Abstract: A waveguide coupler includes a coupling section which evanescently couples an optical signal, received from an input waveguide, with an absorbing waveguide. Structurally, the coupling section is an elongated waveguide with one end butt-coupled to the input waveguide. Further, the coupling section defines an engagement side edge which is positioned at a predetermined distance from a dimensionally compatible side surface area of the absorbing waveguide. In this combination, evanescence from the optical signal is directed laterally from the coupling section, through the engagement side edge of the coupling section, and through an assisting component, to the absorbing waveguide for use with a photodetector.

Abstract: A system for converting an optical signal into an electrical signal includes at least one differential Trans-Impedance Amplifier (TIA). To minimize (preferably eliminate) DC offset issues at the TIA output, an Input Counter-Offset (ICO) circuit is provided to remove the DC component of the initial optical signal from the input to the TIA. To further maximize the removal of DC offset at the TIA output, an Output Counter-Offset circuit is provided to take DC offset from the TIA output for use as a negative feedback directly to the input of the TIA. Modifications of the present invention are also intended for use with two TIA terminations and with a travelling wave photodiode.

Abstract: Circuitry for an optical receiver includes a photodiode for converting an optical signal into a photocurrent having an AC portion Ipd(AC) and a DC portion Ipd(DC). The circuitry includes a circuit element that is connected between the photodiode and the input to a Trans-Impedance Amplifier (TIA). Included in the circuit element is an AC bypass capacitor Cbp and a sensor. In detail, the sensor may be either a current sensor or a voltage sensor. In either case, the sensor establishes a cancellation current for removing the DC portion Ipd(DC) from the photocurrent while the AC bypass capacitor Cbp shunts an AC portion Ipd(AC) to ground. The result is that only an AC portion Ipd(AC) of the optical signal is maintained for input into the TIA.

Abstract: A system for converting an optical signal into an electrical signal includes at least one differential Trans-Impedance Amplifier (TIA). To minimize (preferably eliminate) DC offset issues at the TIA output, an Input Counter-Offset (ICO) circuit is provided to remove the DC component of the initial optical signal from the input to the TIA. To further maximize the removal of DC offset at the TIA output, an Output Counter-Offset circuit is provided to take DC offset from the TIA output for use as a negative feedback directly to the input of the TIA. Modifications of the present invention are also intended for use with two TIA terminations and with a travelling wave photodiode.

Abstract: An EO phase shifter for modulating an electrical signal onto an optical wave is manufactured using CMOS process tools whereby a waveguide core made of EO material has intimate contacts with its electrodes. Specifically, the waveguide core is made of a Silicon-Rich Silicon Nitride (SRN) material which has a high linear refractive index n and a high third order nonlinear susceptibility. The electrodes are made of P or N doped silicon. Also, polarization of the optical wave is oriented normal to interfaces between the waveguide core and the electrodes. With this combination, the EO phase shifter exhibits high optical confinement, low propagation loss, and a high electro-optic overlap integral for modulation.

Abstract: In accordance with the present invention, an elongated phase shifting diode is provided for modulating an electrical signal onto an optical wave. Structurally, the phase shifting diode includes a p doped central stripe that extends through a phase shifting length L of a waveguide. P+ doped finger stripes and N+ doped finger stripes, which are laterally and axially offset from each other, extend into the waveguide for contact with the p doped central stripe along the length L. In combination, the plurality of N+ doped finger stripes and the p doped central stripe create a plurality of PN junctions that are structurally aligned along the p doped central stripe to establish electrically parallel phase shifting functions for the elongated diode.

Abstract: A system and method for controlling the energy flux of a light beam (carrier wave) relies on the manipulation of a light beam's Poynting vector to switch the light beam from one optical waveguide to another. A modulator positioned between the two waveguides has an index of refraction n+ik wherein ik is a loss/gain component. It is the manipulation of this loss/gain component ik by an external stimulus which causes anisotropic changes in orthogonal components of the light beam's Poynting vector. This, in turn, causes changes in the propagation distance of the light beam (carrier wave) over a length L along the waveguides that switch the light beam from one waveguide to the other.

