Abstract: A modular optical platform for selective wavelength switching that can be adapted to perform various other functions, such as dynamic gain equalization (DGE) and add/drop multiplexing (ADM) provides the versatility and modularity that will be essential to the future of the fiber optics industry. The basic platform includes a first lens for directing an optical signal, a diffraction grating for dispersing an optical signal into its component wavelength channels, a second lens for directing the component wavelength channels, and a modifying device for conducting one or more of a variety of functions including switching, DGE and ADM. The first and second lens are preferably replaced by a single concave reflective mirror having optical power.

Abstract: The method and apparatus of laser-induced incandescence (LII) to analyze characteristics of submicron-sized particles are described. LII is recognized as a good tool for determining the characteristics of small particles in a gas, e.g., volume fraction, particle size, and specific surface area. It uses the fact that the incandescence signal is proportional to the volume of the particles. It also uses the fact that transient cooling is dependent on the specific surface area of the particle, which is related to diameter of the particle. In LII, particles are heated by a pulsed laser light beam to a temperature where incandescence from the particles can be distinguished from ambient light. The temperature of particles and their volume fraction governs the incandescence. The temperature decay rate is proportional to the primary particle size. The invention uses an optical arrangement that ensures a near-uniform laser energy distribution spatial profile.

Abstract: The invention provides an optical device including a polarization diversity unit for receiving an input optical signal and producing two beams of light having a same polarization state therefrom, a beam swapping element disposed for receiving the first and second beams of light and for redirecting the two beams of light to a same overlapping area of a modulator, and a reflective surface for reflecting the two beams of light back to the polarization diversity unit where they are combined to form an output optical signal. The beam swapping element is designed and positioned such that the first and second beams of light swap positions upon reflection from the reflective surface and trace out the other's optical path. Advantageously, this optical arrangement essentially eliminates all PDL and PMD.

Abstract: A dispersion compensator has a linearly chirped fiber Bragg grating mounted at two ends of an elongated, channel-shaped heat distributor. The distributor has two thermo-electric coolers at two ends, a heating strip for uniform heating of the distributor, a temperature sensor mounted on the distributor in the middle of the grating region, and longitudinally variable heating means attached to the distributor and extending along its length for effecting a longitudinally varying heating of the grating region. The provision of the heating strip helps maintain linearity of the thermal gradient of the distributor while the longitudinally variable heaters facilitate relatively fast dithering of the temperature of the grating region.

Abstract: The present invention relates to an optical filter comprising an integrated wavelength dispersive element having an input for providing temperature compensation, particularly for providing passive temperature compensation in an arrayed waveguide grating. The present invention has found that by providing an arrayed waveguide grating having a thermally responsive pivotal input structure for changing an angle of a collimated input signal launched into a focusing lens, the input point can be selected in response to changing temperature in order to compensate for thermal drift of the center wavelength. Further, the present invention has found that by providing a reflective lens assembly for focusing an input signal at a selected input point of the input planar waveguide, alignment and tuning of an input and assembly can be improved and simplified.

Abstract: A simple and flexible WDM laser source is disclosed using a loop erbium-doped fiber amplifier (LEDFA) configuration. The loop serves as a mirror and as an amplification medium. The laser cavity was made from the loop mirror and a set of fiber Bragg gratings (FBGs) which select the proper lasing wavelengths. The FBGs can be placed either in parallel or in series at the output of the loop configuration. Optical attenuators are placed in front of the FBG to control the flatness of the laser source output and determine the required lasing condition for each wavelength to avoid competition of the different lasing wavelengths. This configuration is flexible for adding any number of wavelengths as long as enough amplified spontaneous emission (ASE) is generated in the loop. Signal to noise ratio as high as 55-dB can be achieved.

Abstract: The invention relates to replaceable modules for use in optical fiber distribution racks. The modules according to the present invention are mounted in the distribution rack at a slight angle, which enables a simple and effective latching mechanism to connect and disconnect the module therefrom using one hand. Moreover, a preferred embodiment of the present invention minimizes the required size of the module by positioning the input ports at an angle to the remainder of the module body, which has the added benefit of directing the attached cables away from the latching mechanism providing enfettered access thereto. The optical fiber distribution rack according to the present invention includes a sliding lower tray with a sliding upper frame member, whereby full access to both the tray and the frame member are provided.

