Abstract: Optical communications networks are provided that allow network maintainers to monitor or control subsystems using communications links other than optical telemetry links. The communications links may be wireless links or may be based on any other suitable communications links such as links using Ethernet cables or telephone lines. Network subsystems may be provided that include communications circuitry for communicating over the communications links. A network maintainer may use network control and management software implemented on computer equipment at a different location than the subsystems to communicate with the subsystems over the communications links. Because the communications links may function independently from the optical telemetry channels in the network, new subsystems may be added to the network without disturbing the existing network management software or telemetry arrangement.

Abstract: We describe an optical spectral filtering device and associated method for selectively directing a portion of a wavelength multiplexed input signal, entering through an optical fiber, into one or more output signals provided to one or more optical fibers and/or electronic outputs. The optical filtering is accomplished using free-space diffractive wavelength demultiplexing optics combined with a fixed (permanent) patterned structure located in the spectrally dispersed image plane. The structure can block or direct a selected spectral portion of the optical signal to one or more separate outputs, such as an optical fiber or power detector. A single active element in the optical path is used to spatially shift, or steer, the entire input spectrum at the dispersed spectral image plane, to control the portion of the input spectrum illuminating specific features on the permanent patterned structure.

Abstract: Gain-clamped semiconductor optical amplifier devices are provided that have adjustable gain levels. Optical amplifiers and other network equipment based on the semiconductor optical amplifier devices are also provided. The devices may include feedback structures that form a lasing cavity. The optical feedback associated with the feedback structures may be adjusted to control the clamped gain of the devices.

Abstract: An optical device for dynamic gain adjusting includes a dynamic gain adjusting filter having one or more semiconductor optical amplifiers. The dynamic gain adjusting filter may allow dynamically-adjustable spectral gain characteristics. A dynamic gain adjusting filter may be part of an amplifier module or other optical device module, or as an optical module itself. The dynamic gain adjusting filter may be used to reduce gain ripple, control gain tilt, and/or compensate for other gain variations. The one or more semiconductor optical amplifiers of the dynamic gain adjusting filter may be designed and/or controlled to produce different gain profiles. For example, the active region of the semiconductor optical device may comprise several subregions having different structures, dimensions, and/or doping characteristics.

Abstract: Semiconductor optical amplifier devices and optical amplifiers are provided for handling optical data signals carried on wavelength-division-multiplexing channels in fiber-optic links. The optical amplifiers may have multiple semiconductor optical amplifier devices separated by isolators to reduce backwards scattered light and thereby improve their output power handing capabilities. Waveguide structures on the semiconductor optical amplifier devices may be used to provide lateral light confinement during optical amplification. Nonuniform drive current densities may be used along the lengths of the semiconductor waveguide structures to support increased output powers.

Abstract: Fiber-based dispersion compensation elements are provided for use in optical amplifiers and other optical network equipment that handle optical data signals in fiber-optic communications links. The dispersion compensation elements may include chirped superstructure fiber gratings. Systems and method for fabricating the dispersion compensation elements using ultraviolet light are provided.

Abstract: Optical network equipment is provided. The optical network equipment may include optical amplifiers. Control units may be used to control components in the equipment such as gain stage pump lasers. Sensor data may be obtained from sensors in the equipment. The control units may store the sensor data and control data and other information on the operation of the equipment. The stored data may be used in troubleshooting, network maintenance, and set up procedures. Data may be saved when a data storage command is received by the equipment or may be saved when data storage trigger criteria are satisfied. A user may be provided with the ability to customize the trigger criteria and the data storage parameters.

Abstract: Optical network equipment is provided. The optical network equipment may include equipment with optical gain stages such as optical amplifiers. The equipment may be used in fiber-optic communications links in communications networks. The gain stages may be based on optically-pumped rare-earth-doped fiber. The equipment may include optical monitors that are used to measure the power of optical data signals propagating through the equipment. A control unit in the equipment may be used to analyze the optical data signal power measurements. The results of the analysis may allow the control unit to determine whether the amplifier output power is affected by gain transients or drift effects. Gain transients may be suppressed by making pump power adjustments. The control unit may compensate for the effects of drift by making pump power adjustments or by adjusting components such as variable optical attenuators or dynamic filters.

Abstract: Optical amplifiers and optical network equipment are provided that have optical gain stages for amplifying optical signals on a fiber-optic communications link. The optical gain stages may be based on optically pumped fiber such as rare-earth-doped fiber. The fiber may be optically pumped using laser diode pumps. A control unit may be provided in the amplifiers or other equipment to control the laser diode pumps. Optical monitors may be used to measure the optical signals in the amplifiers or other equipment. The pump powers of the laser diode pumps may be adjusted in real time by the control unit based on the measured optical signals to suppress gain transients due to input power fluctuations on the link. To minimize the impact of pump-induced noise, the control unit may avoid operating the laser diodes at powers at which the laser diodes are most susceptible to mode partition noise.

Abstract: An optical amplifier for fiber-optic communications systems is provided. The optical amplifier may have variable optical attenuators for adjusting the power on each of multiple input channels. A multiplexer may be used to combine the input channels onto a single optical path. A gain stage may be used to provide optical gain for the optical signals on the optical path. A control unit may be used to control the variable optical attenuators and the gain stage to produce a desired spectrum.

