Showing papers on "Mode scrambler published in 1999"

Tapered polymer single-mode waveguides for mode transformation

Abstract: This paper presents a tapered polymer waveguide structure for coupling light between optical waveguides with differing geometries. Optical fibers, lasers, and other photonic integrated circuit components can be coupled with tapered waveguides. The polymer waveguide performs a mode transformation between different mode shapes and sizes. For example, the mode transformation can be from an elliptical laser diode mode to that of a circular optical fiber mode. The input and output of a tapered waveguide structure are analyzed, for the case of laser to fiber coupling, in order to determine the effect of misalignments on the coupling efficiency. Adiabaticity in waveguide propagation is discussed. The fabrication of our polymer waveguides is also described.

Intermodal dispersion and mode coupling in perfluorinated graded-index plastic optical fiber

Abstract: Graded-index multimode perfluorinated plastic optical fibers typically exhibit bandwidths much greater than would be expected from their index profiles. To resolve this discrepancy, we have conducted the first measurements of differential mode delay in such fibers. These measurements show intermodal dispersion that increases as the square root of fiber length, implying strong mode coupling in these fibers. Significant power transfer between modes occurs at lengths less than 20 m, so that mode coupling results in improved bandwidth on length scales relevant for local area networks. The observed coupling arises from extrinsic nonuniformities of the waveguide.

Transverse spatial mode transformer for optical communication

Abstract: A transverse spatial mode transformer for transforming an optical signal between different spatial modes is described. The transformer is based on a spatially selective change of the phase of the optical signal wavefront relative to the initial wavefront. As the phase-adjusted optical signal propagates, the transverse intensity distribution changes to correspond to the new spatial mode. The transformer can be used to change the lower order spatial mode of an optical signal to a higher order spatial mode appropriate for a dispersion compensated fiber optic communication system. The transformer can also be used to change a higher order spatial mode to a lower order spatial mode.

Twin coupler with mode scrambling for multimode pumping of optical amplifiers

Abstract: A twin coupler system couples a multimode pump power signal from a pump fiber to an optical information carrying double-clad signal fiber. The twin coupler system includes first and second optical couplers and a mode scrambler. The first optical coupler couples the pump fiber to the optical signal fiber to transfer outer modes of the pump power signal from the pump fiber into the optical signal fiber. The mode scrambler scrambles the modes of the pump power signal remaining in the pump fiber beyond the first optical coupler. The second optical coupler couples the pump fiber to the optical signal fiber to transfer outer modes of the scrambled pump power signal from the pump fiber into the optical signal fiber.

Optical devices based on energy transfer between different modes in optical waveguide

Abstract: Optical waveguide devices (100) based on optical coupling of different modes (110, 130) by using a mediating mode (120). Such waveguide devices (100) generally have at least to coupling regions (104, 106). The first coupling region (104) couples an output mode and the mediating mode, and the second one (106) couples the mediating mode and an input mode that copropagates with the output mode. Under proper conditions, the energy in the input mode can be completely transferred to the output mode, without energy loss to the mediating mode (120).

Dispersion-shifted fiber polarization scrambler based on Faraday effect

Abstract: Demonstration of an all-fiber polarization scrambler based on the Faraday effect is carried out. The device has been constructed using dispersion-shifted fiber that has a major tolerance to bends than standard single-mode fiber. Results about the fiber Verdet constant when 1550-nm light is launched are presented. The performance of the constructed device is also shown. Main features are insertion losses as low as 0.4 dB and scrambling frequency up to 20 kHz. Although here we emphasize its application to low-frequency heterodyne detection, the scrambler is applicable to other systems that are polarization dependent. In particular, it would be useful to overcome problems originated by polarization dependent gain in erbium-doped fiber amplified systems.

Alignment tolerant structures for ease of optoelectronic packaging

Abstract: Expanded mode alignment tolerant optical structures will play an important role in low-cost, large-scale packaging of optoelectronic devices. In this paper, we present two expanded mode structures for operation at 1.55 micrometers . Our devices use single epitaxial growth and conventional fabrication schemes. High butt-coupling efficiencies (> 40%) to a single mode fiber with relaxed alignment tolerances were achieved. The first of our devices uses adiabatic transformation over 500 micrometers . The second device uses resonant coupling over a much shorter region of 200 micrometers . The second scheme offers an interesting possibility for monolithic integration of active-passive components. We present the design and simulation results of such an integrated device.

