Abstract: Methods and devices for processing a signal. The methods include supplying to a first modulator a first RF signal and a first optical signal, wherein the first modulator is configured to output a first output signal; generating a first intensity signal that is based on the first output signal, wherein the first intensity signal is further based on a first biasing parameter; and providing a first intensity signal to a first analog-to-digital converter (ADC) to create a first digital signal processable by a signal processing unit.

Abstract: This disclosure describes a kit comprising component for removing, replacing, and/or sealing toilet parts. In some embodiments, the kit comprises a flush valve assembly, fill valve assembly, a handle assembly, two tools, two gaskets, and packaging that also serves as one or more water containers. In some embodiments, the two gaskets are two conventional gaskets that can be combined to make a third gasket. In some embodiments, the combination of the two gaskets allows the creation of a synergistic gasket for sealing a tank-to-bowl interface than neither gasket could seal individually.

Abstract: RF processing systems and methods. An RF processing system includes an optical storage module, a processing module, and an electro-optical modulation module. The electro-optical modulation module is configured to receive the first signal from the optical storage module, receive the modulation signal from the processing module, and electro-optically modulate the first signal based on the modulation signal.

Abstract: This disclosure describes a kit comprising component for removing, replacing, and/or sealing toilet parts. In some embodiments, the kit comprises a flush valve assembly, fill valve assembly, a handle assembly, two tools, two gaskets, and packaging that also serves as one or more water containers. In some embodiments, the two gaskets are two conventional gaskets that can be combined to make a third gasket. In some embodiments, the combination of the two gaskets allows the creation of a synergistic gasket for sealing a tank-to-bowl interface than neither gasket could seal individually.

Abstract: RF processing systems and methods. An RF processing system includes an optical storage module, a processing module, and an electro-optical modulation module. The electro-optical modulation module is configured to receive the first signal from the optical storage module, receive the modulation signal from the processing module, and electro-optically modulate the first signal based on the modulation signal.

Abstract: A two-way actively stabilized QKD system that utilizes control signals and quantum signals is disclosed. Because the quantum signals do not traverse the same optical path through the system, signal collisions in the phase modulator are avoided. This allows the system to have a higher transmission rate than a two-way system in which the quantum signals traverse the same optical path. Also, the active stabilization process, which is based on maintaining a fixed relationship between an intensity ratio of interfered control signals, is greatly simplified by having the interferometer loops located all in one QKD station.

Abstract: A cascaded modulator system (20) and method for a QKD system (10) is disclosed. The modulator system includes to modulators (M1 and M2) optically coupled in series. A parallel shift register (50) generates two-bit (i.e., binary) voltages (L1, L2). These voltage levels are adjusted by respective voltage adjusters (30-1 and 30-2) to generate weighted voltages (V1, V2) that drive the respective modulators. An electronic delay element (40) that matches the optical delay between modulators provides for modulator timing (gating). The net modulation (MNET) imparted to an optical signal (60) is the sum of the modulations imparted by the modulators. The modulator system provides four possible net modulations based only on binary voltage signals. This makes for faster and more efficient modulation in QKD systems and related optical systems when compared to using quad-level voltage signals to drive a single modulator.

Abstract: A method of autocalibrating a quantum key distribution (QKD) system (200) is disclosed. The QKD system includes a laser ((202) that generates photon signals in response to a laser gating signal (S0) from a controller (248). The method includes first performing a laser gate scan (304) to establish the optimum arrival time (TMAX) of the laser gating signal corresponding to an optimum- e.g., a maximum number of photon counts (NMAX)—from a single-photon detector (SPD) unit (216) in the QKD system when exchanging photon signals between encoding stations (Alice and Bob) of the QKD system. Once the optimal laser gating signal arrival time (TMAX) is determined, the laser gate scan is terminated and a laser gate dither process (308) is initiated. The laser dither involves varying the arrival time (T) of the laser gating signal around the optimum value of the arrival time TMAX. The laser gate dither provides minor adjustments to the laser gating signal arrival time to ensure that the SPD unit produces an optimum (e.g.

Abstract: A quantum key distribution station having the capability of forming decoy signals randomly interspersed with quantum signals as part of a QKD system is disclosed. The QKD station includes a polarization-independent high-speed optical switch adapted for use as a variable optical attenuator. The high-speed optical switch has a first attenuation level that results in first outgoing optical signals in the form of quantum signals having a mean photon number ?Q, and a second attenuation level that results in second outgoing optical signals as decoy signals having a mean photon number PD. The attenuation level is randomly set during QKD system operation so that the decoy signals are randomly interspersed with the quantum signals.

