Abstract: A method can be used for controlling optical power. Output optical power of an optical source is monitored and it is determined whether a preset test control signal is received. When the preset test control signal is not received, a data signal is modulated to output light of the optical source and a bias current of the optical source is adjusted according to an output optical power monitoring result of the optical source to implement automatic power control. When the preset test control signal is received, a test is started and a test signal is superimposed to the data signal to form a superimposed signal. The superimposed signal is modulated to the output light of the optical source. The output optical power monitoring result of the optical source is ignored during the test period to maintain the bias current of the optical source at a preset target value.

Abstract: A two-core optical fiber is provided for use in Brillouin distributed fiber sensor applications and systems. The two-core fiber includes a first and second core. Each core is configured to exhibit a Brillouin frequency shift greater than 30 Mhz relative to the other core. Further, each core possesses temperature and strain coefficients that differ from the other core. The cores can be configured to produce Brillouin frequency shift levels of at least 30 Mhz relative to one another. These differences in shift levels may be effected by adjustment of the material compositions, doping concentrations and/or refractive index profiles of each of the cores. These optical fibers may also be used in BOTDR- and BOTDA-based sensor systems and arrangements.

Abstract: Optical systems operable to emit an output beam having fast-switched wavelengths are provided. In one embodiment, an optical system includes a laser and a wavelength conversion device. The laser emits a pump beam that switches between at least two fundamental spectral peaks at different wavelengths at a wavelength cycling period that is shorter than a response time of the human eye. The wavelength conversion device includes a non-linear optical medium configured to phase match the frequency doubling of the at least two switched fundamental spectral peaks such that an output beam that switches between at least two frequency-converted spectral peaks at different converted-wavelengths is emitted from an output facet of the wavelength conversion device when the pump beam of the optical source is incident on an input facet of the wavelength conversion device.

Abstract: According to one embodiment, an optical sensing system may include a gated optical amplifier, one or more triggering devices, and an optical coupler. The gated optical amplifier can receive a pulse signal and transform the pulse signal into an amplified pulse signal having an amplified peak portion. The triggering devices can control the gated optical amplifier such that the gated optical amplifier is in the lossy state while the baseline portion of the pulse signal is transformed and the gated optical amplifier is in the gain state while the peak portion of the pulse signal is transformed. The amplified pulse signal can be transmitted to the sensing optical fiber and a sensed optical signal can be received, when the sensing optical fiber is connected to the optical coupler. Optionally, a second pulse signal and the sensed optical signal can be combined and detected with a coherent balanced detection technique.

Abstract: A sensing optical fiber comprising: a few-moded multi-segment core, said core comprising one core segment surrounded by another core segment, and at least one cladding surrounding said core; said core having an F factor (?m2) of 100 ?m2 to 350 ?m2, and is constructed to provide (i) an overlap integral between the fundamental optical guided mode and the fundamental acoustic guided mode of greater than 0.7 and (ii) the overlap integral between the LP11 optical guided mode and the fundamental acoustic guided mode at least 0.45.

Abstract: An optical fiber link suitable for use in a mode division multiplexing (MDM) optical transmission system is disclosed. The link has a first optical fiber having a core which supports the propagation and transmission of an optical signal with X LP modes at a wavelength of 1550 nm, wherein X is an integer greater than 1 and less than or equal to 20, the first fiber having a positive differential mode group delay between the LP01 and LP11 modes at a wavelength between 1530-1570. The link also has a second optical fiber having a core which supports the propagation and transmission of an optical signal with Y LP modes at a wavelength of 1550 nm, wherein Y is an integer greater than 1 and less than or equal to 20, said optical fiber having a negative differential mode group delay between the LP01 and LP11 modes at a wavelength between 1530-1570.

Abstract: A distributed Brillouin optical fiber sensing system employs a sensing optical fiber that supports two or more (i.e., few) guided modes. Pump light supported by one of the guided modes is used to form a dynamic Brillouin grating (DBG). Probe light supported by at least one of the other guided modes interacts with the DBG to form reflected probe light that is received and analyzed to determine a Brillouin frequency shift and a reflection location, which in turn allows for making a measurement of at least one condition along the sensing optical fiber. Supporting the pump and probe light in different guided modes results in the optical fiber sensing system having a higher spatial resolution than sensing systems where the pump light and probe light share a common guided mode.

