Abstract: The present invention provides a velocity matched distributed photodetector/modulator (VMDP) for converting between an optical signal and an electrical signal. The converter has twice the theoretical efficiency of any prior art device. The converter wave-guide core is of uniform cross-sectional thickness and composition along the optical path, which makes it easy to fabricate. The converter includes a passive optical waveguide and a plurality of photodiodes. The photodiodes optically couple in series with the passive optical waveguide and electrically couple in parallel with one another to convey the electrical signal there between. The photodiodes exhibit impedance mismatches that generate reflections of the electrical signal, which contribute to a cancellation of reverse traveling portions of the electrical signal.

Abstract: Described embodiments provide a method and apparatus for transmission of optical communications. An embodiment provides an optical transmitter which includes a control circuit to enhance the stability of output power levels, a modulator circuit with precise impedance matching for high frequency performance, and an optical coupling mechanism that relaxes the alignment tolerances between the laser and the fiber and decreases the sensitivity of the gain medium to feedback from devices coupled to the fiber. These features allow the transmitter to deliver an optical output beam which can be modulated over a wide range of frequencies, duty cycles and amplitudes with very precise definition of the rising and falling edges of the waveform. In combination these features result in an optical transmitter that may be fabricated with relatively low cost and a reduced form factor when compared with prior art optical transmitters.

Abstract: An optical receiver may include a photodector defined on a multilayer semiconductor structure. A first electrode may be formed by at least two substantially concentric conductive rings electrically coupled to one another and to a portion of a first layer of the multilayer semiconductor structure. A second electrode may be coupled to a second layer of the multilayer semiconductor structure and configured to transfer current generated by the photodetector in response to optical emissions. A method of fabricating such an optical receiver is also disclosed.

Abstract: An automatic fiber pigtailing machine (AFPM) is disclosed. The AFPM provides precise coupling between a fiber pigtail and an optoelectronic (OE) device based on the fidelity of signal transfer across a junction between the fiber and OE device. The AFPM uses a positioning system with a high frequency closed loop optical feedback of a modulated signal to/from the device under assembly (DUA). Local/global maximums in the fidelity of the modulated signal are correlated with relative orientations/alignment/positions of the various components of the DUA to determine the preferred orientation/alignment/positions between the various components for the completed assembly. In an embodiment of the invention the fiber optic extends from a first surface of a generally rectangular package and the electrical interface to the OE device is defined on a surface orthogonal to the first surface.

Abstract: A high bandwidth RF sampler using equivalent time sampling comprising an RF coplanar waveguide integrated with sampling diodes on a gallium arsenide substrate. A monolithic, integrated coplanar strip nonlinear transmission line is integrated on the same substrate to receive sample pulses. These pulses are reshaped by the nonlinear transmission line to have a very fast edge. This edge is differentiated by a shunt inductance of a short circuit termination of a slot line portion of the RF signal coplanar waveguide. The resulting delta function sample pulses cause the sample diodes and integrated capacitors to develop an intermediate output frequency which is a replica of the RF signal at a lower frequency and no voltage conversion loss. RF signals of up to 300 Ghz can be sampled using this circuit.

Abstract: A nonlinear impedance transformer comprising a plurality of scaled L-C sections. The first section has its inductance and capacitance values selected to establish a characteristic impedance approximately equal to the output impedance of the local oscillator. The last section has its inductance and capacitance values selected to establish an output impedance which substantially matches the input impedance of whatever device to which the nonlinear impedance transformer is coupled. The impedance of each section is scaled logarithmically between the values of the input and output impedances. An FET driver can be integrated on the same substrate as integrated versions of the nonlinear impedance transformer. In such a case, the input impedance of the first section is set to the output impedance of the FET, i.e., about 10 ohms.

Abstract: A high bandwidth RF sampler using equivalent time sampling comprising an RF coplanar waveguide integrated with sampling diodes on a gallium arsenide substrate. A monolithic, integrated nonlinear transmission line is integrated on the same substrate to receive sample pulses. These pulses are reshaped by the nonlinear transmission line to have a very fast edge. This edge is differentiated by a shunt inductance of a short circuit termination of a slot line portion of the RF signal coplanar waveguide. The resulting delta function sample pulses cause the sample diodes and integrated capacitors to develop an intermediate output frequency which is a replica of the RF signal at a lower frequency and no voltage conversion loss. RF signals of up to 300 Ghz can be sampled using this circuit.

Abstract: An integrated coplanar strip nonlinear transmission line comprising a substrate of gallium arsenide upon which a heavily doped buried layer and a lightly doped surface layer of epitaxially grown gallium arsenide are grown. Two parallel conductors are integThis work was funded by the United States Government's Office of Naval Research under contract No. N99914-85-K-0381. The United States Government has a paid up license in this technology.

Abstract: A crystal exhibiting a variable index of refraction in response to a voltage applied across it is driven from a lower voltage signal generator through a passive resonant circuit. The resonant frequency of the circuit is tunable by hand in order to maximize the voltage applied to the crystal from a low voltage signal generator. The impedance of the circuit is also hand adjustable in order to match that of the signal generator. The crystal and driving circuit are packaged together in a single enclosure having optically transparent windows allowing a laser beam to pass through the crystal and be modulated by it according to the frequency of the signal generator.

Abstract: A floating sampler and directional bridge for use in characterizing the impedance of an integrated device under test from D.C. up to frequencies above 100 GHz. The directional bridge has the structure of a Wheatstone bridge with resistor values selected such that when the input impedance of the device under test matches the output impedance of the source, no voltage develops across two nodes of the bridge. When no impedance match exists, a floating diode/capacitor sampler comprised of two diode/capacitor pairs driven by local oscillator strobe pulses samples the voltage difference between the two nodes of the bridge and outputs an IF signal proportional to the difference. Another pair of diode/capacitor samplers outputs an IF signal proportional to the amplitude of the RF excitation waveform.