Patent Application
20080226227
Optical fiber networks are beginning to replace copper networks as the “last mile,” or final leg, of connectivity to homes for services such as telephone, Internet, and television programming. Although not yet ubiquitous, network providers such as telephone companies are actively working to provide a large number of customers with such an optical fiber connection in the near future. Providing an optical fiber connection to a customer typically requires physically installing optical fibers from a distribution point to the customer's location.
It is known that optical fibers are affected by external factors. In particular, external factors such as sound waves and temperature can dynamically affect the optical properties of an optical fiber. It has more recently been discovered that, even when buried deeply underground, the optical properties of optical fibers can be measurably affected by sound above ground, such as by the voice of a person standing over the optical fiber. This is true even where the optical fiber is deeply buried such as six feet underground. It has been further shown that such optical property changes can be measured, thereby effectively allowing someone to listen in on a conversation occurring above ground or otherwise near an optical fiber.
The following presents a simplified summary of illustrative aspects in order to provide a basic understanding of various aspects described herein. This summary is not an extensive overview of the invention. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. The following summary merely presents various concepts in a simplified form as a prelude to the more detailed description provided below.
For example, aspects provide for a method for modifying an optical fiber network of a service provider, wherein the optical fiber network includes a first optical fiber connected to an access point of a human-habitable customer building, the method comprising adding an optical blocker to the first optical fiber at a location that is in a range of 20 to 200 feet from the access point.
Further aspects provide for a network, comprising a plurality of optical pathways coupled to a plurality of customer locations; a distribution and switching center generating a plurality of optical signals for transmission to the plurality of customer locations over the plurality of optical pathways; at each of the customer locations, an optical connector terminating the respective optical pathway; and a plurality of optical blockers physically separate from the optical connectors, each located along one of the optical pathways at a location closer to the optical connector of the respective customer location than to the distribution and switching center.
Still further aspects provide for an apparatus for providing a secure region, comprising a first optical fiber segment; a second optical fiber segment disposed in the secure region; a third optical fiber segment; a first optical blocker optically coupling the first optical fiber segment to a first end of the second optical fiber segment; and a second optical blocker optically coupling an opposite second end of the second optical fiber segment to the third optical fiber segment.
These and other aspects of the disclosure will be apparent upon consideration of the following detailed description of illustrative aspects.
A more complete understanding of the present disclosure may be acquired by referring to the following description in consideration of the accompanying drawings, in which like reference numbers indicate like features, and wherein:
It is noted that the various drawings are not necessarily drawn to scale.
The various aspects summarized previously may be embodied in various forms. The following description shows by way of illustration various examples in which the aspects may be practiced. It is understood that other examples may be utilized, and that structural and functional modifications may be made, without departing from the scope of the present disclosure.
As previously mentioned, sound waves, temperature, and other external factors affects the optical properties of an optical fiber. As will be seen, this may allow someone to remotely monitor these external factors in a region that surrounds an optical fiber. Although there are legitimate uses for such monitoring, there are also uses that are less desirable and potentially illegal.
For instance, in the case of “last mile” optical fiber connectivity, it would be fairly easy to monitor external factors surrounding the optical fiber running through a customer's land and up to the customer's home. This effectively means that someone could remotely monitor conversations by persons located on regions of the customer's land that are near the optical fiber. This is true even though the optical fiber may be buried underground. Presumably, very few if any customers would knowingly consent to such monitoring.
A particularly striking example of another illegitimate monitoring situation is where the customer is a government facility, such as a military base, where classified or other sensitive information is handled. It is conceivable that a terrorist organization or other enemy could listen to conversations occurring on government property near a buried optical fiber. Although typically procedures are in place that limit discussions of sensitive information, the possibility of optical fiber monitoring is yet another potential threat that would need to be dealt with.
As will be described in connection with various illustrative scenarios, an optical fiber link may be modified so as to reduce or even eliminate the possibility of remote monitoring of external factors. The modification may be implemented in a relatively inexpensive way. In a commercial environment, such a modification may additionally provide a source of revenue to a service provider or other network manager.
Before discussing various modifications, an illustrative method by which an optical fiber may be monitored will be described. Referring to
To monitor the varying backscattering intensity, a probe signal 102 may be used. More precisely, probe signal 102 is a light signal of any frequency that is transmitted through optical fiber 101. As optical fiber 101 vibrates, a small amount of probe signal 102 is reflected backward, resulting in a backscattering signal 105 that travels in a direction that is the reverse of probe signal 102. The backscattering signal 105 may have an amplitude, phase, and/or other optical properties that are modulated by the vibrations of optical fiber 101. The modulation of backscattering signal 105 may be measured using sophisticated equipment that is currently available.
Normally, when a person is located near optical fiber 205a, such as on the ground above optical fiber 205a, and speaks, that person's voice will affect optical fiber 205a and thus be susceptible to remote monitoring using a probe signal via optical fiber 205a. To reduce or even prevent this threat, a blocking device may be provided in the optical path to building 201. The blocking device may serve to allow desired signals to pass through the optical path while reducing or even eliminating undesired signals (e.g., backscatter signals) that could be used for remote monitoring purposes.
