Abstract: An optical coherence analysis system comprises a swept source laser for generating optical signals that are tuned over a scan band; an interferometer for transmitting the optical signals over a sample arm and reference arm and combining the optical signals; a k-clock for generating a sampling clock indicating non-linearities in the frequency tuning of the optical signals over the scan band, the k-clock being not delay matched to propagation delays for the optical signals in the interferometer; a sampling system for sampling the optical signals from the interferometer in response to the k-clock to generate interference signals; and a processing system for determining non-linearities in the sampling clock and for transforming the interference signals into an image of a sample in response to the non-linearities. The system compensates for the lack of an electronic delay of k-clock using a nonuniform discrete Fourier transform.

Abstract: An optical coherence analysis system comprising: a first swept source that generates a first optical signal that is tuned over a first spectral scan band, a second swept source that generates a second optical signal that is tuned over a second spectral scan band, a combiner for combining the first optical signal and the second optical signal for form a combined optical signal, an interferometer for dividing the combined optical signal between a reference arm leading to a reference reflector and a sample arm leading to a sample, and a detector system for detecting an interference signal generated from the combined optical signal from the reference arm and from the sample arm.

Abstract: An optical coherence analysis system comprises a swept source laser for generating optical signals that are tuned over a scan band; an interferometer for transmitting the optical signals over a sample arm and reference arm and combining the optical signals; a k-clock for generating a sampling clock indicating non-linearities in the frequency tuning of the optical signals over the scan band, the k-clock being not delay matched to propagation delays for the optical signals in the interferometer; a sampling system for sampling the optical signals from the interferometer in response to the k-clock to generate interference signals; and a processing system for determining non-linearities in the sampling clock and for transforming the interference signals into an image of a sample in response to the non-linearities. The system compensates for the lack of an electronic delay of k-clock using a nonuniform discrete Fourier transform.

Abstract: A tunable laser spectroscopic carpet identification system comprises a tunable laser spectroscopy system for generating a tunable signal that is transmitted to a carpet sample. The system detects the tunable signal after interaction with the carpet sample so that an analyzer is able to relate a spectral response of the carpet sample to a chemical composition of the carpet sample. In one example, the spectroscopy system comprises a laser cavity in which the tunable signal is generated, a semiconductor gain medium in the laser cavity, and a tunable element for controlling a wavelength of tunable signal generated in the laser cavity. To deal with variations in water content, the analyzer estimates a water content of the carpet sample using the spectral response of the carpet sample and then determines the chemical composition of the carpet sample in part based on the estimate of the water content.

Abstract: A frequency swept laser source for TEFD-OCT imaging includes an integrated clock subsystem on the optical bench with the laser source. The clock subsystem generates frequency clock signals as the optical signal is tuned over the scan band. Preferably the laser source further includes a cavity extender in its optical cavity between a tunable filter and gain medium to increase an optical distance between the tunable filter and the gain medium in order to control the location of laser intensity pattern noise. The laser also include a fiber stub that allows for control over the cavity length while also controlling birefringence in the cavity.

Abstract: Optical coherence tomography (OCT) probe and system designs are disclosed that minimize the effects of mechanical movement and strain to the probe to the OCT analysis. It also concerns optical designs that are robust against noise from the OCT laser source. Also integrated OCT system-probes are included that yield compact and robust electro-opto-mechanical systems along with polarization sensitive OCT systems.

Abstract: Apparatus for use in tuning a tunable optical device to a target wavelength, the apparatus comprising: a beam splitter for tapping a portion of the light emerging from the tunable optical device; a walk-off reflector for dividing the portion of the light emerging from the beam splitter into a plurality of beams; a multiple etalon for tailoring the light from at least two of the plurality of beams provided by the walk-off reflector; a multiple detector for detecting light from the multiple etalon and the walk-off reflector, the multiple detector providing a plurality of output signals; and a control unit for controlling the tunable optical device by providing a control signal to the tunable optical device according to the output signals provided by the multiple detector.

Abstract: A real-time control system for an optical phased array is disclosed that comprises a computationally efficient algorithm for calculating phase differences between a plurality of array beamlets and a reference plane wave and further generates phase correction signals that are transmitted to a plurality of phase modulators to realign the array beamlets to compensate for external perturbations and atmospheric aberrations. The phase measurements are based on a phase angle of a complex number comprising square wave functions, and alternately, based on a phase angle of a complex number comprising sine and cosine functions to correct for harmonic content of phase measurements. Furthermore, the phase correction signal is based on the phase measurement times modulo2&pgr;.

Abstract: Apparatus for use in tuning a tunable optical device to a target wavelength, the apparatus comprising: a beam splitter for tapping a portion of the light emerging from the tunable optical device; a walk-off reflector for dividing the portion of the light emerging from the beam splitter into a plurality of beams; a multiple etalon for tailoring the light from at least two of the plurality of beams provided by the walk-off reflector; a multiple detector for detecting light from the multiple etalon and the walk-off reflector, the multiple detector providing a plurality of output signals; and a control unit for controlling the tunable optical device by providing a control signal to the tunable optical device according to the output signals provided by the multiple detector.

