Abstract: A signal conditioning module provides a polarimeter capability in a photometric system. The module may include multiple variable delay polarization modulators. Each modulator may include an input port, and a first arm formed to include a first reflector and first rooftop mirror arranged in opposed relationship. The first reflector may direct an input radiation signal to the first rooftop mirror. Each modulator also may include an output port and a second arm formed to include a second reflector and second rooftop mirror arranged in opposed relationship. The second reflector can guide a signal from the second rooftop mirror towards the output port to provide an output radiation signal. A beamsplitting grid may be placed between the first reflector and the first rooftop mirror, and also between the second reflector and the second rooftop mirror. A translation apparatus can provide adjustment relative to optical path length vis-a-vis the first arm, the second arm and the grid.

Abstract: An optical device is provided with first and second inputs. A first coupler coupled is coupled to the first input and produces at least a first and second output. A second coupler is coupled to the second input and produces at least a first and second output. A third coupler is coupled to the first output of the first coupler and to the first output of the second coupler. A fourth coupler is coupled to the second output of the first coupler and to the second output of the second coupler. First and second crossing waveguides are provided with an angle selected to minimize crosstalk and losses between the first and second cross waveguides. The first crossing waveguide connects one of the first or second outputs from the first coupler with an input of the fourth coupler. The second crossing waveguide connects one of the first or second outputs from the second coupler with an input of the third coupler. A first phase shifter is coupled to the first and second waveguides.

Abstract: A new technique for capturing both the amplitude and phase of an optical waveform is presented. This technique can capture signals with many THz of bandwidths in a single shot (e.g., temporal resolution of about 44 fs), or be operated repetitively at a high rate. That is, each temporal window (or frame) is captured single shot, in real time, but the process may be run repeatedly or single-shot. This invention expands upon previous work in temporal imaging by adding heterodyning, which can be self-referenced for improved precision and stability, to convert frequency chirp (the second derivative of phase with respect to time) into a time varying intensity modulation. By also including a variety of possible demultiplexing techniques, this process is scalable to recoding continuous signals.

Abstract: An optical device extracts an information bearing sideband such as an FSK or SCM signal (label) from a composite signal that includes the sideband and an orthogonally modulated signal such as an intensity modulated signal (payload) by employing polarization beam splitting and polarization transformation. Polarization transformation is accomplished by splicing the optical signal into a polarization maintaining fiber at a desired angle so that it is separated into two orthogonal polarizations that experience differential group delay in the fiber. The fiber is characterized by a beat length Lbeat and the fiber is designed to have a length substantially equal to (Lbeat×fc)/2?f, wherein the sidebands of the composite signal are separated by a wavelength difference ?f and fc is the nominal center frequency of the composite signal. This device has been shown to be useful for extracting GMPLS LSC level wavelength labels from either an FSK/IM composite signal or an SCM/IM composite signal.

Abstract: The inventors propose herein a switch fabric architecture that allows broadcasting and fast channel access in the ns-range. In various embodiments of the present invention, 10 Gb/s receiver modules are based on a novel heterodyne receiver and detection technique, which is tolerant to moderate wavelength drifts of a local oscillator. A gain clipped electrical amplifier is used in the novel receiver as a rectifier for bandpass signal recovery.

Abstract: With a single laser light source, the line width of a beat signal is set to a few tens of kHz or less without it fluctuating over time, and the frequency thereof is set as desired. CW light from a CW laser light source is input into an electroabsorption modulator to which a sine wave electrical signal is applied. A modulation sideband which is made up from line spectra at separations equal to the modulation frequency is generated from the electroabsorption modulator. An optical fiber for higher-order soliton compression broadens the optical spectrum width, and increases the number of line spectra. A tunable wavelength filtering device which is made up from optical fiber gratings and optical circulators chooses two of the line spectra, which are combined by an optical coupler with their beat signal being heterodyne wave detected by a photo-detector.

