Systems and techniques are provided for sensor device. A sensor device may include a housing, a lens inserted into a first opening of the housing, a metal mask covering a portion of the interior of the lens, a passive infrared (PIR) sensor underneath the lens and the metal mask, and a light pipe around the PIR sensor, the lens, and the metal mask. Part of the light pipe may be positioned above an activation mechanism for a button. An airflow gasket may be around the PIR sensor. A filter circuit board may be under the PIR sensor and connected to leads of the PIR sensor. A control circuit board may include the activation mechanism for the button. A backplate may include a slot for attachment to a snap of a magazine in the housing of the sensor device.

Systems and techniques are provided for sensor device. A sensor device may include a housing, a lens inserted into a first opening of the housing, a metal mask covering a portion of the interior of the lens, a passive infrared (PIR) sensor underneath the lens and the metal mask, and a light pipe around the PIR sensor, the lens, and the metal mask. Part of the light pipe may be positioned above an activation mechanism for a button. An airflow gasket may be around the PIR sensor. A filter circuit board may be under the PIR sensor and connected to leads of the PIR sensor. A control circuit board may include the activation mechanism for the button. A backplate may include a slot for attachment to a snap of a magazine in the housing of the sensor device.

A computer-implemented event statistic generation method for intrusion detection comprises processing a plurality of return signals from a coherent optical time domain reflectometer into time domain signals for each of a plurality of sensor bins, the plurality of return signals corresponding to a plurality of stimulation pulses injected into an optical sensor fiber during a time period. For each sensor bin, the method comprises transforming the respective time-domain signal into a corresponding frequency-domain signal, calculating, from the respective frequency-domain signal, a first signal power area of a first frequency band expected to contain system noise, calculating, from the respective frequency-domain signal, a second signal power area of a second frequency band expected to contain any energy related to at least a first event; and generating an event statistic proportional to the ratio of the second signal power area to the first signal power area at least in part by dividing the second signal power area by the first signal power area.

A hollow core fiber (HCF) link is characterized by structural properties selected to support and sustain light propagation in a fundamental mode and in at least one higher-order mode. Connected to a proximal end of the HCF link, there is a mode coupler configured to couple a data signal into the fundamental mode and to couple an obfuscating signal into the at least one higher-order mode for simultaneous propagation of the data signal and the obfuscating signal on the HCF link, where the obfuscating signal substantially overlaps the data signal in spectral content. At a distal end of the HCF link, there is a mode splitter configured to split a first optical signal detected in the fundamental mode from a second optical signal detected in the at least one higher-order mode.

A hollow core fiber (HCF) link is characterized by structural properties selected to support and sustain light propagation in a fundamental mode and in at least one higher-order mode. Connected to a proximal end of the HCF link, there is a mode coupler configured to couple a data signal into the fundamental mode and to couple an obfuscating signal into the at least one higher-order mode for simultaneous propagation of the data signal and the obfuscating signal on the HCF link, where the obfuscating signal substantially overlaps the data signal in spectral content. At a distal end of the HCF link, there is a mode splitter configured to split a first optical signal detected in the fundamental mode from a second optical signal detected in the at least one higher-order mode.

In an optical fiber monitoring system which detects physical disturbance or other parameters such as temperature or strain of a fiber where a monitor signal is transmitted along the optical fiber and analyzed to detect changes which are indicative of an event, a method is provided for periodically checking proper operation of the optical fiber monitoring system. A fiber disturbance actuator periodically causes a pattern of disturbances of a portion of the fiber at a predetermined location thereon where the disturbance is characteristic of the event to be monitored. The monitor signal is analyzed to detect the pattern of changes and in the event that expected changes are not detected, a warning is issued that the intrusion detection system is not properly operating.

In an optical fiber monitoring system which detects physical disturbance or other parameters such as temperature or strain of a fiber where a monitor signal is transmitted along the optical fiber and analyzed to detect changes which are indicative of an event, a method is provided for periodically checking proper operation of the optical fiber monitoring system. A fiber disturbance actuator periodically causes a pattern of disturbances of a portion of the fiber at a predetermined location thereon where the disturbance is characteristic of the event to be monitored. The monitor signal is analyzed to detect the pattern of changes and in the event that expected changes are not detected, a warning is issued that the intrusion detection system is not properly operating.

In an optical fiber monitoring system which detects physical disturbance or other parameters such as temperature or strain of a fiber where a monitor signal is transmitted along the optical fiber and analyzed to detect changes which are indicative of an event, a method is provided for periodically checking proper operation of the optical fiber monitoring system. :A fiber disturbance actuator periodically causes a pattern of disturbances of a portion of the fiber at a predetermined location thereon where the disturbance is characteristic of the event to be monitored. The monitor signal is analyzed to detect the pattern of changes and in the event that expected changes are not detected, a warning is issued that the intrusion detection system is not properly operating.

In an optical fiber monitoring system which detects physical disturbance or other parameters such as temperature or strain of a fiber where a monitor signal is transmitted along the optical fiber and analyzed to detect changes which are indicative of an event, a method is provided for periodically checking proper operation of the optical fiber monitoring system. :A fiber disturbance actuator periodically causes a pattern of disturbances of a portion of the fiber at a predetermined location thereon where the disturbance is characteristic of the event to be monitored. The monitor signal is analyzed to detect the pattern of changes and in the event that expected changes are not detected, a warning is issued that the intrusion detection system is not properly operating.

A clip is provided. The clip includes first and second shells shaped to mate around a band. An inward facing surface of the first shell has a lateral groove shaped to accommodate the fiber optic filament of the band and at least one protrusion. When the first and second shells are mated around the band the at least one protrusion passes through one of the holes in the band and engages a matching groove in an inward facing surface of the second shell. The first and second shells have a shape such that, when the first shell and the second shell mate around the band and lock into the connector, the first shell and the second shell collectively block any exterior light from reaching the light detection circuitry of the connector along the path of the band other than light through the fiber optic filament.