Abstract: An embodiment of a system for performing measurements in a downhole environment includes an optical interrogation assembly configured to emit a pulsed optical signal, the pulsed optical signal including a selected wavelength, and an optical fiber configured to be disposed in a borehole in an earth formation and configured to receive the pulsed optical signal, the optical fiber having at least one measurement location disposed therein and configured to at least partially reflect the pulsed optical signal. The optical fiber has a core and a cladding, at least a portion of the core made from at least substantially pure silica, and the optical fiber has a refractive index profile configured to have a zero dispersion wavelength that is greater than the selected wavelength.

Abstract: An embodiment of a system for performing measurements in a downhole environment includes an optical interrogation assembly configured to emit a pulsed optical signal, the pulsed optical signal including a selected wavelength, and an optical fiber configured to be disposed in a borehole in an earth formation and configured to receive the pulsed optical signal, the optical fiber having at least one measurement location disposed therein and configured to at least partially reflect the pulsed optical signal. The optical fiber has a core and a cladding, at least a portion of the core made from at least substantially pure silica, and the optical fiber has a refractive index profile configured to have a zero dispersion wavelength that is greater than the selected wavelength.

Abstract: A method for producing a protected optical fiber with distributed sensors includes heating an optical fiber preform and drawing the heated optical fiber preform to form a drawn optical fiber. The method also includes coating the drawn optical fiber with a carbon coating after the optical fiber is drawn to provide a carbon coated optical fiber and then writing a series of fiber Bragg gratings (FBGs) into the carbon coated optical fiber to provide a carbon coated optical fiber with FBGs. The method further includes coating the carbon coated optical fiber with FBGs with one or more layers of a polymer to provide the protected optical fiber with distributed sensors, wherein the heating, drawing, carbon coating the drawn optical fiber, writing, coating the carbon coated optical fiber are performed in that sequence while the protected optical fiber is being produced.

Abstract: A universal inline functional module for operation with nonzero average gain G?0 dB over a bandwidth is provided. The module includes at least one optical functional element producing loss over the bandwidth and at least one rare-earth doped fiber segment. The module produces a flat gain spectrum to within a specified tolerance when made to operate at an average gain of 0 dB over the bandwidth.

Abstract: A universal inline functional module for operation with nonzero average gain G?0dB over a bandwidth is provided. The module includes at least one optical functional element producing loss over the bandwidth and at least one rare-earth doped fiber segment. The module produces a flat gain spectrum to within a specified tolerance when made to operate at an average gain of 0 dB over the bandwidth.

Abstract: A multi-channel optical amplifier arrangement operating over a particular bandwidth is provided. The amplifier arrangement includes at least one optical amplifier stage that includes a rare-earth doped optical waveguide, at least one pump source for supplying optical pump energy to the doped optical waveguide, and at least one coupler for coupling the optical pump energy to the doped optical waveguide. The amplifier arrangement also includes a dynamic range enhancer (DRE) having an input and an output and a plurality of distinct optical paths each selectively coupling the input to the output. At least two of the optical paths produce different gain spectra across the particular operating bandwidth. The DRE further includes an optical path selector for selecting any optical path from among the plurality of optical paths such that for all channels in the particular bandwidth the selected path optically couples the input to the output of the DRE.

Abstract: A method for increasing the number of channels amplified by an optical amplifier arrangement is provided. The optical amplifier arrangement includes at least one optical amplifier stage amplifying a first number of channels at a given average gain level. The method begins by selecting a second number of channels to be amplified by the optical amplifier arrangement. At least one additional optical amplifier stage is serially coupled to an input or output of the at least one optical amplifier stage to form a multistage optical amplifier arrangement. The gain shape of the multistage optical amplifier is adjusted to maintain, at the given average gain level or greater, a prescribed degree of gain flatness over an operating bandwidth in which the second number of channels are located.

Abstract: A multi-channel optical amplifier arrangement operating over a particular bandwidth is provided. The amplifier arrangement includes at least one optical amplifier stage that includes a rare-earth doped optical waveguide, at least one pump source for supplying optical pump energy to the doped optical waveguide, and at least one coupler for coupling the optical pump energy to the doped optical waveguide. The amplifier arrangement also includes a dynamic range enhancer (DRE) having an input and an output and a plurality of distinct optical paths each selectively coupling the input to the output. At least two of the optical paths produce different gain spectra across the particular operating bandwidth. The DRE further includes an optical path selector for selecting any optical path from among the plurality of optical paths such that for all channels in the particular bandwidth the selected path optically couples the input to the output of the DRE.

Abstract: A method for increasing the number of channels amplified by an optical amplifier arrangement is provided. The optical amplifier arrangement includes at least one optical amplifier stage amplifying a first number of channels at a given average gain level. The method begins by selecting a second number of channels to be amplified by the optical amplifier arrangement. At least one additional optical amplifier stage is serially coupled to an input or output of the at least one optical amplifier stage to form a multistage optical amplifier arrangement. The gain shape of the multistage optical amplifier is adjusted to maintain, at the given average gain level or greater, a prescribed degree of gain flatness over an operating bandwidth in which the second number of channels are located.