Abstract: An electronic receiver array for decoding data encoded into electromagnetic radiation (e.g., light) is described. The light is received at an ultra-small resonant structure. The resonant structure generates an electric field in response to the incident light and light received from a local oscillator. An electron beam passing near the resonant structure is altered on at least one characteristic as a result of the electric field. Data is encoded into the light by a characteristic that is seen in the electric field during resonance and therefore in the electron beam as it passes the electric field. Alterations in the electron beam are thus correlated to data values encoded into the light.

Abstract: An apparatus and method for demultiplexing multiple wavelengths of light. In one embodiment, an optical signal having a plurality of wavelengths is provided to an optical-to-electrical (OE) circuit configured to convert optical signals into electrical signals. The optical signal may include a plurality of wavelengths. The OE circuit converts the optical signal into a first electrical signal. The first electrical signal is received by a demodulating circuit, which also receives a demodulating signal. The demodulating circuit combines both the first electrical signal and the demodulating signal in order to produce a second electrical signal. Both the second electrical signal and the demodulating signal correspond to one of the wavelengths in the optical signal.

Abstract: An optical receiver adapted to apply multiple-sampling processing to an intermediate frequency (IF) signal generated based on heterodyne detection of an optical communication signal. In one embodiment, the receiver has an optical-to-electrical signal converter coupled to a signal decoder adapted to process the IF signal generated by the converter to generate a bit sequence corresponding to the optical communication signal. To generate a bit value, the signal decoder first obtains two or more sample-bit values by sampling the IF signal two or more times per signaling interval. The decoder then applies a logical function to the sample-bit values, which produces the corresponding bit value for the bit sequence. Due to the multiple-sampling processing, a receiver of the invention does not require the time-consuming fine wavelength tuning of its local oscillator, which advantageously reduces the channel switching time achieved in the receiver compared to that in prior-art heterodyne receivers.

Abstract: An optical device is provided with first and second inputs. A first coupler coupled is coupled to the first input and produces at least a first and second output. A second coupler is coupled to the second input and produces at least a first and second output. A third coupler is coupled to the first output of the first coupler and to the first output of the second coupler. A fourth coupler is coupled to the second output of the first coupler and to the second output of the second coupler. First and second crossing waveguides are provided with an angle selected to minimize crosstalk and losses between the first and second cross waveguides. The first crossing waveguide connects one of the first or second outputs from the first coupler with an input of the fourth coupler. The second crossing waveguide connects one of the first or second outputs from the second coupler with an input of the third coupler. A first phase shifter is coupled to the first and second waveguides.

Abstract: A method and system for converting an optical signal to electrical information signals, including demodulated baseband information signals and modulated baseband signals at multiple harmonics. In an embodiment, the optical information signal is amplitude modulated with information. The method converts an optical signal to electrical charge, accumulates the electrical charge, and periodically transfers the accumulated electrical charge to a storage device, whereby the periodically transferred electrical charge forms the electrical signals. An exemplary system includes an optical transducer and a universal frequency translator coupled to an output of the optical transducer. The optical transducer receives an optical signal and converts the optical signal to electrical charge. The universal frequency translator periodically transfers energy from the electrical charge and forms the electrical signals from the transferred energy.

Abstract: A demodulator includes a 1×m optical coupler and one or more optical device sets. The 1×m optical coupler splits an input signal comprising symbols to yield m signals comprising m/2 pairs of signals. An optical device set is associated with a pair of signals and includes one or more first optical operators, one or more second optical operators, and a set coupler. The first optical operators direct a first signal of a pair of signals along a first path, and the second optical operators direct a second signal of the pair along a second path. The second path introduces a symbol delay between the first signal and the second signal. The set coupler receives the first and the second signal to generate interference. The interference indicates a phase shift between a phase corresponding to a symbol and a successive phase corresponding to a successive symbol.

Abstract: Disclosed herein is an apparatus for controlling a decision threshold voltage to an optical receiver, which is capable of automatically controlling the decision threshold voltage to the optical receiver appropriately to signal level decision on the basis of a low-frequency band signal component of an output signal from the optical receiver. The apparatus is adapted to control the level of the decision threshold voltage to the optical receiver, which converts an input optical signal into an electrical signal.

