Abstract: The gain of a fiber amplifier is typically not uniform across the bandwidth used for amplifying optical communications signals. In a power fiber amplifier unit, having a fiber pre-amplifier and a fiber power amplifier, the gain tilt of the fiber power amplifier is generally set by the level of gain saturation. The gain tilt of the fiber pre-amplifier is adjustable by controlling the population inversion density in the amplifying medium. The gain tilt of the fiber pre-amplifier may be adjusted so as to at least partially compensate for the gain tilt of the power amplifier.

Abstract: Apparatus for coupling light into a fiber, such as a double clad fiber (DCF) having a core having a refractive index n1, surrounded by an inner cladding having refractive index n2 which is surrounded by an outer cladding having a refractive index n3, where n1>n2>n3. An optical coupler medium, referred to as a Fiber Space Division Multiplexor or FSDM, is formed on an exposed portion of the fiber inner cladding at a position along the length of the fiber without interfering with the continuity of its core and provides at, at least one position, the imaging of light external of the fiber into the inner cladding interface and its waveguiding with the inner cladding of the fiber. The FSDM coupler comprises an optical material in optical contact or integrated with the inner cladding and having a refractive index substantially equal to n2. The coupler medium may also be employed with a fiber having no core and where the inner cladding would function as a multimode core.

Abstract: An optical fiber splice apparatus has a covering that surrounds the splice between two optical fibers, and conducts residual pump energy in the fiber claddings away from the splice. This prevents the residual light from reaching components, such as plastic buffers, that are susceptible to failure from excess light absorption. The apparatus may use an optical epoxy covering that surrounds adjoining portions of both fibers, and that has a refractive index higher than that of the outermost fiber claddings. The covering may be surrounded by a glass capillary that is transparent to the residual light, and that conducts light from the covering further away from the splice. The capillary may be mounted in a metal housing by an adhesive epoxy that is transparent to the residual pump light, and can conduct light to an inner surface of the housing, which may be light absorbent to the wavelength range of the residual pump light.

Abstract: Optical pumping arrangements are provided for the broadband or multiple wavelength pumping of optical sources. Sources may be based on Raman gain media and may use multiple output couplers to couple out different wavelength ranges. Cascaded Raman resonator (CRR) configurations may also be used. Overlapping resonators at different wavelengths may be configured to share gain media, and may have separate portions in separate optical paths. Attenuation filters may also be used that are matched to the gain profile of a gain medium, to flatten the gain spectrum and allow equalization of gain to different output wavelengths. In one embodiment, polarization maintaining fiber is used to develop resonant conditions at different wavelengths in different polarization states. Wideband output gratings may be substituted for narrowband gratings to provide CRR configurations with a broader output band. Broadband amplification may also be provided by using a laser source operating in coherence collapse.

Abstract: A monitoring apparatus for a high power light source comprises a fiber medium containing a high power output for an application with a first monitoring tap optically coupled to the fiber medium for removing a small portion of light from the output to monitor the output power level. A photodetector is optically coupled to receive the light portion to monitor the output power level. The photodetector, however, has a predetermined saturation level below the power level provided from the first monitoring tap. Therefore, at least one light attenuator is provided between the first monitoring tap and the photodetector to provide a level of monitoring power within a range below the saturation level of the photodetector to accurately monitor changes in the output power present on the fiber medium of the light source.