Abstract: A thermo-optic lens of the present invention includes a plurality of parallel heating elements having substantially constant center-to-center spacing and respective dimensions varying from the outermost heating elements to the innermost heating elements, and at least two conductive elements for providing a potential across the heating elements. The dimensions of the heating elements are varied such that a parabolic temperature distribution is generated within the thermo-optic lens.

Abstract: A method and apparatus are disclosed for adjusting the phase of an optical signal by varying the path length of the optical signal using one or more moveable mirrors. The phase adjustment techniques of the present invention may be employed in various optical devices, including 1×n optical switches. The position of the mirrors may be controlled, for example, using micromachined control elements that physically move the mirror along the lightpath. An exemplary 2-by-2 optical switch includes two waveguides configured to include a coupler region. A mirror is positioned at the output of each waveguide. The position of at least one of the mirrors may be adjusted along the optical path and the mirrors reflect the light exiting from the end of the waveguides back into the same waveguide after an adjustable phase delay due to the round trip through an adjustable air gap between the waveguides and corresponding mirrors.

Abstract: A design technique minimizes the loss and ripple in the spectral response of an optical filter formed using a pair of gratings connected by an array of optical elements. This filter can be, for example, two waveguide grating routers (WGRs) connected by an array of waveguides. Each WGR includes two star couplers connected by waveguide grating arms. The smoothest spectral response is achieved for a given set of connecting waveguides, by choosing the number of grating arms less than or equal to filling the star coupler central Brillouin zone made by the set of connecting waveguides resulting in the connecting waveguides neither substantially over- or under-sampling the optical spectrum from the waveguide gratings. Exactly filling the Brillouin zone with the grating arms minimizes the loss, and so is the preferred choice.

Abstract: An optical apparatus includes a first wavelength routing device having a first plurality of waveguide arms and a 180° optical coupler, and a second wavelength routing device coupled to the first wavelength routing device, the second wavelength routing device having a second plurality of waveguide arms. Each of the second plurality of waveguide arms has a substantially opposite curvature relative to each of the first plurality of waveguide arms.

Abstract: A router comprises a demultiplexer arranged to receive an input WDM signal containing N wavelengths, and apply its output, namely, the N separated the wavelengths, to a binary tree containing log2K stages of interconnected 1×2 switches. The switches can be integrated, and have their outputs crossing each other at each stage. The outputs of the final stage are applied to, and combined in, K multiplexers, which provide the K outputs of the router. If desired, a set of shutters can be interposed in the waveguides leading to the muliplexer inputs, thereby providing additional isolation.

Abstract: The curvature, tilt, and attenuation of the passband of an optical signal is dynamically controlled by an integrated compensator that is advantageously electrically operated. The compensator arrangement can be replicated, and used to independently and dynamically control the passbands of multiple optical signals having different wavelengths, for example in a multiplexing and/or demultiplexing arrangement. Each compensator includes a “50/50” splitter arranged to divide an optical signal into first and second copies. One copy is applied to a first variable optical attenuator (VOA) via a tunable phase shifter, while the other copy is applied to a second VOA directly. The outputs of the first and second VOA's are then combined, for example in a planar waveguide grating. In the output on the other side of the grating, the two copies interfere.

Abstract: The limitation of N in an N×N Wavelength Grating Router (WGR) is determined to be because of the intrinsic diffraction characteristics of the grating that occurs when N approaches the diffraction order m at which the grating operates. The N in a N×N WGR device is maximized for input signal channels equally spaced either in frequency or in wavelength. For the wavelength case, N is increased by appropriate changes in the spacing of the output ports of the WGR and/or by slightly correcting the by channels wavelengths.

Abstract: A programmable broadband N×N cross-connect switch includes an N×N wavelength coupler combined with N tunable lasers, N modulators and N optical receivers. Each of the N tunable lasers can selectively produce N different wavelengths. The coupler couples the N wavelengths to the N modulators. The N modulators modulate the N wavelengths using N input electrical signals, each modulator being selectable by choosing a laser wavelength. The N optical receivers receive and detect the N modulated wavelengths to produce N output electrical signals therefrom, each receiver receiving and detecting a different one of the N different wavelengths. By selecting a laser wavelength a particular modulator and receiver is selected so that a modulated signal, formed at the selected modulator when an input electrical signal modulates the selected wavelength, is switched to the selected receiver.