Abstract: An optoelectronic RF signal receiver utilizes a first RF to photonic modulator for receiving an optical carrier signal and an electrical signal from a local oscillator and producing an optical carrier signal with first optical sidebands offset from the carrier signal by the local oscillator frequency. A second RF to photonic modulator receives an electrical RF signal and the signals from the first modulator and produces second sidebands to each of the first optical sidebands from the first modulator with each of the second sidebands being offset from the first sidebands by the RF signal frequency. A detector then receives signals produced by the second modulator and produces an electrical IF signal for further processing. The receiver does not utilize a frequency translation device in the RF signal path and thereby eliminates RF loss, noise, and limited dynamic range characteristic of prior art electro-optical receivers.

Abstract: The delay setting of an optical delay line interferometer (DLI) used to decode differentially encoded phase shift keyed signals (DPSK or DQPSK) is controlled using a control signal representative of the ratio Perr2/Perr1 of the rate of occurrence of double errors and the rate of occurrence of errors. The ratio Perr2/Perr1, as the delay setting of the DLI is varied, exhibits a characteristic W-shaped structure consisting of a local maximum at the optimum value and two minima adjacent to the maximum, one on each side of it. This structure is present over a wide range of signal to noise ratio and residual dispersion.

Abstract: When a PLL circuit is used to extract and recover clock component from an information data signal, where an optical receive signal has been converted into an electrical signal, and to monitor the frequency of a recovered clock, a low frequency section frequency detection circuit having a BPF (band-pass filter) where transmission center frequency has been shifted to higher frequency relative to center frequency of the electrical signal and a high frequency section frequency detection circuit having a BPF where the transmission center frequency has been shifted to lower frequency are provided in parallel. Utilizing a slope on one side of each transmission characteristic of the BPF makes it possible to set detection frequency freely and accurately. Therefore, a frequency detection circuit without using a special device in an optical transmitter/receiver, capable of easily detecting accurate frequency shift of f0±?f or more, and of low price and high performance, can be obtained.

Abstract: A frequency-agile optical transceiver includes a shared local oscillator (LO), a coherent optical receiver and an optical transmitter. The LO operates to generate a respective LO optical signal having a predetermined LO wavelength. The coherent optical receiver is operatively coupled to the LO, and uses the LO signal to selectively receive traffic of an arbitrary target channel of an inbound broadband optical signal. The optical transmitter is also operatively coupled to the LO, and uses the LO to generate an outbound optical channel signal having a respective outbound channel wavelength corresponding to the LO wavelength.

Abstract: An optical communications system includes a receiver subsystem with at least two heterodyne receivers. The receiver subsystem receives a composite optical signal having two or more subbands of information and corresponding tones. An optical splitter splits the composite optical signal into optical signals. Each optical signal includes a subband(s) and corresponding tone. Each heterodyne receiver receives an optical signal. The receiver includes a heterodyne detector coupled to a signal extractor. The heterodyne detector mixes the optical signal with an optical local oscillator to produce an electrical signal which includes a frequency down-shifted version of the subband and the tone of the optical signal. The signal extractor mixes the frequency down-shifted subband with the frequency down-shifted tone to produce a frequency component containing the information.

Abstract: The invention relates to the monitoring of polarization mode dispersion (PMD) using heterodyne detection for providing PMD compensation in optical networks, and an apparatus for monitoring PMD. In the present invention, a broadband PMD monitor is disclosed based on heterodyne detection with a tunable laser source which can be fed to a compensator such as an add/drop or other wavelength switch and polarization dependent attenuation means. A signal from a local oscillator is combined with an optical signal and the beat frequency amplitude and phase is analyzed for two orthogonal polarization states simultaneously to obtain a state of polarization. By averaging a plurality of polarization states within a channel, PMD can be estimated for compensation.

Abstract: A Kalman filter is used to estimate the coefficients of an FIR filter to optimize the noise subtraction in a balanced optical heterodyne receiver and related receiver configurations. The Kalman filter is used both statically and dynamically.

