Abstract: A planar optical router consisting of two stages performing stationary imaging has advantages of reduced size, increased number of channels and reduced crosstalk. In one embodiment, each stage of the router includes a waveguide grating, and the router produces several sets of interleaved images, with the property that different sets are characterized by different diffraction orders of the two gratings. The new arrangement substantially increases the number of output waveguides, as compared to previous arrangements using only one set of images, characterized by the same order of the output stage. Moreover, since adjacent sets are characterized by different orders, crosstalk is substantially reduced. In a second embodiment, the number of output waveguides is further increased by including two gratings in the second stage.

Abstract: An optimized planar optical router consisting of two stages performing stationary imaging between an input waveguide and a set of output waveguides has advantages of reduced size, larger number of channels and minimal loss variation in each passband. The new router is an optimized M×N imaging arrangement including two waveguide gratings and n waveguide lenses connected between the principal zones of the two gratings. The largest values of N are realized by using a combination of two techniques that increase N without increasing the size of the two gratings. One technique increases N for a given number n of lenses and, the other, increases n. In one embodiment, each lens produces a periodic sequence of passbands, all transmitted from a particular input waveguide to the same output waveguide, whereas, in a second embodiment, the above passbands are transmitted to different output waveguides. In both cases, the loss caused by secondary images is substantially reduced by including secondary lenses.

Abstract: An optimized planar optical router consisting of two stages performing stationary imaging between an input waveguide and a set of output waveguides has advantages of reduced size, larger number of channels and minimal loss variation in each passband. Each stage is a waveguide grating router, the two stages are characterized by nearly equal free-spectral ranges, and a waveguide lens is connected between the two stages. In one embodiment, the lens is connected between the central zones of the two stages, and the diffraction orders of the two stages vary monotonically from each passband to the next. In another embodiment, the loss caused by secondary images is substantially reduced by using a composite lens providing efficient transmission of both principal and secondary images.

Abstract: An optimized planar optical router consisting of two stages performing stationary imaging between an input waveguide and a set of output waveguides has advantages of reduced size, larger number of channels and minimal loss variation in each passband. The new router is an optimized M×N imaging arrangement including two waveguide gratings and n waveguide lenses connected between the principal zones of the two gratings. The largest values of N are realized by using a combination of two techniques that increase N without increasing the size of the two gratings. One technique increases N for a given number n of lenses and, the other, increases n. In one embodiment, each lens produces a periodic sequence of passbands, all transmitted from a particular input waveguide to the same output waveguide, whereas, in a second embodiment, the above passbands are transmitted to different output waveguides. In both cases, the loss caused by secondary images is substantially reduced by including secondary lenses.

Abstract: A planar optical router consisting of two stages performing stationary imaging has advantages of reduced size, increased number of channels and reduced crosstalk. In one embodiment, each stage of the router includes a waveguide grating, and the router produces several sets of interleaved images, with the property that different sets are characterized by different diffraction orders of the two gratings. The new arrangement substantially increases the number of output waveguides, as compared to previous arrangements using only one set of images, characterized by the same order of the output stage. Moreover, since adjacent sets are characterized by different orders, crosstalk is substantially reduced. In a second embodiment, the number of output waveguides is further increased by including two gratings in the second stage.

Abstract: An optimized planar optical router consisting of two stages performing stationary imaging between an input waveguide and a set of output waveguides has advantages of reduced size, larger number of channels and minimal loss variation in each passband. Each stage is a waveguide grating router, the two stages are characterized by nearly equal free-spectral ranges, and a waveguide lens is connected between the two stages. In one embodiment, the lens is connected between the central zones of the two stages, and the diffraction orders of the two stages vary monotonically from each passband to the next. In another embodiment, the loss caused by secondary images is substantially reduced by using a composite lens providing efficient transmission of both principal and secondary images.

Abstract: A planar optical device useful as a low order wavelength router is realized by using a waveguide grating comprising two curved arrays of opposite curvatures. The diffraction order is determined by the angles of rotation of the two curved arrays, and any nonzero order less than about 30 can be realized. This arrangement is smaller, and performs better than a previous grating using a combination of three curved arrays.

Abstract: A planar optical device useful as a low order wavelength router is realized by using a waveguide grating comprising two curved arrays of opposite curvatures. The diffraction order is determined by the angles of rotation of the two curved arrays, and any nonzero order less than about 30 can be realized. This arrangement is smaller, and performs better than a previous grating using a combination of three curved arrays.

