Abstract: In a Brillouin sensing system using optical microwave frequency discriminators and a scrambler provided by the present invention, a laser signal outputted by a distributed feedback laser is divided into two paths of optical signals through a coupler, one path of optical signal is modulated by a modulator to act as a pump light signal and then is transmitted to sensing fibers through a circulator; another path of optical signal is modulated by another modulator to act as a detecting light signal and then directly enters the sensing fibers. When the frequency difference between the pump light and the detecting light is equal to the Brillouin frequency shift of a certain region in the fibers, the region produces the stimulated Brillouin scattering effect, so that through determining the frequency shift and power of the Brillouin scattering signal, the temperature and stress of the sensing fibers are obtained.

Abstract: In a Brillouin sensing system using optical microwave frequency discriminators and a scrambler provided by the present invention, a laser signal outputted by a distributed feedback laser is divided into two paths of optical signals through a coupler, one path of optical signal is modulated by a modulator to act as a pump light signal and then is transmitted to sensing fibers through a circulator; another path of optical signal is modulated by another modulator to act as a detecting light signal and then directly enters the sensing fibers. When the frequency difference between the pump light and the detecting light is equal to the Brillouin frequency shift of a certain region in the fibers, the region produces the stimulated Brillouin scattering effect, so that through determining the frequency shift and power of the Brillouin scattering signal, the temperature and stress of the sensing fibers are obtained.

Abstract: A polarization scrambler based on Faraday magneto-optic effect is disclosed. A polarization control unit (2) is connected between a first rotator unit (1) and a second rotator unit (3). The first rotator unit (1) includes a first optical fiber circle (11) and a first wire coil (12). The second rotator unit (3) includes a second optical fiber circle (31) and a second wire coil (32). ACs with two frequencies f1 and f2 are respectively introduced into the first wire coil (12) and the second wire coil (32), such that the ACs in the two wire coils are changed to control the polarization angle in the two optical fiber circles to independently change within the range of +/?90°. The polarization control unit (2) can ensure motion trajectories of outputted light polarization pointsare in two orthogonal directions, thus achieving uniform polarization disturbance.

Abstract: A polarization scrambler based on fiber wave plates is disclosed. A ?/4 unit (2) is connected between a first polarization control unit (1) and a second polarization control unit (3) through single-mode fibers; a first motor (11) of the first polarization control unit (1) and a second motor (31) of the second polarization control unit (3) simultaneously forwardly and reversely swing in the range of +/?90°, such that polarization states in the system constantly change, for achieving the purpose of polarization disturbance. The polarization scrambler based on fiber wave plates provided by the present invention has low loss, good effect, low cost and simple structure, and is convenient for manufacturing. Its speed is up to milliseconds to meet demands of most optical fiber sensing systems and optical fiber communicating systems.

Abstract: An optic-microwave frequency discriminator includes: a fiber coupler receives and combines a first laser and a second laser, than the fiber coupler respectively generates and outputs a first light signal and a second light signal; a photodiode module respectively receives the first light signal and the second light signal, and converts the first light signal into a first microwave signal and converts the second light signal into a second microwave signal; a microwave phase shifter generates a shifted microwave signal by introducing a phase shift to the second microwave signal; a 90° microwave bridge combines the first microwave signal and the shifted microwave signal for generating a first bridge signal and a second bridge signal; a normalized balanced detection module generates an error signal; and a control module generates a controlling voltage signal according to the error signal for tuning a frequency of the second laser.

Abstract: A polarization scrambler based on fiber wave plates is disclosed. A ?/4 unit (2) is connected between a first polarization control unit (1) and a second polarization control unit (3) through single-mode fibers; a first motor (11) of the first polarization control unit (1) and a second motor (31) of the second polarization control unit (3) simultaneously forwardly and reversely swing in the range of +/?90°, such that polarization states in the system constantly change, for achieving the purpose of polarization disturbance. The polarization scrambler based on fiber wave plates provided by the present invention has low loss, good effect, low cost and simple structure, and is convenient for manufacturing. Its speed is up to milliseconds to meet demands of most optical fiber sensing systems and optical fiber communicating systems.