Abstract: A method for transmitting high-frequency signals in an optical communication system includes combining an optical signal, the first optical local component from a local light source and the second optical local component from the local light source having a predetermined frequency differential from the first optical local component, selecting the first high-frequency signal which consists of two predetermined electrical components from plural electrical components obtained by the optical frequency mixing process, and mixing the two selected electrical components included in the first high-frequency signal.

Abstract: The present invention relates to a receiver for receiving a time division multiplexed (TDM) optical signal, which is formed of a plurality of interleaved optical pulse streams. Each optical pulse stream includes a plurality of optical pulses. The receiver includes a detector for detecting at least a first optical pulse stream of the optical signal and an optical hybrid for coherently mixing the first optical pulse stream with a reference pulse stream. The first optical pulse stream and the reference pulse stream impinge simultaneously upon the detector.

Abstract: The present invention provides several embodiments of a video carrier signal detection circuit included in an optical transmitter for either disabling an oscillator that provides dithering tones or attenuating the power level of the dither tones. A first detection circuit detects the presence of a video carrier signal by analyzing a known video channel. The power level of a video sync pulse included in the known video channel is then compared to a reference power level. A second detection circuit compares the composite power level of the RF signals in a predetenmined frequency spectrum with a reference power level to determine either the presence of a video carrier signal or an increase in the channel loading. Upon detection of a video carrier signal or an increase in composite power, an enable signal is provided to either the oscillator or an attenuating device depending upon the detection circuit.

Abstract: A wideband communications system uses a photomixer, a radio frequency (RF) mixer, and an antenna. The photomixer is comprised of high speed phototransistors that are illuminated by two laser beams. The laser beams are generated by two lasers, one tunable, and conveyed to the photomixer via fiber optic cables. The two beams are mixed by the photomixer to generate a radio heterodyne signal that is mixed with antenna signals to generate an intermediate frequency (IF) signal based on the differences of the generated heterodyne frequency and the antenna signals. Conventional fiber optic means may be used to convey the IF signals, along with the fiber optic cables to the photomixer, to and from a remote RF head located at some distance from the rest of the communications system to overcome losses in transmission lines.

Abstract: A coherent optical intradyne receiver is described which comprises an optical image reject mixer capable of dividing, mixing and recombining signals from three inputs so as to produce an inphase and a quadrature channel. On each of the channels a same set of image products is cancelled and from which channels, phase modulated signals can be recovered.

Abstract: A light demultiplexer in which a signal and a noise in each channel may be distinctly separated is provided. The light demultiplexer comprises a light-receiving element array for receiving light beams demultiplexed every wavelength from a wavelength multiplexed light beam and arranged in a straight line. The light-receiving element array includes a plurality of light-receiving elements for monitoring signals, and a plurality of light-receiving elements for monitoring noises. The light-receiving elements for monitoring signals and the light-receiving elements for monitoring noise are alternately arrayed in a straight line the direction thereof is the same as that of the arrangement of the demultiplexed light beams.

Abstract: To improve the performance for measuring autocorrelation bit errors of optical signals to be measured, an autocorrelation-bit-error detection apparatus of the present invention using an optical branch system first has an optical branch unit for branching an optical signal to be measured into a plurality of branched optical signals, a plurality of light-to-electricity converters for converting a plurality of branched optical signals supplied from the optical branch unit into electrical signals, a plurality of decision circuits for deciding relations between the electrical signals supplied from the light-to-electricity converters and their threshold values, and a detector for detecting autocorrelation bit errors of the optical signal to be measured in accordance with comparison results between the decision circuits.

Abstract: An optical heterodyne detection system includes a tunable optical pre-selector that is adjusted to track the frequency of a swept local oscillator signal. The tunable optical pre-selector is adjusted in response to a measure of the frequency of the swept local oscillator signal and in response to a measure of a portion of the swept local oscillator signal after the portion of the swept local oscillator signal has optically interacted with the optical pre-selector. In an embodiment, at least some portion of the swept local oscillator signal is modulated before it interacts with the optical pre-selector. In an embodiment, the portion of the swept local oscillator signal that interacts with the pre-selector is detected and used in a feedback control circuit to generate a control signal which causes the error between the center frequency of the pre-selector and the frequency of the swept local oscillator signal to be small.