Abstract: Raman amplifiers are provided for amplifying signals on optical communications links. The Raman amplifiers may be pumped using an unpolarized Raman pump source. Gain for the source may be provided by a semiconductor device that provides linearly-polarized pump light. A polarization-maintaining fiber may be coupled directly to the semiconductor device at a 45° orientation with respect to the polarization of the light emitted by the device. Light from the semiconductor device may be launched equally into both the slow and fast axes of the fiber. A fiber Bragg grating reflector may be used to stabilize the pump. Pump light traveling along the slow and fast axes becomes spatially separated by more than the coherence length of the multiple quantum well device. The pump light exiting the end of the polarization-maintaining fiber is therefore unpolarized.

Abstract: Raman amplifier equipment for fiber-optic communications links is provided. Raman pump light at a first wavelength or wavelengths may be used to optically pump fiber in a communications link to produce Raman gain. Raman pump light at a second wavelength or wavelengths may be used to optically pump the fiber to produce Raman gain for channels at different wavelengths in the communications link. The Raman gain produced by the pump light at the first wavelength or wavelengths increases the reach of the Raman pump light at the second wavelength or wavelengths into the fiber to improve the noise figure of the amplifier.

Abstract: Optical amplifiers and other optical network equipment for handling optical data signals in fiber-optic communications links are provided. Optical fiber that is pumped by laser diode pumps is used to provide optical gain. The laser diode pumps may be based on laser diode devices that do not have temperature controllers and integral back facet monitors. A control unit may be used to keep track of the age of the laser diode pumps. Information on the age of the pumps may be used to determine the maximum allowable drive current for driving the pumps. Information on the age of the pumps may also be used to select an appropriate drive current level during operation of the pumps.

Abstract: Optical amplifiers and other optical network equipment for handling optical data signals in fiber-optic communications links are provided. Optical fiber that is pumped by laser diode pumps may be used to provide optical gain. A circulator may be used in an amplifier to direct the optical data signals through a double-pass portion of the amplifier. A reflector at the end of the double-pass portion of the amplifier may direct forward-propagating optical data signals from the circulator in the backwards direction. Optical components such as spectral filters, and attenuators, gain stages, access ports, and other components may be located in the double-pass portion. A control unit may be used to suppress gain transients in the double-pass portion.

Abstract: Optical amplifiers and other optical network equipment are provided for use in fiber-optic communications networks. The equipment may include dynamic spectral filters and optical channel monitors. Control units may be used to control the operation of the equipment. Components in the equipment may be interconnected using communications paths. The communications paths may include paths such as synchronous and asynchronous paths, point-to-point and multidrop paths, RS-232 paths, two-wire interface bus paths, parallel bus paths, and synchronous serial interface paths. The communications paths may be used to support an extensible equipment architecture that allows equipment features to be changed and added.

Abstract: Optical amplifiers and upgrade modules for the optical amplifier are provided. The optical amplifiers and upgrade modules may be used to amplify optical signals in fiber-optic communications networks. Optical gain may be produced by erbium-doped fiber amplifier stages and Raman amplifier arrangements. When an upgrade module is used to upgrade an amplifier, the light that is provided to the upgraded amplifier may be routed through optical components in the upgrade module. The upgrade module may be used to expand the optical bandwidth of the amplifier or to add Raman preamplification capabilities. When the upgrade module is used to add Raman gain, erbium-doped fiber that was used in the amplifier prior to upgrading may be removed from the optical path during the upgrade process to help maintain the desired spectral shape for the upgraded amplifier. Dynamic and passive filters may also be used to help maintain a desired spectral shape. Hot upgrades may be performed using the amplifiers and upgrade modules.

Abstract: Optical channel monitor depolarizers are provided. The depolarizers may be used to reduce the effects of polarization-dependent loss on optical channel power measurements made in optical amplifiers or other optical network equipment. The channel power measurements may be used in controlling optical amplifiers and other equipment in wavelength-division-multiplexing communications links.

Abstract: Optical amplifier equipment is provided for wavelength-division-multiplexing optical communications links that support multiple channels operating at different wavelengths. The optical amplifier equipment may be based on distributed or discrete Raman amplifiers, rare-earth-doped fiber amplifiers such as erbium-doped fiber amplifiers, or other suitable amplifiers. Optical signals on the link may be monitored using optical monitoring equipment. The optical power of the signals on a particular channel or channels that are always present on the link may be measured. The total power of the optical signals may also be measured. The pump power in the amplifier equipment may be adjusted to suppress gain transients. The pump power may be adjusted based on the measured power of the guaranteed signals. Pump power may also be adjusted based on the measured total power.

Abstract: Optical amplifiers and other optical network equipment is provided for use in fiber-optic communications networks. The equipment may include dynamic spectral filters and optical channel monitors. Temperature controllers may be used to control the temperatures of the dynamic spectral filters, optical channel monitors, and other components such as erbium-doped fiber coils in optical gain stages. Control units in the equipment may provide alarms based on status information and data from the dynamic spectral filters, optical channel monitors, temperature sensors, and other components.

Abstract: Optical detector components in a fiber-optic communication system are temperature stabilized. The optical detector components may be part of an optical amplifier, a receiver, or other optical device. A temperature-controlled housing may be used to stabilize the temperature of a photodiode and/or a transimpedance amplifier of the optical detector. The housing may additionally be used to stabilize the temperature of the coils of a fiber optic amplifier and possibly other components.