Abstract: A system and method for controlling the energy flux of a light beam (carrier wave) relies on the manipulation of a light beam's Poynting vector to switch the light beam from one optical waveguide to another. A modulator positioned between the two waveguides has an index of refraction n+ik wherein ik is a loss/gain component. It is the manipulation of this loss/gain component ik by an external stimulus which causes anisotropic changes in orthogonal components of the light beam's Poynting vector. This, in turn, causes changes in the propagation distance of the light beam (carrier wave) over a length L along the waveguides that switch the light beam from one waveguide to the other.

Abstract: In accordance with the present invention the switching element of an optical switch for switching/modulating an optical signal from one optical waveguide to another is a reverse bias diode. More particularly, the diode is itself an optical waveguide that has been doped to create a predetermined depletion width, Wd, between the N-type and IP-type regions of the diode. In operation, an optical signal is input into the waveguide/diode in a manner that generates a second order mode for the optical signal. The second order mode optical signal then transits the waveguide/diode back and forth through the depletion width Wd. A switching voltage, V?, which is selectively applied to the waveguide/diode, can then alter the depletion width Wd of the waveguide/diode. Consequently, the propagation interference distance, ?c, of the waveguide/diode will also be changed, to thereby direct the optical signal from one output optical filter to another.

Abstract: A waveguide/diode is manufactured by taking into account the effect that losses have on a multi-mode optical signal as it transits through the waveguide/diode. In particular, the loss effects that are caused by higher order modes in the optical signal as it passes back and forth through the cross charge region of a PN junction are considered. The consequent stretching of the cross coupling distance for the optical signal is then evaluated to minimize the required length for the waveguide/diode.

Abstract: An optical modulator for switching an optical signal of wavelength ? from one waveguide-electrode to another requires that both waveguide-electrodes be made of an electrically conducting material. Also, a non-conducting cross-coupling material fills a slot along a length L between the waveguide-electrodes. Importantly, cross-coupling material in the slot provides a separation distance xc between the waveguide-electrodes that is less than 0.35 microns. When a switching voltage V? is selectively applied to the waveguide-electrodes, a strong uniform electric field E is created within the cross-coupling material. Thus, E modulates the cross-coupling length of the optical signal by an increment ±? each time it passes back and forth through the cross-coupling material along the length L. Thus, after an N number of cross-coupling length cycles along the length L, when N? equals one cross-coupling length, the optical signal is switched from one waveguide-electrode to the other.

Abstract: An optical modulator for switching an optical signal of wavelength ? from one waveguide-electrode to another requires that both waveguide-electrodes be made of an electrically conducting material. Also, a non-conducting cross-coupling material fills a slot along a length L between the waveguide-electrodes. Importantly, cross-coupling material in the slot provides a separation distance xc between the waveguide-electrodes that is less than 0.35 microns. When a switching voltage V? is selectively applied to the waveguide-electrodes, a strong uniform electric field E is created within the cross-coupling material. Thus, E modulates the cross-coupling length of the optical signal by an increment ±? each time it passes back and forth through the cross-coupling material along the length L. Thus, after an N number of cross-coupling length cycles along the length L, when N? equals one cross-coupling length, the optical signal is switched from one waveguide-electrode to the other.

Abstract: The present invention pertains to systems and methods for equalizing a digitally modulated input signal for transmission as an optical signal over an optical fiber. In detail, this equalization is accomplished prior to the signal's conversion to an optical signal, and prior to the signal being filtered by a vestigial sideband (VSB) filter. In particular, equalization is accomplished by giving weights to the taps of a tapped delay equalizer, wherein weights for respective taps are derived from the output signal after its conversion to a digital signal at the downstream end of the optical fiber.