Abstract: A method for transmitting high-frequency signals in an optical communication system includes combining an optical signal, the first optical local component from a local light source and the second optical local component from the local light source having a predetermined frequency differential from the first optical local component, selecting the first high-frequency signal which consists of two predetermined electrical components from plural electrical components obtained by the optical frequency mixing process, and mixing the two selected electrical components included in the first high-frequency signal.

Abstract: Generating oscillator signals with which selected signals may be mixed. Such oscillator signals may be generated by dividing a pilot tone, such as a 120 MHz pilot tone found on many cable TV systems. Oscillator signals for demodulating received selected signals may be similarly generated.

Abstract: An apparatus and method is disclosed for receiving packets having a wide dynamic range of power levels over a shared medium in a communications system. The receiver responds to a packet with a different power level within an inter-packet time and maintains a constant logic level for a long string of ‘ones’ or ‘zeros’ within a packet. An AC-coupled pre-amplifier provides a voltage signal having a slowly decaying power level for a long string of ‘ones’ or ‘zeros’ within the packet. A differential amplifier with hysteresis, ignores the slowly decaying power level of a long string of ‘ones’ or ‘zeros’ within the packet and does not overwrite the power level of the long string until it detects the end of the string.

Abstract: Apparatus and methods of measuring optical waveforms are described. In one aspect, an optical waveform measurement apparatus includes a light wave source, a mixer, a down converter, and a controller. The light wave source is operable to provide an adjustable frequency light wave with a frequency that is adjustable over a target frequency range. The mixer is operable to mix a target modulated optical signal with the adjustable frequency light wave to obtain a mixed signal. The frequency down converter is operable to down convert the mixed signal to obtain a down-converted signal. The controller is operable to extract from the down-converted signal amplitude and phase information relating to the target modulated optical signal and to cause the light wave source to incrementally adjust the frequency of the adjustable frequency light wave over the target frequency range.

Abstract: A branch portion 101 branches an inputted electrical signal into an in-phase signal and an opposite phase signal which have an opposite relation as to a phase. A first FM laser 104 converts the in-phase signal into an optical frequency-modulated signal (a first optical signal) having a center wavelength ?1 and then outputs the resultant signal. A second FM laser 105 converts the opposite phase signal into an optical frequency-modulated signal (a second signal) having a center wavelength ?2 and then outputs the resultant signal. The two optical signals are combined and then inputted into an optical-electrical converting portion 106. The optical-electrical converting portion 106 subjects the inputted optical signals to optical heterodyne detection by its square-law detection characteristic, and outputs a beat signal between the two optical signals which is a wide-band FM signal at a frequency corresponding to a wavelength difference ??(=|?1??2|) between the first optical signal and the second optical signal.

Abstract: An apparatus containing an integrated optical circuit that enhances phase stability of the injection-locking process of two slave lasers. The integrated optical circuit helps to reduce phase noise by keeping environmental or mechanical perturbations uniform everywhere on that circuit. Also, the integrated optical circuit provides connections for additional components to be coupled, which can monitor and control the performance characteristics of the integrated optical circuit and the injection-locking process.

Abstract: A method and apparatus are provided for transmitting and receiving multiple RF/microwave subcarriers on a single optical wavelength over an optical link. The method includes the steps of modulating a plurality of RF/microwave subcarrier frequencies with a respective communication signal and modulating an optical carrier wave with the plurality of modulated RF/microwave subcarrier frequencies.

Abstract: A wavelength monitor and control system and method for a WDM optical transmission system is disclosed. The system comprises a heterodyne-based detection device with a real-time externally calibrated tunable laser.

