Fiber optic communication links have long been touted as providing a secure communications channel for sensitive information. This reputation is largely based on the absence of electromagnetic emanations from the fiber. However, unauthorized access to data in optical fibers is a realistic possibility. Unfortunately it is not always possible to encrypt data transmitted via fiber optic links due to the lofty cost of high data rate encrypters. Therefore, on non-encrypted fiber communications channels, some form of tamper detection scheme is desirable to assure security. The limitations of conventional tamper detection techniques suggests that more sophisticated methods be used. Fiber optic links, like all communications channels, have a band-limited frequency response which produces a characteristic distortion of the signals that propagate down the fiber. A technique has been developed to perform a sensitive characterization of the fiber's frequency response function. This characterization can be exploited for detecting tamper in fiber optic communications links.>
Fiber optic communication links have long been touted as providing a secure communications channel for sensitive information. This reputation is largely based on the absence of electromagnetic emanations from the fiber. However, unauthorized access to data in optical fibers is a realistic possibility. Unfortunately it is not always possible to encrypt data transmitted via fiber optic links due to the lofty cost of high data rate encrypters. Therefore, on non-encrypted fiber communications channels, some form of tamper detection scheme is desirable to assure security. The limitations of conventional tamper detection techniques suggests that more sophisticated methods be used. Fiber optic links, like all communications channels, have a band-limited frequency response which produces a characteristic distortion of the signals that propagate down the fiber. A technique has been developed to perform a sensitive characterization of the fiber's frequency response function. This characterization can be exploited for detecting tamper in fiber optic communications links.>
Network security concerns have recently been increased due to the vast amount of information that flows in a single fiber. At the application layer, data security relies on end-user encryption algorithms, many of which are known to be vulnerable, and authentication algorithms are not foolproof as the sophistication of eavesdroppers and unauthorized bad actors increases. As a result, the communications link may be attacked by eavesdroppers to access data, to mimic the source, or to cause service denial. To accomplish this however, the transmission link must be compromised. Therefore, if an a priori link and channel signature has been established at the receiver, then an unauthorized intervention is possible to be detected, reported and counteracted. In this paper we provide an analysis of the link and channel parameters that affect the signal performance, which also constitute the identification signature of the optical channel. When the medium is compromised, the channel parameters are affected and thus the channel performance. We also develop a model and we simulate conditions of channel attack
Security in optical communications has been recently a concern due primarily of the vast amount and the sensitivity of information that a single fiber carries. It is generally accepted that data security is encrypted by the end-user and that the optical network is not easy to tap as it was with wired networks. However, the sophistication of eavesdroppers has increased and if an optical link is accessed, then the encryption code of data can be broken with the use of supercomputers. In addition to data eavesdropping, eavesdroppers may access the link for malicious attacks, or for transmitting erroneous data by mimicking a source. Therefore, it is important that the receiver has the means and intelligence to recognize the signature of the source and the optical channel so that when the link is tapped, the receiver recognizes it and it alerts the network management or it triggers a data rerouting process. In fact, an optical channel, including source, fiber and optical components, has its own optical parameters that constitute a signature. These parameters are the result of linear and non-linear phenomena that affect the quality characteristics of the optical signal and which can not be mimicked. Therefore, the understanding of optical parameters that define the optical channel signature is very critical. In this paper we provide an analysis of the factors affecting the signal quality and thus they constitute the signature of the optical channel, we model the optical channel and demonstrate via simulations that small parametric variation affect the signature of the channel. As a result, monitoring the signal parameters leads to source and channel authentication whereas detecting the parametric variability of channel deducts channel degradation or tapping.
Network security has traditionally been limited to network access and network administration, whereas data security is left to end clients where text is encrypted and decrypted. In the last decade, there has been a rapid increase in bandwidth demand mainly due to the explosion of the Internet and mobile telephony. The explosive bandwidth has been comfortably met with optical networks having many optical channels multiplexed in the same fiber, known as wavelength division multiplexing,. Data rate exceeding 1 Tbps within a fiber implies that there are tributaries that carry sensitive and proprietary data. Although data are encrypted by the end client, there is no assurance that, if captured by an eavesdropper, they may not be decrypted. Therefore, three new requirements emerge; monitor the optical link integrity, detect if an optical channel is compromised by tapping the fiber, and adopt a countermeasure strategy. One way to accomplish this is to monitor the channel performance parameters for changes in real-time. In this paper, we analyze key performance parameters of the optical signal, we describe how these parameters impact the channel performance. In addition, we develop a method to estimate in real-time the bit error rate and signal to noise ratio, and how these can be used to detect fiber intrusion. Finally, we develop a countermeasure protocol that we believe outsmarts the eavesdropper.
Fiber optic networks are used worldwide and have been regarded as excellent media for transmitting time–frequency (TF) signals. In the past decades, fiber-based TF synchronization techniques have been extensively studied. Instruments based on these techniques have been successfully applied. With the increasing application of TF synchronization instruments, their security has become an important issue. Unfortunately, the security risks of fiber-based frequency synchronization (FbFS) instruments have been overlooked. This article proposes a frequency tampering method called “frequency expander.” On a 200-km fiber link, we demonstrate a frequency tampering scenario using a frequency expander-enabled frequency tampering module (FTM). On the user side, the frequency value of the recovered 100-MHz signal can be stealthily altered within a range of 100 MHz ± 100 Hz, while the frequency dissemination stability of the system remains normal. Related to this tampering risk, potential hazards in two different application scenarios, which rely on precise frequency references, are analyzed. Two countermeasures are also proposed to solve this tampering risk.
Fiber optic networks are used worldwide and have been regarded as excellent media for transmitting time-frequency (TF) signals. In the past decades, fiber-based TF synchronization techniques have been extensively studied. Instruments based on these techniques have been successfully applied. With the increasing application of TF synchronization instruments, their security has become an important issue. Unfortunately, the security risks of fiber-based frequency synchronization (FbFS) instruments have been overlooked. This paper proposes a frequency tampering method called "frequency lens". On a 200 km fiber link, we demonstrate a frequency tampering scenario using a frequency lens-enabled frequency tampering module (FTM). On the user side, the frequency value of the recovered 100 MHz signal can be stealthily altered within a range of 100 MHz-100 Hz to 100 MHz+100 Hz, while the frequency dissemination stability of the system remains normal. Related to this tampering risk, potential hazards in three different application scenarios, which rely on precise frequency references, are analyzed. Two countermeasures are also proposed to solve this tampering risk.
Wavelength Division Multiplexing (WDM) is a photonic technology capable to transport over a single fiber more than a Tbit/s aggregate traffic. Currently, WDM is the only deployed method in transcontinental and transoceanic applications. In the optical network, each fiber link consists of segments, each several kilometers long, the connecting points of which are amenable to tapping. When a small amount of optical signal is extracted from a tap, when the signal is properly amplified it can be monitored by unauthorized personnel thus threatening communications and land-security. Since each WDM channel carries traffic from one customer, it is not difficult for the connoisseur to demultiplex a specific channel, isolate a specific payload and break the encrypted datagram. Therefore, in addition to data encryption, high-speed communications security should also rely on securing the optical links. In this paper, we present a WDM link security method that, even if fiber is tapped, constitutes channel monitoring and information decrypting by an eavesdropper or unauthorized personnel virtually impossible. In addition, we describe the circuit building blocks behind the method that makes eavesdropping impossible.