Abstract: A distributed fiber sensor system based on Brillouin scattering. Two DFB lasers are included that are frequency offset locked to each other. The frequency offset is approximately equal to the Brillouin shift in optical fibers of about 11 GHz. The locking is realized by first modulating the output of one DFB laser with an electro-optic modulator to generates side bands that are about 11 GHz from the carrier, and then by locking the other DFB laser to the upper side band with a PID controller which controls its driving current.

Abstract: A fiber optic strain sensor, an optical pulse generator generates an initial optical pulse, and launches it into an optical fiber-optical strain probe chain through an optical circulator. The scattered optical power in the optical fiber and optical strain probe chain is sent to an optical receiver, also via the optical circulator. The optical strain probes are attached to a structure whose strain is to be measured. Strain in the structure causes the fiber bend loss to change in the strain probe, and causes the scattered optical power received by the optical receiver to change accordingly. From the change of the output of the optical receiver and the time required for the scattered optical power to travel from the probe, the strain at each of the probes is calculated.

Abstract: An electric security fence. An electric signal generator generates an initial electric signal. The generated initial electric signal is transmitted through a transmission line. The transmission line will generate a reflected electric signal when the transmission line is disturbed by the presence of a human or animal at a disturbance area. A receiver receives the reflected electric signal and forwards it to a signal processing unit. The signal processing unit calculates the location of the disturbance area after receiving the reflected electric signal. In one preferred embodiment, the signal processing unit calculates the location of the disturbance area by determining the amount of time required for the reflected signal to travel from the disturbance area.

Abstract: A handheld fiber optic current and voltage monitor for applications in high voltage environment. A light source generates constant optical signal that is split by a fiber optic splitter into two paths. One path feeds a DMEMS based current sensor that is driven by a current to voltage conversion device that converts the current in a conductor into a voltage. The other path goes to a DMEMS based electric field sensor driven by a condenser antenna that converts the electric field near a high voltage power line conductor into a voltage. The output optical signals from the current sensor and the electric field sensor are received by respective optical receivers and converted into electric signals. A signal processing unit processes the signals, and a display screen displays the results. All these are mounted on a plastic mast for handheld operation.

Abstract: A handheld fiber optic current and voltage monitor for applications in high voltage environment. A light source generates constant optical signal that is split by a fiber optic splitter into two paths. One path feeds a DMEMS based current sensor that is driven by a current to voltage conversion device that converts the current in a conductor into a voltage. The other path goes to a DMEMS based electric field sensor driven by a condenser antenna that converts the electric field near a high voltage power line conductor into a voltage. The output optical signals from the current sensor and the electric field sensor are received by respective optical receivers and converted into electric signals. A signal processing unit processes the signals, and a display screen displays the results. All these are mounted on a plastic mast for handheld operation.

Abstract: An electric repeater for use in transmission line based electric fences. The electric repeater comprises a forward amplifier, a backward amplifier, a quad pole quad throw signal switch, and a monostable circuit. The short forward electric pulse in the transmission line is amplified by the forward amplifier, and the amplified electric pulse trigger the monostable circuit. The monostable circuit then outputs a n electric pulse with predetermined width. This electric pulse operates the quad pole quad throw signal switch such that the wire pair of the transmission line is connected to the backward amplifier and disconnected from the forward amplifier as soon as the forward electric pulse has passed through the forward amplifier. DC electric power is supplied to the forward amplifier and backward amplifier by the transmission line metal wire pair, and two pairs of capacitors are used to block this DC electric power from entering the input and output of the forward and backward amplifiers.

Abstract: An electric reference signal channel is added to the main signal in a hybrid optical current sensor or voltage sensor. This reference signal has a frequency that is outside the main signal's frequency band. A summing integrator of a summing amplifier combines the reference signal with the main signal, and the combined signals drives an electro-optic device. This electro-optic device drives the input CW optical signal. An optical receiver converts the received optical signal into electric signal. Two band pass filters separate the main signal and the reference signal into their respective paths. A signal processing unit calculates the ratio of the main signal to the reference signal. Therefore, drifts in the optical source and all the optical path are factored out.

Abstract: A fiber optic AC electric field or voltage sensing system is described for applications in high voltage environment, particularly, in the vicinity of a power line. The system is based on diffractive MEMS device. A condenser antenna positioned in the electric field feeds a voltage signal to the diffractive MEMS device, which then modulates the light signal passing through it. In the optical receiver, the electric filed strength is measured from the received optical signal.

Abstract: An electric security fence. An electric signal generator generates an initial electric signal. The generated initial electric signal is transmitted through a transmission line. The transmission line will generate a reflected electric signal when the transmission line is disturbed by the presence of a human or animal at a disturbance area. A receiver receives the reflected electric signal and forwards it to a signal processing unit. The signal processing unit calculates the location of the disturbance area after receiving the reflected electric signal. In one preferred embodiment, the signal processing unit calculates the location of the disturbance area by determining the amount of time required for the reflected signal to travel from the disturbance area.