Mode detection circuit of liquid crystal display

Abstract: A mode detection circuits in LCDs is disclosed, comprising: a first mode signal detection means for detecting an enable/synchronous signal mode in response to a vertical synchronous signal and for generating a first mode detection signal; a second mode signal detection means for detecting an enable mode signal based on a data enable signal and a clock signal and for generating a second mode detection signal; a mode selection means for selecting one of a first mode detection signal and a second mode detection signal from the first mode signal detection means and the second mode signal detection means in response to a mode selection signal and for providing the selected mode detection signal as a mode determining signal.

Compact non-blocking non-dilated optical switch using mode conversion

Abstract: A non-blocking optical switch has a non-dilated architecture wherein dual mode input waveguides are connected to first and second inputs o mode selective couplers through mode conversion devices. Switching is effected by signals from a processing unit applied to a mode converter to convert the signal to be switched from a fundamental mode to a higher order mode. The mode selective coupler then couples the signal to one of the outputs thereof, whereas fundamental mode signals pass through to the other output thereof. An array of rows (layers) and columns of such elements make it possible to switch any incoming signal to be switched to any of a plurality of outputs after reconversion to the fundamental mode.

Optical wavelength adjustor using inclined bragg lattice and mode division directional coupler

Abstract: PURPOSE: An optical fiber wavelength adjuster is provided to ensure good wavelength selectivity, excellent stability and easy productivity by using an inclined Bragg lattice and a mode division directional coupler. CONSTITUTION: A wavelength adjuster is comprised of two mode division directional coupler(730,740), a single mode optical fiber(750), a dual mode optical fiber(760), and an inclined optical fiber Bragg lattice(770) or single mode optical fibers(780,790). The optical fibers(780,790) are connected to the dual mode optical fiber(760). The dual mode optical fiber(760) and the single mode optical fibers(780,790) are connected by aligning core axis linearly so that only LP01 mode of the two optical fibers can pass. An input signal is incident through a terminal(I), a signal separated by the wavelength adjuster is output through a terminal(D). Other signals proceed to a terminal(O), an optical signal having same wavelength as that of the separated optical signal is input through a terminal(A) in the case of addition.

Experimental study of a slot antenna excited by a TE011 mode coaxial cavity

Abstract: A slot antenna is developed to excite the high harmonic waveguide mode for generating large-area plasmas. This antenna consists of a TE011 mode coaxial cavity with the axial slots positioned on equal interval on the inner wall. The waves radiated from those slots can excite the high harmonic mode in the central area. With the azimuthal symmetric wave field of the TE011 mode, the number of the slots can be chosen to match the field pattern of the high harmonic mode. In this report, the dispersion relation of the coaxial waveguide, the coupling scheme and the mode competition of the cavity are studied. A method has been successfully developed to suppress the TE121 mode which is the most competing mode to the TE011 mode.

Supermodes of Grating-Coupled Multimode Waveguides and Application to Mode Conversion Between Copropagating Modes Mediated by Backward

Abstract: An analysis of multimode waveguides where several modes are coupled via quasiperiodic perturbations is presented. The supermodes (or eigenmodes) of the structure are derived and orthonormality considerations are discussed. In addition, a new type of mode converter between copropagating modes is proposed, where mode conversion is mediated by a backward- propagating mode. Adiabatic and nonadiabatic coupling coeffi- cients are considered and the supermode formalism is used to conveniently describe the mode of operation of the device.

New type of single mode optical fibres

Abstract: The new algorithm of single-mode fibres synthesis for given values of phase and group speeds of propagation mode on fixed normalized frequency is proposed and realized. New types of single-mode graded dielectric waveguides with an extended band of single-mode regime and increased cross sections of core are received. The dependence between bandwidth of single-mode regime and values of phase and group speed of propagating mode for fixed frequency is established. The dispersion characteristics and distribution of propagating mode field in synthesized waveguides are calculated.