Abstract: An optical beam path directing system has a field-flattening optically transmissive wedge installed in spatially dispersed beam paths upstream of the planar surface of a micro electro-mechanical switch (MEMS) or liquid crystal array. The parameters of the field-flattening wedge and its location in the diffracted beam paths are defined such that the wedge effectively rotates a ‘best fit’ planar surface approximation of the curvilinear focal plane of a concave reflector into coplanar coincidence with the optical signal-receiving surface of the MEMS. As a result, loss variation is essentially flat and minimized across the optical signal transmission band.

Abstract: The filtering of optical signals, and in particular the interleaving/de-interleaving of optical signals is becoming a necessary step in Dense-Wavelength Division Multiplexing (D-WDM), because of a requirement for smaller channel spacing due to higher levels of traffic. Finite Impulse Response (FIR) filters, including lattice and birefringent waveplate versions, are a particular type of optical filter used for interleavering/de-interleavering optical channels, which can be defined by their transfer function H(f). To ensure dispersion free filtering, the present invention provides a cascaded optical filter, comprising two optical filters, wherein the transfer function of the second filter is the complex conjugate of the first filter, i.e. H2(f)=H1*(f), or the complex conjugate of the first filter H1*(f) multiplied by the transfer function of a dispersion free optical filter G(f).

Abstract: This invention relates to elements such as birefringent crystals, which are used to separate a non-collimated input beam into two orthogonally polarized sub-beams or to combine two orthogonally polarized beams into a single beam. The optical device lessens or obviates the optical path length difference encountered in prior art devices and provides a polarization beam splitter/combiner that has substantially same optical path lengths for two split or combined beams propagating therethrough. Alternatively, the device is designed to provide a selected path length difference to compensate for polarization mode dispersion in other optical devices.

Abstract: An optical cross-connect having an input port for launching a beam of light into the optical cross-connect, at least two output ports, each output port for selectively receiving a beam of light, a dispersive element for dispersing the beam of light into separate wavelength channels, and a switch core for independently switching at least one individual wavelength channel between ports. The switch core includes a cylindrical ATO element, two cylindrical relay lenses, and two opposing deflector arrays. Conveniently, the deflector arrays are either liquid crystal phase arrays or reflective MEMS arrays.

Abstract: A fiber optic wavelength switch that includes a front-end unit having optical ports for receiving and transmitting optical signals; a wavelength dispersion element (e.g., diffraction grating, prism, etc.) for defining a dispersion plane; a light redirecting element (e.g., spherical reflector) associated with the wavelength dispersion element; and an actuation array (e.g., MEMS) operative with the light redirecting element for tilting an optical signal substantially perpendicular to the dispersion plane defined by the wavelength dispersion element. The wavelength switch can be implemented as a one input/output port and several add/drop ports type device, which can add/drop wavelengths from/to the in/out port. The front-end unit having a fiber array coupled to a micro-lens array with optical signals from the micro-lens being directed by a further lens.

Abstract: The present invention relates to an arrayed waveguide grating having a reflective input that permits variable coupling to adjust the center wavelength. The present invention has found that by providing an arrayed waveguide grating having one or more precisely positioned input waveguides coupled through a reflective lens assembly, for providing a lateral offset to a signal propagating from the input waveguide to the planar waveguide, and for focusing a reflected input signal at a selected input point of the input planar waveguide, alignment and tuning of an input and assembly can be improved and simplified. Advantageously, variable coupling parameters can be incorporated into the reflective coupling including input position, waveguide taper and planar waveguide length increment to provide relatively simple tuning in an integrated device. Compensation for polarization effects and thermal effects can also be provided in the reflective coupling.

Abstract: A method and device is disclosed for dispersion compensation of an optical signal. By providing two filters having a sloped dispersion and opposite in sign over a wavelength band wherein one filter is tunable, a controllable amount of dispersion can be introduced to offset or compensate dispersion. Preferably one of the filters is a tunable periodic device in the form of a multi-cavity GT etalon. In a preferred embodiment of the filters can be designed to provide various controllable but different constant amounts of dispersion.

Abstract: In order to calibrate an apparatus for measuring the polarization dependent loss of an optical device under test, a set of nominal polarization states of incident light are generated with a polarization generator. The incident light is then passed through a dot-product conserving polarization rotator at a first setting. A transmission characteristic is measured through a standard optical component with a known polarization dependent loss value for each polarization state. This step is repeated for a number of different settings of the polarization rotator. A polarization dependent loss value is calculated for the standard optical component based on the measured transmission characteristics at each polarization rotator setting. The calculated polarization dependent loss values are then processed to generate an aggregate error value.