Abstract: A micromirror array is used to form optical apparatus useful in WDM optical networks. In one embodiment, the micromirror array is used to insert a desired attenuation in individual channels for purposes such as equalization. In another embodiment, the micromirror array is used to form an optical monitor useful as an optical spectrum analyzer.

Abstract: A micromirror array is used to form optical apparatus useful in WDM optical networks. In one embodiment, the micromirror array is used to insert a desired attenuation in individual channels for purposes such as equalization. In another embodiment, the micromirror array is used to form an optical monitor useful as an optical spectrum analyzer.

Abstract: An optical switch uses a MEMS device to insert a highly reflective shutter in a gap between a pair of coaxially aligned fibers. When the switch is closed, an input optical signal passes with little loss through the gap. When the switch is open and the shutter is positioned in the gap, an input optical signal incident on the shutter is reflected back into the input fiber. Such light is diverted by an optical circulator into a new path.

Abstract: An optical attenuator for use in optical power regulation uses a shutter to control the insertion loss of a gap in a pair of substantially coaxially aligned waveguides, for example a pair of optical fibers. The shutter is part of a MEMS accuator device and is coupled to the movable one of a pair of spaced plates, the movable plate being movable by a voltage applied between the pair of plates. To regulate the power, a small portion of the optical power is abstracted and used to derive a control voltage that is applied to the optical attenuator for varying the attenuation inserted in the optical wave path.

Abstract: Arrayed waveguide grating routers are used to form 1.times.N demultiplexers and N.times.1 multiplexers to form channel drop modules in a WDM optical network. The demultiplexer and the multiplexer are interconnected by optical waveguides in which are inserted optical switches provided by MEMs devices that can be used to reflect incident optical signals backwards for dropping channels or to both transmit and reflect incident optical signals to drop and detect channels.

Abstract: A passive optical network for the downstream dense wavelength division multiplexing communication of data between a host terminal complex (HTC) and a plurality of optical network units (ONUs), and for the upstream communication of data from the ONUs to the HTC. The network includes a routing device for distributing downstream data signals contained in a common frequency band among a plurality of fiber drop lines for providing a corresponding wavelength to a corresponding ONU. The routing device also combines upstream data signals contained in a frequency band other than the downstream common frequency band, which are input to the routing device on the plurality of fiber drop lines, to a multi-wavelength signal which is provided to the HTC. In a preferred embodiment, the upstream data signals are output by the routing device to a broadcast port.

Abstract: WDM optical fiber communications entails bidirectional transmission with at least two WDM channels in opposite transmission directions in a single fiber. As compared with unidirectional transmission, a number of capacity-limiting considerations are relaxed. Operation using in-ground dispersion-shifted fiber permits system capacities of conventional unidirectional WDM.

Abstract: An optical communication system is disclosed including an all-optical device whose output modulated optical beam is locked to an input modulated optical beam. In a specific embodiment of the system, the device may be a self-electro-optic effect device (SEED), which is operated as an oscillator by means of an associated tank circuit. Such an embodiment permits recovery of a clock frequency from a bit stream which is input into the device. When the output of the device is directed into an optical decision element, an all-optical regenerator may be realized.

Abstract: Stability of a pump laser for activating an erbium amplifier is enhanced by a grating which results in laser operation in the coherence collapse regime.

Abstract: An all-optical flip-flop device is achieved by employing two optical amplifiers arranged so that they together operate in only one of two stable states at a given time. In a first stable state of operation, the first optical amplifier behaves as a laser having a first predetermined characteristic wavelength. The arrangement is switched to a second stable state of operation in which the second optical amplifier behaves as a laser having a second characteristic wavelength, where the first and second characteristic wavelengths are at least nominally different, when an optical signal pulse is received at the input of the first optical amplifier. The arrangement is switched back to the first stable state when an optical signal pulse is received at the input of the second optical amplifier.

Abstract: An optical fiber system and method is disclosed that overcomes the effects of polarization gain anisotropy in rare-earth doped optical fiber amplifiers. An optical fiber has at least one rare-earth doped fiber portion for amplifying a light signal. Light signals are passed through the doped fiber portion in a first incident polarized state. This light signal is reflected back from a Faraday effect mirror and through the doped fiber portion in its orthogonal polarized state so as to overcome the effects of polarization gain anisotropy. The rare-earth doped amplifier is preferably an erbium-doped fiber amplifier. A signal is initially passed through one part of a Faraday optical circulator and out a second port into the doped amplifier. On its return pass, the light signal enters the second port and then exits a third port. The optical amplifier can include a wavelength division multiplexor coupler for merging the pump signal with the original light signal.