Abstract: Some embodiments of a distributed Brillouin optical fiber sensing system employs a sensing optical fiber that supports two or more (i.e., few) guided modes. Pump light supported by one of the guided modes is used to form a dynamic Brillouin grating (DBG). Probe light supported by at least one of the other guided modes interacts with the DBG to form reflected probe light that is received and analyzed to determine a Brillouin frequency shift, a phase matching wavelength between probe and pump light, a reflection location, which in turn allows for making a measurement of at least one condition along the sensing optical fiber. Supporting the pump and probe light in different guided modes results in the optical fiber sensing system being able to simultaneously measure temperature and strain and having a higher spatial resolution than sensing systems where the pump light and probe light share a common guided mode.

Abstract: Photodarkening resistant optical fiber lasing media and fiber lasers incorporating the same are disclosed. In one embodiment, an optical fiber lasing medium includes a core portion formed from silica-based glass comprising a rare-earth dopant and deuterium, the core portion having an index of refraction nc, a numerical aperture NAc. A concentration of defect color centers in the core portion is less than 1×1016/cm3. Deuterium is combined with the defect color centers to form reacted defect color centers that do not absorb ultraviolet and visible wavelengths of light. A first cladding portion is formed from silica-based glass, the first cladding portion surrounding and directly contacting the core portion and having an index of refraction n1, wherein the index of refraction n1 of the first cladding portion is less than the index of refraction nc of the core portion. Methods of forming the photodarkening resistant optical fiber lasing media are also disclosed.

Abstract: A multi-wavelength distributed Bragg reflector (DBR) semiconductor laser is provided where DBR heating elements are positioned over the waveguide in the DBR section and define an interleaved temperature profile that generates multiple distinct reflection peaks corresponding to distinct temperature dependent Bragg wavelengths associated with the temperature profile. Neighboring pairs of heating elements of the DBR heating elements positioned over the waveguide in the DBR section are spaced along the direction of the axis of optical propagation by a distance that is equal to or greater than the laser chip thickness b to minimize the impact of thermal crosstalk between distinct temperature regions of the interleaved temperature profile.

Abstract: A nonlinear fluorescence imaging system and method for generating fluorescence imaging includes a pulsed laser source for generating laser pulses at a first wavelength and an optical pulse stretcher including one or more optical pulse stretcher fibers having a first dispersion parameter at the first wavelength. The system also includes a probe for interfacing with a sample to deliver the laser pulses and extract fluorescence signals excited in the sample. One or more optical delivery fibers are included for delivering the laser pulses and collecting nonlinear fluorescence signals. The optical delivery fiber has a second dispersion parameter at the first wavelength which is opposite a polarity of the first dispersion parameter. A detector detects images based on the collected fluorescence signals.

Abstract: Optical systems operable to emit multiple frequency-converted spectral peaks are provided. In one embodiment, an optical system includes an optical source and a wavelength conversion device. The optical source may include a laser configured to emit a pump beam having at least two fundamental spectral peaks. The wavelength conversion device may include a non-linear optical medium configured to phase match the second harmonic generation of each of the at least two fundamental spectral peaks and sum-frequency generation of the at least two fundamental spectral peaks such that an output beam comprising at least three frequency-converted spectral peaks having approximately equal power is emitted from an output facet of the wavelength conversion device when the pump beam of the optical source is incident on an input facet of the wavelength conversion device.

Abstract: Some embodiments of a distributed Brillouin optical fiber sensing system employs a sensing optical fiber that supports two or more (i.e., few) guided modes. Pump light supported by one of the guided modes is used to form a dynamic Brillouin grating (DBG). Probe light supported by at least one of the other guided modes interacts with the DBG to form reflected probe light that is received and analyzed to determine a Brillouin frequency shift, a phase matching wavelength between probe and pump light, a reflection location, which in turn allows for making a measurement of at least one condition along the sensing optical fiber. Supporting the pump and probe light in different guided modes results in the optical fiber sensing system being able to simultaneously measure temperature and strain and having a higher spatial resolution than sensing systems where the pump light and probe light share a common guided mode.

