so that it is opaque to the light emitted. While the sleeve may be applied at a splice, it is also contemplated herein that the sleeve be applied to a single fiber at a location other than a splice. Thus the single optical fiber

includes a covering sleeve, material, or deposition comprised of opaque material that contains and/or absorbs stray emissions from the light therein.

Figure 5 shows a typical fiber optic splice tray 16 covered with an opaque and/or absorptive shield 30. In a standard communications grade splice tray, bare optical fibers are routinely wound to a radius sufficient to allow so- called macro-bend loss. This emission of the escaping light and evanescent wave contains the information transmitted in the fiber, and could be picked up by sensitive electronics.

In Figure 5 a flexible cover separate from the tray is applied in the form of a shield or bag 30 that encompasses the splice tray and optionally could be sealed with an opaque adhesive. Optionally, this could be sealed with a tamper-evident device 31 that can actively or passively alarm upon an attempt at breaching the opaque cover.

Figure 6 shows a typical fiber optic splice tray 32 with an opaque and/or absorptive cover 33. The cover and tray are manufactured from an opaque absorptive material or coated with same as described above. Optionally, this could be sealed with a tamper-evident device that can actively or passively alarm upon an attempt at breaching the opaque cover.

Figures 7 and 8 show a typical fiber connector 9 with an opaque and/or absorptive jacket 35 for inhibiting leakage of cladding modes and other connector related loss mechanisms.

Due to imperfections in manufacturing, and the inability to get a perfectly seamless and concentric contact between connector surfaces and core

alignments, some amount of light is scattered in optical connectors, and a portion escapes from the connector boot.

Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without department from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.