Abstract: A planar optical filter consisting of two stages performing stationary imaging between an input waveguide and a set of output waveguides is characterized by reduced crosstalk and minimal loss variation in each passband. The input stage is a small waveguide grating router, connected to the output stage by a waveguide lens essentially covering the entire central zone of the input router. In one embodiment, the second stage includes two waveguide grating routers and the lens has two separate output apertures, respectively connected to these two routers. In this arrangement, 2N input channels applied to the input port are separated by the first grating into two interleaved sets of N channels each. The two sets are respectively transferred by the composite waveguide lens to the two output gratings which respectively separate the N channels of each set.

Abstract: An optical interconnection apparatus including waveguide arrays such as waveguide lenses, waveguide gratings and star couplers, has improved efficiency realized using a periodic array combined with an arrangement of matching sections. The array is connected to a slab region containing the array focal point and the purpose of the matching sections is to minimize unwanted radiation by the array outside the central zone of the array. This unwanted radiation is primarily caused by two particular unwanted modes excited at the array junction with the slab, and the resulting loss is minimized by properly choosing the average phase shift applied by each section to said unwanted modes.

Abstract: A filtering system for eliminating dispersion caused by filtering an optical signal with a birefringent filter. Dispersion is eliminated by causing each signal to be passed twice through a birefringent filter. Dispersion created by the first pass is canceled out by dispersion created in the second pass. The same filter may be used for both passes with a polarization rotation applied between the two passes. Specifically, the first pass produces dispersion defined by transmission coefficients C and D. Because of the polarization rotation, the second pass creates dispersion defined by the complex conjugates of transmission coefficients C and D, which cancel out dispersion caused by the first pass. Mathematically, each transmission coefficient of the first pass is multiplied by its complex conjugate of the second pass, and the resulting transmission coefficients |C|2, |D|2 are entirely free of dispersion caused by the filter.

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: 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 channels wavelengths.

Abstract: The passband of an optical wavelength router is widened by using a combination of two grating apparatuses with opposite angular dispersions. The passband width approaches the channel spacing, with minimal loss penalty. This technique is particularly attractive for applications requiring a large number of ports with maximum passband width and relatively small loss. The optical wavelength router may be formed using either reflective or transmissive elements formed using grating apparatuses that are free space optical elements or waveguide gratings.

Abstract: When two star couplers are cascaded so as to perform two Fourier transformations without phase distortions, an imaging arrangement results which accurately reproduces at the output the input distribution. In order to achieve high efficiency of power transfer between a relatively large number of input ports and a relatively large number of output ports and a small star-coupler physical size, the input and output waveguides connected to the star coupler must be relatively narrow and be closely spaced at the star coupler. However close spacing gives rise to significant mutual coupling between adjacent waveguides, leading to undesirable crosstalk between the channels of the device. We have discovered that the phase distortion is approximately periodic and may be compensated for by adding or subtracting length to the waveguides between the star couplers.

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 channels wavelengths.

Abstract: An integrated, single output port, tunable multiple wavelength laser apparatus produces one of Na Nb wavelengths using only Na plus Nb selection signals. Each of Nb ports can output Na of the laser wavelengths, the port being selected by the Nb control signals and the particular one of the Na wavelengths being selected by the Na control signal. An Nb×1 router combines the signals from the Nb output ports into a single output.

Abstract: A router combines free-space and guided wave optics to drastically increase the number of channels used in WDM transmission systems. The two-stage router uses the partial demultiplexing characteristic of an arrayed waveguide router (AWR) combined with a free-space optical router to fully demultiplex an input WDM signal. The two-stage router can be used to obtain output wavelength signals in either one- or two-dimensional arrays.

Abstract: A waveguide grating router having an improved passband flatness with lower loss is provided that includes a first optical coupling device having at least one input port, at least one mode converter, and P output ports, where P>2. A second optical coupling device is also provided that has P input ports, least one output port, and at least one mode converter. P optical paths couple the input port of the first optical coupling device to the output port of the second optical coupling device. The mode converters control the magnitudes of various transmission coefficients contributed by the optical paths of the router. The phases of the various contributions are determined by the optical path lengths, and these lengths are chosen so that certain contributions are opposite to other contributions.