Abstract: A polarization scrambler based on Faraday magneto-optic effect is disclosed. A polarization control unit (2) is connected between a first rotator unit (1) and a second rotator unit (3). The first rotator unit (1) includes a first optical fiber circle (11) and a first wire coil (12). The second rotator unit (3) includes a second optical fiber circle (31) and a second wire coil (32). ACs with two frequencies f1 and f2 are respectively introduced into the first wire coil (12) and the second wire coil (32), such that the ACs in the two wire coils are changed to control the polarization angle in the two optical fiber circles to independently change within the range of +/?90°. The polarization control unit (2) can ensure motion trajectories of outputted light polarization pointsare in two orthogonal directions, thus achieving uniform polarization disturbance.

Abstract: An optic-microwave frequency discriminator includes: a fiber coupler receives and combines a first laser and a second laser, than the fiber coupler respectively generates and outputs a first light signal and a second light signal; a photodiode module respectively receives the first light signal and the second light signal, and converts the first light signal into a first microwave signal and converts the second light signal into a second microwave signal; a microwave phase shifter generates a shifted microwave signal by introducing a phase shift to the second microwave signal; a 90° microwave bridge combines the first microwave signal and the shifted microwave signal for generating a first bridge signal and a second bridge signal; a normalized balanced detection module generates an error signal; and a control module generates a controlling voltage signal according to the error signal for tuning a frequency of the second laser.

Abstract: An optical fiber current transformer includes a broadband light source, a depolarizer, a beam splitter, a temperature acquisition unit, a current acquisition unit, a modulation waveform generating unit, a data processing unit and a calculating compensation unit. The broadband light source is connected with the beam splitter by the depolarizer. A first output of the beam splitter is connected with the calculating compensation unit by the temperature acquisition unit. A second output of the beam splitter is connected with the data processing unit by the current acquisition unit. The data processing unit is connected with the calculating compensation unit. The calculating compensation unit is connected with the current acquisition unit by the modulation waveform generating unit.

Abstract: An optical fiber temperature sensor includes an optical transceiver module, a transmission fiber and a sensing head. When the transmission fiber is a polarization maintaining fiber, the sensing head includes a temperature sensing element and a fiber reflector, the temperature sensing element is a section of polarization maintaining fiber. The transmission fiber is fusion spliced with the temperature sensing element, an angle between a polarization axis of the transmission fiber and that of the temperature sensing element is 45 degree at the fusion splicing point. When the transmission fiber is a single-mode fiber, the sensing head includes a polarizer. An angle between a polarization axis of the polarization maintaining fiber connecting the temperature sensing element with the polarizer and that of the polarization maintaining fiber of the temperature sensing element is 45 degree at the fusion splicing point. The present invention is of simple principle and structure, and facilitates manufacturing.

Abstract: An optical fiber temperature sensor includes an optical transceiver module, a transmission fiber and a sensing head. When the transmission fiber is a polarization maintaining fiber, the sensing head includes a temperature sensing element and a fiber reflector, the temperature sensing element is a section of polarization maintaining fiber. The transmission fiber is fusion spliced with the temperature sensing element, an angle between a polarization axis of the transmission fiber and that of the temperature sensing element is 45 degree at the fusion splicing point. When the transmission fiber is a single-mode fiber, the sensing head includes a polarizer. An angle between a polarization axis of the polarization maintaining fiber connecting the temperature sensing element with the polarizer and that of the polarization maintaining fiber of the temperature sensing element is 45 degree at the fusion splicing point. The present invention is of simple principle and structure, and facilitates manufacturing.

Abstract: An optical fiber current transformer includes a broadband light source, a depolarizer, a beam splitter, a temperature acquisition unit, a current acquisition unit, a modulation waveform generating unit, a data processing unit and a calculating compensation unit. The broadband light source is connected with the beam splitter by the depolarizer. A first output of the beam splitter is connected with the calculating compensation unit by the temperature acquisition unit. A second output of the beam splitter is connected with the data processing unit by the current acquisition unit. The data processing unit is connected with the calculating compensation unit. The calculating compensation unit is connected with the current acquisition unit by the modulation waveform generating unit.