Abstract: A distributed Brillouin optical fiber sensing system employs a sensing optical fiber that supports two or more (i.e., few) guided modes. Pump light supported by one of the guided modes is used to form a dynamic Brillouin grating (DBG). Probe light supported by at least one of the other guided modes interacts with the DBG to form reflected probe light that is received and analyzed to determine a Brillouin frequency shift and a reflection location, which in turn allows for making a measurement of at least one condition along the sensing optical fiber. Supporting the pump and probe light in different guided modes results in the optical fiber sensing system having a higher spatial resolution than sensing systems where the pump light and probe light share a common guided mode.

Abstract: Optical systems operable to emit an output beam having fast-switched wavelengths are provided. In one embodiment, an optical system includes a laser and a wavelength conversion device. The laser emits a pump beam that switches between at least two fundamental spectral peaks at different wavelengths at a wavelength cycling period that is shorter than a response time of the human eye. The wavelength conversion device includes a non-linear optical medium configured to phase match the frequency doubling of the at least two switched fundamental spectral peaks such that an output beam that switches between at least two frequency-converted spectral peaks at different converted-wavelengths is emitted from an output facet of the wavelength conversion device when the pump beam of the optical source is incident on an input facet of the wavelength conversion device.

Abstract: Photodarkening resistant optical fiber lasing media and fiber lasers incorporating the same are disclosed. In one embodiment, an optical fiber lasing medium includes a core portion formed from silica-based glass comprising a rare-earth dopant and deuterium, the core portion having an index of refraction nc, a numerical aperture NAc. A concentration of defect color centers in the core portion is less than 1×1016/cm3. Deuterium is combined with the defect color centers to form reacted defect color centers that do not absorb ultraviolet and visible wavelengths of light. A first cladding portion is formed from silica-based glass, the first cladding portion surrounding and directly contacting the core portion and having an index of refraction n1, wherein the index of refraction n1 of the first cladding portion is less than the index of refraction ncof the core portion. Methods of forming the photodarkening resistant optical fiber lasing media are also disclosed.

Abstract: Optical systems operable to emit multiple frequency-converted spectral peaks are provided. In one embodiment, an optical system includes an optical source and a wavelength conversion device. The optical source may include a laser configured to emit a pump beam having at least two fundamental spectral peaks. The wavelength conversion device may include a non-linear optical medium configured to phase match the second harmonic generation of each of the at least two fundamental spectral peaks and sum-frequency generation of the at least two fundamental spectral peaks such that an output beam comprising at least three frequency-converted spectral peaks having approximately equal power is emitted from an output facet of the wavelength conversion device when the pump beam of the optical source is incident on an input facet of the wavelength conversion device.

Abstract: Disclosed herein are methods for laser welding together layers of transparent polymeric materials by first making high-contrast marks in transparent polymeric materials using femtosecond, picosecond or nanosecond pulsed fiber lasers and then creating localized welds at the areas of the high-contrast marks. Such welds can be formed in multiple layers of transparent polymeric materials. Systems for making welds and parts welded together according to the methods also disclosed.

Abstract: Methods for operating diode lasers are provided. According to one method, the diode laser comprises a wavelength selection section, a gain section and a saturable absorber. The method comprises applying a hybrid-control signal comprising a hybrid-control DC bias to the saturable absorber, and applying a hybrid-driving signal comprising a hybrid-driving DC bias and a hybrid-driving AC bias to the gain section. The hybrid signals are selected and the diode laser is configured such that a relatively high hybrid-control DC bias corresponds to a relatively low average of the output power of the diode laser, and a relatively low hybrid-control DC bias corresponds to a relatively high average of the output power of the diode laser. The hybrid-driving DC bias is between a switch-on threshold of the diode laser and a switch-off threshold of the diode laser, and the hybrid-driving AC bias is periodic.

Abstract: A system for passively scrambling and unscrambling a, pulse optical signal transmitted through a multi-mode optical fiber is provided. The system includes a scrambling unit connected between a signal receiving end of said transmission fiber and an optical signal source that includes an optical fiber which creates a differential delay between two groups of optical modes of the signal that is at least one bit period long such that said optical signal is passively scrambled, and an unscrambling unit connected to a signal transmitting end of said transmission fiber having an optical fiber that counteracts said differential delay between said two groups of optical modes of the signal such that said optical signal is passively unscrambled.