Abstract: Packet loss in an optical network transporting Ethernet-based data traffic is reduced using a switch in a transmitting node. When the transmitting node of the optical network detects a fault in an optical link, the switch buffers incoming data traffic until the optical link is reestablished. The switch may be an Ethernet switch that re-routes data traffic along one or more additional optical fibers that are connected in parallel with a defunct optical fiber to reestablish the optical link between two nodes. The switch may also be an optical switch that is configured to re-route optical data traffic from a defunct optical fiber to a redundant optical fiber.

Abstract: A transmitter on an integrated circuit chip is disclosed that employs a laser, modulator, and a dispersion compensator module and a modulator for overcoming chromatic dispersion and polarization dependent loss effects. With the present invention, the dispersion compensator module is placed on a chip, either integrated or monolithic, for operation with a laser and a modulator without the need to compensate for dispersion within a separate unit that is not part of the chip. The dispersion compensator module can be implemented, for example, with a ring resonator, an etalon or a Mach-Zehnder interferometer. In a first aspect of the invention, the optical transmitter module of the present invention provides a cost-effective solution for upgrading from an existing optical network to a faster optical network, such as upgrading from a 2.5 Gbps to a 10 Gbps network.

Abstract: A method of determining an optical distance between two nodes of an optical network for chromatic dispersion compensation includes using existing optical supervisory channel components in each node to measure the “time-of-flight” of an optical signal having a known wavelength. The effective optical distance is determined based on the time-of-flight and known wavelength of the optical signal. The computed optical distance may then be used to compensate for the dispersion experienced by the optical signal when transmitted between the two nodes. Advantageously, the method allows tunable dispersion compensation of a wavelength channel to be periodically optimized at each node in response to incremental changes in environmental factors that affect the chromatic dispersion produced between the two nodes or in response to reconfigurations that affect the chromatic dispersion produced between the two nodes.

Abstract: An optical switch with a compact form factor includes a multiple-fiber collimator and an angle tuning element for deflecting an optical beam from an input fiber into one of at least two output fibers. The angle tuning element may be provided between a pair of coaxially-aligned collimators, one of which is the multiple-fiber collimator. Alternatively, the angle tuning element may be provided between the multiple-fiber collimator and a reflective surface, so that only one collimator is required and the optical switch may be designed to have its input and output ports on the same side.

Abstract: An optical switching device includes an array of liquid crystal macropixels, wherein each macropixel includes at least two liquid crystal subpixels. The subpixels may be controlled together to act as a single polarizing pixel, or independently to act as multiple polarizing pixels. When the switching device processes a WDM having a wide channel spacing, the subpixels are controlled together, and when the switching device processes a WDM having a narrow channel spacing, each subpixel is controlled independently.

Abstract: A transmitter on an integrated circuit chip is disclosed that employs a laser, modulator, and a dispersion compensator module and a modulator for overcoming chromatic dispersion and polarization dependent loss effects. With the present invention, the dispersion compensator module is placed on a chip, either integrated or monolithic, for operation with a laser and a modulator without the need to compensate for dispersion within a separate unit that is not part of the chip. The dispersion compensator module can be implemented, for example, with a ring resonator, an etalon or a Mach-Zehnder interferometer. In a first aspect of the invention, the optical transmitter module of the present invention provides a cost-effective solution for upgrading from an existing optical network to a faster optical network, such as upgrading from a 2.5 Gbps to a 10 Gbps network.

Abstract: An optical amplifier that is configured to amplify multiple optical signals using time-multiplexed optical energy pulses. The time-multiplexed optical energy pulses are supplied to multiple gain blocks of the optical amplifier in an alternating manner and each of the gain blocks uses the optical energy pulses that it receives to amplify one of the multiple optical signals. An optical amplifier may be configured with an optical switch to perform a switching function to direct the time-multiplexed optical energy pulses received from the pump laser to the gain blocks in an alternating manner. The total optical energy contained in each optical energy pulse may be independently controlled by varying its duty cycle or amplitude.

Abstract: An optical device is configured to perform both switching and attenuation of an optical beam in response to a single control signal. The optical device includes a liquid-crystal-based beam-polarizing element having polarization-conditioning regions that are controlled using a common electrode. The first polarization-conditioning region conditions the polarization of the input beam in order to separate the input beam into a primary component and a residual component. The second and third polarization-conditioning regions change the polarization of the primary component and the residual component, respectively. The primary component is directed to an output port after it has been attenuated based on its polarization state. The residual component, after passing through the third polarization-conditioning region, has its intensity further reduced based on its polarization state.

Abstract: A supervisory signal is superimposed onto a high-speed data stream so that the number of optical transceivers needed by an optical network is reduced. The supervisory signal is superimposed onto the high-speed data stream as an in-band modulation of the data stream. To improve signal-to-noise ratio of the in-band supervisory signal, the supervisory signal is first modulated to a higher frequency before it is superimposed onto the high-speed data stream.

Abstract: A method and apparatus for multiplexing multiple Ethernet-based data streams in an optical network reduce the number of optical transceivers required by the optical network. Multiple data streams are multiplexed into a combined data stream, transmitted from a node in the optical network as the combined data stream, and demultiplexed at the receiving node. Data streams are multiplexed and demultiplexed at the bit level, and packets from each data stream are routed based on a VLAN tag that is contained in the header of each packet. By transmitting the information contained in multiple data streams as a single multiplexed data stream, the number of optical transceivers required for the optical network may be reduced by more than half. An optical supervisory channel may also be bundled with one of the data streams to eliminate the need for a dedicated transceiver for the optical supervisory channel.