Abstract: An optical dynamic gain equalization filter (DGEF) comprises a planar arrangement of preferably “perfectly sampled” (or alternatively oversampled) waveguide grating routers (WGR's) connected by individual optical paths each containing a Mach-Zehnder interferometer operated in a push-pull fashion so that a positive phase change in one interferometer arm and a corresponding negative phase change in the other interferometer arm produces a desired change in attenuation while, at the same time, the overall phase of the optical signals after passing through the Mach-Zehnder interferometer is kept constant with respect to the adjacent paths. Alternatively, the above-described arrangement is effectively “cut in half”, and its size effectively also reduced accordingly, using a mirror placed at the midpoint of the device and an appropriate circulator to separate the input and output optical signals.

Abstract: A wavelength division multiplex (WDM) cross-connect architecture that can selectively cross-connect, at a wavelength granularity, wavelength channels from any of a plurality of input WDM optical facilities (e.g., fibers) to any of a plurality of output WDM optical facilities. The architecture is based on multi-wavelength modules, which are capable of routing simultaneously N wavelengths. The number of required modules scales only with k2 or less (i.e., k2 modules with N complexity), where k is the number of input/output fibers. The significant reduction in complexity is traded for a decrease in blocking performance; one of the disclosed architectures is strictly non-blocking in the space domain and rearrangeably non-blocking in the wavelength domain, whereas two others are rearrangeably non-blocking in both the wavelength and space domain.

Abstract: An arrangement is disclosed for providing optical wavelength adding/dropping. The arrangement includes two duplicated-port waveguide grating routers (WGR) and a plurality of attenuator-switches. The first WGR is configured as a 1×2N demultiplexer and the other as a 2N×1 multiplexer. Each WGR includes a duplicated plurality of input or output waveguides, wherein respective pairs of each plurality have substantially identical spectral characteristics. The first plurality of output waveguides of the first WGR is coupled to the first plurality of input waveguides of the second WGR. Attenuator-switches are inserted between these two pluralities of waveguides that can be used to block incident optical wavelengths corresponding to channels to be terminated at the node where the arrangement is provided. The second plurality of output waveguides in the first WGR are drop waveguides where dropped channels exist.

Abstract: A method and apparatus are disclosed for filtering an input wavelength-division multiplexed (WDM) signal comprised of N wavelength channels. The disclosed wavelength blocker includes a demultiplexer for producing a plurality of demultiplexed output signals from the input WDM signal and a multiplexer for producing an output WDM signal. A shutter array selectively passes each of the N wavelength channels using a plurality of shutters. The demultiplexer is coupled to the multiplexer using a plurality of waveguides having approximately equal length, in order to reduce multipath interference. Each of the N wavelength channels are selectively passed or blocked using a thermo-optic or electro-optic control signal to control the state of the corresponding shutter. Crosstalk can be reduced using dilation techniques that position two shutters in series, especially where the shutters are thermo-optic Mach-Zehnder switches.

Abstract: A WDM input signal received at an add/drop node is coupled onto both a “drop” transmission path and a “through” transmission path within the node. Optical channels to be dropped are then processed within the “drop” path, such as by optical demultiplexing. Because a copy of the same WDM input signal is routed on the “through” path, a dynamically configurable and programmable wavelength blocker selectively blocks the optical channels that are being dropped from the WDM input signal and passes through those optical channels not being dropped onto the “through” path. In an “add” path within the node, optical channels are selectively added, such as by using optical multiplexing. Those optical channels from the multiplexed optical signal that are not designated for “add” (e.g., “unused” channels) are selectively blocked within the “add” transmission path.