Abstract: A method for manufacturing an electro-optically coupled switch in accordance with the present invention requires a sequential reconfiguration of a layer of semiconductor material. To begin, a base member is created wherein the semiconductor layer is positioned on a layer of insulator material with the insulator material positioned between the semiconductor layer and a semiconductor substrate. In sequence, with a first etch, the semiconductor layer is etched to create waveguides on opposite sides of a slot. In a second etch, the slot is deepened to expose the layer of insulator material in the slot. With a third contact pad doping process, pads can be positioned on top of the layer of insulator material for electrical contact with the respective waveguides. Metal contacts can then be placed on the contact pads, the slot can be filled with an electro-optical polymer and, if needed, the polymer can be poled.

Abstract: An electro-optically coupled switch includes first and second waveguides which are aligned in parallel to each other, with a thin, flat layer of cross-coupling material sandwiched therebetween. A voltage source is provided to establish a strong uniform electric field that is oriented perpendicular across the entire layer of cross-coupling material between the waveguides. Incorporated with the voltage source is a switch for changing the electric field, to thereby alter the refractive index of the cross-coupling material for transferring the transmission of an optical signal from one waveguide to the other.

Abstract: An electro-optically coupled switch includes first and second waveguides which are aligned in parallel to each other, with a thin, flat layer of cross-coupling material sandwiched therebetween. A voltage source is provided to establish a strong uniform electric field that is oriented perpendicular across the entire layer of cross-coupling material between the waveguides. Incorporated with the voltage source is a switch for changing the electric field, to thereby alter the refractive index of the cross-coupling material for transferring the transmission of an optical signal from one waveguide to the other.

Abstract: An electro-optically coupled switch includes first and second waveguides which are aligned in parallel to each other, with a thin, flat layer of cross-coupling material sandwiched therebetween. A voltage source is provided to establish a strong uniform electric field that is oriented perpendicular across the entire layer of cross-coupling material between the waveguides. Incorporated with the voltage source is a switch for changing the electric field, to thereby alter the refractive index of the cross-coupling material for transferring the transmission of an optical signal from one waveguide to the other.

Abstract: A method for manufacturing an electro-optically coupled switch in accordance with the present invention requires a sequential reconfiguration of a layer of semiconductor material. To begin, a base member is created wherein the semiconductor layer is positioned on a layer of insulator material with the insulator material positioned between the semiconductor layer and a semiconductor substrate. In sequence, with a first etch, the semiconductor layer is etched to create waveguides on opposite sides of a slot. In a second etch, the slot is deepened to expose the layer of insulator material in the slot. With a third contact pad doping process, pads can be positioned on top of the layer of insulator material for electrical contact with the respective waveguides. Metal contacts can then be placed on the contact pads, the slot can be filled with an electro-optical polymer and, if needed, the polymer can be poled.

Abstract: An analog signal processing device for equalizing a low pass filter to create a Nyquist filter in accordance with the present invention includes a low pass filter for passing a predetermined bandwidth, and a tapped delay filter connected with the low pass filter to create the Nyquist filter. In more detail, the tapped delay filter is used to sample an input analog signal having a predetermined symbol rate. The samples from the input signal are then respectively weighted to establish a system transfer function for the Nyquist filter. The purpose here is to minimize both inter-symbol interference and transmission bandwidth. A decision circuit can be provided to convert the input signal into a desired data format for creation of an output signal to be transmitted by the data transmission system. Also, the Nyquist filter can be selectively evaluated as an “eye diagram” and the system transfer function appropriately adjusted accordingly.

Abstract: In accordance with the present invention, a driver chip is provided for transmitting optical signals over an optical fiber. The driver chip includes, in combination, a tapped delay equalizer, an amplifier and control circuitry. Operationally, the tapped delay equalizer modifies an input digital signal to create a compensated signal by compensating for anticipated impairments and distortions introduced during signal transmission. The amplifier then receives the compensated signal to provide gain and bias in order to establish a proper operating point for an E/O device. The control circuitry is interconnected with the tapped delay equalizer and with the amplifier to establish and control tap weights for the tapped delay equalizer to compensate for electrical and optical bandwidth limitations, along with optical dispersion effects.