Abstract: An optical communication system suitable for a coherent optical satellite communication is configured to include an optical transmission device having a laser signal generator, a first reference laser signal generator having a first local oscillating laser signal generator and an automatic frequency controller, an optical receiving device, and a second reference optical signal generator having a second local oscillating laser signal generator. The first reference local oscillating laser signal generator and the automatic frequency controller are used to generate a fixed beat reference optical signal, and thus the optical receiving device is capable of locking the transmitted laser signal according to the fixed beat reference laser signal in a way of heterodyne receiving so as to demodulate the transmitted signal frequency accurately and resolve the problem of laser frequency drifting.

Abstract: A large time constant is caused due to parasitic capacitance at an anode terminal of a photodetector of an optical receiver. Therefore, an optical receiver wherein a variable negative capacitor mainly including an NPN-type transistor operable at high speed is configured and is connected to the input terminal of a preamplifier to which the output of the photodetector is input so that parasitic capacitance caused in the photodetector and due to packaging is equivalently reduced and the fluctuation of parasitic capacitance caused due to manufacturing dispersion is also compensated is provided.

Abstract: A coherent optical communication receiver of a satellite optical communication system, having a telescope, an automatic frequency control circuit and a frequency shift keying demodulator. The automatic frequency control circuit has a local oscillating laser, a light polarization controller, a optical coupler, a photo-detector, a microwave matching network, a microwave mixer, a frequency discriminator and a low pass frequency filter. The coherent optical communication receiver can receive a frequency control signal of a distant laser signal to perform a heterodyne receiving between the emitter and the receiver distant away from each other. With the consideration of the decay of vibration and atmosphere, the quality of the satellite optical communication can still be maintained. The structure and fabrication of the receiver are simple with a low fabrication cost, and the receiver is suitable for being applied to high speed satellite communication system.

Abstract: Implemented in both coherent and non-coherent optical systems, a receiving device including a cross polarization interference canceler (XPIC) is described. For these embodiments, the XPIC optimizes bandwidth efficiency of an optical communication link by enabling the reconstruction of two optical signals transmitted with generally orthogonal polarization states and routed over a single fiber optic transmission medium in the same frequency band.

Abstract: A tunable optical local oscillator is used for optical heterodyne signal detection using an electrooptic Mach-Zehnder modulator to produce a rapidly tunable optical signal from a tunable RF frequency generator. A combination of the Mach-Zehnder modulator and optical fibers for providing stimulated Brillouin scattering are used to suppress unwanted signals for providing a spectrally pure optical local oscillator waveform. Suppression of unwanted optical signals, up to 50 dB, generated by the Mach-Zehnder modulator is obtained, resulting in high spectral purity of the optical local oscillator waveform with an extended tuning range of the tunable optical oscillator equal to the operating bandwidth of up to 60 GHz of the Mach-Zehnder modulators.

Abstract: A receiver (EMP1, . . . , EMPn) is disclosed for receiving optical signals from an optical transmission network (NET) serving to transmit coded, multiplexed optical signals. The receiver (EMP1, . . . , EMPn) includes a means (DEK1) for detecting the optical signals to be received, e.g., a Fabry-Perot filter, and processing means (O/E1, 0/E2, 5) to compensate noise present in the detected optical signals by combining the detected optical signals with compensation signals. The means (DEK1) is adapted to transmit optical signals to be received and reflect optical signals not to be received. A further means (K1), e.g., an optical coupler, is provided for deriving the compensation signals from at least part of the reflected optical signals and then applying the compensation signals to the processing means (O/E1, O/E2, 5).

Abstract: A branch portion 101 branches an inputted electrical signal into an in-phase signal and an opposite phase signal which have an opposite relation as to a phase. A first FM laser 104 converts the in-phase signal into an optical frequency-modulated signal (a first optical signal) having a center wavelength &Dgr;1 and then outputs the resultant signal. A second FM laser 105 converts the opposite phase signal into an optical frequency-modulated signal (a second signal) having a center wavelength &Dgr;2 and then outputs the resultant signal. The two optical signals are combined and then inputted into an optical-electrical converting portion 106.

