Abstract: This invention describes new developments in Sagnac Raman amplifiers and cascade lasers to improve their performance. The Raman amplifier bandwidth is broadened by using a broadband pump or by combining a cladding-pumped fiber laser with the Sagnac Raman cavity. The broader bandwidth is also obtained by eliminating the need for polarization controllers in the Sagnac cavity by using an all polarization maintaining configuration, or at least using loop mirrors that maintain polarization. The polarization maintaining cavities have the added benefit of being environmentally stable and appropriate for turn-key operation. The noise arising from sources such as double Rayleigh scattering is reduced by using the Sagnac cavity in combination with a polarization diversity pumping scheme, where the pump is split along two axes of the fiber. This also leads to gain for the signal that is independent of the signal polarization.

Abstract: A fiber optic transmission system with low cost transmitter compensation includes an electro-absorption modulated laser operable to generate an optical signal for transmission over a fiber optic communication link. The system further includes a Raman amplifier stage coupled to the communication link, the Raman amplifier stage having a gain medium including a dispersion compensating fiber. The dispersion compensating fiber is operable to at least partially compensate for a distortion caused by the electro-absorption modulated laser. The Raman amplifier stage is operable to at least partially compensate for a loss associated with the dispersion compensation fiber.

Abstract: In one embodiment, an optical amplifier includes a gain medium operable to receive a plurality of signals each having a center wavelength and a noise figure associated with at least a portion of the amplifier and varying as a function of wavelength. At least two of the plurality of signals have launch powers that are a function of a magnitude of the noise figure measured at or near the center wavelength of that signal.

Abstract: A nonlinear polarization amplifier stage includes a gain medium operable, to receive a multiple wavelength optical signal. The amplifier stage also includes a pump assembly operable to generate at least one pump wavelength for introduction to the gain medium. The amplifier stage further includes a coupler operable to introduce the at least one pump wavelength to the gain medium to facilitate amplification of at least a portion of the multiple wavelength optical signal through nonlinear polarization. In one particular embodiment, at least a wavelength or an intensity of the at least one pump wavelength is manipulated to affect the shape of a gain curve associated with the multiple wavelength optical signal in the amplifier stage.

Abstract: An optical switch element is described, which includes a fixed layer disposed outwardly from a substrate and a movable mirror assembly disposed outwardly from the fixed layer. The moveable mirror assembly is operable to move relative to the fixed layer responsive to a voltage applied to the movable mirror assembly. In a particular embodiment, the movable mirror assembly includes an inner strip spaced apart from the fixed layer by a first distance and an outer strip disposed approximately adjacent to the inner strip and spaced apart from the fixed layer by a second distance which is greater than the first distance. The optical transmission of the optical switch element changes depending on the position of the movable mirror assembly.

Abstract: A fiber optic transmission system for a metropolitan area network includes a plurality of interface devices operable to be coupled to a fiber optic transmission link carrying an optical signal and having a length of 300 km or less. The link has a transmission loss associated with an unpumped state of the link, and the plurality of interface devices collectively introduce a loss of at least 6 decibels to the link. The system also includes a distributed Raman amplifier stage coupled to the link, the distributed Raman amplifier stage operable to pump at least a portion of the link to reduce the transmission loss of the at least a portion of the link compared to its unpumped state, the reduced link transmission loss facilitating allocation of at least a portion of a gain to at least partially offset the loss associated with the plurality of interface devices.

Abstract: A broadband fiber transmission system includes a transmission line with at least one zero dispersion wavelength &lgr;o and transmits an optical signal of &lgr;. The transmission line includes a distributed Raman amplifier that amplifies the optical signal through Raman gain. One or more pump sources are included and operated at wavelengths &lgr;p for generating a pump light to pump the Raman amplifier. &lgr; is close to &lgr;0 and &lgr;0 is less than 1540 nm or greater than 1560 nm.

Abstract: A broadband fiber transmission system includes a transmission line with at least one zero dispersion wavelength &lgr;o and transmits an optical signal of &lgr;. The transmission line includes a distributed Raman amplifier that amplifies the optical signal through Raman gain. One or more semiconductor lasers are included and operated at wavelengths &lgr;p for generating a pump light to pump the Raman amplifier. &lgr; is close to &lgr;o and &lgr;0 is less than 1540 nm or greater than 1560 nm.

Abstract: A non-linear optical loop mirror for processing optical signals comprises an optical fiber, a bi-directional amplifier, and a coupler. The optical fiber has a signal input and a signal output. At least a portion of the optical fiber includes a dispersion compensating fiber. At least a portion of the optical fiber forms a loop. The dispersion compensating fiber has an absolute magnitude of dispersion of at least 20 ps/nm-km for at least a portion of wavelengths in the optical signals. The bi-directional amplifier is coupled to the optical fiber. The coupler is coupled to a first portion of the optical fiber and a second portion of the optical fiber to form a fiber loop.