Abstract: An integrated optical device is provided for distributing optical pump energy. The device includes at least one input port for receiving optical energy, a plurality of output ports, and a user configurable optical network coupled to the input port for distributing the optical energy among the output ports in a prescribed manner in conformance with a user-selected configuration.

Abstract: An optical module is provided for performing a prescribed function such as dispersion compensation, for example. The optical module is to be integrated between stages of a multi-stage rare-earth doped optical amplifier. The module includes an input port for receiving optical energy from one stage of the rare-earth doped optical amplifier and a rare-earth doped planar waveguide coupled to the input port. An optically lossy, passive element is provided for performing the prescribed function. The optically lossy, passive element is coupled to the planar waveguide for receiving optical energy therefrom. An output port is coupled to the optically lossy, passive element for providing optical energy to another stage of the rare-earth doped optical amplifier.

Abstract: An integrated optical device is provided for distributing optical pump energy. The device includes at least one input port for receiving optical energy, a plurality of output ports, and a user configurable optical network coupled to the input port for distributing the optical energy among the output ports in a prescribed manner in conformance with a user-selected configuration.

Abstract: In accordance with the invention, a multiwavelength light source comprises a length of optical waveguide amplifier, a multiwavelength reflector for reflecting a plurality of different spectrally separated wavelengths optically coupled to one side of the amplifier and a low reflection output coupled to the other side. A broadband source is provided for passing broadband light to the multiwavelength reflector. In the preferred embodiment, the reflector is a plurality of reflective Bragg gratings, the waveguide amplifier is a length of rare-earth doped fiber (e.g. EDF) and the broadband source is the amplifier pumped to generate ASE. In operation, broadband light is transmitted to the gratings. Light of wavelength channels corresponding to the reflection wavelengths of the gratings is reflected back through the amplifier for further amplification before it arrives at the output.

Abstract: L-band EDFA (Er-doped fiber amplifier) characteristics are improved by provision of filter means in the C-band, the filter means having a figure of merit greater than 400dB.multidot.nm. The filter means can be discrete and/or distributed filter means. In preferred embodiments, two or more full C-band blazed fiber Bragg, gratings are used.

Abstract: We have found that the conversion efficiency of a Er/Yb-doped cladding pumped fiber amplifier increases with increasing signal input power. Thus, preamplification of the input signal by means of an Er-doped fiber amplifier can result in increased conversion efficiency of the cladding pumped power amplifier. Such increased efficiency is desirable, lessening heat removal problems and/or facilitating increased reliability.

Abstract: A wideband optical amplifier employs split-band architecture in which an optical signal passes through a common amplification stage and is then split to pass through parallel gain stages, each of which may be optimized for a particular band being traversed. A broadband grating reflector is used after the input gain section to reflect the signals of one of the bands so that they again will pass through the common input gain section before passing through gain section of the split structure dedicated to their particular wavelength. Meanwhile, the other signals pass through the reflector and move on through the gain section pertinent to their wavelength.

Abstract: In accordance with the invention, a temperature-dependent rare earth doped waveguide optical amplifier is compensated by a temperature-dependent loss filter. The filter characteristics are designed to be temperature-dependent filters so that the gain characteristic of the amplifier is compensated over a practical operating temperature range. In essence, the amplifier comprises a length of optical waveguide for transmitting optical signals, a rare earth doped amplifying region in the waveguide for amplifying the transmitted optical signals, a pumping source for optically pumping the amplifying region, and a temperature-dependent loss filter. A typical design compensates an EFDA to a variation of less than 1 dB over a temperature range of -40.degree. C. to 85.degree. C. and a spectral range of at least 20 nm.

Abstract: We have found that it is possible to make a multistage optical fiber amplifier having a substantially flat gain band of spectral width of 40 nm or more, excellent noise figure (e.g.,<4 dB) and output power. Such amplifiers can advantageously be used, for instance, in multichannel WDM systems and analog CATV systems. A significant aspect of the amplifier is the provision of an optical loss element (exemplarily a multi-grating optical fiber filter) that provides, at least at one wavelength in the gain band, an attenuation of more than G/3 dB, where G is the average amplifier gain (in dB) in the gain band. A further significant aspect of the amplifier is the use of relatively longer amplifier fibers, which facilitates attainment of high output power and low noise figure. Exemplarily, the amplifier is a 2-stage amplifier comprising silica-based Er-doped amplifier fiber, with three-Gaussian filters between the stages.

Abstract: Multistage Er-doped fiber amplifiers (EDFAs) are disclosed. They comprise a first stage that comprises Er and Al, and further comprise a second stage that comprises Er and a further rare earth element, exemplary Yb. Such multistage EDFAs can have advantageous characteristics e.g., a relatively wide flat gain region (e.g. 1544-1562 nm), and relatively high output power, without significant degradation of the noise figure. Exemplary, the amplifiers are used in WDM systems and in analog CATV systems.