Abstract: A Kalman filter is used to estimate the coefficients of an FIR filter to optimize the noise subtraction in a balanced optical heterodyne receiver and related receiver configurations. The Kalman filter is used both statically and dynamically.

Abstract: An optical signal receiver apparatus is comprised of a photodiode for converting an input photo-signal into a photoelectric current and an integrated circuit having a transimpedance amplifier for converting the photoelectric current into a voltage signal and amplifying it. The power source line of the photodiode can be shortened by supplying a power source current to the photodiode through a current detector in the integrated circuit. In addition, a current drain circuit is used to drain a DC current from the input side of the transimpedance amplifier on the basis of the detection result obtained by the current detector. The current drain circuit is operated when a photoelectric current is output from the photodiode.

Abstract: With a single laser light source, the line width of a beat signal is set to a few tens of kHz or less without it fluctuating over time, and the frequency thereof is set as desired. CW light from a CW laser light source is input into an electroabsorption modulator to which a sine wave electrical signal is applied. A modulation sideband which is made up from line spectra at separations equal to the modulation frequency is generated from the electroabsorption modulator. An optical fiber for higher-order soliton compression broadens the optical spectrum width, and increases the number of line spectra. A tunable wavelength filtering device which is made up from optical fiber gratings and optical circulators chooses two of the line spectra, which are combined by an optical coupler with their beat signal being heterodyne wave detected by a photo-detector.

Abstract: A photoreceiver assembly for accurately separating at least one low level, high frequency signal carried from a large, low frequency pulse. Illustratively, in one exemplary embodiment, the photoreceiver assembly extracts a high frequency ultrasonic signal from the optical frequency of light by shining that ultrasonic base band signal onto a photodetector for conversion into an electrical signal in the bandwidth of interest. The photoreceiver assembly includes a photodetector and a splitter coupled to the photodetector. The splitter is also coupled to a plurality of transimpedance signal paths. In operation, the splitter receives a current from the photodetector, separates, and directs the current to the plurality of transimpedance signal paths. In one exemplarily embodiment, the photoreceiver further includes a transimpedance amplifier assembly coupled to at least one path of the transimpedance signal paths.

Abstract: An optical heterodyne detection system in accordance with an embodiment of the invention includes two optical receivers for separately measuring the power of an input signal and a local oscillator signal before the signals are combined. The measurements of the input signal and the local oscillator signal are then utilized to enhance the heterodyne signal to noise ratio by removing the intensity noise contributed by the input signal and the local oscillator signal. By measuring portions of the input signal power and the local oscillator signal power and then subtracting out the scaled quantities from the photocurrent measurement during signal processing, the signal to noise of the heterodyne signal is improved beyond that which is accomplished by known balanced receivers.

Abstract: Apparatus and methods of measuring optical waveforms are described. In one aspect, an optical waveform measurement apparatus includes a light wave source, a mixer, a down converter, and a controller. The light wave source is operable to provide an adjustable frequency light wave with a frequency that is adjustable over a target frequency range. The mixer is operable to mix a target modulated optical signal with the adjustable frequency light wave to obtain a mixed signal. The frequency down converter is operable to down convert the mixed signal to obtain a down-converted signal. The controller is operable to extract from the down-converted signal amplitude and phase information relating to the target modulated optical signal and to cause the light wave source to incrementally adjust the frequency of the adjustable frequency light wave over the target frequency range.

Abstract: A single high resolution holographic pickup, for reading/writing both a CD and DVD optical recording medium, has an electrical tuning control for applying a DC and AC signal to a tunable Bragg cell, which AC is phase locked with respect to the fundamental repetition frequency of the recorded data on the CD to produce accurate tracking. A special high resolution holographic lens is recorded within the Bragg cell that focuses the light signals read off of the optical storage mediums upon a pickup detector, and its focal length is varied to read a selected CD and or DVD from a group of CDs or DVDs in response to changes in the DC applied to the Bragg cell. The holographic lens within the Bragg cell is formed by an interference pattern produced by interfering light emitted from the tip of a one micron optical fiber and a plane broad light beam.