Abstract: An optical device includes: a first polarization beam splitter (PBS); a first set of optical rotators optically coupled to the first PBS; a second PBS optically coupled to the first set of optical rotators; a first reflection interferometer (RI) optically coupled to the second PBS; a second RI optically coupled to the first PBS; a second set of optical rotators optically coupled to the second PBS; a third PBS optically coupled to the second set of optical rotators; and a third RI optically coupled to the third PBS. Preferably, the optical device is an Optical Add/Drop Multiplexer and may further comprise an Input Port optically coupled to the first PBS, an Output Port optically coupled to the second PBS, and an Add Port optically coupled to the third PBS.

Abstract: A portable nondestructive testing instrument uses high-speed phase-stepping shearography, and vacuum stressing, to produce images of disbonds, impact damage, or delaminations, in metal or composite structures. The invention is especially useful in the inspection of large areas where only external access is feasible, such as in large aircraft, space vehicles, boats, or civil engineered structures having multiple bond lines. The invention includes a novel combination of components and techniques, including a high-spatial-resolution CCD sensor, low-voltage piezoceramic phase stepping, rapid phase stepping, a fast phase calculation technique, a fast image smoothing technique, and an implementation of all of the above in a portable unit. Specially designed timing and control algorithms allow data acquisition, transfer, calculation, smoothing, and display at rates of up to two times per second.

Abstract: A method for compensating for chromatic dispersion of an optical signal includes: receiving the optical signal from an input fiber; collimating the optical signal using a collimator; delivering the collimated optical signal to a Gires-Tournois interferometer; reflecting a chromatic-dispersion-compensated optical signal from the Gires-Tournois interferometer to the collimator; focusing the chromatic-dispersion compensated optical signal into an output fiber. The compensator in accordance with the present invention provides flexibility in producing periodically varying chromatic dispersion so as to compensate for unwanted periodic chromatic dispersion produced in an interferometric interleaved channel separator. Also, the compensator enables compensation of fiber optic chromatic dispersion.

Abstract: The present invention provides the method and apparatus for multi-pass photonic processors with the use of circulators and multiple-fiber collimators. In one embodiment of the present invention, a circulator and a reflective element are placed at either end of a chain of cascaded processors. The circulator at a first end routes the light signal to be processed and passed from one processor to the next, the reflective element at a second end reflects the light to be reprocessed and passed from one processor to the previous, the light signal eventually reaches the circulator again and exits. In another embodiment of the present invention, multiple fiber strands are connected to the collimator of a photonic processor. Furthermore, all fiber strands are paired in order to reroute the light signals for reprocessing in the photonic processor.

Abstract: The invention provides a dispersion compensation system and method formed by cascading a series of GT cavities with three setting parameters, reflectivity, resonant wavelength, and free-spectral-range. In one aspect of the invention, the GT cavities can synthesize any shape of combined dispersion compensation, including positive, negative, slope dispersion compensation. In another aspect of the invention, the GT cavities are tunable or dynamic to accommodate various types of dispersion compensation. Advantageously, the present invention provides an effective cost solution for a more precise dispersion compensation tuning.

Abstract: A portable nondestructive testing instrument uses high-speed phase-stepping shearography, and vacuum stressing, to produce images of disbonds, impact damage, or delaminations, in metal or composite structures. The invention is especially useful in the inspection of large areas where only external access is feasible, such as in large aircraft, space vehicles, boats, or civil engineered structures having multiple bond lines. The invention includes a novel combination of components and techniques, including a high-spatial-resolution CCD sensor, low-voltage piezoceramic phase stepping, rapid phase stepping, a fast phase calculation technique, a fast image smoothing technique, and an implementation of all of the above in a portable unit. Specially designed timing and control algorithms allow data acquisition, transfer, calculation, smoothing, and display at rates of up to two times per second.