Abstract: A cosite interference rejection system allows cancellation of large interfering signals with an optical cancellation subsystem. The rejection system includes an interference subsystem coupled to a transmit system, where the interference subsystem weights a sampled transmit signal based on a feedback signal such that the weighted signal is out of phase with the sampled transmit signal. The optical cancellation subsystem is coupled to the interference subsystem and a receive antenna. The optical cancellation subsystem converts an optical signal into a desired receive signal based on an interfering coupled signal and the weighted signal. The weighted signal is therefore used to drive the optical cancellation subsystem. The rejection system further includes a feedback loop for providing the feedback signal to the interference subsystem based on the desired receive signal.

Abstract: A method of synchronizing the operation of a two-way QKD system by sending a sync signal (SC) in only one direction, namely from one QKD station (ALICE) to the other QKD station (BOB). The one-way transmission greatly reduces the amount of light scattering as compared to two-way sync signal transmission. The method includes phase-locking the sync signal at BOB and dithering the timing of the quantum signals so as to operate the QKD system in three different operating states. The number of detected quantum signals is counted for each state for a given number of detector gating signals. The QKD system is then operated in the state associated with the greatest number of detected quantum signals. This method is rapidly repeated during the operation of the QKD system to compensate for timing errors to maintain the system at or near its optimum operating state.

Abstract: Systems and methods for compensating a QKD system for variations in temperature are disclosed. One of the methods includes identifying an optimum detector gating signal timing as a function of temperature for a single-photon detector (SPD) control board in one of the QKD stations. The detector gating signal timing versus temperature information is stored in a look-up table in a memory unit. The QKD system's temperature is monitored during operation and the timing of the detector gating signal is adjusted based on the operating temperature and the corresponding timing value adjustment in the look-up table. The result is a compensated detector gating timing signal provided to the SPD that yields an optimum number of photon counts even as the temperature of the QKD station varies.

Abstract: Systems and methods for compensating a QKD system for variations in temperature are disclosed. One of the methods includes identifying an optimum detector gating signal timing as a function of temperature for a single-photon detector (SPD) control board in one of the QKD stations. The detector gating signal timing versus temperature information is stored in a look-up table in a memory unit. The QKD system's temperature is monitored during operation and the timing of the detector gating signal is adjusted based on the operating temperature and the corresponding timing value adjustment in the look-up table. The result is a compensated detector gating timing signal provided to the SPD that yields an optimum number of photon counts even as the temperature of the QKD station varies.

Abstract: A bulk-optics assembly for a transmitting/receiving QKD station (BOB1) in a two-way autocompensating QKD system (101) is disclosed. The assembly consists of a first beamsplitter (104) having a high (e.g., 90:10) beamsplitting ratio, a 50:50 beamsplitter (106) and a polarizing beamsplitter (108). The assembly also optionally includes a polarizer (102), and/or a fixed attenuator (FOA), and/or an optional blocking filter (110) downstream of the polarizing beamsplitter. The compact bulk-optics assembly is easier to manufacture than a fiber-based optical system, and is simpler and more compact than prior art bulk-optics assemblies for QKD systems.

Abstract: A method of using a single single-photon detector (SPD) in a quantum key distribution (QKD) system is described. The method includes modulating a phase of a quantum signal a first time at a first QKD station by applying a first phase modulation randomly selected from a set of four possible phase modulations. The method also includes modulating the phase of the quantum signal a second time. The second modulation involves applying a second phase modulation randomly selected from the same set of four possible phase modulations. The method is a modification of the BB84 protocol and represents a higher level of quantum security than either the BB84 or B92 protocols when using a QKD system with a single SPD.

Abstract: A two-way actively stabilized QKD system that utilizes control signals and quantum signals is disclosed. Because the quantum signals do not traverse the same optical path through the system, signal collisions in the phase modulator are avoided. This allows the system to have a higher transmission rate than a two-way system in which the quantum signals traverse the same optical path. Also, the active stabilization process, which is based on maintaining a fixed relationship between an intensity ratio of interfered control signals, is greatly simplified by having the interferometer loops located all in one QKD station.

Abstract: A multi-stage polarization transformer is described that includes a first polarization transformer stage that receives an optical signal at an input and that generates a first transformed optical signal at an output. The first transformed optical signal has a polarization state within a first predetermined range. A second polarization transformer stage receives the first transformed optical signal at an input and generates a second transformed optical signal at an output. The second transformed optical signal has a polarization state within a second predetermined range. The second predetermined range is less than the first predetermined range.

Abstract: A bit interleaved polarization multiplexer is described that includes a first and a second modulator. The first and the second modulator modulate a first and a second electrical modulation signal, respectively, onto an optical signal and generate a modulated optical pulse train at a first and a second optical output, respectively. An optical beam combiner combines the modulated optical bit stream generated by the first and the second modulators into a polarization multiplexed optical pulse train. A relative position of each pulse in the polarization multiplexed optical pulse train is determined by an optical path length propagated by the pulse and a relative order of each pulse in the polarization multiplexed optical pulse train is determined by a relative phase of the modulation signal that generated the pulse.