Abstract: A real-time control system for an optical phased array is disclosed that comprises a computationally efficient algorithm for calculating phase differences between a plurality of array beamlets and a reference plane wave and further generates phase correction signals that are transmitted to a plurality of phase modulators to realign the array beamlets to compensate for external perturbations and atmospheric aberrations. The phase measurements are based on a phase angle of a complex number comprising square wave functions, and alternately, based on a phase angle of a complex number comprising sine and cosine functions to correct for harmonic content of phase measurements. Furthermore, the phase correction signal is based on the phase measurement times modulo2&pgr;.

Abstract: The present invention provides several apparatus, methods, and computer program products for phase shifts in an optical signal generated by an optical device. The present invention includes a optical phase modulator for altering the phase of the optical signals output by an optical device. The present invention also includes a detector assembly that receives an interference signal generated by an optical interference of a power signal and a reference signal. The detector assembly generates a lockin signal representing the optical phase difference between the power signal and the reference signal. Connected to both the detector assembly and the optical phase detector is a processor. The processor receives the lockin signal from the detector assembly and compares the lockin signal to at least one predetermined set point value. The predetermined set point value represents either a desired maximum lockin signal value or a range of acceptable lockin values.

Abstract: A system such as for sensing strain or temperature of an aircraft and for transmitting information in communication systems. A sensor array includes a first light responsive Bragg grating sensor having a first operating bandwidth and a second light responsive Bragg grating sensor having a second operating bandwidth. Each sensor modifies light provided to it at a wavelength indicative of changes in strain or temperature. The second sensor operates within a bandwidth which is different from the operating bandwidth of the first sensor. A tunable light source such as an LED and tunable etalon provides light for illuminating the first and second sensors, the provided light having a wavelength which varies within a band including the first and second bandwidths. A detecting circuit provides signals representative of light modified by the first and second sensors. A processor processes the representative signals to determine the strain and/or temperature.

Abstract: A dual frequency laser amplifier includes a beam generator for generating first and second source laser beams, and a co-doped optical fiber including first and second dopant ions having first and second gain bandwidths corresponding to the respective wavelengths of the first and second source laser beams for selectively forming first and second diffraction limited output laser beams responsive to the relative radiated power between the first and second source laser beams. A dual frequency laser oscillator and a method for generating the first and second output laser beams at any predetermined radiated power distribution are also described.

Abstract: An optical switch network which includes a plurality N of cascaded optical switching stages, each mth one of the switching stages including 2.sup.m-1 Mach-Zehnder interferometers, where m=1 through N. The input port of the Mach-Zehnder interferometer of a first one of the optical switching stages receives an optical input signal, and the 2.sup.N-1 Mach-Zehnder interferometers of the Nth one of the optical switching stages provide a total of 2.sup.N output ports. Each of the Mach-Zehnder interferometers is preferably an unbalanced Mach-Zehnder interferometer, and the optical input signal preferably has a wavelength which is a selected one of 2.sup.N selectable wavelengths. The plurality N of cascaded optical switching stages provide 2.sup.N possible optical paths, whereby the optical input signal is automatically routed along a selected one of the 2.sup.N possible optical paths in dependence upon its selected wavelength.

Abstract: A system and method for absolute, high resolution and accurate strain measurement includes a low-coherence light source (12) transmitting light through a strain sensor (18) and into an interferometer (26). The interferometer (26) has a high-coherence light source (48) that parallels the light from the low-coherence light source (12). The output of the interferometer is detected by a photodetector (46). The photodetector (46) is connected to a phase measuring circuit (30), that is in communication with a controller (28). The controller (28) is also connected to a motor (44) that adjusts the optical path lengths in the interferometer (38). The phase change in the high-coherence source from the fringe pattern (68) of the strain sensor (18) before and after a strain is applied to the device under test is used to determine the strain.

Abstract: A monolithic integrated photoreceiver comprising a p-i-n photodiode and a heterojunction bipolar transistor is realized in a structural configuration that allows the photonics and electronics to be separately optimized in addition to maintaining materials compatibility. These desirable features are accomplished by growing the epilayers of the photodiode and heterojunction bipolar transistor in a single epitaxial growth run. The p-i-n epilayers of the photodiode are grown first on a non-patterned substrate, followed by the direct epitaxial growth of the heterostructure bipolar transistor over the photodiode structure. Selective wet chemical etching over a portion of the entire structure was used in order to delineate the mesa structures of the p-i-n photodiode and transistor such that no contiguous conductive semiconductor layer exists therebetween.

Abstract: Briefly, in this invention, the output optical power of an optical amplifier is determined by detecting and measuring the electrical signal induced on the bias lead of the optical amplifier when an optical data stream with additional amplitude modulation passes through the optical amplifier. This additional amplitude modulation can consist of a base band signal, a pilot tone and/or a sub-carrier which is amplitude modulated, frequency modulated or phase modulated. The modulation depth and bandwidth of the additional amplitude modulation should be kept small enough that the data stream is not excessively affected. The induced electrical signal provides a measurement of the optical power at the output facet of the optical amplifier. Control of the output power of the optical amplifier is effected by controlling the bias current applied to the bias lead of the optical amplifier.