Abstract: One embodiment of the present invention sets forth a system for compensating for the detrimental effects of all-order polarization mode dispersion. The system includes a broadband polarization correction module cascaded with a broadband phase correction module. Each of the modules includes an AWG chip as a wavelength dispersing element, as opposed to a bulk optic grating. Thus, aligning the optical components used to separate light beams of different wavelengths within the system is simpler, and the size of the overall system is reduced. Further, the AWG chip may be more easily aligned with the other optical components within the system, with the alignment being more robust, both mechanically and thermally, relative to prior art systems that include bulk optics. Since AWG chips may be fabricated using well-known fabrication techniques, overall manufacturability is also improved and costs are reduced.

Abstract: One embodiment of the present invention includes a plurality of first optical elements and a second optical element optically coupled to one another in cascaded fashion. Each first optical element has a group delay response characterized by a first period such that only one group delay peak occurs within a first channel. By contrast, the second optical element has a group delay response characterized by a second period, which is less than the first period, such that more than one group delay peak occurs within the first channel. The preferred embodiment uses cascaded GT etalons to provide the desired group delay responses. One advantage of the present invention is that the passband of the dispersion compensator is increased relative to prior art designs without increasing insertion losses. Alternatively, the same passband common in prior art designs may be achieved with fewer GT etalons, thereby reducing insertion losses.

Abstract: A reconfigurable thin film based dense wavelength division multiplexing (DWDM) device is described for hitless switching of wavelengths by employing a reconfigurable filtering device. The reconfigurable filtering device is based on a mechanical switching of a filtering chip which has a thin film coated a first one-half of a first face for interference wavelength filtering and has a gold-mirror coated on a second one-half of the first face for high reflection.

Abstract: A packaged stack of optical devices includes two or more WDM optical devices, the stack having a reduced per-channel manufacturing cost and an improved mean time between failure relative to individual optical devices. WDM optical devices, which may be contained in a packaged stack, include wavelength selective switches, optical add-drop multiplexers, and dynamic gain equalizers. The optical switching devices in the stack may be configured so that one or more optical elements are shared by multiple switching devices. Optical components that may be shared between the switching devices contained in the stack include cylindrical lenses, diffraction gratings, mirrors, and beam steering units.

Abstract: A bistable liquid crystal-based optical device operates with reduced or zero power consumption and maintains a switching state during power loss. The optical device includes a bistable liquid crystal material that maintains a stable molecular orientation in the absence of an electrical field. The optical device further includes a beam steering device positioned downstream of the liquid crystal, such as a birefringent crystal or Wollaston prism. The molecular orientation of the liquid crystal modulates the polarization state of an incident light beam, and the beam steering device directs the beam along a first optical path, a second optical path, or both paths, based on the polarization state of the light.

Abstract: An optical device for a wavelength division multiplexing system has a telecentric lens system and a signal-processing optical element, where the signal-processing optical element performs switching, attenuation, or other optical signal processing for the optical device. The telecentric lens system acts as a self-compensating optical system to minimize sensitivity of the optical device to unwanted displacement of an input image from the optical axis of the optical device. The optical device may include multiple telecentric lens systems, in which case the optical device is also less sensitive to precise alignment between the telecentric lens systems.

Abstract: An optical switching device for wavelength divisional multiplexed signals uses cascaded arrays of optical steering devices for 1×N routing of WDM optical signals, where N=4, 8, 16, etc. Two cascaded arrays provide 1×4 switching; three cascaded arrays provide 1×8 switching; and so on. Each array is configured with independently controlled optical steering devices so that each wavelength channel of the WDM signal may be routed to any of N output ports. The optical steering devices may be micro-mirrors, liquid crystal-based polarization modulators, or a combination of both. By incorporating cascaded optical steering devices into a single WDM switching device, cost effective 1×N switching of WDM optical signals may be realized.

Abstract: An optical switch for performing high extinction ratio switching of an optical signal includes a beam polarizing element and one or more optical elements. The optical elements are configured to direct an optical signal along a first or second optical path based on the polarization state of the optical signal as it passes through the optical elements. The optical switch performs high extinction ratio switching of the optical signal by preventing unwanted optical energy from entering an output port by using an absorptive or reflective optical element or by directing the unwanted optical energy along a different optical path.

Abstract: A fiber lens assembly is configured to optically couple an optical fiber to a signal processing device having free-space optical elements. The fiber lens assembly includes a diverging lens having a focal length that may be around 2 to 6 times the diameter of the optical fiber core. Sensitivity of the fiber lens assembly to angular misalignment and positional displacement is reduced by coupling the optical fiber to the signal processing device using a diverging lens rather than a collimating lens, and by configuring the diverging lens with a suitable focal length.

Abstract: An optical device that processes a wavelength divisional multiplexed (WDM) optical signal includes an arrayed waveguide grating (AWG) and a polarizing liquid crystal array. The AWG demultiplexes and/or multiplexes the wavelength channels of the WDM signal. The liquid crystal array modulates the polarization state of individual wavelength channels so that each wavelength channel may be routed along an optical path based on the polarization state of the light.