Abstract: A flat-top arrayed waveguide grating with a Hyper-Gaussian distribution function and a modified sinc design exhibits a very low chromatic dispersion, low loss and requires a relatively small number of waveguides. Controlled loss is introduced into certain waveguides of the array by creating gaps (unguided regions) between the waveguides to produce a desired predetermined amplitude distribution. The gaps are preferably arranged in the middle of the array.

Abstract: The present application relates to a method of fabricating planar circuits using a photolithographic mask set, to the photolithographic mask set, and to a planar circuit fabricated with the photolithographic mask set. The instant invention involves separating a photolithographic mask into two parts, namely, a master mask and one or more slave masks. The master mask and the one or more slave masks form a photolithographic mask set that is used iteratively to fabricate the planar circuits. In particular, the master mask is used as a template to provide the general layout for the planar circuit, while each slave mask is varied to tune and/or tailor the planar circuit. Since only a small portion of the planar circuit is redesigned and/or rewritten as a new mask (i.e., the slave mask), the instant invention provides a simple and cost effective method for optimizing planar circuits.

Abstract: An apparatus for monitoring an input optical signal at a plurality of distinct optical frequencies is disclosed wherein a demultiplexing arrayed waveguide grating (AWG) having a plurality of M>1 Vernier input ports is disposed between an optical switch and a photodiode array coupled to the output ports of the AWG. In operation, the optical switch sequentially provides the input optical signal into each of the Vernier ports, and signals detected by photodiodes are stored in a memory unit. The apparatus is capable of monitoring the input optical signal with a frequency step which is M times smaller than a frequency spacing between the AWG transmission bands, and obtain M frequency-resolved readings from each photodiode.

Abstract: A demultiplexer/multiplexer is disclosed wherein an arrayed waveguide grating having a reflector at an end includes selectable signal path blockers. The arrayed waveguide device has a common input/output port for launching radiation in the form of an input signal having n wavelengths therein and for receiving back via the reflector at the input/output port a selected channel of the input signal. In operation a multiplexed signal have n channels is launched therein and a selected channel is output for analysis or further processing.

Abstract: A planar waveguide Mach-Zehnder interferometer (MZ) has improved performance as a variable optical attenuator as well as a thermo-optic switch (TOS) with reduced polarization dependent loss (PDL) in high attenuation states. The PDL was reduced by correcting for the increased birefringence that occurs on heating one waveguide arm by making the two waveguides inherently asymmetric, such that when one of the waveguides is heated, the differential birefringence of the two arms becomes zero. This asymmetry can be realized simply by changing the width of one of the waveguides. The modified device allows for very small PDL in the high attenuation state of a VOA and for theoretically perfect contrast in a TOS in the off state, with only a small penalty in PDL of the on state.

Abstract: A flat-top arrayed waveguide grating with a Hyper-Gaussian distribution function and a modified sinc design exhibits a very low chromatic dispersion, low loss and requires a relatively small number of waveguides. Controlled loss is introduced into certain waveguides of the array by creating gaps (unguided regions) between the waveguides to produce a desired predetermined amplitude distribution. The gaps are preferably arranged in the middle of the array.

Abstract: A method of modifying the spectral distribution of an optical signal includes the steps of splitting the signal among a plurality of optical paths, delaying the propagation of the signal through one or more of the optical paths by a time duration which results in the desired spectral distribution when the signals at the output ends of each optical path are recombined, and then recombining those outputs. An apparatus for changing the spectral profile of an optical signal includes an input waveguide and a plurality of tapped delay lines. Each of the tapped delay lines has a delay element configurable to impart a predetermined delay to the signal propagating down the delay line. Couplers split an optical signal, propagating on the input waveguide, among the tapped delay lines. The delays imparted to the signals on each line are chosen so as to effect the desired change to the spectral profile.

Abstract: A polarization-insensitive broad-band variable optical attenuator (10) includes a first Mach-Zehnder interferometer (MZI) stage (12) having a polarization dependence loss of a first polarity, and a second Mach-Zehnder interferometer (MZI) stage (14) coupled in series, or cascaded, to the first Mach-Zehnder stage (12) and having a polarization dependence loss of an opposite polarity to the first polarity.

Abstract: A grating is provided having a generally s-shaped waveguide configuration. The grating includes a plurality of waveguides arranged adjacent to one another to form an array. The array includes a first portion bending in a counter-clockwise direction, a second portion bending in a clockwise direction, and a third portion extending in a straight direction. The arc length of each waveguide along the counter-clockwise bend portion varies from one waveguide to the next. At its minimum, the arc length is nearly zero. The different arc lengths along the counter-clockwise bend cause some waveguides to be longer than others. This results in a clear separation of the individual waveguides. Further, the overall dimension of the grating is smaller than conventional devices which leads to reduced cross-talk.

Abstract: A planar waveguide Mach-Zehnder interferometer (MZ) has improved performance as a variable optical attenuator as well as a thermo-optic switch (TOS) with reduced polarization dependent loss (PDL) in high attenuation states. The PDL was reduced by correcting for the increased birefringence that occurs on heating one waveguide arm by making the two waveguides inherently asymmetric, such that when one of the waveguides is heated, the differential birefringence of the two arms becomes zero. This asymmetry can be realized simply by changing the width of one of the waveguides. The modified device allows for very small PDL in the high attenuation state of a VOA and for theoretically perfect contrast in a TOS in the off state, with only a small penalty in PDL of the on state.

Abstract: A method of modifying the spectral distribution of an optical signal includes the steps of splitting the signal among a plurality of optical paths, delaying the propagation of the signal through one or more of the optical paths by a time duration which results in the desired spectral distribution when the signals at the output ends of each optical path are recombined, and then recombining those outputs. An apparatus for changing the spectral profile of an optical signal includes an input waveguide and a plurality of tapped delay lines. Each of the tapped delay lines has a delay element configurable to impart a predetermined delay to the signal propagating down the delay line. Couplers split an optical signal, propagating on the input waveguide, among the tapped delay lines. The delays imparted to the signals on each line are chosen so as to effect the desired change to the spectral profile.