Abstract: An all-optical inverter device is achieved by employing an optical amplifier having a optical filter positioned in a feedback loop arranged so that an output signal of the optical amplifier having a first characteristic wavelength is inversely related to an input signal to the optical amplifier having a second characteristic wavelength.

Abstract: For a group of optical amplifiers, pump beams from an array of lasers are mixed together to form a plurality of composite pump beams. Each composite pump beam is distributed to the pump port of a particular optical amplifier. The composite pump beam improves the reliability of each optical amplifier. Rather than having catastrophic failure of an optical amplifier occasioned by the failure of its pump laser, it is now possible to maintain full operation of the group of optical amplifiers even though one or more lasers fail.

Abstract: Indiscriminately exciting the modes of a multi-mode optical fiber amplifier is avoided by an optical fiber amplifier design in which the excitation of pump modes in the core of a multi-mode fiber is controlled by controlling the pump light launching. The pump light is directed substantially along the center axis of a multi-mode fiber within a predetermined launch angle. Rather than exciting all modes, only lower order modes are affected.

Abstract: In a transmission system having concatenated optical amplifiers, gain saturation of the optical amplifiers at any stage is caused by the extraction of power from the amplifier by the ASE and amplification of the signal and of the ASE from previous stages. Three methods of operating transmission systems are classsified as free-running, constant-total power and constant-signal power. Differences in performance of the three systems arise from the propagation of signal power and the buildup of the ASE. It is now disclosed that the buildup of ASE noise in a system of either lumped or distributed concatenated optical amplifers can be limited by operating at least a plurality of the optical amplifers to provide unsaturated gain which is greater than the loss of the system and/or each optical amplifier is operated in its saturated state.

Abstract: This invention relates to an Erbium-doped fiber amplifier having multiple stages of amplification for providing enhanced performance. More specifically, optical means is located intermediate first and second stages of doped optical amplifying fibers adapted to receive a pump signal at a pump wavelength where the optical means is adapted to modify the net gain characteristics of the multi-stage amplifier. Presently, all known Erbium-doped fiber amplifiers utilize relatively simple single stage amplifiers which support required ancillary optically passive components such as isolators, filters, pump multiplexers, power monitors and the like at either end of the amplifier.

Abstract: An optical communication system is disclosed including an all-optical device whose output modulated optical beam is locked to an input modulated optical beam. In a specific embodiment of the system, the device may be a self-electro-optic effect device (SEED), which is operated as an oscillator by means of an associated tank circuit. Such an embodiment permits recovery of a clock frequency from a bit stream which is input into the device. When the output of the device is directed into an optical decision element, an all-optical regenerator may be realized.

Abstract: In this invention there is disclosed a multi-stage optical fiber amplifier for providing a new functon, that of gain equalization. The disclosed multi-stage optical fiber amplifier comprises at least two stages of amplification where each stage comprises an amplifying fiber having a different gain spectrum. In one embodiment the two stages, which can be pumped separately, have different dopant compositions to provide each stage with a different gain spectrum. The disclosed multi-stage optical fiber amplifier provides overall gain spectrum equalization of the amplified channels of long haul transmission lines. Typically, gain equalization can adjust the gain of one channel while maintaining the gain of a second channel constant. When used in combination with automatic gain control, the amplifier gain can be equalized dynamically to compensate for random variations in the relative optical power of wavelength-multiplexed signals to prevent system impairment caused by low-power channels.

Abstract: This invention relates to an Erbium doped fiber amplifier having improved operating characteristics. Parameters which determine the operating characteristics of an erbium doped fiber amplifier are the concentration of erbium in the core of a fiber; the ratio of the radius of the core of the fiber doped with erbium relative to the radius of the core of the fiber, and, the length of the fiber. It is now recognized that improved fiber amplifier performance can be obtained by varying the core-cladding refractive index difference of the fiber. The various parameters are here defined for providing an erbium doped fiber amplifier having optimum gain characteristics.

Abstract: This invention is a rare earth doped optical amplifier with increased gain and lowered pump thresholds. The amplifying scheme is based on a 3 level lasing system rather than the more prevalent 4 level lasing system. Additionally, the transmission mode of the optical fiber at the pump wavelength has a radius which is substantially equal to or greater than the radius of the distribution profile of the rare earth ions in the fiber amplifier core. With the inventive amplifier, a gain of 37 dB and a saturation power of 11.3 dBm has been obtained with only 54 mW of launch power at .lambda.=1.49 .mu.m.