Abstract: An electric repeater for use in transmission line based electric fences. The electric repeater comprises a forward amplifier, a backward amplifier, a quad pole quad throw signal switch, and a monostable circuit. The short forward electric pulse in the transmission line is amplified by the forward amplifier, and the amplified electric pulse trigger the monostable circuit. The monostable circuit then outputs a n electric pulse with predetermined width. This electric pulse operates the quad pole quad throw signal switch such that the wire pair of the transmission line is connected to the backward amplifier and disconnected from the forward amplifier as soon as the forward electric pulse has passed through the forward amplifier. DC electric power is supplied to the forward amplifier and backward amplifier by the transmission line metal wire pair, and two pairs of capacitors are used to block this DC electric power from entering the input and output of the forward and backward amplifiers.

Abstract: Apparatus and methods for wire insulation in transmission line based electric fence are described in this invention. An insulator holds a wire pair that form the transmission line in its wire clamps. The insulator has a rain shed that sheds the wire clamps from getting wet by rain water. The insulator also has a pair of rain water divert guides that guide rain water accumulated on the wire to flow to the guide instead of to the wire clamps. This invention also describes a wire heating method that uses electric current to heat the fence wires such that the wire/wire clamp contact point will be kept dry and ice, snow accumulated on fence wires will be melted. Performance of the transmission line based electric fence can thus be greatly improved in advert weather conditions.

Abstract: An electric security fence. An electric signal generator generates an initial electric signal. The generated initial electric signal is transmitted through a transmission line. The transmission line will generate a reflected electric signal when the transmission line is disturbed by the presence of a human or animal at a disturbance area. A receiver receives the reflected electric signal and forwards it to a signal processing unit. The signal processing unit calculates the location of the disturbance area after receiving the reflected electric signal. In one preferred embodiment, the signal processing unit calculates the location of the disturbance area by determining the amount of time required for the reflected signal to travel from the disturbance area.

Abstract: An electric security fence. An electric signal generator generates an initial electric signal. The generated initial electric signal is transmitted through a transmission line. The transmission line will generate a reflected electric signal when the transmission line is disturbed by the presence of a human or animal at a disturbance area. A receiver receives the reflected electric signal and forwards it to a signal processing unit. The signal processing unit calculates the location of the disturbance area after receiving the reflected electric signal. In one preferred embodiment, the signal processing unit calculates the location of the disturbance area by determining the amount of time required for the reflected signal to travel from the disturbance area.

Abstract: System and method for supervisory signal modulation on Wavelength Division Multiplex (WDM) channels wherein variable optical attenuators (VOAs) are used for amplitude modulation of the supervisory signal. Alternatively, at least two spectral bands of the supervisory signal are amplitude modulated by means of VOAs at a same frequency but in phase difference, preferably in anti-phase such that the signal resulting from the combination of the two spectral bands is maintained at a predetermined value, preferably at a minimum value and more preferably at zero value.

Abstract: A carbon monoxide (CO) detection unit incorporates a sensor which is a film or layer of NixCo1-xOy where x is from 0.1 to 0.9, e.g., spinel. The CO is detected by measuring the change in the electrical properties of the sensor. The detector can measure CO concentrations below 100 ppm and is capable of operating at room temperature and can be applied to domestic, industrial, medical and vehicular use.

Abstract: System and method for supervisory signal modulation on Wavelength Division Multiplex (WDM) channels wherein variable optical attenuators (VOAs) are used for amplitude modulation of the supervisory signal. Alternatively, at least two spectral bands of the supervisory signal are amplitude modulated by means of VOAs at a same frequency but in phase difference, preferably in anti-phase such that the signal resulting from the combination of the two spectral bands is maintained at a predetermined value, preferably at a minimum value and more preferably at zero value.

Abstract: A carbon monoxide (CO) detection unit incorporates a sensor which is a film or layer of NixCo1-xOy where x is from 0.1 to 0.9, e.g., spinel. The CO is detected by measuring the change in the electrical properties of the sensor. The detector can measure CO concentrations below 100 ppm and is capable of operating at room temperature and can be applied to domestic, industrial, medical and vehicular use.

Abstract: A carbon monoxide (CO) detection unit incorporates a sensor which is a film or layer of NixCo1−xOy where x is from 0.1 to 0.9, e.g., spinel. The CO is detected by measuring the change in the electrical properties of the sensor. The detector can measure CO concentrations below 100 ppm and is capable of operating at room temperature and can be applied to domestic, industrial, medical and vehicular use.

Abstract: A carbon monoxide (CO) detection unit incorporates a sensor which is a film or layer of NixCo1-xOy where x is from 0.1 to 0.9, e.g., spinel. The CO is detected by measuring the change in the electrical properties of the sensor. The detector can measure CO concentrations below 100 ppm and is capable of operating at room temperature and can be applied to domestic, industrial, medical and vehicular use.

Abstract: A method is described of stabilizing the output of a mode-locked fibre ring laser (1). The fibre constituting the laser (1) includes a dopant in its core. The method comprises the steps of adjusting the length of the ring laser (1) to minimise variations in its cavity length, and hence lock the phase of the laser output pulses with that of its drive source (2), and subjecting a portion (1a) of the fibre of the ring laser (1) to vibrations at a predetermined frequency whose period is less than the dopant ion upper state lifetime.