Abstract: The present disclosure describes semiconductor external cavity laser with wide bandwidth frequency modulation capabilities. The laser is preferably packaged in a standard form-factor package, such as a 14-pin butterfly package. The front end of the cavity comprises an integrated planar circuit (e.g., silica-on-silicon planar lightwave circuit with Bragg gratings), and the “back facet” of the laser is implemented as a high-reflection (HR) coated LiNbO3 phase tuning section in the double pass configuration. AC-voltage signal applied to the electrodes of phase tuning section modulates a refractive index of the propagating TE-polarization mode of external cavity and produces frequency modulation. Such frequency modulation is not associated with any thermal behavior of the gain element included in the external cavity laser, and has a negligible phase delay over a wide bandwidth.

Abstract: Embodiments of the present invention use an external cavity laser source with dual input terminals, such as bias current for a gain section, and a voltage signal for a modulator section. An aspect of the present invention provides an ultra-low frequency noise external cavity frequency modulated (FM) semiconductor laser source frequency stabilized by a dual electronic feedback circuitry applied to semiconductor gain section and a modulation section. A further aspect of the present invention provides an optical frequency discriminator based on homodyne phase demodulation using an unbalanced Michelson interferometer with fiber optics delay and a symmetrical 3×3 optical coupler.

Abstract: The present invention relates to distributed acoustic sensing using fiber-optic system. More particularly, the present invention describes use of frequency pulse labeling techniques and wavelength pulse labeling techniques for providing high bandwidth acoustic sensing in applications such as infrastructure monitoring. In one embodiment, a segmented sensing fiber is used with corresponding circulators in an architecture that controls the interrogation of each segment of the fiber. In another embodiment, a single continuous length of sensing fiber is used, but a plurality of pulse sequences with different wavelengths are used to interrogate. In both configurations, heterodyne beat frequency components are rejected by a processing scheme, resulting in a simple direct measurement of baseband phase information.

Abstract: The present invention relates to external cavity laser (ECL) apparatuses and manufacturing processes, and more particularly to implementing low noise narrow bandwidth ECLs on planar lightwave circuit (PLC) platforms for harnessing high-performance, high-stability operation from a compact-footprint, low-power packaged device. An ECL device with narrow linewidth and low noise is disclosed, the device comprising a PLC device and a gain chip butt-coupled to each other. The PLC device has a planar Bragg grating (PBG) integrated onto a rectangular waveguide. The PLC device has anti-reflection coatings (ARC) on its input facet and output facet. The waveguide is designed to be selective of a single polarization. The gain chip has high-reflection coating (HRC) on a back facet and an ARC on a front facet. An operating wavelength of the ECL is aligned to a longer wavelength red slope of a reflectivity spectrum of the PBG. The operating wavelength may be tuned thermally, electrically, or thermo-electrically.

Abstract: The present invention provides a semiconductor laser that operates with a frequency feedback control loop for frequency-noise reduction. The frequency-reduction architecture utilizes a homodyne optical phase demodulation approach. Such phase demodulation can be implemented with help of an unbalanced Michelson interferometer with fiber optics delay and symmetrical ‘n×n’ optical coupler. The entire demodulator is packaged in a small form-factor package which doesn't have any mechanical resonance in the sensing bandwidth, and has very low sensitivity to the external acoustic or vibration induced noise sources.

Abstract: A planar photonic waveguide incorporating a Bragg grating having an asymmetric reflectance spectrum (200). In one embodiment, “red” side lobes (210) are suppressed relative to “blue” side lobes (220). In another embodiment, blue side lobes are suppressed relative to red side lobes. The waveguide has a core with dimensions which vary along the length of the grating so as to produce the asymmetric reflectance spectrum. Where red side lobes are suppressed, the width of the core is greatest in the middle of the grating and decreases symmetrically towards each end.

Abstract: An optical phase lock loop (OPLL) system is disclosed that includes a master external cavity laser (ECL), and a substantially identical slave ECL. The master and slave ECLs are fabricated using a planar semiconductor device with waveguide-integrated planar Bragg gratings (PBG). Both the master and slave ECLs have a narrow linewidth and a low frequency-noise. Each of the ECLs has their own controller-modulator circuits for thermal tuning or electrical tuning via direct modulation. A laser-select-logic (LSL) module receives and processes a filtered phase error signal from a loop filter coupled to an electronic PLL device, and directs the processed phase error signal to one or both of the master and slave controller-modulators according to a logical determination of a required mode of operation of the OPLL system in order to achieve a stable and identical phase performance of the master and the slave ECLs.

Abstract: Systems and methods are disclosed for distributed temperature and strain sensing along a length of an infrastructure. Two optical sources, such as, external cavity lasers with a narrow linewidth, are used for launching a probe signal into a sensing fiber coupled to the infrastructure, and for producing a local oscillation signal, respectively. The optical sources are coherently locked with a predefined frequency offset with respect to each other, the predefined frequency offset being in the order of the Brillouin frequency shift. The optical sources are included in an optical phase lock loop (OPLL) system. A balanced heterodyne receiver for narrow band detection at radio frequency (RF) bandwidth receives an optical signal generated by coherent mixing of a backscattered probe signal with the Brillouin frequency shift and the local oscillation signal, and produces an output indicative of one or both of a measured temperature and a measured strain.

Abstract: The present invention relates to various methods of fabricating Planar Bragg Gratings (PBG) in a doped waveguide in a Planar Lightwave Circuit (PLC) device, suppressing unwanted parasitic grating effects during fabrication of the device. One approach to reduce parasitic gratings is to use a hard mask before the waveguide photolithography and etch, that results in a steeper sidewall angle that reduces or eliminates the parasitic grating effect. Another method of reducing parasitic grating effect is to deposit a layer of developable Bottom Anti Reflective Coating (BARC) prior to depositing the photo resist for waveguide etch. A third method of resisting parasitic gratings comprises using a planarizing undoped silica layer as a barrier layer on top of the core. During subsequent high temperature annealing germanium outdiffuses laterally into the cladding.

Abstract: The present invention relates to external cavity laser (ECL) apparatuses and manufacturing processes, and more particularly to implementing low noise narrow bandwidth ECLs on planar lightwave circuit (PLC) platforms for harnessing high-performance, high-stability operation from a compact-footprint, low-power packaged device. An ECL device with narrow linewidth and low noise is disclosed, the device comprising a PLC device and a gain chip butt-coupled to each other. The PLC device has a planar Bragg grating (PBG) integrated onto a rectangular waveguide. The PLC device has anti-reflection coatings (ARC) on its input facet and output facet. The waveguide is designed to be selective of a single polarization. The gain chip has high-reflection coating (HRC) on a back facet and an ARC on a front facet. An operating wavelength of the ECL is aligned to a longer wavelength red slope of a reflectivity spectrum of the PBG. The operating wavelength may be tuned thermally, electrically, or thermo-electrically.

Abstract: An optical phase lock loop (OPLL) system is disclosed that includes a master external cavity laser (ECL), and a substantially identical slave ECL. The master and slave ECLs are fabricated using a planar semiconductor device with waveguide-integrated planar Bragg gratings (PBG). Both the master and slave ECLs have a narrow linewidth and a low frequency-noise. Each of the ECLs has their own controller-modulator circuits for thermal tuning or electrical tuning via direct modulation. A laser-select-logic (LSL) module receives and processes a filtered phase error signal from a loop filter coupled to an electronic PLL device, and directs the processed phase error signal to one or both of the master and slave controller-modulators according to a logical determination of a required mode of operation of the OPLL system in order to achieve a stable and identical phase performance of the master and the slave ECLs.