Onetta, Inc.

Yongan Wu

Jun Ye

Chia-Chi Wang

Yan Sun

G Victor Treyz

James W Sulhoff

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.

Gain-clamped semiconductor optical amplifiers with adjustable gain levels

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.

Dynamic gain flattening in an optical communication system

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.

Semiconductor optical amplifier systems

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.

Optical amplifiers with stable output power under low input power conditions

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&deg; 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.

Pumps for Raman amplifier systems

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.

Optical amplifiers with age-based pump current limiters

Novel optical amplifier designs are disclosed. The optical amplifier generally comprises an amplification section having an anti-reflection coating on a first end face and a reflector optically coupled to a second end face. The amplification section of the amplifier interacts with the input and reflected optical signals to produce an amplified optical signal. The amplification section may include rare earth doped glass amplifiers (e.g., erbium-doped amplifiers), rare earth doped waveguide amplifiers (e.g. erbium-doped waveguide amplifiers), polymer amplifiers or parametric amplifiers. The amplifier may include a waveguide structure proximate the amplification section to confine optical signals within the amplification section and/or guide signals into and out of the amplifier. The amplifier may be combined with optical components for coupling signals between optical fibers and the amplifier. The waveguide may have a modified &ldquo;V&rdquo; shape where the &ldquo;V&rdquo; with at two legs. At least one leg of the &ldquo;V&rdquo; is bent so that both legs intersect the first end face substantially parallel to each other.

Double-pass optical amplifier

Multiwavelength Raman pumps for Raman amplifiers are provided. The multiwavelength Raman pumps may be based on semiconductor devices that have multiple source regions, each of which handles pump light at a different wavelength. An optical coupler such as a lens and isolator arrangement or an integral fiber lens may be used to couple pump light from the multiwavelength Raman pump into a fiber. A depolarizer may be used to depolarize the Raman pump light provided by the Raman pump. Gratings may be used to define the lasing wavelengths for the Raman pump. A number of tunable sources may be used on the semiconductor device. A fiber Bragg grating may be used to form an external cavity or coupled cavity arrangement for the semiconductor device.

Multiwavelength pumps for raman amplifier systems

A method and apparatus for shutting off a source of optical power to an optical fiber in the event of a cut in the fiber are disclosed. Embodiments of the invention are particularly suited in fiber optic communications systems that use Raman pumps for signal amplification. Optical power from the pump to a fiber is shut off in response to a change in a supervisor signal provided to a first end of the fiber. The supervisor signal is generally operated in an &ldquo;always-on&rdquo; mode to provide for fail-safe operation. The apparatus generally comprises a controller coupled to the source of optical power and means for coupling a supervisor signal, which has been provided to a first end of the fiber, to the controller. The method and/or apparatus may be incorporated into an optical communications system having an optical fiber and two or more hubs coupled to the fiber.

Safety latch for Raman amplifiers

Optical amplifiers with variable optical attenuators that are adjusted using a sublinear control scheme are provided. Instead of increasing the attenuation of the optical attenuator by Y dBs for each desired Y dBs in decreased optical amplifier gain, the attenuation of the variable optical attenuator is increased by less than Y dBs. This sublinear control scheme improves the noise figure performance of the optical amplifier at the expense of increased gain ripple. The overall performance of the optical amplifier may be improved, particularly in conditions in which the attenuations produced by the variable optical attenuator are relatively large.

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San Jose, CA, United States of America

Yongan Wu