Chung Shan Institute of Science and Technology

Shin-chu Huang

Shih-Chu Huang

Wuu-Wen Lin

Jiunn-Song Tsay

Heng-Shan Hsu

Chung-Sung Tsay

Shoren-Chien Hung

Hermann Lin

Chun-Long Chang

Hung-Lung Chao

A counting signal processing method for a fiber optic interferometric sensor including following steps is provided. An output intensity of the fiber optical interferometric sensor is converted into an electrical signal having the form V+Vcos &#x3c8;(t). Then, the number of times Nthat the maximum peak values are greater than a first counting level Sand the number of times Nthat the minimum peak values are smaller than a second counting level Swithin a specific period of time Tare counted. When the value of N, Nor (N+N) is greater than a threshold counting number C, a detectable induced signal occurring in a sensing area is inferred. Then, whether the detectable induced signals are caused by an intruder or otherwise is judged through an alarm identification logic, and an alarm device is triggered to send out an alarm according to the result of the judgment.

Counting signal processing method for fiber optic interferometric sensor

An on-line Sagnac interferometric distributed fiber-optic leakage detection device comprising a light generator, an optical fiber coupler, a hollow pipeline, a Faraday rotator mirror, a sensing optical fiber, a delaying optical fiber, a photo detection device and a spectrum analyzer. Signals resulting from a leaky pipeline are obtained by the linear leakage detection system. The signals are analyzed by the spectrum analyzer to discover any null frequency shift so that exact location of the leakage point along the hollow pipeline can be computed.

On-line Sagnac interferometric distributed fiber-optic leakage detection device

A polarization-insensitive fiber-optic interferometric sensor system has an erbium-doped fiber amplifier (EDFA) at a location between a light source and a sensing array to serve as a post amplifier. An output end of the sensing array is coupled to another EDFA, and further coupled to a receiver, in which this another EDFA is used as an in-line amplifier. As the sensor system is applied for a light source with multiple wavelengths, a dense wavelength division multiplexers (DWDMs) is used to combine the multiple wavelengths into one for amplification, and another DWDM is used to decouple the multiple wavelengths.

Optically amplified WDM/TDM hybrid polarization-insensitive fiber-optic interferometric sensor system

An optical intensity modulator with optimized extinction ratio (ER) is provided. The optical intensity modulator has a modulator used to receive a light source, such as a laser source, and export an optical pulse. An optical divide is used to receive the optical pulse and decouple it into a first optical pulse and a second optical pulse. An optical receiver is used to receive the first optical pulse and convert it into an electrical pulse signal. A signal processor is used to receive the electrical pulse signal from the optical receiver and digitize it into a digital reference signal. A DC-bias generator coupled to the signal processor and the modulator is used to provide a precise DC bias to the modulator according to an output of the signal processor. A current reference signals is compared with a previous reference signals and is adjusted in the signal processor so as to obtain the precise DC bias. The optical intensity modulator further includes a pulse generator, used to provide a pulse signal for the modulator and a trigger signal to the signal processor.

Intensity modulator with optimum extinction ratio of an output optic pulse

A method of calibrating a three-axis magnetometer is provided. In accordance with the method, calibration is effected by first establishing a three-axis magnetic field simulator having a center position portion. Suitable measures are taken to substantially compensate for the earth's magnetic field at least at that center position portion. A three-axis magnetometer is then disposed in the magnetic field simulator and successively actuated in predetermined manner to generate a set of measured parameter values. The measured parameter values are normalized using a predetermined standard output factor, and a square pre-calibration matrix C is generated from the normalized measured parameter values. An inverse matrix operation is thereafter performed upon the pre-calibration matrix C to generate a square calibration matrix D having a plurality of coefficients respectively indicative of orthonormal compensation coefficients. This square calibration matrix D is then applied to a subsequent measurement of the magnetometer to generate a corresponding compensated measurement.

Method of calibrating a three-axis magnetometer

This invention concerns with a time-division multiplexing system of polarization-insensitive Michelson interferometric fiber optic sensors, where the compensating interferometer is equipped with a 3.times.3 coupler. It uses the two reflections from the Faraday rotator mirrors of sensor interferometer and compensating interferometer, respectively, in a totally passive manner, to overcome the polarization-induced signal fading in the multiplexing sensor system. The compensating interferometer with matching optical paths is used to reduce the phase-induced intensity noise, at the same time it allows the use of laser source with proper coherence length to reduce the crosstalk between sensors and the crosstalk caused by Rayleigh scattering. This system allows the use of low-loss conventional single-mode optic fiber as lead fiber, and offers advantages in building the fiber optic sensor array system with long-distance lead fiber. Furthermore, this system is characteristic of good performance on lead fiber insensitivity. The use of 3.times.3 demodulation circuits increases the sensor bandwidth significantly without increasing the sampling rate.

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Kaohsiung, Taiwan

Shih-Chu Huang