Abstract: In one aspect of the invention, an apparatus operable to convert wavelengths of a plurality of optical signals includes a coupler operable to receive a pump signal and a plurality of input signals each input signal comprising at least one wavelength different than the wavelengths of others of the plurality of input optical signals. The apparatus further includes an optical medium operable to receive the pump signal and the plurality of input signals from the couplet, wherein the pump signal and each of the plurality of input signals are synchronized to overlap at least partially during at least a part of the time spent traversing the optical medium to facilitate generation of a plurality of converted wavelength signals each comprising a wavelength that is different than the wavelengths of at least some of the plurality of input signals. Various embodiments can result in low cross-talk and/or low polarization sensitivity.

Abstract: A non-linear optical loop mirror for processing optical signals comprises an optical fiber, a bi-directional amplifier, and a coupler. The optical fiber has a signal input and a signal output. At least a portion of the optical fiber includes a dispersion compensating fiber. At least a portion of the optical fiber forms a loop. The dispersion compensating fiber has an absolute magnitude of dispersion of at least 20 ps/nm-km for at least a portion of wavelengths in the optical signals. The bi-directional amplifier is coupled to the optical fiber. The coupler is coupled to a first portion of the optical fiber and a second portion of the optical fiber to form a fiber loop.

Abstract: In one aspect of the invention, a gain equalizer comprises a wavelength division demultiplexer operable to separate one or more communication bands into a plurality of wavelengths and an array of phase shifter stages. Each phase shifter stage comprises a micro-electro-optic system (MEMS) device comprising a moveable mirror layer operable to receive a first copy of an input signal from a beam splitter and to reflect the first copy of the input signal for combination with a second copy of the input signal at an output to form an output signal. The moveable mirror layer is displaceable in a substantially piston-like motion to introduce a phase shift between the first and second signal copies at the output, the amplitude of the output signal varying depending on the displacement of the moveable mirror layer.

Abstract: In one aspect of the invention, an optical switching element includes a variable blazed grating operable to receive and reflect one or more input signals while the grating remains in a first position and to receive and diffract one or more input signals while the grating remains in a second position. The switching element further includes a first circulator operable to receive from the variable blazed grating a first output signal traveling approximately along the path of an input signal to the grating but in an approximately opposite direction to that input signal, and to redirect the first output signal from the path of the input signal.

Abstract: A Raman amplifier assembly includes a Raman amplifier configured to receive a signal from a signal source. The signal travels in an upstream direction in the Raman amplifier. A first pump source is coupled to the Raman amplifier. The first pump source produces a first pump beam that travels in a downstream direction and is counter-propagating relative to the signal. A second pump source is coupled to the Raman amplifier and produces a second pump beam that travels in the upstream direction. The second pump source has an average relative intensity noise of less than −80 dB/Hz.

Abstract: In one of several embodiments, a method of communicating optical signals comprises communicating a plurality of optical signals over an optical communications medium, wherein each of at least some of the plurality of optical signals comprises a launch power that is a function of a noise property measured at or near a center wavelength of that signal. Launch powers of the plurality of optical signals primarily decrease with increasing center wavelengths of the plurality of optical signals.

Abstract: An optical amplifier includes at least one Raman amplification stage. The Raman amplification stage includes one or more pump sources operable to generate a plurality of pump signals capable of being delivered to a gain medium carrying an optical signal. In one particular embodiment, at least one of the plurality of pump signals comprises a time modulated pump signal and wherein an amplified spontaneous emission penalty associated with the at least one time modulated pump signal comprises no more than fifteen (15) decibels.

Abstract: A broadband nonlinear polarization amplifier includes an input port for inputting an optical signal having a wavelength &lgr;. A distributed gain medium receives and amplifiers the optical signal through nonlinear polarization. The distributed gain medium has zero-dispersion at wavelength &lgr;0. A magnitude of dispersion at &lgr; is less than 50 ps/nm-km. One or more semiconductor lasers are operated at wavelengths &lgr;p for generating a pump light to pump the distributed gain medium. An output port outputs the amplified optical signal.

Abstract: A method of broadband amplification divides an optical signal of wavelength of 1430 nm to 1620 nm at a preselected wavelength into a first beam and a second beam. The first beam is directed to at least one optical amplifier and produces an amplified first beam. The second beam is directed to at least one rare earth doped fiber amplifier to produce an amplified second beam. The first and second amplified beams are combined.

Abstract: An optical switch element is described, which includes a fixed layer disposed outwardly from a substrate and a movable mirror assembly disposed outwardly from the fixed layer. The moveable mirror assembly is operable to move relative to the fixed layer responsive to a voltage applied to the movable mirror assembly. In a particular embodiment, the movable mirror assembly includes an inner strip spaced apart from the fixed layer by a first distance and an outer strip disposed approximately adjacent to the inner strip and spaced apart from the fixed layer by a second distance which is greater than the first distance. The optical transmission of the optical switch element changes depending on the position of the movable mirror assembly.

Abstract: A multi-stage Raman amplifier includes a first Raman amplifier stage having a first sloped gain profile operable to amplify a plurality of signal wavelengths, and a second Raman amplifier stage having a second sloped gain profile operable to amplify at least most of the plurality of signal wavelengths after those wavelengths have been amplified by the first stage. The second sloped gain profile is approximately complementary slope to the slope of the first sloped gain profile. The combined effect of the first and second Raman stages contributes to an approximately flat overall gain profile over the plurality of signal wavelengths.