In this example, distribution optical fiber 207 is optically connected to optical fiber 205a via an optical isolator 208. An optical isolator is a known device that allows optical signals to travel substantially only in one direction through the device; it is analogous to a one-way street. In this example, optical isolator 208 is configured so as to substantially block optical signals from traveling upstream from building 201 to distribution optical fiber 207, while allowing optical signals to travel downstream from distribution optical fiber 207 to building 201. Thus, the region near optical fiber 205a between optical isolator 208 and the termination/access point at service receiver 203 may be considered to be secure from remote optical fiber monitoring. This region may be of any size, however it may be expected that the customer would want to maximize the size of the region as much as possible or practical. Thus, it may be expected that the customer would desire for optical isolator 208 to be as far from building 201 as possible or practical. For instance, one practical location would be to place optical isolator 208 injunction box 206, which already exists in conventional optical “last mile” paths. In a typical installation, one may expect optical isolator 208 to be in the range of D=20 to 200 feet from building 201, however D may be shorter than 20 feet or longer than 200 feet.
An example of how optical isolator 208 may provide a secured region is described with reference to
The above discussion has been in the context of a unidirectional downstream signal, such as a television signal. However, many services utilize bidirectional signals, such as Internet and telephone services. Accordingly, an example of how a bidirectional “last mile” secured connection may be configured is shown in
An optical circulator is a known device that has three nodes, one of which is bidirectional and two of which are unidirectional in opposing directions (i.e., outgoing and incoming). A signal that is sent into the bidirectional node is output only at the outgoing unidirectional node. A signal that is sent into the ingoing unidirectional node is output only at the bidirectional node. An optical circulator is analogous to a merge or split between a single two-way street and two separate one-way streets going in opposite directions.
An example of how optical circulator 302 may provide a secured region is described with reference to
In both the bidirectional and unidirectional situations, it has been assumed that the modulated backscattering signal 1003 or 1103 is generated from backscattering of a probe signal separate from the main signal. However, a separate probe signal is not necessary for remote monitoring. Remote monitoring may be performed, for instance, of a backscattering signal generated from backscattering of the main signal (e.g., signal 1001 or 1101) itself.
An overhead view of a set of bidirectional “last mile” links is illustratively shown in
In the present example, each bidirectional optical path between optical fiber 207 and buildings 201, 402, 403 shares junction box 206. However, each of buildings 201, 402, 403 may have its own junction box. Moreover, each junction box may be on a customer's property or off the customer's property, as appropriate and practical. Property lines are illustratively shown in
It may be reasonably expected that the distance (e.g., distance D in
The customers of
It may be desirable to protect region 701 from remote snooping. For instance, there may be a concern that someone located outside of region 701 may try to listen in on someone located inside of region 701 by listening to the effects of sound waves on optical fiber 702 within region 701. To provide protection against this where a main signal 705 being sent along optical fiber 702 is a one-way signal, a pair of optical isolators 703, 704 may be inserted in series at or near the entrance to and exit from region 701 along optical fiber 702, as shown in
Where a main signal 805 is bidirectional, then a pair of optical circulators 803, 804 may be inserted in series at or near the entrance to and exit from region 701 along optical fiber 702. In addition, optical fiber 702 between optical circulators 803, 804 may be divided into two parallel optical fibers 702c,d. Using such a configuration, any backscattering originating within region 701 on optical fiber 702c of main signal 805 or a co-directional probe signal would be prevented by optical circulator 803 from leaving region 701. And, any backscattering originating from region 701 on optical fiber 702d of main signal 805 or a co-directional probe signal would be prevented by optical circulator 804 from leaving region 701. Moreover, any probe signal attempting to pass into region 701 in an opposite direction on optical fiber 701c or 701d as main signal 805 will be prevented from entering region 701 by optical isolator 803 or 804. Accordingly, a certain amount of privacy within region 701 may be attained.
Referring still to
Any optical blocker as described herein may be provided as a dedicated optical blocker or integrated with another device performing a function other than optical blocking. In the dedicated configuration, the optical blocker may be, for instance, an optical isolator having a housing with an optical input and an optical output disposed at the housing (e.g., at opposite ends of the housing). In this configuration, no other device is disposed within the housing, and the input optical fiber and the output optical fiber may be connected directly to the optical input and output, respectively. In the integrated configuration, the optical blocker may be integrated with another device within the same housing and/or attached to the exterior of the housing.
It has been previously described how an optical isolator can prevent signals from traveling backwards through the optical isolator, and how an optical circulator can prevent certain signals from traveling in certain directions through the optical circulator. However, in practice an optical isolator or circulator may be more effective in some optical frequency ranges and less effective in others. Put another way, certain frequencies of optical signals may be blocked less than others. Accordingly, depending upon the frequency of any probe signal being used, the backscattering of the probe signal (which is typically at the same frequency of the probe signal) may be blocked to a greater extent or to a lesser extent. To provide even greater security in a situation where the probe signal is of a frequency substantially different from the frequency of the main signal, one or more filters may be added in series with an optical blocker. The filter may be physically separate from the optical blocker or may be integrated with the optical blocker as a single device with a single housing.
For example, referring to
However, filters may alternatively or additionally be installed at the unidirectional ports, such as shown in
Thus, methods and apparatuses for providing privacy features on an optical fiber link have been described. By providing such features, the effects on the optical fiber link by certain outside influences, such as acoustical waves, may be prevented from being remotely monitored from a position outside the link.