Abstract: A design technique minimizes the loss and ripple in the spectral response of an optical filter formed using a pair of gratings connected by an array of optical elements. This filter can be, for example, two waveguide grating routers (WGRs) connected by an array of waveguides. Each WGR includes two star couplers connected by waveguide grating arms. The smoothest spectral response is achieved for a given set of connecting waveguides, by choosing the number of grating arms less than or equal to filling the star coupler central Brillouin zone made by the set of connecting waveguides resulting in the connecting waveguides neither substantially over- or under-sampling the optical spectrum from the waveguide gratings. Exactly filling the Brillouin zone with the grating arms minimizes the loss, and so is the preferred choice.

Abstract: A method and apparatus are disclosed for simulating planar waveguides having a rectangular cross-section using a beam propagation method and design tool based on the FFT-BPM. Constraining the beam propagation method to planar waveguides having rectangular cross-sections significantly reduces the computational complexity and increases accuracy. The beam propagation method can be performed entirely in the angular spectrum domain. The constrained shape of the waveguide allows the structure to be accurately specified by its width and center-to-center arm spacing, thereby avoiding transverse spatial quantization.

Abstract: A method and apparatus are disclosed for filtering an input wavelength-division multiplexed (WDM) signal comprised of N wavelength channels. The disclosed wavelength blocker includes a demultiplexer for producing a plurality of demultiplexed output signals from the input WDM signal and a multiplexer for producing an output WDM signal. In addition, a shutter array selectively passes each of the N wavelength channels using a plurality of shutters. The demultiplexer is coupled to the multiplexer using a plurality of waveguides having approximately equal length, in order to reduce multipath interference. The shutters may be embodied, for example, as Mach-Zehnder switches, electro-absorption modulators or Y-branch switches. Each of the N wavelength channels in the incoming signal are selectively passed or blocked using a thermo-optic or electro-optic control signal to control the state of the corresponding shutter.

Abstract: A method and apparatus are disclosed for selectively passing or blocking an optical signal using an opaque or reflective shutter that is selectively positioned in or out of the light path. The disclosed wavelength blocker can be employed to filter input wavelength-division multiplexed (WDM) signal comprised of N wavelength channels, where a mechanical shutter array selectively passes each of the N wavelength channels. Each mechanical shutter may be controlled, for example, by a micromachine control element that physically lifts the shutter into or out of the lightpath. The disclosed wavelength blockers may be utilized in wavelength-selective cross connects, as well as other optical devices. In an exemplary wavelength-selective cross connect, an array of mirrors are employed in a planar waveguide having two sets of waveguide gratings intersecting at an angle.

Abstract: A wavelength-selective cross connect (WSC) switch is disclosed that can selectively pass a multi-wavelength incoming signal received on a given incoming port to a corresponding output port in a bar state; or cross the received signal to an opposite output port in a cross state, using only two wavelength blockers and a number of optical circulators. Power splitters divide the power of each incoming signal in half and the half-power signals are applied to the two wavelength blockers surrounded by corresponding optical circulators. Each of the wavelength blockers control either the bar state or the cross state. The outputs of the two wavelength blockers are combined to produce an output signal at each of the output ports. Thus, the wavelength-selective cross connect can selectively pass or cross an incoming signal to an appropriate output port, as desired. The disclosed wavelength-selective cross connects can be serviced without interrupting traffic.

Abstract: A thermo-optic interferometer switch is arranged to operate in a Push-pull mode by placing approximately a quarter-wavelength effective path-length difference (90 degree bias) between the arms of an interferometer switch in the zero-drive state, and then driving one arm to activate the switch to one state (e.g., the bar state), and driving the other arm to go to the other state (e.g. the cross state).

Abstract: Segmentation is used not only in the grating side of a star coupler, but also on the input/output side of a star coupler, in order to minimize the amount of light that is lost. Thus, our invention is to place segmentation in the input and/or output ports of optical planar waveguide grating routers with high spectral sampling, for the purpose reducing insertion loss. In one embodiment, the star couplers in the waveguide grating router are arranged with segmentation on both input and output sides; alternatively, segmentation is used only on either the input or output side of the star coupler.